GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Topic started by: QVTom on January 27, 2012, 05:41:29 AM
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I finally had some time to work on one of my projects for a change. The kids and wife are asleep, I'm half asleep but got these upper sears complete :) Sometimes you just need to make some time.
I took some pictures to serialize the process. This is my first time using photobucket and linking to picts as imgages.
I hope you enjoy. Comments welcome of course :)
Edit: Scan down to my last post to see the new stuff.
S7 Air hardening tool steel. 0.188 wide - Overkill with out a doubt.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-26_21-48-26_844.jpg)
Cut to size and ready for the first operation.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-26_21-53-43_281.jpg)
Operation 1 finished - drilled for alignment pins and slotted for the cross pin.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-26_22-34-44_458.jpg)
Got to have a fixture for the next op. Pins will align and tapped holes will hold the part.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-27_00-53-55_436.jpg)
Op1 on fixture, ready for op2 - Contouring the profile.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-26_23-33-04_329.jpg)
Op2 finished, part still on the fixture.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-26_23-42-33_398.jpg)
Finished parts. Only 1:15 am !
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-27_00-54-53_89.jpg)
Post complete. 1:50am
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Very nice work what gun is that for. If you make them for a 22XX and a 13XX im sure they will sell i for one would buy one.
Mike
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Really nice work! Thanks for taking the time to take pics and to post it for us to see.
-Matt
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Very nice work what gun is that for. If you make them for a 22XX and a 13XX im sure they will sell i for one would buy one.
Mike
+ 1 to Mike's comments, and make some triggers too!
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Very nice work what gun is that for. If you make them for a 22XX and a 13XX im sure they will sell i for one would buy one.
Mike
+ 1 to Mike's comments, and make some triggers too!
Thanks for the kind words.
These parts are for a springer of my own design. I have been working on the design for about 6 months in my spare time and believe it is now ready to make a prototype. The sear group seemed like a good place to start, not too difficult and of high importance.
My goal is to reach 34% efficiency, yielding a 38fpe gun. I know it sounds like a reach, however it turns out, I'm sure the pursuit will be rewarding.
As for making sear parts for other guns. It sounds intriguing but the liability issue has me spooked. There are many other accessories that don't carry the same price for failure or carelessness that the trigger group does.
-T
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What machine are you using? Nice pics and love the smell of coolant!
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What machine are you using? Nice pics and love the smell of coolant!
The machine is a Daewoo 3016L VMC. A very sweet machine with an oil chilled high speed spindle.
-T
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Another productive late night. This is the lower sear. The process is similar but different enough to post some more picts.
This part stars with some 1018 steel gear stock
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-31_14-26-50_442.jpg)
The next step is to make another fixture. Again pins for alignment, tapped hole and clamps to hold the work.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-31_23-30-46_4.jpg)
The gears have been bored and parted on the lathe and are mounted on the fixture. Ready for hole drilling and the rough cut on the profile.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-31_22-03-53_945.jpg)
Parts with hold down screws installed and ready to have the clamps removed for the profile finish pass.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-31_22-35-05_982.jpg)
Ready to remove from the fixture.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-31_23-02-58_508.jpg)
Finished parts. I scribed them with numbers so the sets would be easy to identify.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-31_23-31-45_600.jpg)
If you got this far you can see how they are going to interact.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-01-31_23-32-29_672.jpg)
If anyone can help me with the pict. rotation I would appreciate it. It is driving me crazy!!!
Edit: Ignore the above statement. The picts seem to have corrected themselves!
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you hobb your own gears or sombody else ,nice work.sounds like a big project ,good luck with it.
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Wonderful workmanship.... I wish I had some clue as to how it all works, though.... :o
Bob
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I have to tell you that I can't wait for this thread to continue. This really is some good stuff.
Darrin
PS: Don't sleep so much! Get back to work... ;D
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you hobb your own gears or sombody else ,nice work.sounds like a big project ,good luck with it.
I have made gears in the past out of necessity using gear cutters but true hobbing is a discipline in itself. In this case I used stock purchased from Stock Drive Products.
-T
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Wonderful workmanship.... I wish I had some clue as to how it all works, though.... :o
Bob
I thought that last picture in the series would give a lot away :) As I add parts I'm sure you will figure it out :)
-T
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Nice!....Dual opposing pistons for recoilless operation?
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Nice!....Dual opposing pistons for recoilless operation?
Boyd, you are correct !
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Dual opposing pistons
Well I kinda figured that from the two sears facing in opposite directions.... I guess I'll just have to wait to see how they are controlled from a single trigger.... :o
Bob
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Dual opposing pistons
I guess I'll just have to wait to see how they are controlled from a single trigger.... :o
Bob
Couldn't have said it better. I think of it as a dead reckoning system, make accurate calculations, perform them properly and you should end up at the correct spot. Of course its always the outside influences that you don't fully comprehend that cause all the problems.
BTW - Glad to have you back!
-T
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38FPE springer?! I'm in 8)
Nice work too. I rebuild machine tools for a living but am little more than a hack when it comes to running one.
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Working on the compression tube and the end caps now.
These are the front and rear ends for the compression tube. The front is threaded and the rear will bolt in with some shoulder screws. The rear is not complete, it will hold the cocking lever and some linkage so there is a lot to do still.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-09_23-26-14_911.jpg)
Compression tube ready to thread the end. This was a real PITA because the headstock of my lathe will not swallow a diameter this large. So I threaded it hanging 12" out of the chuck. It took a while to dial out the run-out and had to thread at 75 rpm to keep the tube from singing too much. Maybe my next project should be a steady rest :)
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-07_11-33-20_173.jpg)
Trimming to length. Again, hanging way out there.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-07_11-23-09_632.jpg)
I'll need an expanding mandrel for the next step.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-08_17-15-50_545.jpg)
Mandrel ready
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-08_17-32-54_656.jpg)
Tube all set up with the indexer, the plug in the left end threads in just the the end cap will and stabilizes the part nicely
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-09_21-26-09_0.jpg)
Finished compression tube. I may be the coolest weight reduction job or the ugliest. Not sure yet :)
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-09_23-25-22_150.jpg)
Tube with front cap installed.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-09_23-26-49_147.jpg)
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Cool Stuff there Bud. I love seeing progress pictures from craftsman.
Nice work.
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I gotta ask.... What is the bore and stroke(s) of this monster.... :o
Bob
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I gotta ask.... What is the bore and stroke(s) of this monster.... :o
Bob
The bore is 1.79" and the combined stroke is 3.5" for a total 8.8ci. My goal with this unit is to test the cocking and release mechanisms, general layout and also the materials/coatings. I'll be surprised if I hit the efficiency number I'm looking for with this short of a stroke. My other goal is to stay under 9lbs scoped :0
-T
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The biggest swept volume I have seen in a Springer is 87 cc.... That's only 5.3 CI.... so you're already wayyyyyyyy into uncharted territory AFAIK....
Bob
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Tom,
I am drooling on my keyboard. I just saw this thread for the first time and with each post I read, my eyes got bigger and bigger !
You obviously know what you are doing, or at least have it 99% figured out. I am truly impressed. Have you looked at the inner workings of the Whiscombe or is this all yours?
Man, I could just go on and on about this. Nice choice with the S-7 material. Wow, so many questions. Do you think you will need a ratcheting cocking lever? A pair of short stroke, but very stout springs to push the 1.79 pistons 1.75 distance. Even if it doesn't work as you hope, it will be a marvelous gun.
Lloyd
P.S. Is this the gun in your Avatar?
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LLoyd,
I'm not sure I have it 99% worked out but have been noodling the design for some time. When I started this design I had not heard or seen a Whiscombe. I didn't think opposing pistons was unique but maybe to air guns. Then when reading a thread on this wonderful forum, something like 'if you could have only one springer', I learned of the Wiscombe. Of course I did some research to see what is was and was surprised to find the opposing piston concept. It was kind of nice to have the basic concept validated! It took me a while to figure out how the Whiscombe worked as there is not a lot of detailed info, some pictures and brief descriptions. The only similarity is the the opposing pistons.
My pistons are sync'd by release not gears, I have a single stroke side lever that will cock one piston on the back stroke and the other on the return stroke. Because I cock only one piston at a time and the relatively short stroke, the leverage is huge and should yield a very low force. Under 20 lbs if I did my math correctly :) The gun is powered by a pair of 25mm gas die springs.
The avatar is the gun but a very early rendering, much has changed.
I have to say that I have taken much inspiration from following your projects and also rsterne's love of analysis. You guys convinced me that I was missing out on the most enjoyable aspect of our hobby. Sincere Thanks!
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Getting closer. This is the finished rear cap/lever mount and added the hex to the front cap. I think I'll finish the trigger/sear mounting next. It could be while as I'm starting to get behind on the work that pays the bills.
Final operation on the end caps.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-13_17-45-03_152.jpg)
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-14_11-42-59_567.jpg)
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-14_12-08-12_421.jpg)
Assembled compression tube
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-14_13-55-52_787.jpg)
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-02-14_13-56-09_425.jpg)
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Tom,
Having access to the CNC turning and milling capability, plus the programming SW, and of course, the ability to use it, must be really nice.
Lloyd
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Tom,
Your ideas and machine work are beyond words! Thank you for choosing to share this project with the GTA!
Matt
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I took machine shop in h.s. and regret not following thru but seeing work like this makes me respect
the machinist and engineer ................. great work !!!!!!!!!
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Tom,
I am curious, is that your shop or equipment, or do you have a nice boss, or what?
I can really appreciate the effort that has gone into this project, and still a long way to go. Truly incredible.
Lloyd
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so is this supposed to be a springger setup like a pcp with the breech on top of the airtube ?
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Tom,
I am curious, is that your shop or equipment, or do you have a nice boss, or what?
I can really appreciate the effort that has gone into this project, and still a long way to go. Truly incredible.
Lloyd
Lloyd, my boss is a real !@@. Seriously, I'm the boss and the machines are mine. They reside in my shop (the barn) about a 1000ft down my drive from my house, very convenient :) I have written lots of checks to several equipment finance companies over the years. Getting the machine is easy, just sign next to the X, keeping it is another matter though :)
I'm very happy with the progress and hope I don't become stalled. I have a barrel coming this week and almost done with the sear/catch mounting. Next will be the receiver and transfer ports. I plan to make two different designs that have some adjustment via sleeves to test some ideas. They will be crude form follow function prototypes. Oh yes, I still need pistons and seals! Maybe I should have started my first design as a PCP :)
My shop
(http://i1147.photobucket.com/albums/o553/QVTOM/2011-02-20_07-09-25_130.jpg)
-T
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so is this supposed to be a springger setup like a pcp with the breech on top of the airtube ?
Kind of, the transfer port is in the center top of the comp. tube because the pistons travel from the ends toward the center, the only viable layout to minimize the dead space and keep compression ratio at a maximum. The actual port/breech seal is still up in the air until I get the power plant functioning well enough to test some different designs.
-T
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In awe.. makes wish I had learned some shop skills.
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That is a fine project that you are undertaking. I am kind of on the edge of my seat until you pull the trigger for the first time. Simultaneous (is that even possible?) release of two separate pistons.
Your machining skills are impressive.
Piston seals can be easy. Just use o-rings.
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Great work and a very interesting idea. Good luck. Thanks for sharing your work with us.
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That is a fine project that you are undertaking. I am kind of on the edge of my seat until you pull the trigger for the first time. Simultaneous (is that even possible?) release of two separate pistons.
Your machining skills are impressive.
Piston seals can be easy. Just use o-rings.
Yes, the release. Is it possible? Well nobody wants the answer to that question more than me :) It seems possible as long as the mechanism is accurate, the springs are well matched, the piston and seal drag is consistent and both seals are performing correctly. One leaky or damaged seal and the system fails to some extent.
Considered o-rings but I have some concerns: 1) rolling in the gland 2) limited choice of materials. Of course, there are the square and X cross sections but they have even fewer size and material choices. I successfully made and tested a turned cup seal made of PTFE on my Gamo springer, it has over 3k cycles and is still going strong. I've scaled up that design, hopefully it will wok as well.
Thanks to all who have given their words of encouragement.
Tom
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Even if the timing is off by a little, it will still work. It will just have an interesting "kick".
I'm on an o-ring kick right now. I have not decided if they are better or worse than the parachute seal. That x-ring that you mentioned looks interesting. Mcmaster has a good selection of them. I'm going to order a pack of the Viton x-rings in 1" inch x 1/8".
If you decide to try something other than the parachute seal, this larger size might work for you:
http://www.mcmaster.com/#6540K162 (http://www.mcmaster.com/#6540K162)
Another interesting link:
http://www.allsealsinc.com/parker/dynamic-oring-sealing.pdf (http://www.allsealsinc.com/parker/dynamic-oring-sealing.pdf)
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Simply Put,,Awesome work Tom!!!!
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Tom,
You have probably already seen this Parker seal design guide, but I think it is a very good reference.
http://www.parker.com/literature/Engineered%20Polymer%20Systems/5340_2008.pdf (http://www.parker.com/literature/Engineered%20Polymer%20Systems/5340_2008.pdf)
There is a tremendous amount of info, and a good design decision tree on page 4-2. if your piston has a removable seal retainer on it, the seal can be clamped such that there is no movement in the piston groove during the reversal. And maybe an o-ring expander in the lip to keep light pressure on the cylinder bore. I had Wyatt seal make some custom lip seals made from graphite filled teflon with a spring expander. For customs, they were pretty reasonable, and they were a whole lot better than my attempts had been, LOL.
This is a very intriguing project!
Lloyd
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Lloyd, Thanks for the link, lots off great application info. I hadn't seen that particular publication before but do have most of their printed handbooks that go back many years. Remember when companies used to have librarians? When you wanted a data book, you would have to call the librarian and they would mail it to you. Then the librarians were replaced by fax-on-demand, not a very good interim solution. Now we have the internet. How did we ever manage?
Shotchmo, thank you too. I have had some mixed results in the past with o-ring gland data from Parker's handbook but I do think it is a fantastic reference and a good starting point for o-ring usage. One thing I'm sure you already know about o-rings is that there is no single application, they are used and abused in so many unique ways that there is no right or wrong, just what works or doesn't.
This the turned seal from PTFE for the Gamo. Made as a test of the material, it has been performing exceptionally well. I have put more the 3k cycles on the seal with pellets from 11-22grains. My benchmark pellet, the 14.3 CHP, is still giving 720fps. I plan to use the basic design except for the mounting. I need to have the seal behind the front of the piston to prevent the seal from extruding into the transfer port. So I will have a removable front piston cap made from Delrin that will retain the seal, doing away with the silly tapered spud attachment and the need to stretch the seal to get it on. PTFE doesn't stretch well easily becomes permanently elongated.
(http://i1147.photobucket.com/albums/o553/QVTOM/2011-07-26_15-12-36_348.jpg)
Append:
I just realized with my piston design there is the possibility of using off the shelf lip seals! I will need to adjust the bore to a standard diameter. Sometimes it hard to resist re-inventing the wheel or blindly following what other have done. ie. scaling up a commercial airgun seal.
Tom
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It's been a slow week for progress but I did manage to get a little closer.
Sear parts in place sans torsion springs and opposing bracket. Still needs some shim washers for the lower sears, the posts for the torsion springs, extension for the trigger, then I can install the opposite bracket and snug up the screws for a complete fit and function test of the trigger/sear group :)
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-03-08_22-05-00_819.jpg)
Miles to go before I sleep........
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Looking better all the time. In my mind, there are still several parts that I can't visualize. Guess I will just have to wait!
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Wonderful work.
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by the size of this thing is it correct to call it an air rifle or a cannon.LOL nice work .....dave
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Looking better all the time. In my mind, there are still several parts that I can't visualize. Guess I will just have to wait!
Maybe this will help :)
(http://i1147.photobucket.com/albums/o553/QVTOM/trigger.jpg)
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by the size of this thing is it correct to call it an air rifle or a cannon.LOL nice work .....dave
Carbine, not cannon :) Only 22cal. Really not as big as it looks. Just .4" diameter larger than Gene's reservoir on his PCP project.
It's going to look something like this
(http://i1147.photobucket.com/albums/o553/QVTOM/concept.jpg)
Tom
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Looking better all the time. In my mind, there are still several parts that I can't visualize. Guess I will just have to wait!
Maybe this will help :)
Ahhhh! Definitely. With the linkage you have, it looks like the release of the gas springs will be self-synchronizing. Even if one of the sears releases slightly ahead of the other, that action will immediately kick the other sear over thru the meshing of the gear sectors. Very clever.
Is the helix on the bolt to add to the sexiness factor?
Are the piston faces going to impact each other? If so, a disk of this material bonded to the face could help damp any rebound, if that is a concern.
http://www.earsc.com/HOME/products/DampingandIsolation/IsolationMaterials/index.asp?SID=151 (http://www.earsc.com/HOME/products/DampingandIsolation/IsolationMaterials/index.asp?SID=151)
Its an energy absorbing sheet where if you laid an 1/8" thick piece of it on an anvil and hit it with a steel hammer, the hammer would stop like a dead-blow plastic hammer. It works well in controlling over-travel impact in shock events. It kills the rebound bounce and amplification and resonance.
Tom, again, that is a very impressive project!
Lloyd
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Interesting material, but I don't think it will stand up to the temperatures inside a springer.... If you want to get a feel for what is happening inside a springer, download the spreadsheet from this page.... http://www.prosperousa.com/resources.html (http://www.prosperousa.com/resources.html)
Click on the link "Internal Ballistics Calculator".... You can change the variables and see what happens to temperatures, pressures, piston slam and bounce, etc.etc....
Bob
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Interesting material. Maybe similar to sorbothane? I'm still unclear how much force is involved when the pistons contact each other at the ends of their stroke, there are so many variables involved it makes my head spin :). One thing is for sure, factory urethane piston seals seem to survive repeated contact with the chamber face and combustion, so a urethane type buffer most likely would work as well. Yes the the temps will spike extremely high but it is only for an extremely short duration.
I've seen the interior ballistic calc. and I'm skeptical.
Lloyd, the helix on the bolt is purely sex appeal :)
You will have to wait to see what's inside, better that the outside :) :)
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I've seen the interior ballistic calc. and I'm skeptical.
I take it you're not a Cardew's fan then.... I might be considered a Cardew's Agnostic.... but I find it hard to deny their experimental results when they eliminated springer combustion in a Nitrogen atmosphere.... I've learned never to dismiss a theory unless I have a better one....
Bob
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Interesting material, but I don't think it will stand up to the temperatures inside a springer.... If you want to get a feel for what is happening inside a springer, download the spreadsheet from this page.... http://www.prosperousa.com/resources.html (http://www.prosperousa.com/resources.html)
Click on the link "Internal Ballistics Calculator".... You can change the variables and see what happens to temperatures, pressures, piston slam and bounce, etc.etc....
Bob
I had forgotten about that calculator. It is fun to adjust the variables and watch the trends.
Trust me on the the ISOLOSS material, empirical testing has shown it will definitely work to calm down a springer that has a too-powerful spring. At least in one application. ;) ;) I think the instantaneous heat goes out with the air.
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Interesting material. Maybe similar to sorbothane? I'm still unclear how much force is involved when the pistons contact each other at the ends of their stroke, there are so many variables involved it makes my head spin :). One thing is for sure, factory urethane piston seals seem to survive repeated contact with the chamber face and combustion, so a urethane type buffer most likely would work as well. Yes the the temps will spike extremely high but it is only for an extremely short duration.
I've seen the interior ballistic calc. and I'm skeptical.
Lloyd, the helix on the bolt is purely sex appeal :)
You will have to wait to see what's inside, better that the outside :) :)
Tom, The characteristics of ISOLOSS are similar to sorbothane, but a different manufacturer, and a harder material. Very durable and will take repeated impacts such as in low frequency vibe testing. They also mold it into little round isolators that fit on screws to attach and isolate fans and delicate equipment. It absorbs the energy instead of rebounding. It would be worth looking at probably only if you discover a rebound problem.
Lloyd
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More of a believer than agnostic. The nitrogen experiment and transfer port photos both support their theory nicely. They have convinced me that combustion exists but have failed to quantify it. I believe the the "event" is very short lived and the amount influence on system performance can vary from none to some.
I don't think the Prospero spreadsheet takes combustion into account and uses some "fiddle factors" to adjust results. I haven't spent too much time with it because it's locked and the math can't be studied. That's why I'm skeptical.
-Tom
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Ahhhhhh.... that makes sense.... Yeah, I see they use fiddle factors to look after any possible combustion.... which might be as good as any as there seems to be no way to quantify it.... I played with the spreadsheet enough to see what happened when you changed pellet weight.... and it seemed relatively consistent to how my springers FEEL when fired....
Bob
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Tom, I have been following your post for weeks now. Amzing talent you have with machining and math. I check your post every day and sometimes twice a day for updates....:) Can't wait to see and hear more.
Thanks so much for sharing you skills with us.
Gene
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Wow. Probably the coolest project I've seen. I've been missing out- I can't wait to see how this turns out!
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Tom, I have been following your post for weeks now. Amzing talent you have with machining and math. I check your post every day and sometimes twice a day for updates....:) Can't wait to see and hear more.
Thanks so much for sharing you skills with us.
Gene
Thanks Gene, I really enjoy this place. Especially the way everyone shares their ideas, work and expertise with nothing asked in return. Well maybe a dialog :) It could be a while before their is more; I just got called to Federal Court as a Juror which means a 65 mile drive to and from. I'm hoping to get excused........
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Wow. Probably the coolest project I've seen. I've been missing out- I can't wait to see how this turns out!
The coolest? Really? Thanks :) :) I though only my kids thought I was the coolest :)
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You have a good chance of getting excused if you are self-employed.... especially if you have to close down your business to attend court....
Bob
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Tom, I have been following your post for weeks now. Amzing talent you have with machining and math. I check your post every day and sometimes twice a day for updates....:) Can't wait to see and hear more.
Thanks so much for sharing you skills with us.
Gene
Thanks Gene, I really enjoy this place. Especially the way everyone shares their ideas, work and expertise with nothing asked in return. Well maybe a dialog :) It could be a while before their is more; I just got called to Federal Court as a Juror which means a 65 mile drive to and from. I'm hoping to get excused........
federal court, hmm be interested in knowing what the charges are. if some one has to go to federal court they did something really bad
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You have a good chance of getting excused if you are self-employed.... especially if you have to close down your business to attend court....
Bob
Exactly the case for me. I filled out the "excuse" form and sent it in. Hopefully they will see it my way.
-Tom
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Tom, I have been following your post for weeks now. Amzing talent you have with machining and math. I check your post every day and sometimes twice a day for updates....:) Can't wait to see and hear more.
Thanks so much for sharing you skills with us.
Gene
Thanks Gene, I really enjoy this place. Especially the way everyone shares their ideas, work and expertise with nothing asked in return. Well maybe a dialog :) It could be a while before their is more; I just got called to Federal Court as a Juror which means a 65 mile drive to and from. I'm hoping to get excused........
federal court, hmm be interested in knowing what the charges are. if some one has to go to federal court they did something really bad
Should I send them your name? This guy Mike would like to go in my place :)
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I remember all the years the compay I worked for got me out of jury duty. Hope it works out that you do not have to participate. Ya folks here on the GTA sure are free with help and advice. I learn so much from the pictures and posts. Like a whole nudder education. Even old coots can still learn... :)
Good luck and hope to see you back soon.
Gene
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Progress has been slow mainly due to my shop being busy. I had some time this evening with my kids away on sleep overs and the wife busy with her community obligations.
One shop, one gun and one beer :)
Sorry for the blurry pictures. For some reason my phone is not focusing correctly, I must have dropped it too many times :'( Some day I will invest in a real digital camera that can do decent macro.
Stock drilled and reamed for pivot pins and linkage. Bolted down for the contouring of the top side of lever.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-05-09_22-55-15_640.jpg)
Top side done. Ready to flip over
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-05-10_12-03-00_851.jpg)
A couple of levers. The sharpie hashed section will be removed in another operation. Yea, I missed a few pictures :)
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-05-10_12-04-05_906.jpg)
Lever installed in rear block.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-05-11_21-36-41_910.jpg)
Rear view. Unfortunately there is a small interference inside the rear block that prevents the lever from closing all the way. It is a minor thing, the pocket in the rear block will need to be milled deeper by ~0.050. No mater how many times you check the model some things are always missed. The lesson is - If you modeler has interference checking, make sure it is turned on!
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-05-11_21-40-16_749.jpg)
Next up is the cocking bar and its linkage. Stay tuned!
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Tom,
The CNC capability really lets the creativity come thru. It gets better every time!
Lloyd
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I Ha friend who was a machinist and showed him your pics from this thread and he was impressed at what you were doing. great work i cant wait till this thing is shooting......dave
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Thanks Dave and your friend as well :)
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This part is for Lloyd, made from 7075 AL. We wouldn't want to build a gun from rubbery material........ :)
All kidding aside. I was my intention to make this lever from 400SS or 17-4SS so it could be hardened but I thought I would make a test part or three from the AL to check the geometry. Once the cocking mechanism is completely proven , I will remake make from a more suitable material. Here are a few pictures.
The part in sitting on the vise is the first operation and the part in the soft jaw is the same part flipped over for the second op.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-05-16_18-32-53_470.jpg)
This what is revealed after milling away the excess material
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-05-16_18-35-57_302.jpg)
A view of the lever and rear block with the new linkage installed.
(http://i1147.photobucket.com/albums/o553/QVTOM/rearleverview.jpg)
Tom
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Beautiful work!!!
Bob
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Thanks Bob.
One more link closer :) Sorry Lloyd, not 7075 :)
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-05-17_22-21-02_62.jpg)
Tom
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Tom,
I do love linkages. I get to do some of that at work with 4 link systems and it's kind of amazing the ranges of motion and leverages you can get. Beautiful work Tom, and I am sure the gummy aluminum will work just fine, LOL.
Just very, very, nice! I continue to be impressed!
Lloyd
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I forgot to mention that the dog bone link is 4130 :) Not bubble gum ;)
Tom
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What a wonderful execution. You are a talented man!
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Tom she is coming along great. Hope you do not have anymore interuptions.. :) I am following your thread very closely. Learning something every time you post now. Wish I had some of your talent and knowledge.
Absolutely beautiful craftsmanship.
Gene
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When I first saw your cocking lever, I wondered how you were going to get enough throw to cock the thing. I think I see how it works now. I still want to see it in action cocking each piston separately.
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Very nice work! Keep the updates coming! ;D
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When I make another lever for my rifle, I'm going to incorporate an offset handle like you did. I did not think it would be needed but after using my straight lever, I'm sure it would improve the ergonomics.
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The jury is still out on the ergonomics, It's hard to tell how it will feel until the power plant is in. My handle extends a bit past the receiver so it wasn't completely necessary to offset, mostly I wanted it to look different from the norm and be user friendly as well. In your case, with the extended receiver, I think the offset will be invaluable and look cool to boot!
One thing is for sure, it's hard to beat the break barrel for ergonomics. Side levers still fell a bit unnatural to me . At least its designed for a lefty :)
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I've been secretly sneaking some time to work on some parts. I've got some travel for work coming next week and have lot to do to get ready but I really wanted to make some kind of progress before I leave.
So here are some pictures. I've left out all the set-up and op-by-op stuff because I think you guys may be getting a little tired of "more of same". On to the pictures.
This is the cocking bar, pawls and center guide. These parts are made from 7075 AL and will be hard anodized after testing.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-06-16_22-01-14_577.jpg)
A close up view of the parts. The bar has an undercut slot so it can ride on the center support, similar to a 1911 slide and receiver. The pawls will ride on some dowel pins with torsion springs to actuate them.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-06-16_22-01-28_662.jpg)
End View.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-06-16_22-02-23_417.jpg)
This is what it looks like when assembled. I fixed a couple of clearance issues with the handle and rear block, now the handle will cycle thru the full range of motion.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-06-16_22-06-19_279.jpg)
One more of how it looks when the handle is stowed.
(http://i1147.photobucket.com/albums/o553/QVTOM/2012-06-17_10-00-05_25.jpg)
The next step will be the pistons and seals. When they are done I will do some fit and motion testing, then take it all apart and have the compression tube, pistons and cocking parts plated. When they return from plating it will be time to add a receiver and test fire!
I'm starting to think that this gun is going to work :) and very excited about the cocking system. So far it is operating perfectly.
Tom
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It's really making sense now. The pawls either bypass, or catch, depending the direction of motion, so that is how you get the cocking one piston at a time working. Slick!
I know what you mean, it's hard to keep away from a project like that unless you just hide it away somewhere.
Lloyd
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That is an ingenious mechanism! It must have come to you in a dream.
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That is an ingenious mechanism! It must have come to you in a dream.
Thanks, The best part is I think it is actually going to work! I spent a lot of time sketching different schemes in various positions of travel and scratching my head a lot. Most of the discarded ideas use a scissors type linkage to cock both pistons conventionally on the back stroke. I think some of those would have worked out well but I was concerned that the cocking effort would be too much due the the high spring force that is required to get the FPE in to the system with the relatively short strokes of the design.
Then I got the idea, it was not in a dream, but an undisclosed location where there is generally ample time to run ideas around in my head :)
Tom
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Funny how those inspirations come sometimes!
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Tom,
I just finished this thread and after 40 years machining, I can honestly say I am impressed, very impressed! I have worked with some extremely talented toolmakers over the years, but your their "Daddy". ;D
Seriously, thanks for sharing this project. I don't know springers from a hole in the wall, but I sure know genius when I spot it!!! Looking forward to the finished carbine and testing. You're getting close now....
Rich
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but your their "Daddy". ;D
Thanks Rich, your comment gave me a chuckle first thing this morning and that's always a good thing. :)
Tom
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Glad to start your day off right! Can't wait to see what's coming next.
Rich
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This is the piston concept. Caution, no actual pictures of parts yet :)
(http://i1147.photobucket.com/albums/o553/QVTOM/PistonConcept.jpg)
Front cap - Made from delrin or delrin AF, it protects the seal from extruding into the transfer port. I plan to leave 0.005" clearance with the compression tube wall.
Seal - Turned from PTFE and has a integral o-ring which serves to center the piston head in the bore. I don't know if it is a good idea but it is basically free to add when making the seal. Only testing will tell. May eventually turn into a simple o-ring seal.
Piston - 7068 AL with Tufram 4L coating. Similar to typeIII anodize but harder, more wear resistant, PTFE impregnated and RC60-65 in hardness. Referred to as a synergistic coating because of the way it bonds into the base metal and supposedly won't chip or peel. I have a customer who uses it frequently so I can toss my parts into their lot :)
Locating Rings - Idea taken from the Scothmo Express, They will be either PTFE o-rings or turned Delrin AF. I plan to test both to see there is any measurable performance difference. Also will try with one and two rings to see if there is a drag penalty.
Roll pins - Because locating rings will need to pass over the cocking slots I'd prefer that they don't rotate and possible tear themselves up.
Screw - Holds the whole mess to the gas spring.
Well it seems that I have made some work for myself ;D ;D
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Nice design.... seems a bit complex, but I'm sure it will work great....
Bob
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Tom,
Yup, plenty of activity going on there! Let us know how the machining of the ptfe goes. That is one that will take all the tricks. An integral o-ring? Like an expander? I am sure you already have it in the design, but you might need an o-ring somewhere around the screw threads to stop any blowby.
I am not familiar with either that aluminum or coating. Will have to look it up.
Good stuff!
Lloyd
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Lloyd,
I hadn't give much thought about the screw other than the 90deg. taper of the flat head would adequately seal against the Delrin. I could put an o-ring in there. somewhere.
The o-ring built into the seal is really more of a locator to prevent the piston from cocking in the bore. It will sized to just barely touch the chamber walls with no compression or squish. It is visible in the picture if you look closely. A square profile may be better for drag, more like a piston ring. I'm clueless when it come to one shape another, round has less contact area but may tend to roll and bind where the square has more contact but may be more stable.
Tom
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Tom,
OK, makes more sense now. So this is a PTFE lip seal with an o-ring "shaped" integral heel to keep it all centered, with uniform force around the circumference of the lip seal. I have a feeling you might have to machine the "expansion groove" in the seal out to a dimension to accept an o-ring down inside it that will serve to apply expansion pressure on the O.D. of the lip seal. Otherwise, the seal may not have enough time to energize and expand to form an air-tight seal during that short power stroke. The o-ring expander will keep the PTFE lip seal always at the ready. Google PTFE Lip Seal Design, and then click on the Parker design guide. The Parker design guide has a nice decision tree but many of the differences in the design are very subtle and very difficult to achieve without tools of the right geometry. Problem is, I don't even know that that geometry is.
Material is important too. I have found the graphite filled PTFE to wear pretty well. Plain PTFE will work fine for a while and then literally loose its edge. I will say though, that once you hit the right combination of lip design and expander and fit to the bore, it will work very well.
For the o-ring around the flat head screw, machine a .050 deep counter-bore inside the head of the aluminum piston, that is .125 larger in dia than the actual diameter of the threads of the flat head screw. Then use an 0xx series of o-ring to fill the counter-bore and seal any leakage around the flat head screw. The o-ring cross section is .070 dia, and .020 compression is adequate to seal the screw. The leakage may be inconsequential in your dynamic and instantaneous application. I have used this method to seal normally-static applications, but the dynamic should work similarly.
Lloyd-ss
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Absolutely amazing!!!!
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I been a little distracted due to my new PCP and some travel but my heart is still with the spring piston gun :) I'm down in the shop working on the pistons, I'll have some new pictures for you all soon :)
Tom
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That's the spirit Tom !!
Like the Sirene's call, it keeps beckoning you back.
Lloyd-ss
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I been a little distracted due to my new PCP and some travel but my heart is still with the spring piston gun :) I'm down in the shop working on the pistons, I'll have some new pictures for you all soon :)
Tom
Are we there yet?.......................Are we there yet? ;D ;D ;D
great project and excellent craftsmanship...also congratulations on the new PCP.
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Just found this thread ... Indeed quite the project.
Simple awesome tool and die maker skills at work on this one !!
Progress seems to have stalled ? Last Post August 21st ???
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I wonder if Walther got the idea for the synthetic "piston rings" from you. I've never seen them in an air rifle before I saw them in your design. I hope that you finish her soon!
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QVtom , Ive been watching with keen interest , your development , particularly of the pistons with guide rings.
I want to "shoot from the hip " a bit here and suggest to you that the drag induced by the inclusion of the guide rings is going to offset the benefit of them being there at all , and this will be detrimental to the overall function efficiency of this apparatus.
On the opposite end of the piston you have a delrin ring securing the seal and being .0025" clear of the bore's diameter , which I believe is excellent.
Can I suggest that instead of "circumferential guide rings ", machine 3 small flats into the OD of the piston , 120 degrees apart around it's circumference , and insert 3 small pieces , " buttons ", of wear resistant material into the flats to provide a linea and axial guide with near zero drag.
Friction is the going to be the killer of your design efficiency , and for this reason I feel by making a change to the guides , friction will be hugely reduced ...... very simply .
Im keen to hear your comments regarding my suggestion , Regards supaflee
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This is a fantastic thread.. Machining at it's best 8) I will be following and learning as this beauty comes to life
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I wonder if Walther got the idea for the synthetic "piston rings" from you. I've never seen them in an air rifle before I saw them in your design. I hope that you finish her soon!
\
Nope, I got the idea from the Scotchmo Express. I think this method has been around for a while, the reason manufacturers haven't picked it up is that it doesn't lend itself to the drawn tubes that most use for their piston skirts. There is just is not enough material to add ring grooves and they would have to leave their presses behind.
QVtom , Ive been watching with keen interest , your development , particularly of the pistons with guide rings.
I want to "shoot from the hip " a bit here and suggest to you that the drag induced by the inclusion of the guide rings is going to offset the benefit of them being there at all , and this will be detrimental to the overall function efficiency of this apparatus.
On the opposite end of the piston you have a delrin ring securing the seal and being .0025" clear of the bore's diameter , which I believe is excellent.
Can I suggest that instead of "circumferential guide rings ", machine 3 small flats into the OD of the piston , 120 degrees apart around it's circumference , and insert 3 small pieces , " buttons ", of wear resistant material into the flats to provide a linea and axial guide with near zero drag.
Friction is the going to be the killer of your design efficiency , and for this reason I feel by making a change to the guides , friction will be hugely reduced ...... very simply .
Im keen to hear your comments regarding my suggestion , Regards supaflee
You make a valid point about the friction but I think its overall impediment to the system is less than you think. Consider the gas spring force averages 500lbs, this number takes into account the guide bushings, dust wipers and seal drag. The spring easily overcomes its sources of drag.
The way I perceive the drag is that the worst thing that can happen is to have the piston cock and create a extremely high point load on the cylinder wall and drive the drag coefficient thru the roof. Keeping all the elements lined up axially will keep the part/part forces low thus keeping the friction low. As long as nothing get askew the drag should be parasitic and easily offset by adding more spring force if necessary.
As for buttons, I'm sure they would work well too, but would require more effort with my methods of manufacture.
Now for some progress............
I made these pistons awhile ago. They are turned from 7068 Aluminum, this is a very interesting product from Kaiser that I was introduced to my one of my customers. It has yield values that approaches 100ksi, this exceeds most untreated steels! My plan is to have them treated with Tufram, this will bring the surface hardness up to RC60. This is a grand experiment, only testing will tell how the sear engagement area will hold up.
First operation. I cut the material to make two pistons from one section, the face and OD will be turned then flipped to face, turn and part off.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/2012-11-30_15-38-52_679.jpg)
Here is the part turned around and held in some machined-in-place soft jaws that will be used for the second op as well.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/2012-11-30_16-20-50_368.jpg)
Second piston machined and parted off. Parts catcher is handy and prevents damage from dropped parts.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/2012-11-30_16-26-52_266.jpg)
Second Op. Boring out the ID.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/2012-11-30_16-54-03_126.jpg)
Next, the parts are mounted to a fixture on the indexer in the mill. I use some writing paper as shims in the chuck to get the part completely concentric. Paper is about 0.002, make great ships and is always around :)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/2012-12-01_15-59-33_321.jpg)
Finished Piston with cocking and sear slots and ring pin holes drilled.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/2012-12-01_15-45-42_422.jpg)
Some different views of the finished pistons.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/2012-12-01_10-19-22_952.jpg)
This material has very similar machining properties to 12L14 steel, as can see the parts have an incredible surface finish :).
Tom
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Tom, Nice work as always, blah, blah, blah, ;)
I never heard of that alloy, wow! the strength to weight ratio for non-ferrous is better than anything except maybe some of the super strength Ti alloys. I didn't see as tube, though??
Is your Avatar going fast in the wrong direction? ??? been bothering me. Maybe you are shooting the pellets backwards?
Lloyd-ss
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I'm always impressed with what a REAL machinist can produce.... My parts always need the lathe file and sandpaper.... *eyeroll*....
Bob
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Tom, Nice work as always, blah, blah, blah, ;)
I never heard of that alloy, wow! the strength to weight ratio for non-ferrous is better than anything except maybe some of the super strength Ti alloys. I didn't see as tube, though??
Is your Avatar going fast in the wrong direction? ??? been bothering me. Maybe you are shooting the pellets backwards?
Lloyd-ss
I haven't seen any tube but have never really looked. I think that material was purchased from CA Aerospace Material in LA.
Avatar bothering you? Sensitive are we? We've all seen the picture of the backward revolver, you know it will kill you but there is something compelling you to pull the trigger :) It was supposed to be slow-mo and the fast backwards is unintended consequence of the looping of the GIF. WHEN I get some more time I 'll fix it but for now you can can see a shrink ;)
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Ouch! Ok, I will just try and look away for the time being.
At least its not like some of those annoying animated ads that pop up in the sidebars sometimes.
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you know lloyd if the avatar is bothering you all you need to do is hit esc ;) ;D
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you know lloyd if the avatar is bothering you all you need to do is hit esc ;) ;D
Darn, you are right!! I felt kinda bad doing it though, like I stepped on a big bug. :'( I had to turn it back on. :-[ I am going to go run a machine now and think happy thoughts. ;)
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Im pleased that you looked into my theory regarding induced drag .
Are we likely to see it shoot this side of Christmas ,,,,,that would be real cool to see some preliminary trials being done?
Regards Supaflee
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Is this gun ever finished ?... i've been reading the whole thread and got me real excited now :) lol
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Not yet but getting close. It will definitely be at the GTA fun shoot regardless of outcome.
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Tom,
This is one heck of a project, and the quality is certainly built into it with every part and piece. Are we going to get a pool going on the performance of it, LOL?
I am just so impressed with all the different methods and tricks and that you have used during this build. Everything is unique. I think you threw the "Design for Manufacturability" manual out the window on this one. An obvious "labor of obsession." I totally understand. Will it be as much fun after it is all finished as it is during the build process? That can be a dilemma sometimes.
Lloyd-ss
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I feel I need to come clean. There are actually two versions of the design that I have been working on. One has a 2.5" combined stroke and the other a 3.5" combined stroke, both share the 2.79" bore. So if you start a pool, you will need two. Originally, I was thinking 28 and 38 fpe respectively, Those numbers were based on an efficiency of .35. After testing several transfer port designs on my single piston 1.79 bore X2.5" stroke test rig, I my original #s may be a bit optimistic.
The 2.5" stroke unit is the closest to completion so those will be the first #s in.
The first clue I will drop is that the skirts on 14.1 JSBs fired from the test rig are so badly blown out that the pellet is actually ~50 thou shorter when recovered
Yes a labor of some type :) I always feel the love when parts come off the machine, Hard to say when the whole thing is complete.
Tom
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Hi Tom - I just wanted to congratulate you for getting .. 'this far' ... with the project.
I have much enjoyed this thread and all your amazing machine work, incredible design and execution of it.
I live very close to you in Santa Clarita, and I also own 6 different Whiscombe airrifles.
I also own and run the web site www . whiscombe . net , anyway being a huge fan and collector of these twin piston airrifles you can imagine
that I am very interested in seeing your new design get off the ground / lathe ! and out to the range ! LOL !
Anyway if you are ever interested in seeing some Whiscombes in person I'd be more than happy to bring some over for you to inspect, heck you can even dismantle one if you want to get a good look at the linkage, cocking arm, trigger, sears, pistons etc etc ....
happy to help out in any way that I can. All the best and continued success with the twin piston project.
Kind regards
James Brinkley
PS. Send me a pm if interested and I'll email you and send my cell #
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Hi Tom - I just wanted to congratulate you for getting .. 'this far' ... with the project.
I have much enjoyed this thread and all your amazing machine work, incredible design and execution of it.
I live very close to you in Santa Clarita, and I also own 6 different Whiscombe airrifles.
I also own and run the web site www . whiscombe . net , anyway being a huge fan and collector of these twin piston airrifles you can imagine
that I am very interested in seeing your new design get off the ground / lathe ! and out to the range ! LOL !
Anyway if you are ever interested in seeing some Whiscombes in person I'd be more than happy to bring some over for you to inspect, heck you can even dismantle one if you want to get a good look at the linkage, cocking arm, trigger, sears, pistons etc etc ....
happy to help out in any way that I can. All the best and continued success with the twin piston project.
Kind regards
James Brinkley
PS. Send me a pm if interested and I'll email you and send my cell #
James, that is an incredible offer and thanks for the encouragement! Even though my project doesn't share much other than the opposing pistons with the Wishcombe, I'd be nuts to turn down a hands on look see.
Your website is a very nice tribute and has may beautiful pictures and some good reading as well.
Tom
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Ok, finally decided on a breech design. As you can see I decided to keep it simple :)
Chips start flying tonight!
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/breechsnap_zps417b7da7.jpg)
Yes, it is a lefty :) :)
some screen shots of first op from CAM
(http://i1147.photobucket.com/albums/o553/QVTOM/breechsnapop1_zps8f8de2f3.jpg)
(http://i1147.photobucket.com/albums/o553/QVTOM/breechsnapop1_p_zps41290890.jpg)
First op finished.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/IMG_20130321_220955_557_zps6c0bae3e.jpg)
Finish the front face, drill and ream for barrel. I used a dial indicator to make sure the bores will be perfect to the scope rails.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/IMG_20130321_223940_442_zps8e10cfb7.jpg)
Second op finished.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/IMG_20130321_224734_274_zpsfa5de6f0.jpg)
Next the rear of the breech is drill and bored for the bolt.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/IMG_20130321_233418_355_zps0aedc9a7.jpg)
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Watching... Always watching... Great stuff Tom. I'm in northern LA right now - so close, yet so far away!
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Finished the breech ( receiver?)
Last operation. I have a real dislike for parts that need to be machined on all 6 sides. Someone need to give the designer a good whack on the noggin.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/boe007_zpse5e9f7c5.jpg)
Some more views.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/boe013_zpsdf416e36.jpg)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/boe012_zps6d31b2b8.jpg)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/boe010_zps3037ec65.jpg)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/boe009_zpsac45705f.jpg)
Breech mounted on "shorty" the 2.5" stroke tube. Both the 2.5 and 3.5" stroke tubes take the same breech/receiver.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/boe006_zpsfb59d450.jpg)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/boe004_zps0d77c107.jpg)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/boe002_zps63af267c.jpg)
Next is the bolt handle and some breech bushings for the transfer port.
Tom
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Tom,
So how does your head feel? Did it get hit on all 6 sides, LOL?
Gotta love the CNC capability!
Lloyd
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(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/boe086_zps246d0aa9.jpg)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/boe085_zps4748183e.jpg)
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Spectacular work Tom. Looks like you are in fluid motion with your machining.
Thanks for sharing
Gene
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What more to be said than ..... O'my
Tom, some mighty fine engineering going on here, Love it love it love it !!!
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I'm so totally amazed with the progress on this build!
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I am SOOOOOOOOO jealous.... I stumble along with my Atlas lathe with a milling attachment and I can't even believe it's possible to achieve what you do.... Simply AMAZING !!!
Bob
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lovely work! I am just amazed!
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Thanks all. I have good and bad news to report, no picts but maybe I'll get some up later.
The good news is that the cocking bar with the pawl system functions flawlessly. When the lever is pulled back, the rear piston catches the sear as designed and the pawl for the front piston pops in place with an authoritative click :) When the handle is pushed forward the front sear catches, then with a slight release of pressure on the handle the front pawl retracts and the handle can be stowed completely :) :). I never imagined that this part of the design would function so positively the first go around. :) :) :)
Now for the bad news.... The cocking effort was way more that calculated and expected. I knew the sliding link was going to be a high friction spot due to it's high point load but never thought it could be SO BAD. I took a major short cut and it bit me big time. Shame on me. Luckily I just have a bruised ego considering other types of things that can go wrong with guns.
The cocking system does work but I fear it won't last long with the stresses at play. I had an alternative linkage design that eliminated the sliding link, I decided against using because added more parts. (the short cut). Time to integrate that design into the existing parts.
So a minor set back.
Tom
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As we so frequently say ...... Unless ya got pictures it did not happen :P
All kidding aside Tom, Hope you get it sorted out sooner than later, we are all waiting and watching ;)
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Did you fire it?
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As we so frequently say ...... Unless ya got pictures it did not happen :P
All kidding aside Tom, Hope you get it sorted out sooner than later, we are all waiting and watching ;)
Not enough pictures for ya? I thought by now I would/should have some credibility after 7 pages of pictures :)
Did you fire it?
Nope. I haven't mounted the barrel yet or finished the bolt. I did finish the bolt handle though.
Tom
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Tom,
Too bad about the sliding link, but I know you will get the other linkage up and running. Considering the complexity of this project, I would have expected a lot more uh-ohs. LOL
The sear engagement sounds like a major success. Did you have a chance to try the sear "release" yet.
This project might be called "The Air Gun Chronicles of QV Tom."
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Tom,
This project might be called "The Air Gun Chronicles of QV Tom."
Funny, the makings of a good reality show. Parts thrown, words bleeped, tools breaking, arguments with staff, designer lost in forums looking for solace.
Tom,
The sear engagement sounds like a major success. Did you have a chance to try the sear "release" yet.
Not yet. Must get the energy in the system reliably first, then let it out :P
I'm sure there will be more oops and oh-ohs to come. Actually it's already happened!
I got the new links installed, quite the learning curve. In an attempt not to have to make too many new parts I settled on a reduced ratio for the cocking lever. I had 120 degrees of travel and now I have 80. Mistake!!! A 33% reduction in leverage is just too hard, although the new linkage does operate smoothly. Tomorrow I will de-gass my springs and charge them to 1200 PSI, this will give about a 33% reduction in force allowing me to continue with testing of the release and transfer port. If all goes well I then will redesign the linkages to get back to the 120 degrees of travel , beef up some of the parts that seem undersized, and charge the springs back to 2500 psi.
Tom
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I've been very busy with work lately so I have not had much time to ponder on the linkage issues. I finally found some time to develop some concepts I had discounted earlier in the development. I think I have found a system where the geometry is not to offensive and the ratio is exactly where I originally designed.
http://www.youtube.com/watch?v=xWP21NhhdsE&feature=youtu.be# (http://www.youtube.com/watch?v=xWP21NhhdsE&feature=youtu.be#)
I didn't say it was simple, feeling compelled to please Lloyd, it had to be at the bloody edge of manufacturability.
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Nuttin showing up Tom ???
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Strange, looks fine on my screen. Using Chrome.
Tom
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Strange, looks fine on my screen. Using Chrome.
Tom
Firefox here and no image or video links to view ???
See an edit time stamp 10:10 still NADA
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Changed posting to Youtube.
http://www.youtube.com/watch?v=xWP21NhhdsE&feature=youtu.be# (http://www.youtube.com/watch?v=xWP21NhhdsE&feature=youtu.be#)
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Yea, small font link to an automated CAD drawing ?
Is that correct ?
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Should be a video (actually animation)
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Should be a video
Is a 12 second Photobucket animated CAD drawing showing a cocking arm I guess pivoting on what looks like roller chain links moving some other parts.
EDIT ... Cool got a viewable link now.
Yea, the complexity of this rifle is something else !!
Waiting to see pics of the REAL DEAL when your ready to share ;D
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Yep, didn't think you were going to see actual parts in action? Vaporware LOL. I'm going to build after the Fun shoot, too much going on this week.
Tom
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Tom
same here as Scott
blank on original post
and able to see the animation on your link
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Strange, looks fine on my screen. Using Chrome.
Tom
Ditto. Nice linkage...
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I'm not sure why your original post of the linkage didn't come through, but I'm copying it here to see if it'll work for me. I grabbed the IMG tag from the box to the right of the video. Previewing it here shows the video below this text, albeit with quite a gap of empty space between this text and the video. Clicking on the image that shows below takes one to the video in Tom's photobucket album. The link that is working here is one that starts with a URL= right after the [ bracket.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/th_newlever_zps6c8a4bb9.jpg) (http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/newlever_zps6c8a4bb9.mp4)
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Okeydoke, I went back, quoted Tom's original linkage video post to see what he had there. I'm attaching a .jpg of the original text together with the one that I used. I still don't know if the one I used is visible to anyone but me, but here's the information just in case. Also attached is an image of the actual photobucket page with a black X next to the code string copied from there to embed the video link here.
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Tom,
They gave me the title of machinist at work last year. Thanks for totally destroying that for me. I'm not a machinist anymore after looking at your work, I'm a hack with a piece of metal and a treadle powered lathe. I will have to tell my boss I want to be a mechanic now as I have seen a real machinist (or should I say artist?) at work and I couldn't come that close if the good lord handed me an extra 300 years. LOL. You are tops
Pat
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I think Tom is more of an engineer than a machinist at this point. Or maybe a good combination of both. Great work, Tom.
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Moving forward on the new linkage design. These are some photos of the new rear block ready to receive the lever, linkage and compression tube.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/concept001_zps7e2b98a0.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/concept001_zps7e2b98a0.jpg.html)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/concept002_zps32af1db1.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/concept002_zps32af1db1.jpg.html)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/concept003_zps01b6ce21.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/concept003_zps01b6ce21.jpg.html)
Next is the new( another) Cocking handle.
Tom
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More cocking system parts.
I tried something different with these links. I wanted a strong and wear resistant material but didn't want to go thru the hassle of trying to harden tool steel or have to send them out and wait so I chose pre-hardened 4142 chrome molly steel. I have some experience with machining P20 mold steel but was a little worried that the 4142 might be a little harder in rockwell and harder on tools. It turns out that the 4142 is a fine steel to machine and the results are great. I used a 100deg. carbide spot drill, hss drill and a carbide reamer to make the cross pin holes. I had to keep the surface speed very low (40sfm)f or the HSS drill, it had no issues drill the 20 or so holes for these parts. The profiles were machined with a 1/8" Hanita Varimill. These are amazing solid carbide tools that have staggered flute geometry to prevent chatter and leave a fantastic surface finish.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/concept007_zps08405977.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/concept007_zps08405977.jpg.html)
Drilled and reamed blanks.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/concept004_zps230ac5b2.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/concept004_zps230ac5b2.jpg.html)
Blanks mounted on quick and dirty fixture.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/concept005_zpsbdebd0ce.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/concept005_zpsbdebd0ce.jpg.html)
A full set of links contoured and ready to remove.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/concept006_zps0b609cb7.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/concept006_zps0b609cb7.jpg.html)
The twins :)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/concept008_zpsa1b710a0.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/concept008_zpsa1b710a0.jpg.html)
Tom
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Very nice and just Like a Soap Opera .... a climax is nearing 8)
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Very close Scott, just 2 more parts to remake.
Another thought on the pre-hardened chrome molly steel. With a rockwell in the c scale mid 40s it may make a good trigger a sear material. I know most trigger group pars I've worked on aren't any harder than the mid to high 40. The advantage is to avoid the pit falls of home heat treating.
Tom
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Tom,
I really wish you would of had this done for the fun shoot, I would have loved to see it...
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I did my best but unfortunately there is life and then there are airguns. There is always next year :)
Tom
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Hanita varimill, 1/8" dia. Very interesting. There seems to be a lot of positive feedback about them in various places.
Lloyd
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(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/N-Forcer010_zps1ba97fe1.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/N-Forcer010_zps1ba97fe1.jpg.html)
Wooo Hooo! New cocking links, lever, rear block, bar support and cocking bar installed with both gas spring and charged up to 2500 psi. The action is silky smooth and completely silent when cocking. The previous version had some massive friction and a very springy feel, this one is super solid and completely without flex thanks to some thicker walls, use of 7075 in the handle and the 4142 steel used for the internal levers. Cocking force is about 35-40 lbs (guessing). Its a strange shape to hold with out the stock so I assume that it will feel like less effort when the stock is complete.
Everything is installed except for the barrel, bolt, trigger group and stock. Exactly 4.0 lbs as seen in the pictures. Toss the rest of the parts without the stock and its just under 5 lbs. The goal of a 7 pounder with irons seems feasible at this juncture.
Some more views........
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/N-Forcer011_zps0ca92b5f.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/N-Forcer011_zps0ca92b5f.jpg.html)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/N-Forcer012_zpsb881d8d9.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/N-Forcer012_zpsb881d8d9.jpg.html)
And no I haven't shot it yet so don't ask :) Next is to mount the barrel and install the trigger group and then it is ready for the first test as a complete unit.................
Tom
Edit: this project has chewed up some serious time this week! All the assembly and disassembling, chick and egg conundrums......
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Looking good Tom, when does it go into production?
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Production? LOL Isn't this thread quite the production? Contemporary drama or maybe a saga :)
I'd have to move 50-100 yearly to even consider producing. And there is still the question of performance.....
Tom
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Tom, if the performance turns out as great as what we are seeing n your thread, you may have to produce a batch...:) When you are all done and have it all together, your final pictures of the completed shooter may just be the cats meow..:)
Gene
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Awesome! Production is in the works... Tom, add me in line for a signed limited number QVTom rifle please! ;) ;) ;)
(https://dl.dropboxusercontent.com/u/3582675/Shut-up-and-take-my-money.jpg)
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hey it was my idea, I get Signed Rifle #2, he of course gets to keep #1....
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I'm fine with #3 then. 8)
Look whatcha started.. ;) ;)
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@ Larry. I especially like the episode where Homer starts an internet business and he is popping up everywhere, Bill Gate pays him a visit and tells his boys "Buy him out", they then proceed to trash his office.
You are on the list. Its a very short one. LOL
@Gene. We can only hope :) Meow............
Got a Big Cat over here today. I couldn't resist the side-by-side comparison. Who da Big Cat now!!!
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/concept009_zps4666ff70.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/concept009_zps4666ff70.jpg.html)
Tom
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Do two items qualify as a list? Not sure a we actually have a list yet!
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#1: Tom
#2: Al
#3: Larry
#4: ?
There list started....
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For those of you that are on the list....... :) Although the linkage was performing well I noticed some stretch in one of the links so I decided to do some serious analysis. Based on what I leaned I made more design changes and now believe I have a solid system that will last.
This is based on 115 ft/lbs of input power... That's 125 degrees of travel @ 42 lbs. cocking force for both the back and fore stroke.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/FEA1_zps256c147b.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/FEA1_zps256c147b.jpg.html)
Anyhoo, time to make some more parts :)
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Can't wait to see the revised version! :)
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New link made for 4140 steel. They should be good in their annealed state but they can always be heat treated to ~ 85ksi if necessary.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/IMG_20130722_121931_182_zpsdd5fb268.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/IMG_20130722_121931_182_zpsdd5fb268.jpg.html)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/IMG_20130722_144456_957_zps6dccf5de.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/IMG_20130722_144456_957_zps6dccf5de.jpg.html)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/IMG_20130722_151116_435_zpsf5024400.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/IMG_20130722_151116_435_zpsf5024400.jpg.html)
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More links. 4142 prehard.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/links_zps9685a8e1.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/links_zps9685a8e1.jpg.html)
The single link on the bottom is the old version that was stretching. New link much beefier.
Tom
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More links. 4142 prehard.
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/links_zps9685a8e1.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/links_zps9685a8e1.jpg.html)
The single link on the bottom is the old version that was stretching. New links on the left are much beefier. :)
Tom
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I did a little lol about the "very low" sfm for the 4142 pre heat treat. In a previous life I made a lot of stuff from aermet 100 which is close to inconel 100, much was done with carbide but a few holes were drilled with HSS tooling, which loafs along at something like 15-18 SFM according to machineries handbook ??
The aermet 100 IS a nice material to do exactly what you describe, make a part that can be hard and strong but NOT require heat treat post machining. The employer at that time used a clamp made from a steel that was heat treated post machining, well one whole batch got ruined in heat treat. Prompting them to try the aermet 100. Looks like it is about 40 rockwell C in the annealed state.
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Remember those old "Where's the beef?'" commercials? I think it's been found.
There's an old pin-and-link type railroad bridge near where I live that uses links smaller than those.
I'll stop now. ;)
Very nice, Tom. And the FEA must be very helpful in tough situations like this.
Lloyd
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I haven't posted on my project in a while, mostly due to time constraints not a waning interest. The following are some pictures from the past few months and some conclusions.
\
I'll try to get some finished photos or video up in the next week or so.
Breech design
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/linkage008_zps963f340a.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/linkage008_zps963f340a.jpg.html)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/linkage007_zpsf80c8157.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/linkage007_zpsf80c8157.jpg.html)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/linkage006_zps3d07d1e4.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/linkage006_zps3d07d1e4.jpg.html)
Gas spring charging contraption
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/373_zps876b2037.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/373_zps876b2037.jpg.html)
Piston weight adjustment (bad idea)
Before lightening
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/618_zps9935f7bc.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/618_zps9935f7bc.jpg.html)
After lightening
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/615_zps9fb854d0.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/615_zps9fb854d0.jpg.html)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/616_zpsa2c22451.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/616_zpsa2c22451.jpg.html)
The gun is shooting :) and I have been tuning. I've learned a lot during the tuning process, mostly about how little I understood spring guns when I started the design.
Piston weight is probably the most important design element. I started with HS aluminum pistons that were discarded very early on due to the coating that was intended to provide hardness and wear resistance didn't penetrate the 7063 alloy to a sufficient depth. The next set were made from 4130 and they are the ones pictured above. Initial performance with the 4130 pistons was terrible, the gun was producing about 10 fpe. That was about a 1/3 of where I wanted to be so I wrongly decided to lighten the pistons. The lightening of the pistons reduced the velocity by over 100 fps! At least I was on to something, so I incrementally added some brass rings in between the gas spring and piston skirt. Each ring weighed almost an ounce and added about 40 fps. With the brass weights I was able to bring the piston weight from .4 lbs to almost .95lb each. There was no more room for brass, I had reached the max weight with this method. Next I removed the brass weights and poured lead into the pistons, with a little fiddling I got the piston weight matched and was at 1.35 lbs each. Performance was 23 fpe at this point and still far from the design goal. Charging this gas springs from 1600 to 2300 psi increased power to 25 fpe. 2300 psi equates ~ 550 lbs. of force which made the cocking force uncomfortable.
My conclusion is.............. Large piston face/short stroke is unworkable. The large piston face area makes them prone to bounce and it is impossible to make them heavy enough to overcome the bounce. I believe that if I had more space for heavier pistons I could get closer to the design goal. I have an uncompleted longer stroke version with the same bore that could fit heaver pistons but to have 3 lbs. of piston weight seems silly and will make the gun too heavy. Even with the longer stroke, I believe I'd still be on the wrong side of the swept area/piston face curve. The 1.79 dia. piston design ends here. Lesson learned :)
Now for some good news.......... Completely sans-recoil, if it wasn't for the noise you wouldn't know that it fired! Really, the gun has no motion or vibration period. It's that smooth!
I've considered de-tuning to 18 fpe and using for FT but rejected this idea for a new line of development. As I said, the 1.79 bore is dead.
A sneak look at my new version. A longer stroke and smaller bore. Cocking, sears and breech design will remain the same. One advantage of the longer stroke is that it simplifies the cocking linkage somewhat. Yeah :)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/teaser1_zpsafa7c329.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/teaser1_zpsafa7c329.jpg.html)
(http://i1147.photobucket.com/albums/o553/QVTOM/Springer%20Project/teaser2_zps607f6f25.jpg) (http://s1147.photobucket.com/user/QVTOM/media/Springer%20Project/teaser2_zps607f6f25.jpg.html)
Tom
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The king is dead, long live the king.... *RIP*
Sorry to hear that, Tom, it was a gorgeous project from start to finish.... Oh well, you'll enjoy the next one even more, right?.... Happy New Year !!!
Bob
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Bob, Happy New Year!
If power was the only design goal I'd be very disappointed. Actually, I'm excited about the new design. I see the potential and hopefully can avoid some of the pitfalls. Besides, It's looks good on my wall. LOL!
Tom
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Sort of left speechless ... wow, countless hours in brain power and machine time.
We're left feeling that experience is indeed not getting what you wanted .... next :P
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In break barrel guns I have always associated long stroke with increased hold sensitivity. I have always wondered why there are no short stroke magnums with bigger tubes. Now I know! Thanks for the insight! Great work on the gun, I know it hasn't met your expectations in terms of power, but it has blown me away. I can!'to wait to see where you go from here...
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If you keep the 1600 psi in the gas spring and settle for the 23 fpe, that actually sounds like a really awesome plinker! Especially if you are saying the firing cycle is dead smooth. I'd certainly enjoy plinking with a home-made wonder like that. Perfect for back yard. Even though it's not what you had planned on, I gotta say congratulations on a fine creation! From all the photos you posted thus far, it really looks like an amazing rifle. I'm still on the list right? haha ;)
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Now we're talking... This is some impressive work despite it not meeting your expectations. I am INSANELY JEALOUS of your SOlidworks capabilities. I recently acquired a nice clean Cincinatti Arrow 500 VMC and got it working. Looks like yours is a HAAS perhaps? Nice machines. I ran some briefly in a local shop and they have some nice features. The Whiscombe Air Rifles are works of art and you have created something very similar. I don't honestly see the necessity of it being overly light but that is personal preference. The Whiscombe rifles are not exactly light having shot quite a few over the years. They are however extremely well made and some are precision accurate. What you are doing is very interesting here and I have enjoyed reading the thread. I would love to try something similar. I have built several actions over the years including a decent FT rifle PCP. There seems to be a lot more going on in this mechanism than meets the eye and you have come a long way to getting it working. I think the smaller diameter pistons and slightly longer travel would be the ticket as you have found more like the Whiscombe rifle but you may have something to add here that the other guns do not have. I like your cocking design. That it seems to me to be the most complex part of these rifles. Your transfer port looks quite large too there is a LOT to be gained in sizing that correctly. You may find that the gun shoots to your specs with the slight adjustment of things like that. I LOVE the blow thru bolt you made and that breech is very nice altho the area near the transfer port seems a little thin in cross section. It appears that the port area is a seperate piece that is inserted there no? Lovely work again and I hope to be able to use my VMC for something beautiful like that soon. I am currently covered up with some Custom Woodworking projects that are making me more money than I have been able to get with the Machining despite my best efforts. Personally I like it that way as I would rather do the wood work during the day and then moonlight with some cool airgun stuff anyways. Either way you have some impressive skills man and I look forward to reading and seeing more of your airgun adventure. Please post whenever you are able. Thanks for sharing this impressive work. Peace
Pete
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Tom,
When you start on the new design, please link it back here for ease of locating and continuity of the project....
Al
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My conclusion is.............. Large piston face/short stroke is unworkable. The large piston face area makes them prone to bounce and it is impossible to make them heavy enough to overcome the bounce.
Yes, I know it has been years, but, to quell piston bounce, ponder this idea:
Place a reed-valve inside your breech bolt (as used on some two-stroke bike engine intakes) . The valve would snap shut due to the pressure differential, just as the pistons start to bounce back. That would trap the bulk of the air behind the pellet, regardless of what the pistons felt like doing.
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How did I never see this thread! I love to read these type builds!
Did you ever try any other versions of this concept?
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Tom went on from here and developed his SLAYER 357 Bull Pup .... AMERICAN AIR ARMS company too
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My conclusion is.............. Large piston face/short stroke is unworkable. The large piston face area makes them prone to bounce and it is impossible to make them heavy enough to overcome the bounce.
Yes, I know it has been years, but, to quell piston bounce, ponder this idea:
Place a reed-valve inside your breech bolt (as used on some two-stroke bike engine intakes) . The valve would snap shut due to the pressure differential, just as the pistons start to bounce back. That would trap the bulk of the air behind the pellet, regardless of what the pistons felt like doing.
I'm sure there are many ways to subdue piston bounce but the increase in complexity at some point becomes untenable. Slide weights, reed valves, etc. are all good ideas but they need to be applied to a design that is not basically flawed. The piston face area/stroke ratio must be reasonable from the start.
The Whiscombe with its two pistons mechanically connected has a distinct advantage in the area/stroke department; each piston shares each other's mass.
Thanks for the interest!
Tom
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Yeah, I guess you can say the Dark Side has consumed me.
Tom
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How did I never see this thread! I love to read these type builds!
Did you ever try any other versions of this concept?
I did design a smaller diameter longer stroke version but never built it. Instead I went to PCPs
Tom
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I'm sure there are many ways to subdue piston bounce but the increase in complexity at some point becomes untenable.
After thinking about this some more, I concluded that to keep the overall rifle weight down, exploring what can be done with a single stroke pneumatic was indicated. (Or at most, two strokes: preferably on opening and closing).
After all, an air "spring" has very little mass, and requires no piston duplication for inertial jolt cancellation...
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Just another gun, I will need if you bring to market! LOL
Bill C!
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How did I never see this thread! I love to read these type builds!
Did you ever try any other versions of this concept?
I did design a smaller diameter longer stroke version but never built it. Instead I went to PCPs
Tom
Tom any prediction on when the Evol will open back up! I check every day! LOL
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This is amazing! Love the craftsmanship and design!