Author Topic: NEW picts added - Project conclusion (Read 49745 times))

rsterne · « **Reply #20 on:** February 10, 2012, 01:01:25 PM »

I gotta ask.... What is the bore and stroke(s) of this monster....

Bob

QVTom · « **Reply #21 on:** February 10, 2012, 01:58:40 PM »

Quote from: rsterne on February 10, 2012, 01:01:25 PM

I gotta ask.... What is the bore and stroke(s) of this monster....

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

rsterne · « **Reply #22 on:** February 10, 2012, 02:59:31 PM »

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

lloyd-ss · « **Reply #23 on:** February 11, 2012, 09:34:39 AM »

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?

QVTom · « **Reply #24 on:** February 12, 2012, 03:40:53 AM »

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!

QVTom · « **Reply #25 on:** February 14, 2012, 06:10:26 PM »

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.

Assembled compression tube

lloyd-ss · « **Reply #26 on:** February 14, 2012, 07:27:44 PM »

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

Toolmaker · « **Reply #27 on:** February 14, 2012, 07:29:37 PM »

Tom,
Your ideas and machine work are beyond words! Thank you for choosing to share this project with the GTA!

Matt

joesnextoy · « **Reply #28 on:** February 19, 2012, 02:46:24 AM »

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 !!!!!!!!!

lloyd-ss · « **Reply #29 on:** February 20, 2012, 06:51:29 PM »

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

MustangMike · « **Reply #30 on:** February 20, 2012, 08:40:40 PM »

so is this supposed to be a springger setup like a pcp with the breech on top of the airtube ?

QVTom · « **Reply #31 on:** February 20, 2012, 10:31:48 PM »

Quote from: lloyd-ss on February 20, 2012, 06:51:29 PM

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

-T

QVTom · « **Reply #32 on:** February 20, 2012, 10:39:21 PM »

Quote from: mustangmike on February 20, 2012, 08:40:40 PM

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

Petey · « **Reply #33 on:** March 05, 2012, 08:47:30 PM »

In awe.. makes wish I had learned some shop skills.

Scotchmo · « **Reply #34 on:** March 05, 2012, 09:44:21 PM »

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.

bradyman1 · « **Reply #35 on:** March 05, 2012, 11:03:05 PM »

Great work and a very interesting idea. Good luck. Thanks for sharing your work with us.

QVTom · « **Reply #36 on:** March 06, 2012, 01:08:29 AM »

Quote from: Scotchmo on March 05, 2012, 09:44:21 PM

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

Scotchmo · « **Reply #37 on:** March 06, 2012, 03:33:06 PM »

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

Another interesting link:

http://www.allsealsinc.com/parker/dynamic-oring-sealing.pdf

Bandit_46 · « **Reply #38 on:** March 06, 2012, 07:49:26 PM »

Simply Put,,Awesome work Tom!!!!

lloyd-ss · « **Reply #39 on:** March 08, 2012, 06:27:59 AM »

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

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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NEW picts added - Project conclusion

Author Topic: NEW picts added - Project conclusion (Read 49745 times))

joesnextoy