Author Topic: NEW picts added - Project conclusion (Read 49801 times))

QVTom · « **Reply #100 on:** December 06, 2012, 02:40:26 PM »

Quote from: Bryan on November 10, 2012, 09:45:32 AM

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.

Quote from: Supaflee on November 10, 2012, 10:47:18 PM

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.

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.

Second piston machined and parted off. Parts catcher is handy and prevents damage from dropped parts.

Second Op. Boring out the ID.

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

Finished Piston with cocking and sear slots and ring pin holes drilled.

Some different views of the finished pistons.

This material has very similar machining properties to 12L14 steel, as can see the parts have an incredible surface finish

.

Tom

lloyd-ss · « **Reply #101 on:** December 06, 2012, 10:44:08 PM »

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

rsterne · « **Reply #102 on:** December 06, 2012, 11:38:36 PM »

I'm always impressed with what a REAL machinist can produce.... My parts always need the lathe file and sandpaper.... *eyeroll*....

Bob

QVTom · « **Reply #103 on:** December 07, 2012, 01:13:46 PM »

Quote from: lloyd-ss on December 06, 2012, 10:44:08 PM

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

lloyd-ss · « **Reply #104 on:** December 07, 2012, 11:11:33 PM »

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.

1377x · « **Reply #105 on:** December 08, 2012, 02:26:50 AM »

you know lloyd if the avatar is bothering you all you need to do is hit esc

lloyd-ss · « **Reply #106 on:** December 08, 2012, 09:01:18 AM »

Quote from: 1377x on December 08, 2012, 02:26:50 AM

you know lloyd if the avatar is bothering you all you need to do is hit esc

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.

Supaflee · « **Reply #107 on:** December 11, 2012, 11:46:03 PM »

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

venxxxxx · « **Reply #108 on:** February 26, 2013, 06:23:19 PM »

Is this gun ever finished ?... i've been reading the whole thread and got me real excited now

lol

QVTom · « **Reply #109 on:** March 01, 2013, 08:11:44 PM »

Not yet but getting close. It will definitely be at the GTA fun shoot regardless of outcome.

lloyd-ss · « **Reply #110 on:** March 02, 2013, 02:58:39 PM »

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

QVTom · « **Reply #111 on:** March 02, 2013, 04:38:07 PM »

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

AngliaUSA · « **Reply #112 on:** March 09, 2013, 01:02:54 AM »

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 #

QVTom · « **Reply #113 on:** March 10, 2013, 01:13:44 AM »

Quote from: AngliaUSA on March 09, 2013, 01:02:54 AM

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

QVTom · « **Reply #114 on:** March 19, 2013, 10:36:46 PM »

Ok, finally decided on a breech design. As you can see I decided to keep it simple

Chips start flying tonight!

Yes, it is a lefty

some screen shots of first op from CAM

First op finished.

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.

Second op finished.

Next the rear of the breech is drill and bored for the bolt.

sperho · « **Reply #115 on:** March 21, 2013, 03:06:29 AM »

Watching... Always watching... Great stuff Tom. I'm in northern LA right now - so close, yet so far away!

QVTom · « **Reply #116 on:** March 23, 2013, 08:17:27 PM »

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.