Author Topic: NEW picts added - Project conclusion (Read 49747 times))

QVTom · « **Reply #40 on:** March 08, 2012, 05:35:51 PM »

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.

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

QVTom · « **Reply #41 on:** March 09, 2012, 02:15:48 AM »

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

Miles to go before I sleep........

lloyd-ss · « **Reply #42 on:** March 09, 2012, 07:52:19 AM »

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!

bradyman1 · « **Reply #43 on:** March 09, 2012, 08:53:43 PM »

Wonderful work.

Muppit · « **Reply #44 on:** March 09, 2012, 09:28:44 PM »

by the size of this thing is it correct to call it an air rifle or a cannon.LOL nice work .....dave

QVTom · « **Reply #45 on:** March 10, 2012, 01:49:45 AM »

Quote from: lloyd-ss on March 09, 2012, 07:52:19 AM

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

QVTom · « **Reply #46 on:** March 10, 2012, 02:03:32 AM »

Quote from: Muppit on March 09, 2012, 09:28:44 PM

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

Tom

lloyd-ss · « **Reply #47 on:** March 10, 2012, 06:58:36 AM »

Quote from: QVTom on March 10, 2012, 01:49:45 AM

Quote from: lloyd-ss on March 09, 2012, 07:52:19 AM
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
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

rsterne · « **Reply #48 on:** March 10, 2012, 12:38:00 PM »

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

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

QVTom · « **Reply #49 on:** March 10, 2012, 01:35:33 PM »

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

rsterne · « **Reply #50 on:** March 10, 2012, 01:54:01 PM »

Quote

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

lloyd-ss · « **Reply #51 on:** March 10, 2012, 02:48:54 PM »

Quote from: rsterne on March 10, 2012, 12:38:00 PM

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

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.

lloyd-ss · « **Reply #52 on:** March 10, 2012, 02:58:44 PM »

Quote from: QVTom on March 10, 2012, 01:35:33 PM

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

QVTom · « **Reply #53 on:** March 10, 2012, 03:00:47 PM »

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

rsterne · « **Reply #54 on:** March 10, 2012, 03:39:58 PM »

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

gene_sc · « **Reply #55 on:** March 10, 2012, 08:05:16 PM »

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

Bryan Heimann · « **Reply #56 on:** March 10, 2012, 08:32:04 PM »

Wow. Probably the coolest project I've seen. I've been missing out- I can't wait to see how this turns out!

QVTom · « **Reply #57 on:** March 12, 2012, 03:32:50 AM »

Quote from: gene_sc on March 10, 2012, 08:05:16 PM

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........

QVTom · « **Reply #58 on:** March 12, 2012, 03:56:33 AM »

Quote from: Bryan on March 10, 2012, 08:32:04 PM

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

rsterne · « **Reply #59 on:** March 12, 2012, 05:28:32 PM »

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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NEW picts added - Project conclusion

Author Topic: NEW picts added - Project conclusion (Read 49747 times))