GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Show us your Custom Airgun Parts (TRICKS-N-TIPS) => Topic started by: Motorhead on August 21, 2013, 04:13:58 AM
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Original getting the rifle here ;D http://www.gatewaytoairguns.org/GTA/index.php?topic=51434.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=51434.0)
So being not able to leave anything alone and quite frankly NOT liking the shot cycle tore the little ( Webley Tracker ) down for an inspection ???
Tar lube job ... YUCK ! what a muck fest to clean up and get out of there.
Once cleaned all looked really good and wear was nominal, so no major repairs needed ;)
Remembered reading about how the Teflon piston seals in these went away ( Wore out ) pretty quickly so looked a little closer.
Yea not too efficient just being a plug type seal running at near to compression chamber I.D. :o
So OFF IT CAME getting a Delrin replacement with an o-ring groove. 70 duro viton o-ring fitted for a light fit and now we have a seal that will make this little gun hopefully a far more consistent & powerful shooter.
(http://i1320.photobucket.com/albums/u532/scott_schneider1/DSCF9056_zps743232a2.jpg)
Old Teflon seal ring and backing washer.
(http://i1320.photobucket.com/albums/u532/scott_schneider1/DSCF9058_zps2ace384b.jpg)
(http://i1320.photobucket.com/albums/u532/scott_schneider1/DSCF9057_zps5b2618dd.jpg)
New seal holder made with an I.D. shoulder so when pressed onto pistons stub it snaps into place.
(http://i1320.photobucket.com/albums/u532/scott_schneider1/DSCF9059_zps0de5d879.jpg)
New seal holder and o-ring
(http://i1320.photobucket.com/albums/u532/scott_schneider1/DSCF9062_zpsbb47d2d0.jpg)
Bearing surfaces polished and ready for install.
Next was replacement of funky steel shorty spring guides each end of spring that together really gave little to no actual guiding or damping attributes :P
Over onto the lathe making up piston end guide to same factory length, rear guide a full 3" long. There ends are within 1/4" of touching at full cock. Both Snug fitted to spring I.D. adding @ 1/4 more thickness at ends to pre-load spring a tad more ;)
(http://i1320.photobucket.com/albums/u532/scott_schneider1/DSCF9063_zps0e72b25b.jpg)
Assembled with lightly oiled compression tube an light moly on spring and guides ... All back together ;D
It's late & headed to bed ... Chrony numbers first chance I get time.
BTW .... Sounds solid making a very firm THUMP when shot and dieseling just a tad :P
Update : ** Chrony data = 625 fps with 7.9g CPHP making 9.22# energy.
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Me likes, gotta figure that o-ring seal setup out and try it on a few guns...
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Great job on a pro tune job Scott. You did it the right way for sure bro. One thing is for sure is that you can't use o"rings on just any air rifle. The tube in that Barnett must be very true in its design and shape. That is the only way that that system will work. Great craftsmanship sure makes the difference.
Keep us posted on the outcome. A am positive it will be a good report and deffinetly a difference between the pre tune.
Gene
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Well ... been an interesting couple days fooling with the gun and fine tuning things. What has become apparent is that Delrin used as the O-ring holder material is NOT the right stuff to use here :P ... It DOES NOT have enough resiliency and the repeated impacting of compression chamber roof is beating it up pretty badly.
*Delrin when crushed will crumble and fracture into pieces where Nylon will just crush and stay together.
So ... made another of the same shape/size from Nylon ( Which is a LOT tougher material !! ) Installed and shot @ 50 taking apart for inspection ;D ;D Much better now with the impacting showing no fatigue to the nylon what so ever.
Shot cycle also less violent telling me the slight resiliency of the nylon is also absorbing impact energy & vibration.
We're learning here ..... :o
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I think NCED uses Aluminum for his, but I am not sure...
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Did changing to nylon have any effect on the velocity, or just on the smoothness of the shot cycle?
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Did changing to nylon have any effect on the velocity, or just on the smoothness of the shot cycle?
No difference in velocity being o-ring sealing it all up did not change .... just shot cycle smoothness changed slightly.
Primary reason to get LONG TERM reliability from the conversion parts made.
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Your project is very interesting, for how long have you been testing your piston holder becouse i would like to implement it into my air gun so i would like to ask you few questions about it.
Wich type of nylon have you used ( can you give me exact name and type of that nylon something like... idk. 6.6 nylone , 6 nylon , 6.9 or some other...)
I would like to install it in Hatsan 125 compresion chamber that have 29mm diamter,
So i'm wondering wich o-ring would be suitable for this diameter, so can you give me the inner diameter size of o-ring and its tickness, and wich materials are the best for o-ring.
How deep and wide it should be carved in a seal holder for that o-ring, expressed in a mm.
Thanks.
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Your project is very interesting, for how long have you been testing your piston holder becouse i would like to implement it into my air gun so i would like to ask you few questions about it.
Wich type of nylon have you used ( can you give me exact name and type of that nylon something like... idk. 6.6 nylone , 6 nylon , 6.9 or some other...)
I would like to install it in Hatsan 125 compresion chamber that have 29mm diamter,
So i'm wondering wich o-ring would be suitable for this diameter, so can you give me the inner diameter size of o-ring and its tickness, and wich materials are the best for o-ring.
How deep and wide it should be carved in a seal holder for that o-ring, expressed in a mm.
Thanks.
Nylon was MDS grade.
0-ring a Metric sized VITON
Ring YOU NEED and sizes etc ... need to research o-ring specs and determine that yourself for task at hand.
** Note that 0-ring piston seals ONLY work well in VERY STRAIGHT & TRUE compression bores with a VERY FINE surface finish.
Given a choice would use a fitted parachute type seal quite honestly ;)
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Scott, have you gotten some time to shoot the gun a bit since the tune? How are you enjoying use of it?
I have my own Spitfire that needs some TLC. It's quite Twangy as you say. I was thinking of using the Macarri kit for the Vulcan, although I'm not sure it will fit.
Mike B
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Scott, have you gotten some time to shoot the gun a bit since the tune? How are you enjoying use of it?
I have my own Spitfire that needs some TLC. It's quite Twangy as you say. I was thinking of using the Macarri kit for the Vulcan, although I'm not sure it will fit.
Mike B
Funny you should mention the macarri VULCAN seal .... had one added to an order a few weeks ago in hope it would fit ... sadly it DID NOT being to large in diameter.
Doing further reading on some of the UK forums it seems many machine the piston nub head shorter and smaller to center a fabricated back up washer, drill & tap the piston using a TX 200 parachute seal with a cone washer & screw to secure it.
Quite a few ways to skin a cat here ... pick your poison and DIVE IN !!