Jibbity Posted August 7, 2012 Report Share Posted August 7, 2012 I have to start by apologizing for posting this twice. I put it n the AUG picture thread, but would like to reach a larger audience for feedback and suggestions, hopefully from someone whohas done something similar. This should apply pretty directly to P90s as well. The cuts are rough, had to go with what was on hand, which apparently was no good for cutting aluminum. The one thing not shown in the photos, I cut back the rails in the gearbox for the piston so that there is room to push in the spring guide and rotate it a quarter turn. The spring guide is a modified v3, arms are trimmed to allow for rotation with the gearbox closed. This is a JG V3 gearbox, which has decent thickness on that back wall. The AUG (and likely the P90) is well suited as I can use a metal back plate to lend some extra support. I have around 1500 rounds through it @ 370 fps, flawless so far. Has anyone else done this? Comments or suggestions? Link to post Share on other sites
hwagan Posted August 7, 2012 Report Share Posted August 7, 2012 Have you noticed any rotation of the spring guide during prolonged use? That'd be my only concern; Other than that, nice simple looking mod! Link to post Share on other sites
Tom Andrews Posted August 7, 2012 Report Share Posted August 7, 2012 That would be my concern as well. But a simple plate across the plate you already have would be one solution. Link to post Share on other sites
Jibbity Posted August 7, 2012 Author Report Share Posted August 7, 2012 There is a spring guide shaped indent in the back wall of the gearbox. The spring pushing the guide into the indent prevents rotation of the guide. Link to post Share on other sites
Stinky Posted August 9, 2012 Report Share Posted August 9, 2012 Nice mod, brave one as well. Link to post Share on other sites
Jibbity Posted August 9, 2012 Author Report Share Posted August 9, 2012 Nice mod, brave one as well. At the moment I am blessed by the gods of the airsoft graveyards with an abundance of V3 shells, well... Two extra anyhow. I have pretty high confidence that it will last, under normal use, that is. Link to post Share on other sites
crackisbad Posted August 9, 2012 Report Share Posted August 9, 2012 I've been thinking about this for my AUG for quite some time so I'm happy to see someone else take the plunge IIRC Lonex GB shells are made of a stronger material, correct? That might be a good shell for this mod Link to post Share on other sites
Jibbity Posted August 9, 2012 Author Report Share Posted August 9, 2012 IIRC Lonex GB shells are made of a stronger material, correct? That might be a good shell for this mod I have never seen one in person, so it is hard to comment. It does require decent thickness on the back wall of the gearbox. The SHS 9mm GB thag I have kicking around is too thin in the back to be suitable for the application. Also, more $ at risk. Personally, I get perverse pleasure from building my guns as cheaply as possible. Link to post Share on other sites
crackisbad Posted August 9, 2012 Report Share Posted August 9, 2012 lol, fair enough Link to post Share on other sites
Jibbity Posted August 9, 2012 Author Report Share Posted August 9, 2012 If you have access to a lonex shell, I would be interested in the thickness in that back wall. Link to post Share on other sites
Stinky Posted August 9, 2012 Report Share Posted August 9, 2012 I will try this on the shell I am going to mod for my SR3M, might as well as I am eventually taking the whole back off to shorten it. Its an ancient TM V3, I will measure the shell thickness while I am at it. Link to post Share on other sites
crackisbad Posted August 9, 2012 Report Share Posted August 9, 2012 Which is interesting because a CYMA gearbox I have laying around is about 1.95mm thick. Link to post Share on other sites
Jibbity Posted August 9, 2012 Author Report Share Posted August 9, 2012 Excellent! I will measure my JG shell and we can get a bit of a database going for this. Likely, 1.6mm of aluminum is superior to 1.96mm of pot metal. Edit: are lonex shells aluminum? That may be a bad assumption on my part. Link to post Share on other sites
Stinky Posted August 9, 2012 Report Share Posted August 9, 2012 Looking at my old TM V3 the area that takes the load from the spring is specific and indicated by burnishing after some use. And the other side For this mechbox at least the area outlined in red seems to be the only area carrying a load from the spring guide, the rest plays a role in overall structure but is not directly resisting the spring guide, ether it flexes enough the surface has not been burnished or it just doesn't even contact the spring guide due to small surface imperfections. Link to post Share on other sites
crackisbad Posted August 9, 2012 Report Share Posted August 9, 2012 Cool! And I'm sure it is the case that pot metal GB have to be thicker. I'm not quite sure what Lonex GB are made of, I think what I heard was aluminum, but I'm not 100% Link to post Share on other sites
Jibbity Posted August 9, 2012 Author Report Share Posted August 9, 2012 Interesting Stinky. Most of that load bearing area remins if you reduce he width of the base of the spring guide like I did. Did you get the thickness of that area? Link to post Share on other sites
Stinky Posted August 9, 2012 Report Share Posted August 9, 2012 The back of the old TM V3 is 1.7mm measured with digital calipers. its 1.7mm at the tab slots for the spring guide as well. Given the wear pattern it appears this mod should be doable without loosing much strength as long as I don't cut away more then needed on both the shell and spring guide. The spring pushes on the flange of the spring guide, I need to keep as much of the shell under that base flange as possible and keep as much of that area on the spring guide as possible, balancing cutting each to achieve the maximum support while allowing the guide to pass through the hole in the shell. edit: OOPS, that wont work! Need enough space for the whole spring, which means it has to be a metal base at least on the spring guide as it supports the whole spring and transmits that to whats left of the tabs... hrmm this really removes most of the support! I only have a plastic spring guide to spare right now and dont want to cut my brass with bearing spring guides, which are supporting m160's at 500fps anyway and not good candidates. Will build this with the plastic one and a very light spring I guess, and get an aluminum guide to cut down for anything over 350fps again wont work, need metal guide to have a chance at not breaking given the spring is loading just the tabs which have to be cut short! Link to post Share on other sites
Jibbity Posted August 9, 2012 Author Report Share Posted August 9, 2012 I had the exact same thought process...funny. I was originally going to just cut a thinnish slot, basically the width of the tabs, until I remembered that I actually have to get a spring in there. If you are using linear springs, you may be able to thread the spring in and out through the slot. That would, however, be much less 'quick'. Link to post Share on other sites
Stinky Posted August 9, 2012 Report Share Posted August 9, 2012 Yeah, the only reason i want this is to change very heavy springs without opening the shell and wishing I had a third hand to keep everything from flying apart. And it wont work for those heavy springs anyway without a good aluminum shell. I am sure my potmetal TM would snap under load. Bummer but I cant do this mod with what I have. I would maybe try it with a CNC shell IF I had money to burn on such things and then some more money to burn on modding them. 7075 aluminum would make me feel much more comfortable with supporting just the short tabs. Link to post Share on other sites
Jibbity Posted August 10, 2012 Author Report Share Posted August 10, 2012 I will do some testing with heavier springs at some point. I'm pretty confident that it will take the load. At least in the AUG where I have the back plate for secondary support. Besides, weren't you going to cut the back off that box anyhow? Why not let those springs do some of the work for you? Link to post Share on other sites
Jibbity Posted August 13, 2012 Author Report Share Posted August 13, 2012 @ Stinky, did you ever measure the thickness at the back of that TM gearbox? You should post it up. Link to post Share on other sites
Stinky Posted August 13, 2012 Report Share Posted August 13, 2012 Older TM V3 is 1.7mm average, potmetal so it varies a bit from 1.67-1.71mm. I am going to cut the back off and reattach so I'm not going to do this mod, though I will later if I get a 4th v3 to mod (that is aluminum). JG v3 is aluminum right? that may be a good pickup to have a backup mech since my current backup is going under the knife for the SR3M mod. Link to post Share on other sites
Jibbity Posted August 15, 2012 Author Report Share Posted August 15, 2012 The JG box is definitely pot metal. Link to post Share on other sites
Jibbity Posted August 16, 2012 Author Report Share Posted August 16, 2012 Another 800 or so rounds last night, 350fps, 30ish rps. I did get a bit cocky and strip my piston by dropping an m165 in there and shooting full auto. Full autopsy to come, but the shell looks fine. It may be time for a full metal tooth piston... Link to post Share on other sites
dog_soldier13 Posted August 18, 2012 Report Share Posted August 18, 2012 Any one try this with a pot metal gearbox yet? Link to post Share on other sites
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