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Overspin??

2K views 27 replies 6 participants last post by  Guges Mk3 
#1 ·
Completely new build that half-cycles every other full trigger pull in semi, full auto works fine. I’ve read countless other threads with similar symptoms, but I’m wondering if a Gate Titan or other higher-end MOSFET with active breaking is my only solution.
This issue only occurs in an 11.1 LiPo, it fires as expected with a 7.4, but the ROF is poor.
Build list:
CA V2 9mm Shell, polished and radius’d
SHS 13:1 Gears
FLT bushings on step and sector
Stainless bearings on bevel
Shimmed and AOE corrected
SHS Full steel 15 tooth piston
ZCI stainless full cylinder
Lonex Cylinder head
Lonex tapper plate
Lonex nozzle
Retro arms steel cut-off lever
Retro arms CNC trigger
Lonex trigger contacts
(first attempt used original CA wiring harness and contacts, had same issue)
Guarded SP 140 Spring (have tried SP110, 120, and 130)
ZCI 22tpa motor

I really took my time with this build and tried to make it as durable as possible. I guess I’m looking for ideas to actually correct the issue versus “fixing” it with active breaking. Any input would be much appreciated.
 
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#2 ·
You shouldn't have this issue with that gear ratio, motor and spring...

I had some issues with the retro arms trigger tolerances awhile back, I wonder if that has anything to do with your particular build. I'm taking about the height of the trigger, too high and the cutoff lever can't kick the trolley off causing full auto in semi, too low and the trolley slips before the trigger is fully pulled causing half shots. Different trigger trolleys with different triggers can change this interaction broadly. Making unpredictable behavior unless you know what to look for. Try putting the gearbox together without the compression parts/motor, hold the trigger in semi and rotate the sector back until it kicks the trolley while looking down the cylinder windows. You could be able to locate what is going on from doing so.

This is fixable without spending 150 bucks for an electric trigger board.

Good luck!
 
#3 ·
Thank you...I did give the trigger some thought but the thing that confounds me is the problem disappearing with the weaker battery. I do know the CA triggers have less material where it meets the trolley than most other triggers which caused the trigger to not reset properly in a different build and shell but had not experienced any of those issues with the speed trigger and Lonex contacts in this shell but I guess it’s time to try the CA trigger and see if anything improves. I really appreciate you taking the time to share your thoughts.
 
#5 ·
Well it working with a weaker battery has me more puzzled.

Unless the overspin lands it right back to almost cutting off again. Where is it landing in the cycle with the overspin in semi with the stronger battery? If the piston is basically all the way back that could be a possibility, but the cutoff lever should only engage once the piston is let go, but it could basically have the cutoff lever halfway up, making the phenomenon happen where it wants to shoot every other shot... yeah a video would definitely help. Even hearing the sound could make it easier to identify.
 
#6 ·
I'd try shortening the spring on the trigger switch, it can often fix overspin issues in my experience. No need for a super expensive computer mosfet.
 
#7 ·
Actually the weaker battery is a clue. It means the power is at a level that is not useable to keep the motor running...thus it cuts a fraction of a second quicker.
 
#8 ·
Update: Well, FML. I was making a video of it so I could post it and, well, I guess my radius job didn’t turn out so well. I guess I will just appreciate what I learned during this build and look for a new shell. Thank you to those who shared their ideas and knowledge.
 

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#10 ·
Update: Well, FML. I was making a video of it so I could post it and, well, I guess my radius job didn't turn out so well. I guess I will just appreciate what I learned during this build and look for a new shell. Thank you to those who shared their ideas and knowledge.
Thats a bummer. The guarder sp140 is a powerful spring, when you corrected AOE did you just space the piston head out with washers or with a shock absorbing pad? Even so I'm surprised you cracked it with the radius job. I've been running a sp130 spring on a very similar build short stroked by 3 for about 5 years every other, roughly 1-2k shots each time, however i have a 1/4" shock absorbing pad and I have my metal hop up unit pressing against the front of the shell with quite a bit of pressure and have lucked out so far.
 
#9 ·
You didn't have a curve in the right spot.

Comeplete G&P Mechbox is 45.00 shipped from me....
 
#13 · (Edited)
Not true. You are making some generalized assumptions that all things are equal in Airsoft...its far from it.

You will see how durable a well made and put together G&P box from the factory runs in stock form...but since you are driving it above spec...your mileage will vary.

And your mechbox is a CA unit? I can see a "ic Army". That mechbox alloy is rather brittle...compared to a G&P unit.
 
#15 ·
Yes, SHS blue with the thrust bearing metal head bc the first piston I tried broke. I thought the neoprene washer, though pretty rigid, was enough to dampen the impact of a 30 gram piston even with the stiff spring. The results prove otherwise, and I’ve checked the radius job I did vs. the guide here and a couple YouTube clips and can’t figure out what I did wrong in that procedure.
 
#16 ·
Yes, SHS blue with the thrust bearing metal head bc the first piston I tried broke. I thought the neoprene washer, though pretty rigid, was enough to dampen the impact of a 30 gram piston even with the stiff spring. The results prove otherwise, and I've checked the radius job I did vs. the guide here and a couple YouTube clips and can't figure out what I did wrong in that procedure.
I would go with a plastic piston head with a proper buffer glued on the cylinder head. Sorbo pad or some other soft material. There used to be a detailed thread on ASM about radiusing. Including digital diagrams showing the beneficial effect of it. When you radius you want to not only make a round cutout, but also prevent a thin edge anywhere on the curve, thats where a crack would try to start. I wouldn't let it bother you, just find a new shell and take a bit more precaution, it likely will not happen again.
 
#17 ·
Thanks, I’m going to keep at it until I get it right. I’ve really enjoyed the process and even the frustrating results of my inexperience, although the shell cracking is kind’ve a kick in the nuts bc I have a pristine CA body but have had fitment issues with some non-CA shells so I bought the one I ruined and gutted it. I’m trying to confirm whether the RA cnc shells fit and if so may go that route.
Thanks again for the help, I really appreciate it.
 
#21 ·
Thanks man, you’ve been a ton of help and make spaces like this so valuable. I guess I really underestimated the spring and never thought I’d be near pushing the limits of the shell to consider an STS...hindsight and $18 probably would’ve kept it from cracking and I’d have been able to try to solve the original issue. But I’ll definitely have more ideas to draw from and regardless of what shell I end up with I’ll definitely be adding a shock transfer block to the mix. Thanks again for the positive reinforcement and great information.
 
#22 ·
Thanks man, you've been a ton of help and make spaces like this so valuable. I guess I really underestimated the spring and never thought I'd be near pushing the limits of the shell to consider an STS...hindsight and $18 probably would've kept it from cracking and I'd have been able to try to solve the original issue. But I'll definitely have more ideas to draw from and regardless of what shell I end up with I'll definitely be adding a shock transfer block to the mix. Thanks again for the positive reinforcement and great information.
So they go by the name shock transfer system apparently, STS, sorry for the incorrect term.

Also is there anywhere that even has sorbo pads for m4's that are in stock anymore? I can't even find one around these days.
 
#26 ·
OEM units of just shells sold?
 
#28 ·
Airsoft is all batch manufacturing. Some OEM's tweek the line, some don't.

It's what's available in "made" guns versus someone like Evike who bought some shells and are just reselling it. Any of the shells Evike gets...nothing special.

Then the other issue is that the beefier mechboxes don't easily fit in an off brand receiver.

I am thinking the 2GX V2 mechbox by KWA...that thing is the #1 OEM Cast shell on the market, but you can't get that thing in very many receivers outside of KWA.
 
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