Pistons Keep Stripping

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LazzurusMan

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Running 11.1 lipos with 19:1 gears I keep stripping pistons. 

Just wanted to check if this is normal, or if something is set up wrong. The three pistons that have been stripped had poly teeth, new one (not stripped yet) has a full metal rack. Am I likely to strip this one too? 

 
Nah it's not normal, even with poly teeth,  Guessing you are running 18:1 gears, what spring and motor?

My advice is switch to a 7.4v battery.

 
there's a lot of possibilities.

its possible a steel rack may survive, but equally possible the rack will just get ripped out the back or something else in the geartrain will break (ie teeth)

gearing and battery aren't the only factors, for example if you're using a standard motor compared to say an asg 40k will determine wether or not PME is the issue.

 
I have not set aoe, as I only put the piston in yesterday. Im also running an asg infinity 30k motor. I'm planning on a serious updrade this friday.

Full shim job, new gears (can't decide between 16:1 or 13:1 if anyone can help with that too), new 7mm bearings as mine are still stock and getting old and a set of nylon washers to set the aoe.

Hopefully that'll all help fix the issue and I'll finally be able to go a whole day without stripping a piston. 

 
LazzurusMan said:
I have not set aoe, as I only put the piston in yesterday. Im also running an asg infinity 30k motor. I'm planning on a serious updrade this friday.

Full shim job, new gears (can't decide between 16:1 or 13:1 if anyone can help with that too), new 7mm bearings as mine are still stock and getting old and a set of nylon washers to set the aoe.

Hopefully that'll all help fix the issue and I'll finally be able to go a whole day without stripping a piston. 
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Your AEG should work perfectly fine with a plastic piston and there must be an underlying reason behind it. A metal piston rack is not a "cure" for breaking pistons. It just masks the problem and cause other more expensive breakages. 

You really need to set AOE. It is the most likely reason why you have stripped so many pistons. 

 
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LazzurusMan said:
I have not set aoe, as I only put the piston in yesterday. Im also running an asg infinity 30k motor. I'm planning on a serious updrade this friday.

Full shim job, new gears (can't decide between 16:1 or 13:1 if anyone can help with that too), new 7mm bearings as mine are still stock and getting old and a set of nylon washers to set the aoe.

Hopefully that'll all help fix the issue and I'll finally be able to go a whole day without stripping a piston. 
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my last ak build ran one of those motors on 13:1 on 7.4v came out ~20rps, i'd put good money on that same setup with 11.1v eating any piston you throw at it.

whats your current rof? setting aoe properly won't hurt but if the problem is pme then something is still gonna get shredded.

if your goal is better semi auto response then you're going to be much better off running a lower powered battery and using a mosfet with precocking to make up the difference.

if you do want to preserve auto rof then you're gonna have to start looking at short-stroking, which will depend on the barrel length/cylinder volume you've got to play with. however what i will say is if you can't get someone to call a hit at 20rps then that's a failure of the target not the gun and doubling the rof will not solve the problem.

 
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If running an asg infinity 30k motor, I'd stick with a set of Rocket or stock 18:1 and 7.4v, better efficiency that way.  20 is plenty.  As  @Adolf Hamster states you're going to have to go with a higher spring and short stroke if you want to use 11.1v effectively.

 
I'll be setting aoe when I put some new gears in, probably still gonna go for 13:1, but I'll also get my hands on a 7.4 and stop using the 11.1s.

Short stroking etc sounds like more work than it's worth if I'm able to get 20+ rps with a lower gear ratio and 7.4 lipos. 

 
I'm trying to figure out how poor AOE could result in stripping teeth out of the middle of a piston.  I get that it might wear the 2nd tooth from the back, but it's engaging at the minimum of spring tension, and once it engages with the rear tooth, it's not going to pull any differently than if you had the AOE spot on.

Not that I have anything better to suggest, I've yet to succeed in stripping even a plastic piston.

 
So, my "friend" that seems to think they know everything about airsoft doesn't know as much as they think. 

My gearbox has never stripped a piston per say. The first time the piston head came off and the piston got stuck, hence the stripping of the piston, this time the aoe wasn't set by the shop that did the work after the last big break (won't name names) and the rear of the piston got chewed up. 

So, in theory if I set the aoe properly and shim the gears properly I should be able to run 18:1 gears perfectly safe on my 11.1 lipos. 

Though I am very tempted to run 13:1 and maybe drop to 7.4s. 

 
AOE probably isn’t the biggest issue here. The correct, factual advice has been said already. I’ve done a few high speed builds and I’ve made all the mistakes, I only stopped stripping pistons when I listened to hamster and sittingduck.

In all likeliness whats going to happen as soon as you push any UK spec build up near 30rps is premature engagement. This is simply because the springs we use for our velocity limits don’t return the piston quickly enough before the next revolution of the gearset. If the piston gets caught by the sector before its fully returned, chances are the teeth are going to get obliterated or (in the worst cast scenario with a metal rack) the sector gear or bushing/bearing is going to get obliterated.

There’s no reason why you cannot make a decently reliable high speed build at UK spec mind, my Leviathon in my M4 (36-37rps) is showing 43,000 rounds since I last rebuilt her!

What you’ll need to do is short stroke the piston and sector gear. There are tonnes of guides on short stroking on YouTube, watch a couple and you’ll get the idea. Essentially you’ll be taking teeth off the piston and sector to allow it to be released earlier, ensuring that it can return fully before the next cycle. I’ve settled on removing three teeth from almost everything I build now. If 7:45 brain works properly, teeth come off the pick up end of the sector and the release end of the piston or you could have timing issues. If I’ve got that wrong, there will be plenty of replies to point that out…

Removing teeth is going to reduce your output velocity, a decent rule of thumb is 10-15fps per tooth. At this point you’ll need a stronger spring, depending on barrel length+cylinder volume this will vary but I’ve found that 3tooth short stroke and an M115-M120 seems to land on the UK limit in most circumstances.

Removing the teeth isn’t hard, you’ll need a metal rack piston, stick the rack in a bench vice and dremel or file away until the teeth are history! Same with the sector, just be extra careful not to damage any teeth on either side you don’t want to remove!

Easy enough to do, and you should be able to run your 18:1 with the 30k and 11.1 for a decent period of time. Good pistons to use are the SHS ones although the new gear parts ones @ak2m4 is selling look very similar. Either way AK2M4 sell both, get one!

Ali

 
So, I've just got the gearbox open, and regardless I need to replace my gears as my pinion gear on the motor has started to eat the teeth on my bevel gear (probably mu fault, probably my really bad shimming).

If I was to take two teeth off the new sector gear, run 13:1 gears, set aoe and spend a day shimming the new gears, would that still be safe with 11.1 lipos and my asg 30k motor?  I've seen videos that say to only short stroke the gear so you can still use the piston in another setup if needed. Also, as a side note, should a motor spark at all when run? I tested the motor out of the gun the other day and when the motor stopped there were sparks at the contact end.

I also want to thank you all for your replies, if at any point it's seemed like I'm not taking anything you say in, I am, I'm just trying to also keep any unnecessary cost (such as two new lower voltage batteries) and still get decent rof and trigger response.

 
13:1 gears with a 30k motor and 11.1 could be as high as (30kx1.55/13) 35ish RPS. Two teeth off is still likely to have PME at that speed! 
 

As an example, I’m running 6 teeth off on my M4 (dsg) and an M140 spring to avoid PME at 37rps. 
 

Honestly, I wouldn’t worry about not being able to use a piston in another build, it’s a totally sacrificial component and you’ll get through plenty over time with high speed builds.

Is this your only AEG? Very important question here, as that will definitely determine what sort of RPS to aim for

Ali

Edit - forgot to add, 30-40rps is seriously uncool in game without the facility for a burst mode. My high speed stuff is always locked to 3-5 rd burst depending on how dense the woodland is. Play like you’d like to be played against, no one likes being hosed

 
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Alimcd said:
13:1 gears with a 30k motor and 11.1 could be as high as (30kx1.55/13) 35ish RPS. Two teeth off is still likely to have PME at that speed! 
 

As an example, I’m running 6 teeth off on my M4 (dsg) and an M140 spring to avoid PME at 37rps. 
 

Honestly, I wouldn’t worry about not being able to use a piston in another build, it’s a totally sacrificial component and you’ll get through plenty over time with high speed builds.

Is this your only AEG? Very important question here, as that will definitely determine what sort of RPS to aim for

Ali

Edit - forgot to add, 30-40rps is seriously uncool in game without the facility for a burst mode. My high speed stuff is always locked to 3-5 rd burst depending on how dense the woodland is. Play like you’d like to be played against, no one likes being hosed
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It's my only working aeg. I also have a cm16 that needs a new motor. 

So, if I was to go with 13:1 gears, should go for a lower speed motor or switch to 7.4v batteries? 

I really don't want to be that guy that gives people nasty bruises from 30+ pellets hitting them at once. A little over 20rps would be fine. I need new gears regardless, and I would like good trigger response hense the 13:1 choice. Also, if my motor is going (like I said, I see sparks when it runs and that worries me) then a lower speed motor wouldn't be a problem. 

Sorry I keep asking all these questions, I just don't want to have to do all this again in a few weeks after breaking my gun..... Again. 

 
I would be going 7.4v. 11.1v is unnecessary and can turn parts into consumables if setup wrong as you have discovered. 

 
LazzurusMan said:
It's my only working aeg. I also have a cm16 that needs a new motor. 
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If it’s essentially your main gun. Stick it at c.20. There’s nothing worse than having to do the walk of shame after your only pew has destroyed itself halfway into the first game of the day.

If it were me, I’d stick with the ASG motor, they’re awesome. Get a standard ratio or 16:1 gearset from AK2M4 and run the 18:1 on 11.1 (25ish) or the 16:1 on 7.4 (18ish). The ROF figures are rough and depend on shimming/motor height etc. At 25ish, a tooth or two of the sector/piston rack would be fine. Two teeth off, grab a M110 and you should be sending comfortably under the 350fps limit.

The sparks are fairly normal, motors will always do that unless brushless. It will cause a build up of carbon over time, reducing the motors efficiency. Brushes can be replaced, don’t sweat it. It’s worth having a read up on Mosfets, they’ll increase the ROF slightly and protect your trigger contacts. Are you handy with a soldering iron?

 
Alimcd said:
If it’s essentially your main gun. Stick it at c.20. There’s nothing worse than having to do the walk of shame after your only pew has destroyed itself halfway into the first game of the day.

If it were me, I’d stick with the ASG motor, they’re awesome. Get a standard ratio or 16:1 gearset from AK2M4 and run the 18:1 on 11.1 (25ish) or the 16:1 on 7.4 (18ish). The ROF figures are rough and depend on shimming/motor height etc. At 25ish, a tooth or two of the sector/piston rack would be fine. Two teeth off, grab a M110 and you should be sending comfortably under the 350fps limit.

The sparks are fairly normal, motors will always do that unless brushless. It will cause a build up of carbon over time, reducing the motors efficiency. Brushes can be replaced, don’t sweat it. It’s worth having a read up on Mosfets, they’ll increase the ROF slightly and protect your trigger contacts. Are you handy with a soldering iron?
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Already got a gate Nano aab mosfet fitted. I'm not too bad with a soldering iron either. 

So, an 18:1 gearset and a 110 spring (I'm currently running a guarder sp100 at around 315 on 0.2s) with two teeth off the sector gear should do the trick with 11.1s?

 
That should behave at 25rps and give you an output that’s well within UK limits. 
 

The Gate is a great little piece of kit and paves the way for things like the MERF or Warfet with their timing based burst modes. 
 

Having active break enabled will increase wear on the motor. Test the gun is semi with it disabled and check that it’s required instead of just running with it on.

Id get a shopping basket going at AK2M4 now. I’m pretty sure @Asomodai gets frequent flier miles there! 
 

There’s a few things that @ak2m4 sells that I’d be tempted to pick up at the same time as gears/spring. Super lube is great stuff and efficiency is key with any build. Spare shims never go amiss either! 
 

Final thing to do to make sure you’re leveling the playing field is to never, never touch a 0.2g bb again. Switch out to 0.28’s and you’ll see improvements in consistency of groupings and a bit of an improvement in range

 
LazzurusMan said:
I'm currently running a guarder sp100 at around 315 on 0.2s) with two teeth off the sector gear should do the trick with 11.1s?
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I'm confused a little, are you saying you've already taken 2 teeth off the sector gear?  sp100 should be getting your around 360fps with 0.2g on a normal build

 
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