complete striping of a piston...

[ErikMendel]

hey guys bought a G&G m4
upon the guns showing at my door replaced all the stock internals with a systema full tune pro kit... and a systema atoz motor
kit came with m130 spring
helical gears and pollycarb piston all the good stuff. shimmed and Aoe perfectly.
reassembled the gun and had the all to typical over spin issues on semi fire mode but worked extremely well on auto.(so well the gun wouldnt keep feeding as fast as the motor would pull the spring) i used the gun 20k rounds and opened the gear box again.... every thing looked perfect no wear on any parts. suspecting that a sector clip would help i decided to make one last night. after that i swiss cheesed the piston then took the last tooth off the sector gear and the piston and put the gun back together. never have i seen such a line of bbs erupt forth from the barrel for about 100 rnds then weeeerrrackkk....... and nothing apon opening the box i find my new piston with out a single tooth left.... 9.6 1600mah nicd which the stk gun came with. upon putting my spare piston in lack of swiss cheesing due to my new embarresment of last modification...... 10 rounds later ....... no teeth left again... i did see some ones reply on this forum that removing the last tooth of a sector gear would strip pistons. however i have seen many videos claiming this will increase rof.. please dont reply if your answer is shimming or aoe. as these were not changed and not an initial issue when the gun worked. i know that my shimms were returned where they should have been as i opened the gun 4 more times to assure the shimms were accurate. what causes an entire rack of piston teeth to disappear like that? never have i had a piston with such profound grinding.... any advice

[dodgetheram]

When u short stroke your gearbox, dont you have to remove twice the teeth from the piston that u remove from the sector gear?

[ErikMendel]

in theory you dont even have to remove the teeth from the piston by removing the sector gear tooth it makes the piston release sooner regardless of the pistons teeth being their or not the weight loss could be good though

[cetane]

How many steel teeth? If its a single steel tooth piston & you got -1 tooth on sector gear, plastic piston tooth will not hold up to being the release tooth on piston. It will break. Then next tooth will break next cycle then all will get ground down.

[ThunderCactus]

^ that

[dodgetheram]

Originally Posted by cetane

How many steel teeth? If its a single steel tooth piston & you got -1 tooth on sector gear, plastic piston tooth will not hold up to being the release tooth on piston. It will break. Then next tooth will break next cycle then all will get ground down.

That makes sense, I've only use pistons with 4+ metal teeth. But then wouldn't all poly pistons with no metal teeth just sheer away instantly?

[ThunderCactus]

Yes, that's what we're implying
All pistons have 1+ metal teeth. You just cannot get them with all poly teeth for that exact reason.

[ErikMendel]

ok but if that were true then what about pistons that dont have any steel teeth like this guns stk piston worked perfect for the 1000k rnds i snaped off before gutting it the piston was perfect... the one that stripped was the SYSTEMA ENERGY POLY-CARBONATE PISTON with only 1 steel tooth which i left but was no longer functioning due to the removal of a sector gear tooth. have either of you seen this personally?? i have heard these claims before however i have tech friends that swear you can release from plastic teeth that you will need to replace your piston quicker but net instantly.

[Stealth]

Your first post was extremely confusing, but let me try to clarify.

If you're removing teeth from your sector gear to short-stroke, you don't have to remove the corresponding # of teeth from your piston. But, every tooth that you remove the sector gear is one tooth back from the first metal release that will now be your new release tooth. So, if you remove 3 teeth from your sector gear, your 3rd last tooth will now be your new release tooth. If this tooth is not metal, your piston will be destroyed quickly.

The reason why people remove corresponding teeth from the piston is to reduce weight - why keep excess metal on the piston assembly as dead weight?

[ErikMendel]

i think im starting to see your point after looking at all the half teeth racks available can anyone confirm this from personal experience. i was hoping to replace this piston with systema again... yeah i was afraid of that..... thanks stealth

[lurkingknight]

don't bother overpaying for the systema, there are tons of options out there that are cheaper and will do exactly the same job. But hey, it's your money. :P

[MaciekA]

Originally Posted by lurkingknight

don't bother overpaying for the systema, there are tons of options out there that are cheaper and will do exactly the same job. But hey, it's your money. :P

+1, there's no need to buy Systema gears, pistons, or motors.

Go to Stealth's store and buy yourself a couple of those SHS lightened full metal rack pistons. If you truly have no issues with AoE, shimming, or compression, then you should be fine after that.

Also, forget about swiss cheesing unless you are running on 3 cell LiPos.

[Deathfox]

So what im getting from this is; he had no issues till he wanted to swiss cheese the piston, and short-stroke the piston and sector gear (one tooth). He did this correctly! it is REALLY important to take off the same amount of teeth from the piston and sector gear. If not you will wreck pistons really easy. And to make sure the releasing tooth on the piston is METAL

i believe the first piston blew because you swiss cheesed it. To use a M130 spring with a swiss cheesed piston is a lot of stress, also the piston is moving forward faster and bouncing off the cylinder head so the sector gear doesnt engage properly and wrecked it because it keeps engaging the piston on the wrong teeth.

The second piston probably blew because the new piston had more teeth than the sector gear and the sector gear was releasing on poly teeth and this WILL break a piston very quickly . I noticed in your post you didnt say you removed a tooth from the new piston, which would make sense why it broke in ten shots

But seriously, if you want to short-stroke your pistons, get pistons with more than one metal teeth (at least 3), then you can short-stroke to your hearts content without compromising stability in the tooth rack. And if your goal is to get better ROF, get a lower rated spring. Like a M100 or M115. Then you can start swish cheesing, short sroking and stuff. But that spring (m130) is too strong for a swiss cheesed piston, will break often.

[MaciekA]

Originally Posted by Deathfox

But that spring (m130) is too strong for a swiss cheesed piston, will break often.

I agree with the sentiment of your post, but I think you are mistaken about the point I've highlighted above.

An M130 spring is not too strong for swiss-cheesing. The rack does not get shredded because the piston has been lightened; the rack gets shredded because a tooth encounters a piece of steel travelling at an unfortunate angle and/or extreme speed relative to its capacity for impact. The solution here is to improve angle of engagement, shorten return time and use stronger materials on the rack.

Lightening can reduce the likeliness that you encounter pre-engagement in the first place, which satisfies one of the goals above (shortening of return time), and to that end you can see companies like SHS producing lightened pistons that have full metal racks. I'm using one of these in an M130 setup as we speak, and it's absolutely fine.

[Deathfox]

My statement was bias, i personally dont believe in swiss cheesing pistons. Im weary on it because it does change structural integrity of the piston.
The gun in question never had a problem with it for 20k rounds, then he short stroked it and then swiss cheesed it and failed almost right away. So im still standing by my statement because the gun had no wear before those modifications... and those modifications would have made it less of a chance for for the "crashing problem" as you stated. So i still say its the piston bouncing off the piston head And causing a engagement problem. I would suggest a sorbo pad because this would keep it from "bouncing" off the cylinder head. This is a common problem in high rof setups, and you cant get the best of both worlds (FPS & RPS)

. Ive never found the need to use swiss cheesed pistons because i can manage to get 45rps on a single sector without swiss cheesing. And i get great piston life (with AoE)

But i will have to agree with ya on SHS metal rack pistons. They are great pistons (and cheap)