Tappet Plate broken in M4

[padraigthesniper]

Hello guys,

I had a gun issue during a game, got home and disassembled the gear box and have discovered the tappet plate has broken off. I can figure out how to replace it but I want to know what cause's this issue. I have a perun mosfet installed and used a 7.4v lipo with a stock motor to drive the gun, the tappet plate broke after long bursts of full auto. The gun shoots quite fast with gears and bearings is this normal wear and tear or another issue? What is the best way to prevent this in the future and would recommend any upgrades I'm thinking of replacing the motor with a high torque nice one from ak2m4's shop.

View attachment 103629

 

[Dan Robinson]

I'd say it has snapped through fatigue.  Looking at how gearboxes work recently and trying to get mine back together, that particular bit where it snapped is taking the brunt of the rotational forces as well as being hit by that timing plate as it comes round.

 

[ak2m4]

you've got a little bit of trim coming off the fin on the broken tappet plate, could be the delayer isn't needed?  try it without just in case.  also before you put it all back together check that the pickup tooth on the piston isn't rubbing against the flat part of the sector gear

 

[SSPKali]

I would check the new tappet plate runs smoothly and freely in the gearbox shell before putting it all back together - minimise any drag that might increase the shock loading on the fin as the timing pin spins round and grabs it

Fit just the tappet plate (no gears, cylinder, piston etc...) and check that when the GB shell is screwed together (no, holding it closed with your hands isn't the same!) that it can slide back and forwards with zero resistance.

 

[Rogerborg]

As above, and don't sweat it.  It's a cheap part made of whatever recycled milk cartons and dildos got thrown into the melting pot that day, and subject to a lot of stress and flexing.  I've not had one go yet, but I'd consider them consumables.

 

[padraigthesniper]

Thanks for all the tips guys, opened up the gun installed a new tappet plate and upgraded high torque motor from ak2m4's site and it seems to be shooting better than before. Got another tappet plate ready if it decides to break again. The spring on the tappet plate seemed very strong when I was putting in the new one I assume they are supposed to be like that. All worked out in in the end thanks guys.