G&P All Metal Pistons, Accept No Substitute, Err.. (pics)
 

I had a very interesting and entertaining catastrophic failure with my high speed build today. The AEG in question is my possessed/cursed Diablo:

http://dl.dropbox.com/u/1149620/airs...%2052%20PM.jpg

Random build details:

Modify 8mm steel ball bearings
G&P all-metal short-stroked piston (the one that comes with G&P's C8s.. It's what I had handy when putting together this build last week)
SHS M120 spring
SHS 13:1
G&P M170 motor
G&P trigger assembly
11.1V Turnigy nano-tech 25C
XT60 wiring, 16AWG
Extreme-Fire SW-SF MOSFET
Modify cylinder + head + nozzle + hopup + barrel
Madbull red bucking
G&G GR16 mechbox shell, one of the only things left from the original gun (SOCOM Gear PWS Diablo)

Note, I never adjusted for AoE since I didn't plan to keep this metal piston in this gun -- I figured I'd run it for a game or two without too many problems. I was wrong ;)

Brought it out to a game today, fired like a champ at 32rps @ 395 to 400fps. The bucking and its H-nub performed beautifully and I'm really happy with the accuracy with Modify's hopup and hybrid barrel.

During the final game of the day, I got the telltale sound of a piston breaking or possibly a gear tooth snapping. I was very curious to see what the damage would be since I didn't hear any rattling (so no rear-of-piston snap-off) and couldn't imagine how an all-aluminum piston could possibly break a tooth. I get home a short while ago, pry the thing apart and discover this:

http://dl.dropbox.com/u/1149620/airs...%2051%20PM.jpg

http://dl.dropbox.com/u/1149620/airs...%2008%20PM.jpg

Your eyes are not failing you. The M170 motor and SHS gears managed to rip the rack right out of this piston and shove it all the way back to the rear of the mechbox. Pretty awesome.

http://dl.dropbox.com/u/1149620/airs...%2033%20PM.jpg

http://dl.dropbox.com/u/1149620/airs...%2044%20PM.jpg

Needless to say I'll be working on my AoE when my Lonex replacement piston and sorbo pads come in the mail next week! :)

Side note, anyone think this piston can be salvaged with glue or something?

Lol! Bizarre!

Would AoE adjustment prevent this from happening?

Just out of curiosity, is that a ventilated piston head? I always thought ventilated would be good for a high speed setup???

haha what the-

very interesting indeed.

Sounded a lot worse today.

i guess the gears were moving too fast +the stiff spring caused the teeth to pull off.

That is a common problem on really any piston with a full metal rack. The only way that you can prevent this is to epoxy the rack onto the piston body itself. At the pick up tooth the plastic there is very thin, and that is all that is holding your rack in place from sliding off the rear of the piston. The piston is not salvageable. The rack is.

It should stop it from happening. I had a similar failure last week in this same gun but with a polycarb piston, also not AoE'd, but it took the end of the rack clean off. I've been waiting for an order of sorbo pads to come in from Clandestine Airsoft in the US. It didn't arrive early enough for this weekend's game :)

Yes, it is a ported G&P piston head.

The entire piston in this case is aluminum, even the body. I'm curious if that would change your assessment of whether it's salvageable.

For some reason I had hoped the rack was actually *part* of the piston body, but in retrospect that would have probably caused my sector gear to explode.

Aluminium is a fairly weak and bendable material. Doesn't surprise me that it did that. A small 'bar' of aluminium taking all the stress of the spring through the rack made it break. Just get a shs, epoxy the rack and call it a day. They are cheap.

It's the metal that G&P decide to use. They'll spend the money on only half of the part, and the other 50% gets shit metal. Same as their gears, bears and now piston. It seem like the G&P reliability that once was praised upon is gone. I guess they thought they could get away with 50% quality and 50% shit.

I don't want to place all the blame on G&P here, there's definitely a lack of AoE in this particular setup. It is a pretty funny thing to see upon opening up your mechbox..

I have used the Lonex pistons with good results in high fps setups.

I also have Prometheus pistons and they are super strong.

I have a Lonex piston coming in to replace this one. I'll be adjusting for AoE with a 40 duro sorbothane pad. I'll let you guys know if it survives this time :)

Well at least we we have proof that SHS makes pretty strong gears; G&P gears would've definitely stripped or broken at the axles. Also, Modify makes white piston heads now or is that a stock G&P one?

If you think about it, this has nothing to do with AOE. The little piece of metal at the front that broke and not the teethes in the rear. That whole rack is held forward with a single piece of metal and nothing at the rear to support it. Poor design.

Yep, that's the stock G&P piston head, secured with a hex screw into a big metal cylinder behind the piston head that has a large flathead groove in it.