Richie! my piston exploded!

plastic_axe

hi :rolleyes:

my gun died earlier and after a lengthy disassembly and testing i discovered that my piston had all but shattered, causing it to jam, and that pieces of it had clogged up the gears causing even more jamming.

the pieces are all clear and i can replace the piston no prob but my question is will it just happen again? is there generally a cause for exploding pistons? there was an awful lot of wear on the piston head as well as a decent chunk missing and 4 of the teeth had been broken off.

(the question is also open to people that aren't richie btw )

thanks in advance

Beast ASI

Got a pic of the piston?

What setup are you running?

What do you mean by wear on the piston head? :S

Won't know til I see a pic of it

NakedDex

Shattered pistons aren't too common but aren't unheard of, even in stock set ups. What rifle did you have it in, and was it the original?

plastic_axe

tm g36c with ms90 spring, steel bushings and shims, tightbore barrel and stock hop up.
8.4v battery and stock motor.

the piston looks like someone's been chewing it.
just occurred to me this very moment as i look at it that the screw in the piston head was very loose. possible damage causer maybe...

running with that idea:
screw breaks piston head -> head jams -> gears strip piston teeth.
plausible?

edit: i'm not sure where my camera is but if i can get a pic up i will.

Beast ASI

TM piston? That's suprising, they're normally *excellent* pistons - I've got one running in a 38rps setup atm actually.

The only thing I could think of would be pre engagement whereby the piston isn't all the way forward before the sector gear tries to pull it back again, but since it's not a high rof setup I'm not really sure.....

To prevent it in future remove the 2nd tooth and about 1/2 of the third, or just both and adjust the AOE (Angle of engagement.)

plastic_axe

forgot to mention, not a tm stock piston. had to replace when i was upgrading the spring.

ill keep that in mind, step 1 is picking up a new piston anyway.

RC car fanatic

I have a question about a piston but its not about it breaking,if thats ok?
I recently replaced my stock TM piston with another one but I'm not sure what brand it was beacause its from an older gun,its clear and I was assuming it was a star piston.Is that right?

Beast ASI

I'd just keep the stock TM in both cases, they're very underrated, and great once setup correctly.

RC: Could be a Element one possibly or VFC.... Don't know what the star piston looks like.

plastic_axe

getting the head off the stock marui piston proved to be bloody impossible.
apparently there's a technique to it.

Masada

yup, you wrap some cloth around the head itself and grab it with a pliers or similar, that way you dont damage the rim.
Ive found in a lot of cases though, then head will just turn independently of the piston and wont loosen the screw. in this case you can just pry out the little circular piece thats stuck in the top of the piston head and remove the screw from there.,

Its not that uncommon for a piston to go like that though. its often the very back of the piston that goes first from impact on the sector gear, then them bits that are left over can wreck the gears. another common cause is when the piston head comes off the piston and stays forward in the cylinder, the gun usually still fires but not propery and the sector gear comes around for a crunching with the piston.,

plastic_axe

judging by the damage on the actual head of the piston i'm pretty sure the latter happened.
anyway, ill be heading up to eirsoft tomorrow for a new one

plastic_axe

the saga continues.

new piston installed and working fine.

HOWEVER

my gun isn't firing in semi. i'm 99% sure the problem is the fire selector contacts, one of which seems to be missing some copper plating.
is there a way to make it start conducting again?

i should add, this wasn't a problem yesterday so i must have scratched it during the aforementioned fix.

Masada

nah it wont be electrical, mare likely the selector plate or the cut off lever that would be causing it.,

plastic_axe

selector plate was what i meant there, the slidey plastic bit with the copper on.
the contact on the gun side seems to be scratched or at least missing some copper.

i cleaned it up there and gave it a talking to and semi worked for 4 shots then nothing again. the contacts just seem to be failing.

Masada

are they pressed in too much? you could try wedging them out a little, it could be that they are too low as the selector plate is passing over them for semi. are you getting full auto when in semi or nothing at all?

plastic_axe

it was nothing at all in semi, and i fixed it. wedged em out a little and presto.

and guess what....

the piston seized.

i'm quitting, there's an underlying problem here that i can't find and i'm just fixing symptoms. i'll be seeing you in the next couple of days.

Masada

lol., try pushing the piston back a bit with a thin screw driver down through the air nozzle, then fire it again., if that dont work drop it up to me.,:)

plastic_axe

positive: the motor works.

negative: naturally i noticed that the fuse i took out was a 15A and not a 5A, what with that wonderfully well inscribed 1 to the left of the 5. unfortunately my local electrical shop does not stock anything above an 8, so where might one pick up such a fuse? maplins?

Masada

thats way too little a fuse for an AEG, you need probably a minimum of a 20A to be sure.,

plastic_axe

editing last post so i seem like less of a spacker.

Masada

Halfords and maplin have them.,:) get some 25's and 30's there.,

plastic_axe

ok, i don't want to jinx it but i think it's fixed.

if anyone reading this is religious i invite you to pray for the well-being of my gun.

Masada

ROFL.,


on a side note, a few people have told me that when looking for fuses in maplin they dont actually stock the 25A and the 30A., this is bullsh*t and them people workin in there just dont wanna bother checking for ya or they havent a clue, not sure which.
I was in there today and there was rakes of them there.,:)

NakedDex

vtec wrote: »

them people workin in there just dont wanna bother checking for ya or they havent a clue

Depends on who you get. Usually the ones that know couldn't be arsed and the ones that could be arsed don't have a clue. Sometimes you get lucky and get the one who doesn't know AND couldn't be arsed.

plastic_axe

yeah i got one of the couldn't be arsed guys and got a 15A.
it works though and that is what was in the gun originally so fingers crossed.

Gizmodeon

Richie! my piston exploded!

possibly the funniest thread title ever......:D