Pistons

[ILLusion]

If your high ROF gun is chewing up pistons, then that means your gun is not properly built.

If you install an aluminum piston, one/some/all of these things will happen:

1) Your aluminum piston will strip almost as fast as a polycarbonate one
2) The teeth between the sector gear and the bevel gear will strip
3) Your pinion gear will strip
4) The sectored teeth of the sector gear will shear off

Ultimately, the result won't be good UNTIL YOU FIX YOUR PROBLEM.

The primary cause of stripped pistons in a high ROF setup is an imbalance somewhere, causing the sector gear to collide with the piston before it has returned to battery. Either speed up the forward motion of the spring (but not too much, or it could make the situation worse), short stroke it, and/or remove the second tooth.

[ILLusion]

Originally Posted by Styrak

...no.

No one does that. I'm not even sure what that would accomplish. Stripping your entire piston from the head back?

A lot of people do that. It's called short stroking.

Perfectly fine for an MP5, with the short barrel, half the piston stroke is wasted anyways, covering the distance from the end of the cylinder till the port closes. It's a great way of increasing ROF, durability and reliability in ultra high speed setups.

[ILLusion]

Originally Posted by milehigh

Well if you take a few teeth off the butt end of the piston, how would the sector gear catch it to pull it back?

You remove the 2nd tooth to increase overall survivability. Typically, the 2nd tooth is the one that's most likely to crash in to the sector gear if the ROF is excessive. Removing it is one way of saving your gears and the overall piston.

When you short stroke, you just remove teeth from the sector gear, but that means you have to make sure your piston has metal teeth for the last one that the modified sector gear will engage. Prometheus and Modify are good candidates, because 7 of the last teeth are metal.

[milehigh]

Originally Posted by ILLusion

A lot of people do that. It's called short stroking.

Perfectly fine for an MP5, with the short barrel, half the piston stroke is wasted anyways, covering the distance from the end of the cylinder till the port closes. It's a great way of increasing ROF, durability and reliability in ultra high speed setups.

Thanks for your input!

[Big Pepa]

Originally Posted by ILLusion

If your high ROF gun is chewing up pistons, then that means your gun is not properly built.

If you install an aluminum piston, one/some/all of these things will happen:

1) Your aluminum piston will strip almost as fast as a polycarbonate one
2) The teeth between the sector gear and the bevel gear will strip
3) Your pinion gear will strip
4) The sectored teeth of the sector gear will shear off

Ultimately, the result won't be good UNTIL YOU FIX YOUR PROBLEM.

The primary cause of stripped pistons in a high ROF setup is an imbalance somewhere, causing the sector gear to collide with the piston before it has returned to battery. Either speed up the forward motion of the spring (but not too much, or it could make the situation worse), short stroke it, and/or remove the second tooth.

I see where you are coming from and I'll recheck to make sure everything is balanced properly but... The gun is shimmed right, I got a sector chip on it, every part in the gear box is aftermarket except for the cylinder. It's shimmed very precisely, it's even got a cheetah mosfet on it.

I honestly think the problem is that the 9.6v battery coupled with the systema turbo motor and m90 spring produces way too much torque. I think the problem is with the Systema motor itself. When I ran this rig without the mosfet it was overcycling like hell (and breaking pistons). Now it's just breaking pistons from time to time. (I play airsoft about 4 times a week out here since I work at night - Just saying because the mosfet cure was not too long ago)The motor has a lot of torque. When I ran on a EG700 or even EG1000 I had no problems with piston breakage. As soon as I put the turbo motor in I have been breaking a piston ass end every other game.... about 2k or so bbs later.

I could be wrong... please tell me if I am because I'd rather have a polycarb any day of the week.

The current piston I have in the gun has lasted me 3 games so far... I think it's a good one but the reason for this post is that I just KNOW that it's going to end up failing. I honestly just want to know the con's of the aluminum piston.

I think M902323 (sorry I can't remember the numbers) summed it up perfectly when he said that it's really a choice between breaking a piston in the sort run or breaking the gears in the long run. I honestly just don't want to operate on the gun right now for a long time... it's a time sink.

Is the danger to the gears that great? I have prometheus high speed gears installed.

Thanks for all the input.

[ILLusion]

Originally Posted by Big Pepa

I see where you are coming from and I'll recheck to make sure everything is balanced properly but... The gun is shimmed right, I got a sector chip on it, every part in the gear box is aftermarket except for the cylinder. It's shimmed very precisely, it's even got a cheetah mosfet on it.

I honestly think the problem is that the 9.6v battery coupled with the systema turbo motor and m90 spring produces way too much torque. I think the problem is with the Systema motor itself. When I ran this rig without the mosfet it was overcycling like hell (and breaking pistons). Now it's just breaking pistons from time to time. (I play airsoft about 4 times a week out here since I work at night - Just saying because the mosfet cure was not too long ago)The motor has a lot of torque. When I ran on a EG700 or even EG1000 I had no problems with piston breakage. As soon as I put the turbo motor in I have been breaking a piston ass end every other game.... about 2k or so bbs later.

I could be wrong... please tell me if I am because I'd rather have a polycarb any day of the week.

The current piston I have in the gun has lasted me 3 games so far... I think it's a good one but the reason for this post is that I just KNOW that it's going to end up failing. I honestly just want to know the con's of the aluminum piston.

I think M902323 (sorry I can't remember the numbers) summed it up perfectly when he said that it's really a choice between breaking a piston in the sort run or breaking the gears in the long run. I honestly just don't want to operate on the gun right now for a long time... it's a time sink.

Is the danger to the gears that great? I have prometheus high speed gears installed.

Thanks for all the input.

It looks like the imbalance is coming from a slow forward movement of your piston. An M90 spring is not fast enough to return the piston to battery before the sector gear comes swinging around again, which is why you're experiencing a collision. Increase to an M100 or chop out the 2nd piston tooth or short stroke the setup. ... or do all 3. If you don't feel like doing the short stroke mod, at least try moving to the stronger spring and taking out the 2nd piston tooth first. It's a relatively easy mod to do on polycarbonate, but regardless, it looks like you will need to perform at least 2 of the suggested changes/mods in order for your setup to be balanced.

Fix that issue of collision FIRST, before considering upgrading to an aluminum piston. Otherwise, you'll be wasting money with yet another destroyed piston, OR the added stress on the gears will strip their teeth, assuming the piston doesn't get stripped first.

[Big Pepa]

I'd love to increase to a M100 but they are illegal to buy in Japan (anything that produces over 1j with 0.2s is). Retailers won't sell them and if you get caught with one in your air gun you are looking at 10 years or more in a Japanese jail. (to be honest most of the guys I play with have m100s or m110s but they bought them a long time ago when they were legal).

Being a white guy in Japan doesn't help either. I'd be all over the front page of every freeken newspaper out here if I got caught with something illegal.

That said, I'll chop out the second tooth and see how that goes... I don't feel comfortable short stroking the setup.

[ILLusion]

Try shaving the 2nd tooth first, on a cheap piston. Run it. If it strips, then you'll have to short-stroke.

[Big Pepa]

What do you think of adding washers to the spring guide to preload the spring?

Think that would help?

[Styrak]

Originally Posted by ILLusion

A lot of people do that. It's called short stroking

Well yeah, but you buy a special sector gear for that wouldn't you? Not machine/file your full sector gear?

[ILLusion]

Originally Posted by Big Pepa

What do you think of adding washers to the spring guide to preload the spring?

Think that would help?

That can work as well. Just make sure you don't preload the spring so much that the piston can't pull back all the way. There's only so much the spring can compress.

[ILLusion]

Originally Posted by Styrak

Well yeah, but you buy a special sector gear for that wouldn't you? Not machine/file your full sector gear?

Both are viable options, although modifying it yourself is cheaper and more accessible PLUS you get to continue using the gear set that you like.

People have been modifying their own for years. There's no reason why you can't modify it yourself.

[Aquamarine]

Originally Posted by Big Pepa

Super Core is Polycarb. My local guy can't get his hands on one either.

Echigoya carries them. Order one online. They ship to Japan... as they are in Japan.

[Blackthorne]

Originally Posted by milehigh

I've never shaved teeth before, but wouldnt it make sense to remove the last tooth or two from your sector gear, rather than your piston?

Originally Posted by Styrak

...no.

No one does that. I'm not even sure what that would accomplish. Stripping your entire piston from the head back?

YouTube - Shortstroke Mod on ICS MP5 SD6 -ASTKilo23-

[Multikam]

I think if your rof is too high there isn't a piston out there that can handle such demanding use. Maybe you should lower the rof (lower the battery voltage or change to torque gears).