Building a 76rps gun

[Skywalker]

so what you're saying is that you want to sell it.... haha. do you have a full gearset?

... I have a p90 laying around that i need to do something with

[Dominum]

What kind of P90? I just have the DSG, I would sell it, and then would just buy the full gearset when I decide to do my build.

[Skywalker]

its a echo1...


i'd be redoing all the internals in a similar fashion. where do i get the other 2 gears that would work with it? does it not matter what gears mesh with the DSG

[Dominum]

It matters, but most will work. I used standard ratio Systema reinforced gears. Obviously no helicals, and I think they are stnd ratio, though some similar ratios may work. Use something strong.

[Skywalker]

Dual Sector gearset came in. its pretty crazy.

I need to put a heavier spring in the gun... but right now with a 9.6 1600mah and a bravo cyclone high torque motor... I'm estimating that its at, if not over, 40rps. will calculate exact number tomorrow.

[Dominum]

You can also use a spacer on the spring guide. Too week a spring will result in the sector outrunning the return of the piston and will cause failures.

[Skywalker]

yeah i've got the spacer on a m120 spring...

which was still possibly too weak, because the teeth on my piston (which was just a yellow CA piston, i knew it would die) got ripped right off in under 200 rounds.

Gunna grab a couple full metal tooth pistons, and a m150 spring and try that

[Dominum]

I am surprised it lasted that long considering it's front tooth was no longer metal after you shaved off the 8 teeth required.

[Skywalker]

Figured I'd throw an update in on this build...

So. Put the gun together... G&P m170 motor with riotSC high speed dual sector gears... a generic metal tooth piston modified to be lightweight etc... and a m150 spring with the spring guide spacer.

Works great, never calculated it but I'd say it was around 40rps, except I need to use a 11.1v 2800mah 20c lipo or stronger battery to get the thing to fire. Also, on full auto I loose a lot of FPS, I believe because the tappet plate spring is not strong enough to seal the air nozzle in the little amount of time it has to seal when the gears are spinning on full auto.

Next steps are... put a mosfet in (I did melt the trigger contacts together momentarily)... switch to riotSC's custom sized spring for the gearbox (much easier to install than a m150 with a spacer) ... shorten the tappet plate spring to make it stronger... maybe put a capacitor in... and try out some other motors 'til i find something that will pull it powered only by a 11.1v 1350mah 12c lipo (a stick type that will actually fit in the body of the gun).

Any ideas, comments... etc... post em up!

[Dominum]

Clock the ROF using an audio editor on your PC.

[Skywalker]

Yeah I know, I just didn't take the time to do it... and now that big battery is with a friend.

Oh I was also thinking about a 14.8v 2100mah 35c.

[Dominum]

Did you custom wire it with something huge that can handle that? If so, go for it. I have a 20C 4000mah 11.1v I will be putting in my M60 if I can fit it.

[Skywalker]

Well when I drop the mosfet in I'll just have steevo's wiring, I didn't notice what the gauge is, I'm sure you know. I kind of figured the only real way to find out is to try it.

I am worried about the amount stress this is putting on the motor though. Yes melting the trigger is to be expected without a mosfet, but my motor was burning pretty good too... idk. Hopefully re-wiring it solves that issue. Otherwise I'll be going through motors really quick.

[Dominum]

His wire will handle it, just make sure you get rid of the old crap.

[Gabe]

After reading through the thread I noticed that nobody cautioned you about ROF that high. It's doable, but when it goes too high it can render the gun pretty much useless. At a meet and greet 3 or so years ago at Robin's house, he ran a Systema CMB (m100 or 110, can't remember) with a Systema Turbo and a LiPo (an early one, they weren't anywhere near as common as they are now), want to say 11.1v. All were installed in a CQB built G3, barrel was probably around 247mm or so.

Anyway, right out of the box, these Systema components made the ROF so high that bb's were hitting each other as they left the barrel. The lead bb would be hit by the following one traveling in the pocket of turbulence it produced. A similar (and more familiar) comparison would be a car 'drafting' another vehicle, but in this case the bb just collides with the one in front. Only a few shots (out of many fired) seemed to actually make it 5 feet out of the barrel without being knocked aside by a following shot.

TLDR version: ROF can be too high. This isn't paintball.