issues with my high speed build.

[lurkingknight]

I think your main hangup is probably going to be the tamiya and need of a mosfet.

can you stuff one of those 9.6 4000mah packs in somewhere? That will significantly boost your output amps.

Bearings will give you maybe as much as 5 more rps.

I'll put my 65C 2200mah 7.4 on the g36 and see what that nets when I get home, it's running a lonex a1 so the rof may be higher, but probably not by much. I don't think it's 30rps... I'm going to take a shot at guessing it's closer to 26-28.

[Stealth]

1) Is the CYMA Motor a ferrous or neo motor?
2) The piston head and shell have nothing to do with your ROF, your shimming is everything. People think shimming is easy, and for the most part, it is. But time and time again, John will always shim something better than me, because he takes an hour to shim a mechbox to perfection and I take 30 minutes.
3) Using a lighter piston never hurts but this is probably not the source of your problem. Nobody should still be using aluminum piston heads and metal washers these days.


Some suggestions to increase your existing system efficiency:
1) Before you step up to a mosfet, upgrade the wiring to 16awg minimum and use a CONTINUOUS length of wire, each connection/solder joint you make is going to introduce parasitic resistance across the system.
2) Re-shim. Go to bearing bushings, although if you shimmed correctly it shouldn't make a huge difference.
3) Remove all unnecessary weight off the piston
4) Test that there is free movement of piston along its entire stroke
5) Ensure that the bearing spring guide's bearings are smooth
6) Test out airseal - should seal with the piston moving quickly, and allow air if moving slowly.

You're going to hear me say it again, you're setting yourself up for failure since you're constrained by space. Most people would naturally realize the space benefits of a lipo battery and go that route. Anyway, you need the extra power of a higher-voltage battery. If you are going to stay NIMH, like TC said, you'll need to go to 10.8v, but then, what's the point? You might as well go lipo at that point and enjoy the additional power an equivalently-sized 11.1v lipo will give. Drop in one of the Traxxas mini batteries and I'll guarantee you're going to be up at 30rps instantly.

[wind_comm]

since you're cramped for space, try a picossr and rewire the whole thing with 16 awg. it ought to help a boatload.

cyma motors are also slow as dicks, neo or not...so...yeah, you might want to try a different motor.

[Stealth]

My money is on motor and battery.

Cheaper to try a new battery for 30 bucks. Your mini NiMH isn't supplying enough current. You're starving the motor.

Alternately you can blow 60 bucks on a new motor but you're stuck with the same problem essentially. You're still going to starve the new motor but you're hoping you don't need to feed it as much juice in order to get to your wanted performance level.

BTW every single 13:1 setup that I've built has drawn at least 17A continuously. In comparison when using 18:1 gears I can build something that draws 11A. YMMV as current draw depends immensely on the motor. Numbers quoted are for ferrite motors made by King Arms, VFC, and TM.

John

[Hectic]

It is shimmed well (at least as well as can be in the crappy shell)
Im a lil OCD, okay alot OCD and i spent over an hour shimming tested it out and still wasnt happy and tore it all apart and shimmed the damn thing again (moving the one troublesome bushing i spoke of earlier) and spending nearly an hour shimming it agin till i was satisfied.
I was impressed by the wires in this gun they are alrdy 16 or 18 (not quite sure ill take another look but ill go over to that silver type stuff you sell Stealth as i think i still have enough of it around. Will also remove the tamiya connector and just run a lil extra length to assist in removing the gearbox as oppsed to the connector.
I will likely have to go poly for a piston head as i said befor about my parts guy not having POM as i figure aluminium will be too heavy.
I have ample room for a fet just not a battery (its just the way the sd handguard is set up so i guess ima have to go over to lipos then to take advantage of a high rof build if my other efforts dont pan out.

Is a ploy head really that bad?
So motor (is a lonex A1 okay for this?)
Shell (lonex so ill have bearing and a much smoother finnish inside and beter fitment of parts for ease of install)
And ill try n reduce a lil more weight off the piston and see how that does me.
Im greatfull for any further input. Thanks guys!

[Stealth]

Before you blow more money on new motors and parts, head to your local parts guy and borrow a 7.4v lipo capable of delivering more than 15A of current. If everything works perfectly then walk out of there with the lipo in hand.

Current draw = C rating x Capacity

Originally Posted by Hectic

It is shimmed well (at least as well as can be in the crappy shell)
Im a lil OCD, okay alot OCD and i spent over an hour shimming tested it out and still wasnt happy and tore it all apart and shimmed the damn thing again (moving the one troublesome bushing i spoke of earlier) and spending nearly an hour shimming it agin till i was satisfied.
I was impressed by the wires in this gun they are alrdy 16 or 18 (not quite sure ill take another look but ill go over to that silver type stuff you sell Stealth as i think i still have enough of it around. Will also remove the tamiya connector and just run a lil extra length to assist in removing the gearbox as oppsed to the connector.
I will likely have to go poly for a piston head as i said befor about my parts guy not having POM as i figure aluminium will be too heavy.
I have ample room for a fet just not a battery (its just the way the sd handguard is set up so i guess ima have to go over to lipos then to take advantage of a high rof build if my other efforts dont pan out.

Is a ploy head really that bad?
So motor (is a lonex A1 okay for this?)
Shell (lonex so ill have bearing and a much smoother finnish inside and beter fitment of parts for ease of install)
And ill try n reduce a lil more weight off the piston and see how that does me.
Im greatfull for any further input. Thanks guys!

[lurkingknight]

What I worry about going with a new motor or more power on a 90 spring is overspin... you're going to be bursting in semi auto with an A1 on a medium/high output battery.

[Stealth]

He's super reluctant to get a new battery so I think he should be OK.

Originally Posted by lurkingknight

What I worry about going with a new motor or more power on a 90 spring is overspin... you're going to be bursting in semi auto with an A1 on a medium/high output battery.

[Hectic]

Originally Posted by lurkingknight

What I worry about going with a new motor or more power on a 90 spring is overspin... you're going to be bursting in semi auto with an A1 on a medium/high output battery.

So perhaps stick with the 9.6 or even an 8.4 and the a1 or a dicferent motor all together?

[ThunderCactus]

If it's the stock wires, they're not nearly as good as the upgraded stuff. My G&P 249 used 14awg stock, upgraded it to 18awg silver plated copper and it still gained quite a bit of speed.

As for motor draw, without doing a ton of research, typical discharge for an NiMH battery is something like 2-6C, and highly dependent on who made the cell. According to the few RC forums I googled, the performance is just plain disappointing compared to LiPo. Someone feel free to correct that if I'm wrong.
Stealth's numbers for draw are spot on, now your 9.6v battery, I'm assuming 1500mah (intellect says 1600mah but that's bullcrap) at the peak of 6C (which I understand from RC guys to be extremely hard on the batteries) produces a mere 9A. Which is just fine for any stock marui aeg, and most stock guns.
But lower gear ratio means more torque on the motor and more amperage required. So you're absolutely starving the motor. Again I'm not sure how a 10.8 would stack up to a 7.4 on the 13:1 gearset, but since you don't have room for a 10.8, I don't see that you have much choice lol
And since the LiPo's are only around $10 each for that size, there's no harm in you trying a 7.4 before moving onto an 11.1!
Not to mention if you're using a 7.4, you could probably stuff 2000-2600mah in the same space as the 9.6 mini.

Motor may help a bit, but you'll never get full potential out of it unless you've got a battery than can keep up with demand
And for size reference, my old PTW batts were 20C 1800mah 11.1v and the size of an 8.4v mini. So a comparable 7.4 could be 20-25C and ~2500mah, maybe more around the size of a 9.6v

[lurkingknight]

there's different ways to approach it...

optimize the electrical first.. that's always going to help... then try higher discharge battery... since a high discharge lipo from stealth is like.. all of 20 bucks. Whereas the next step in motor is a neo magnet motor at 35+ (shs) 55+ (lonex) though if you go higher battery and motor, you run the risk of overspinning and if that happens you'll need to go from the other way... ie start with a 120 spring, cut teeth off the piston and sector to short stroke it back down to the fps you want.


edit:

on TC's post, if we follow the amperage to the battery, we look at a tunigy nanotech 7.4v lipo 20c at 1800mah ... 20x1.8= 36amps

[Hectic]

Okay so if im understanding correctly my battery is only capeable of turning my motor so fast because it maxes out it speed as it reaches the maximumbamperage the battery can give it.
So no matter what the gear ratio light piston and soft spring can provide in tearms of rof will never be realised if the motor cannot get more amps from the battery to turn faster.
So i can put a fancy motor and better wires and a fet to gain a lil rof but untill i feed the motor the amps it needs to turn faster i will never get the most rpm out of the motor thus never getting the most rps out of the barrel.

Sorry if thats over complicated thinking but is that basically the bottom line here?

[lurkingknight]

I would go bigger battery first... you could end up starving your new motor of amps as well with only 9 amps max output from your current battery.

[Hectic]

Well thats what im thinkin. I can buy a motor do wires lighten the piston more and piston head and still likely not reach my goal. or i can just pull the merf outta my m4 (cause i never will use both guns at once) and just stick a big lipo (maybe even an 11.1) in and almost definatly hit or exceed 30rps.

And with that idea in mind i have 2 questions for Stealth about the merf
1. Do i have to wire if to the trigger for arch protection if i go with an 11.1 (will be mostly semi shooting.)
2. If i have to. I only have the trigger wire with the 2 leads. If i remove one of the leads pin and all can i just use the dbl lead plug with the one wire and install it like that?

[Stealth]

Like I said, go and borrow a 7.4v lipo battery before burning more money. A mosfet, new motor, and whatever you want to buy wont help your cause.

Yes to both questions. Plug wire to the top port. With the double cable you're going to get confused.