motor leads getting warm.

[Jimski]

hey all
when using my 11.1 lipo on my m4 that has a mosfet and uprgrade motor, motor leads don't get warm.
when using the same battery on my mp5 that has no upgrades, the motor leads get very warm on 'furious single' mode.(lots of shot in single)
-is it something that a motor or mosfet can get rid of, hence no heat on the m4 ?
-is it related to something else ?

thank you!

[Hectic]

i dont think anything is wrong. At least not majorly.
especially in quick semi you will generate heat. Bad shimming. Motor height adjustment. a strong spring. Can all cause heat but "a little warm" is somewhat normal. I had badly.shimmed an m4 once and if you dummped a mid cap in semi in quick order the grip would be hot. Like almost too hot to hold.with.bear hands. in full auto it would.only.get warm. I reshimmed and.it was better. Still would get warm but not hot. 400fps 13:1 gears 11.1 1200mah lipo merf 3.2 was the setup

[Jimski]

Ah ok thx.I'll definitely check the mechbox.

[lurkingknight]

semi fire is a lot harder on the motor than full auto. More power is required to get the system moving from a dead stop. Basically you spike the system every time the trigger itself is pulled.

More pulling means more surging which generates more heat.

Some motors get hotter than others in this kind of heavy use. Some motors also draw more amps (stronger neo magnet motors).

It would be helpful to know what the amperage draw is on your motor, if you have access to a watt meter it can help determine if you have good shimming or not as well.

I've observed stock motor setups drawing as low as 13amps and higher powered motor setups on massive springs and fast gears drawing 30 amps constant, with spikes into 50-60amps.

mosfets also take some resistance out of the wires since they bypass part of the wiring, you could be seeing some benefit from the upgraded gun.


To give you some comparison, I just happened to reshim my g36 on 13:1s this week. I replaced the soft lonex pinion that was getting mangled in the shs bevel, and the profile of the pinion changed, requiring a change in shimming. The gun drew 24-26amps on an 11.1v lipo before the pinion change. After with no change to the shimming it could not adjust below 29amp draw.

After reshimming the bevel to match the pinion much better, the draw dropped to 22amps. The motor ran much cooler after extended firing than before the adjustment in shimming.

You may want to test the system with a less powerful battery. Stronger motors and big batteries sometimes hide sounds suggesting motor height or shimming issues because they cycle happens so fast with 13:1 gears.

[Jimski]

Oh , this gun runs with no heat with a 9.6 nimh.

[ThunderCactus]

there's more wattage coming out of a lipo, therefore more heat
The resistance in the shitty stock wiring alone will cause a lot of heat buildup

[Jimski]

aside from shimming, what's the best way to avoid this heat build up? what wire do you use?

[ThunderCactus]

low resistance silver coated copper, in as large a gauge as you can fit
And also add a mosfet
heat will buildup ONLY where the resistance is, so if heat builds up in the wiring, it's a wiring problem. Heat will buildup in the trigger because that adds a huge amount of resistance. There's also the arcing issue of using an 11.1

Anyway, the wiring will fix the heat buildup in the wiring, but not in the trigger. And since you're rewiring the gun anyway, might as well get a mosfet too

[Azathoth]

Originally Posted by Jimski

aside from shimming, what's the best way to avoid this heat build up? what wire do you use?

When you say motor leads I assume the terminals on the motor and the wiring to the motor is getting hot. So what quality wires/solder/flux are you using for the connection?

Solve with low resistance single strand silver wire with teflon jacket (MILSPEC) in the LOWEST gauge you can fit (thicker wires) and quality solder/flux.

[Jimski]

ok thanks a lot for the advice gentlemen.

Azatoth unfortunately it is a stock motor in a mp5, it isn't soldered, it uses some kind of plug.I will try to replace them with something better when rewiring...

[lurkingknight]

unfortunately it's not like a v6 or v3 so you can't solder the wire directly to the motor tabs. Those guns have a slight edge in that you can eliminate those points of resistance because the slip on connectors can also be a source of resistance. I would invest in a pico fet at the very least if you're going to rewire the gun.

[ThunderCactus]

you can still solder them direct to the brush hoods, it just makes it a pain for any gunsmith to work on the gun after lol

[lurkingknight]

yeah no, I wouldn't do that... you probably couldn't get the motor into the gearbox with that much slack.. and if that didn't work you'd have to take the end bell apart.

[ThunderCactus]

Not sure what you mean, I've worked on 4 M4's that had the leads soldered to the motor. No extra slack on the wires, you just don't hold them there by hand like a derp when you're soldering them lol
It's not difficult to do, it's just a pain to work on afterwards.

[Jimski]

mmh yes, but since I don't plan on opening my guns every day, it could work out...