Burning smell ?

[CQB-Man]

Hi guys,

I just purchased a kwa m4 CQB off a forum and I can smell a slight burning smell from the gun on Semi and full auto is this normal ? Also the handgrip gets quite warm quickly on a 8.4v battery ?

please help guys I dont know much about guns and I'm not sure if this is normal.

Cheers

[chemo]

Re: Burning smell ?

I sometimes have this problem but when I am constantly on full auto, but I'm guessing low awg wiring?

[loki7491]

Re: Burning smell ?

No, it is not normal!

I have never known an AEG where it is normal to feel heat through a pistol grip.

You have an electrical fault of some description. The motor is trying to draw too much current from the battery and over heating. The most common fault is the motor working too hard either because of internal failure or because of incorrect adjustment of the motor into the gearbox.

There is the chance it is a battery or wiring fault, but that is less likely.

1. I suggest you strip down the pistol grip and test the motor out of the gun.
If the motor overheats, disconnect and put to one side.

2. Repeat with a spare / borrowed motor.

3. If the motor stays cool (you don't melt your hand when touching it) your original motor was at fault. Replace it.
If the borrowed motor over heats, the gun or the battery is at fault.

4. Repeat steps 1 & 2 with with a different battery
No overheating, battery is goosed. Bin it.
Overheating, fault lays within the wiring of the gun - go to somebody with tech know how, give puppy eyes, open wallet!

If you have entirely no idea about what i just wrote, find tech guy, give puppy eyes, open wallet!

In all seriousness, less than 15 mins to locate fault to motor, battery or gun... more time to fully diagnose if fault located in gun.

Hopefully you will know somebody or can do this yourself... save your £££££s for the important stuff like replacement parts, not fault diagnosis.

[RedHawk]

Re: Burning smell ?

Loki, another cause is that the gear is pushing down too hard on the bevel gear. This can cause friction, and as 99% of the motor is metal it conducts through said metal and can be felt on the pistol grip.

Alternately as you said the motor could just be a sh*t motor in which case needs replacing.

The only other cause I could think of is the fuse or wiring. When I had a MOSFET on my AK47 Spetsnaz, the grip warmed up as did the wiring, removed the MOSFET and it worked fine.

[Orion1]

Re: Burning smell ?

Contact the person and explain the situation.

[loki7491]

Re: Burning smell ?

Are you sure?

I know poor engagement (too far in) would cause the motor to over heat through working too hard (drawing too much current from the battery) but he would have to be using the "empty a box mag in a single trigger pull" for the friction heat to pass through the bevel gear, down the spindle, heat the air inside the motor to such a level that it in turn heats through the motor walls and then heats the gun handle!

You are correct in your diagnosis of incorrect adjustment causes overheating,, but i think your reasons for why are a little off centre.

I could be wrong as i have never tried to do it, but i am sure the motor would overheat due to excess current faster than it would due to transfer of friction heat.

EXAMPLE: FOR THE LOVE ALL THAT IS RIGHT WITH THE WORLD - DO NOT ACTUALLY DO THIS!!!
Spin a drill against the element from your toaster or kettle and see how long it takes it to get red hot... then plug them in, turn them on and time that method!

[Orion1]

Re: Burning smell ?

My mate had a old 2003 ICS that heated up its pistol grip when you fired.

Not sure if it helps but just a bit of info.

[loki7491]

Re: Burning smell ?

Do you mean it over heated in normal operation and it lasted for years and worked fine?

or

It overheated cos it was bustimicated and needed some sort of work to rectify the problem?

[Orion1]

Re: Burning smell ?

Just get in contact with the guy and get your cash back.

[RedHawk]

Re: Burning smell ?

Are you sure?

I know poor engagement (too far in) would cause the motor to over heat through working too hard (drawing too much current from the battery) but he would have to be using the "empty a box mag in a single trigger pull" for the friction heat to pass through the bevel gear, down the spindle, heat the air inside the motor to such a level that it in turn heats through the motor walls and then heats the gun handle!

You are correct in your diagnosis of incorrect adjustment causes overheating,, but i think your reasons for why are a little off centre.

Well it's a shame I have first hand experience telling me otherwise then isn't it. You're right in saying that too much contact with the bevel gear would cause heat energy, but it's also due to friction between the pinion and bevel gear. When the motor can't spin properly the energy doesn't become kinetic, rather transforming into heat energy (it doesn't just disappear ). If your pinion head isn't properly engaging, or is pushing too far in then both of the above become a problem. You're underestimating the effect of friction, which happens when two surfaces rub together.

I installed a G&P M120 motor in my Spetsnaz and while adjusting the pinion gear height it was crunching (rather badly) on the bevel gear. The motor cage wasn't at the right angle and for some reason was pushing the head way too far towards the bevel gear in comparison to my AK-74. I was only using an 8.4v 1600 mah battery and after having shot the gun 5 times for 5 second bursts the motor was almost too hot to handle. The pinion gear was hot too - go figure.

[loki7491]

Re: Burning smell ?

I have an HND in engineering, i am fully converse with friction, heat transfer, the specific heat capacity of matierals and their relationship with other with regard to heat transfer... i also know that it doesn't just disappear.

Over time, friction will heat and that will transfer... however, firing on semi auto or even full auto bursts, there will not be sufficient time in between periods of not shooting for the heat to build up to the level you are referring to.

Electrical current heats up more efficiently (faster) that that sort of friction ever could.

Friction welding went out when God was still at primary school (aside from specialist applications) and the use of electricity has been used ever since.

If i can use 24volts @ 300amps to arc air gouge through reinforced steel joints, i am pretty sure that 9.6 volts or similar with a lower ampage can heat a motor faster than friction in a short trigger pull.

Anyways, we are hijacking this thread, feel free to PM me if you would like to continue this.

[baddbaz]

Re: Burning smell ?

Also the bearings / bushings in gearbox could be binding/ seized or collapsed which will cause the motor to strain and overheat whilst trying to move the gears or could be no grease/ lubricant in gearbox causing the same binding issues with the gears . The wiring shouldn't overheat unless the motor is struggling to move something that is binding . If a v worn gun could even be the motor shaft bearings have worn out !!!!

[seansamurai1]

Re: Burning smell ?

Loki is right though, the motor height if adjusted wrong will add extra load onto the motor making it work harder and creating higher current draw to force the motor to turn, in turn this high current draw causes heat. Energy cannot be destroyed, only converted.
The mosfet issue is because the gates more than likely not opening correctly causing the mosfet to draw more current which in turn heats up the system.

[sparrowhawk]

Re: Burning smell ?

anyway so you need to lower you motor a little bit to reduce the friction and reduce the current draw caused by the extra friction, or get a motor that needs less draw, or change the battery to something that gives out more amperage,anything over 40 amps should be ok...... did the seller provide the battery or you?

[Fabio]

Re: Burning smell ?

Check your motor or battery, could be the motor height