Modified Xmod motor running VERY HOT!!!
 

My Xmod is on 2x2 FETs with Atomic's 7.4V 2S2P Lipo Pack and an Atomic Stock R motor - I cannot even use it for more than 5 mins before the motor is EXTREMELY hot! I can even smell it if I take the body off. If I let it cool down it runs fantastic again but it should not be like this correct?

What could be wrong? :(

um probably frying the motor... try getting a larger stack of fets as well as inventing some new cooling methods

first off, do u have a heat sink?

what's "extremely hot"
i could smeel my stage 2 upgrade if i drive it extremely hard too, but its not what i would call "emtremely hot" its just hot, which is fine for me

My rule of thumb is if it's not smoking, melting, or burning it'll do.


But then again have like 5 blown boards in my junk bin lol

did you flip the motor brushes?

Gear lower and check for ANY binding.

As said if you haven't flipped the brushes, DO SO. If you have, Gear lower AKA bring the gear ratio UP or in other words gear for torque.

Hi guys,

Yeah I do have a heatsink on top and I did flip the brushes as per atomicmods video. I did not change the gear ratio though, what do you guys suggest?

Oh and when I say its hot, its VERY hot. Last night I let it spin off the ground (while holding it) for about 20 seconds and I saw a little smoke :( It still runs the same though... wierd...

did you break the motor in before running? and do you use come drops? and lastly, how freely does the car roll?

How long have you had this setup? I think the problem might be is that the Stock-R cant handle the 2s2p, as crazy as it sounds it seems like it is getting too many amps and heating up. After all 2s2p is nearing the overkill zone. I would recommend the lowest or second to lowest ratio for gearing cuz witht he 2s2p you will still be going uber fast.

Yes I used the comm. oil and I did break it in. It does not roll VERY freely but it does have the AWD kit installed...

Thats what a friend of mine said too.... what gearing do u guys suggest I use?

welll sadly, in order to get any gearing done you will need the stage 2 motor kit for the gears. You want the largest spur and the smallest pinion (in this case, an 8 tooth). or doing something liek thsi might help too http://www.freewebs.com/frxcustomxmo...se%20xmods.jpg

If you need some gears send me a PM. I have a spare set.

Thanks but nm, I was showing a friend how fast it was and in less than TWO mins in burned the motor out, melted the wires on the motor - I am not upgrading the motor on it again - probably gonna return to AAA's and put in the Speedy07BB motor.

I think the Lipo's I bought from this guy on Ebay were kinda messed up too. They were atomicmods but he let them go totally dead it seems (I checked when I receieved them)... although charging them worked out, they just seem to go dead sooo fast and get hot too.

Just for future reference this is not a viable solution. A larger stack of FETs will never help the motor run cooler.

The second suggestion is good though.

Ok just a quick question, if I switch back to 4xAAA and the Speedy07BB which is made for a stock setup, will the 2x2 FET stack be okay or will it affect anything? ie. Can I just leave the FET stack in there??

yes u can, nothing will happen but more acceleration will be gained

Not a HUGE amount, but he is right. Acceleration will be improved, but not by a lot. Most likely not noticable.

Your motor is running hot because of:

1. High or low gear ratio
2. The lithium adds lots of extra power.. therefore it will obviously heat up more
3. You have not properly broken in your motor, so your brushes are barely having any contact with the commutator, so all the power goes to whatever contacts with the commutator. Stock, there is not enough contact, so your motor starts to spark and heat up, when you see 1 wide streak, that is when you know the brushes are fully in contact with the commutator.
4. Check for bad solder joints, loose screws (poor contacts = higher resistance = heat)
5. You have a dirty drive train (clean out your bearings and possibly replace your gears if they are worn out)

I have run a speedy 07 bb in my mini-z (mr03) and when you have 2x2 fets (my car), you will notice there is a slight bit more punch. Reason for this is that there is less resistance when your fet stack increases. Compared to your stock fets, if you stack those, you will notice your motor will not gain full power and the punch will be less compared to higher grade fets and stacks. To comment on someone's post about gearing down, that is actually worse than gearing up. The reason is because the motor will reach a certain rpm faster compared to a lower gear ratio. More teeth = more effeciency, so you want to get the lowest ratio you can before you start to drastically loose acceleration and start noticing heat issues....

good info glad i read this before going out and buying stuff