Motor melt down...
 

Hello guys,

Could someone tell me how can i solve the problem as my title says?

I m running a reedy kr 12x1 motor in my lazer zxr with mrt pro esc and nosram 3700 mah cells + 4200 ib cells . All the soldering iron which holds brushes, capacitors and wires on the motor after 2-3 minutes of running is melting. The strange part to me is that it is happening everytime i use the intellect cells . Motor was recently skimmed and fresh lay down brushes were installed, I dropped from 19t pinion to 16t but problem continued . For some reason though all previous mentioned is not happening when i m using my 3700 mah Nosram cells and i m able to empty a whole pack without a scratch. Is it possible that batteries might be the problem???If yes how can i fix it ?.?

Any advise will be highly apreciated,

Thanks

have you tried a different motor?

Check your motor for any possile shorts, i.e make sure nothing in the slots of the comm. Check the windings look ok, and on a KR check the magnets havent moved. Also check the timing (position of the brushes relative to the magnets).

Other possibility is something in the drivetrain of the car is binding... take the pinion of and check everything rotates nice and free.

More capacity equals more run time, and this can cause the motor to overheat.

I assume you are running on grass, 16 to 100 gear ratio is too long for running on grass with a 12x1. I used 15-16 with 12x3 while running on dirt many years ago with that car and 1700 cells and it gets extremelly hot.

Might be worth checking the solder your using as well!!

I can try a more "heavy duty solder" ... You have any suggestions about the brand or type which i can use???

I believe (although don't quote me) that silver solder has a higher melting temperature than regular solder, the high silver content should increase the conductivity too.

JVC 100 watt, the very best

The reason it is only happening when using the IB4200s is because of the cells. IB4200s have a higher voltage than other cells, which is why even though they are the least reliable cells you can get all the top touring car racers won't use anything else. It sounds like using the 3700s the motor is just within its limits and using the 4200s just goes over the limits.

A 19 tooth pinion is too big for 12 turn motor, the 16 tooth pinion should help but the motor should not be getting too hot to melt solder. As the motor has recently been rebuilt if the timing on the endbell was not set correctly and is too far advanced the motor will overheat very quickly. Lowering the timing on the endbell will reduce the current draw so making the motor run cooler.

The timing is set at the lowest point....what if i remove 1 cell and make them 5cell? Will it be improved?

You will have 16.66666% less voltage so that will solve some of the problems, but you will also have 16.66666% less power!

Use Deans solder and a decent iron. Have you got any holes in your shell? You might just have no ventilation to help cool everything.

Removing a cell will not neceserily lower the running temp you will lose a bit of top end and also some bottom end grunt but you probably wont lose any runtime either, you could possibly gain some.:o It`s true, the only problem is when running IB`s with 5 cell they will only be good for about 5 runs before they lose their edge.

The KR isn`t really the best motor to be using off road in my opinion as i have found they are all revs, ideal for on road but wouldn`t really pull the skin off a rice pudding.

Buy a checkpoint or a brushless;)

My 12x1 KR is ballistic both on acceleration and top end, try gearing it properly ;)

I suppose we just wound the timing up till the endbell nearly fell off and geared them to the moon.

Good old tourers:yawn:

As Southwell said my KR goes like crazy with the 3700s on. Also afterwards i m able to hold the motor in my hand without getting burned,which i suppose is a good sign of proper gearing and good performance. All the problems start with the IB 4200s on....I ll try to change the solder with DEANS , make a few holes near the motor area and see the outcome this saturday. Hope it works ...:rolleyes:

Don't forget to cut out the back section of the shell to allow proper air flow.

Well friends as i told you 4 days ago today i went at my local track and tried my car to see how the motor would respond on the changes made (used deans solder + holes on the body for ventilation).Also i tightened the slipper so that i dont waste time on motor rev up , and the result ....?!?!??!
- 1st pack (nosram 3700) - worked perfect - inspected motor and no problem seen , brushes are still ok , solder is in place
- 2nd pack (nosram 3700) - worked perfect - inspected motor and no problem seen ,brushes are still ok, solder is in place

- 3rd pack (ib 4200) - worked perfect with motor temp around 75oC - but now brushes have taken a dark blue colour and their size is reduce by 15%, solder is in place

- 4th pack(ib 4200) - after 2 minutes of run motor stopped . took it for inspection - 1 brush was unsoldered , brush size was decreased almost 70% , colour was like an aubergine and last ,rotor (at the point were brushes are touching) was black like coal.

I honestly dont know wht to do......

Reedy motors in 4wd's do not last long, you would have unsoldered because it overheated, probably from wrong gearing or the worn brushes and ib cells. Put a V2 in it and you should find it is better. When i tried a KR in my 4wd it lasted two runs before it needed skimming, my V2 lasts at least a meeting.