Juicer/Drill Problem: Rotor Repair/Replacement

Hi Guys,

I have a juicer and a drill machine and both show same symptoms. Both get excessive hot and a burning smell is emitted when used for sometime. Also they lose power when this happens. Juicer auto shuts when this happens and then becomes operative after 10-20 minutes while drill, having no protection mechanism, keeps emitting smoke with burning smell and I have to stop it.

I suspect it is the rotor which is causing this. bushes seem fine and also shopkeeper suggest they are fine. They advise to change whole motor for juicer while for drill they advise to buy new instead of trying to repair.

I am looking for my options. is there a way I can only get a rotor from somewhere and replace it instead of replacing whole motor? I love to do it DIY.

Thanks,
Nasir.

Your motors are lacking proper “Commutation” due to the shorted commutator. Take out the rotor, clean the gap (very carefully) between adjacent copper strips on the commutator. There would be lot of carbon, dust, oil etc. Use a sharpened wood stick / tooth pick type thing or some plastic tool. After cleaning, wash the commutator gaps with Alcohol using old tooth brush.

Examine the surface of commutator where carbon brushes make contact. If worn out, you need to get it flat on a lathe.

Change the carbon brushes and hopefully all your issues should be solved.

Thanks for the reply Ijaz bhai. I already cleaned the strips with ctc and tooth brush and they seem clean. Also I took out the carbon brushes and took to the shop to buy similar type but shop keeper said these brushes are not so worn out and can work fine.

However as you advised I will open it up again and get new brushes. A small portion of strips area is little damaged. I am attaching image of the rotor so you can see the current position and advise.

https://file.io/o4CFCq

Cheers!

Check spring tension behind each brush. Also see if brush contact pattern on carbon is shiny or has carbon smoke burn marks. Maybe brush contact with commutator was too light, increasing resistance and causing overheating…

If you have (or can borrow) a multimeter, check the resistance of stator windings to see if they are equal and reasonable. Also check resistance of each pair of rotor windings through opposite commutator bars to see if they are equal. Maybe one winding has failed due to age, humidity or overload.

Finally, check all wiring and switch for loose connections/carbon buildup.

Thanks for reply @AIF bro. I will certainly check and possibly replace brushes. Yes I have DMM and can check resistance of stator and rotor accordingly and will report back.

Cheers!