Installing Motor Capacitors

[EddieO]

Motor caps do nothing I have ever found to make the comm last longer. This has been tested over and over...the slot car guys will do anything to make a comm last longer and they don't add caps to any motor. They simply swallowed the noise the comm created that would that cause radios to glitch. I (among many others) have done blind tests with or without caps installed....and saw no difference in wear. Caps are installed on the endbell, where they won't do anything useful to the comm until after its already happened really, especially the size we use.

There are other devices that can be used to alter comm wear, but they need to be installed on the armature itself....they won't do anything up on the endbell...

Later EddieO

 

[Olle P]

The claim that those tiny capacitors prolong the commutator's lifespan is interesting. Do you have any proof?

No proof, just sound reasoning:

1. Sparks occur at the commutator.
2. The sparks add wear to the commutator. (As well ass white EM noise.)
3. The capacitor(s) are there to reduce (eliminate?) the sparks, and by doing so the wear should be reduced as well.

 

[EddieO]

No proof, just sound reasoning:

1. Sparks occur at the commutator.
2. The sparks add wear to the commutator. (As well ass white EM noise.)
3. The capacitor(s) are there to reduce (eliminate?) the sparks, and by doing so the wear should be reduced as well.

The reasoning is flawed though.

The sparks are created at the comm, by the act of the switching and friction (mostly). Nothing coming IN the motor really causes them...so the sparks happen after the power has passed through the caps....and once they happen, the cap can't go back and reduce them....they simply filter out the byproduct of their creation, the EM noise.

The caps do not reduce the arching at the comm....they simply swallow the noise the sparks make after the fact...

Later EddieO

 

[JohnRobHolmes]

I did testing earlier this year and found no measurable difference in wear between a motor with emf caps and without. I used 13t motors driving fans. In a situation with constant reversing the results may be different.

There is a major difference with higher slot motors and round brushes though. 5 slot armatures wear longer than 3, and round brushes can double motor life.