Re: Legally Increasing Motor Performance
 

Where's Richard when we need him?

(Sorry Richard. See what happens when you do something valuable - you get people like me asking for more. Just think of it like my version of the Founder's Award).

Actually, I want to say "thank you" again for Richard's Tetrix motor characterization that he did. That was one of the most influential publishings in the history of FIRST.

Re: Legally Increasing Motor Performance
 

This has been a great discussion thus far, and is much better than the fragmented and contradicting bit of info I pulled off the internet last night.

So, the target motors are:

• Short duty cycle applications where weight & maximum power are key
• Motors without internal circuitry

For example, we wouldn't do this to our FP-673 motor on our lift for the 2011 game since we can counterbalance the lift to reduce the load, thus giving us a 0.5 second lift if we gear for it.

Yet if we found a usage for the RS-395 motor on a lightweight appendage, there may be merit in this.

Re: Legally Increasing Motor Performance
 

I am following this thread with interest, because I have no experience with RC race car motors, and had not previously heard of underwater "wear in" as a method of reducing commutator friction. I had noticed a similar effect when testing fuel pump motors that run submerged.

In most of the applications for which I have designed or specified electric motors, service life requirements would preclude any pre-treatment that can reduce the life of bearing surfaces. However, RC racing and FRC don't have that constraint -- so this seems like a reasonable idea.

I'll try to conduct some before-and-after tests to quantify the benefit of underwater wear-in for Tetrix motors, when we get some spare time in my lab. Can someone provide a protocol for this, based on experience with Tetrix or similar motors?

Re: Legally Increasing Motor Performance
 

Richard,
Our mechanical team simply connected them to a power supply and dunked them in a bowl of tap water. Let them run over night, and then blew the water out with compressed air. One of the motors failed after a lengthy practice one day so the crew took it apart. There was a noticeable effect on the contour of the brushes. While we took no accurate data, the drive team is convinced that the run current went down while the speed went up.
I would conclude that the brushes produced a lower resistance due to the contour, brushes likely stayed in contact with the various commutator segments for a longer period of time, and had sufficiently worn the bearing surfaces to produce less friction. I can buy the increase in speed due to the contact time and reduction in friction. I suspect that the current reduction may have more to do with the reduced friction than with anything else.

Re: Legally Increasing Motor Performance
 

For championships, we ran all of our motors under water for at least two hours and noticed an increase in performance.

We bought a bottle of distilled water, submerged the motors in the water and then hooked them up to a power supply. We set the power supply to 5vdc and let them run in for 2-2.5 hours.

Before we ran the motors in, their free load current draw was ~.25A. When we finished running them in and dried them off their free load current draw was ~.15A.

We saved the water from the first 2 or 3 motors and you'd be surprised the amount of junk that came out of those motors.