Trued Armatures

[eap9]

I would to know if the armature timing becomes more advanced when the commutator diameter gets smaller from being trued?

I have had these experience on my 38 degree x-12 arms that after I have trued it twice, the motor loses torque but gains more rpm.

[wjdougherty]

I would think it less likely caused by the comm shifting thereby causing a change in timing. Could it be more likely a case of smaller circumference of the comm allowing the comm to rotate through it's surface faster??
WJD

[ET37]

Armature timing does increase as the comm gets smaller!

[jake]

I think it's because the com, being smaller in diameter, is swept through a greater arc by the brush, which, although the same size, is wider than before relative to the com. There are cases where the brush will cover the com TOO much and you'll get more heat and some loss of performance.

Regards/jj

[eap9]

My next problem is since the motor's torque has decreased and the rpm increased, I have to compensate by lowering the gear ratio. As a result the brake increases which is not so ideal for wing car racing.

Should I just use stronger mags with extended tips to increase the torque so I can use a higher gear ratio and reduce the brakes?

[Phil I.]

;) Cut the trailing edge of the brush to shortin the overlap time! It will cut some heat and brake. Do the leading edge if you want to kill some timing.
PHIL I.;)

[eap9]

Hi Phil1. Can you please elaborate more as I dont know what you mean by cutting the leading or trailing edge of the brush.

[Phil I.]

When the comm is cut, the brushes will wrap around the comm more cause the comm is smaller than the width of the brush. The smaller, the more wrap around. The timing on both sides is more so you have higher,50 V 48 deg.timing as an example, and more overlap ,where the brushes are shorted out. What you can do is cut the trailing edge 1/64 in. back 1/3 of the way towards the spring. This will kill about 3-5 deg.overlap. Or you can go to virtical brushes and hoods that do the same but are $.
I have thinned some when they have run hot. It helped on some, some it didnt!:D
Good luck,
PHIL I.