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Originally Posted by Schmitty!
We connecting a 0.1uF 50V ceramic capacitor (available at any Radio Shack) from the positive motor lead to the case and a second capacitor from the negative motor lead to the case. The problem instantly went away and we've never seen it since.
From my interpretation of <R55> they are trying to protect against DC current through the frame like typically done in an automobile. This practice can be very damaging if it’s not handled properly. I believe connecting a small capacitor between the motor leads and the motor case (which may be connected to the frame) should not cause problems and shouldn’t be covered by this rule. Is this correct?
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In fact, a team in the Galileo division (was it 177?) mentioned a similar issue, with respect to the Globe motors interfering with the camera (due to brush arcing, especially on worn-out motors with large spark gaps at the commutator). They pointed out that a capacitor would attenuate the problem, but they also noted (correctly) that they were not permitted to install one as per <R59> since the capacitor is a custom circuit, and can't be connected in a way that "alter[s] the power pathways between...[the] speed controller/relay, and motor". Also, as you noted, <R55> remains in force and provides for no exceptions. For this past season, it wouldn't have been legal.
That team felt that it was an item worthy of FIRST's consideration for next year, because the effect ought to be minimal. Note, however, that I believe that their proposed solution involved a non-polarized capacitor across the leads, instead of to the frame or case of the motor.