fyrstormer
RCC Addict
As the title states, this question is for JohnRobHolmes, but the reason I posted it publicly is because the answer may be of interest to people other than myself.
When I first started my grand adventure into running brushed motors, I quickly found out about the existence of "standup" and "laydown" brushes. At first I didn't understand the difference, but once I actually got two motors with those different brush configurations in my hands, I was able to see that laydown brushes contact each pad on a standard 7.5mm commutator for a larger percentage of the armature's rotation, so each armature coil will stay energized for longer. This obviously means the motor will produce more torque, but I also noticed a big problem: Standup brushes already come close to touching opposite edges of the same comm pad, and laydown brushes actually do. That means there's a period of time during each phase of the armature's rotation where laydown brushes cause a transient short-circuit through the comm pad they are both touching. For a high-speed application such as racing, these transient short-circuits exist for such a short amount of time that the effects are probably insignificant. But for a crawler application where the motor may be stalled or nearly-stalled for several seconds at a time, these transient short-circuits could pose a serious risk of overheating the comm and/or burning the edges of the brushes. So I have stuck to running standup brushes in all of my brushed motors thus far.
However, after examining my new CrawlMaster motor, this problem doesn't appear to exist for a 5-slot motor. The comm is divided into 5 pads instead of 3, so each pad is narrower, and even the extra width of laydown brushes will never cause them to contact both edges of the same pad at once. So it would seem that 5-slot motors could benefit from the higher torque generated by running laydown brushes, without a significant risk of damage to the comm or brushes due to transient short-circuits at low RPM. Buuuuuut, the armature coils in 5-slot motors span 2 armature slots apiece, so the coils overlap each other unlike the coils in a 3-slot motor, and that may cause effects that I don't know how to predict using my meat-brain.
So, finally, my question: Is there any chance that running laydown brushes in a 5-slot motor, thus keeping each coil energized for longer, could cause the overlapping coils to end up "fighting" each other due to generating overlapping magnetic fields of opposing polarity? If the coils won't end up fighting each other at any point during the armature's rotation, then I'm inclined to try laydown brushes and enjoy some extra torque from my motor; otherwise, I'll stick to standup brushes like I've been doing thus far.
When I first started my grand adventure into running brushed motors, I quickly found out about the existence of "standup" and "laydown" brushes. At first I didn't understand the difference, but once I actually got two motors with those different brush configurations in my hands, I was able to see that laydown brushes contact each pad on a standard 7.5mm commutator for a larger percentage of the armature's rotation, so each armature coil will stay energized for longer. This obviously means the motor will produce more torque, but I also noticed a big problem: Standup brushes already come close to touching opposite edges of the same comm pad, and laydown brushes actually do. That means there's a period of time during each phase of the armature's rotation where laydown brushes cause a transient short-circuit through the comm pad they are both touching. For a high-speed application such as racing, these transient short-circuits exist for such a short amount of time that the effects are probably insignificant. But for a crawler application where the motor may be stalled or nearly-stalled for several seconds at a time, these transient short-circuits could pose a serious risk of overheating the comm and/or burning the edges of the brushes. So I have stuck to running standup brushes in all of my brushed motors thus far.
However, after examining my new CrawlMaster motor, this problem doesn't appear to exist for a 5-slot motor. The comm is divided into 5 pads instead of 3, so each pad is narrower, and even the extra width of laydown brushes will never cause them to contact both edges of the same pad at once. So it would seem that 5-slot motors could benefit from the higher torque generated by running laydown brushes, without a significant risk of damage to the comm or brushes due to transient short-circuits at low RPM. Buuuuuut, the armature coils in 5-slot motors span 2 armature slots apiece, so the coils overlap each other unlike the coils in a 3-slot motor, and that may cause effects that I don't know how to predict using my meat-brain.
So, finally, my question: Is there any chance that running laydown brushes in a 5-slot motor, thus keeping each coil energized for longer, could cause the overlapping coils to end up "fighting" each other due to generating overlapping magnetic fields of opposing polarity? If the coils won't end up fighting each other at any point during the armature's rotation, then I'm inclined to try laydown brushes and enjoy some extra torque from my motor; otherwise, I'll stick to standup brushes like I've been doing thus far.
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