RC Drive (sensored) RPM specific judder and power interrupt

[mlt34]

With hindsight I'd have been better fitting the Halls internally, as I've done on a few other motors.

That's awesome that you're running a milling machine off an outrunner. In regards to internal halls, do you lose the ability to adjust timing that way? I assume you mean placing the halls in between stator arms at 120 degree angles, which would mean you're stuck with no adjustment longitudinally around the motor, right?

[mlt34]

I believe my problem was with eddy currents inthe aluminum around the bell causing magnetic fields that confused the halls. Of course this didn’t dawn on me until my next build. This design also had aluminum about the bell. Jeremy was kind enough to point out that I would be losing power by creating eddy currents. It seems reasonable to me that eddy currents were also causing my problems on build 4.

Bubba

That's very interesting. My mounting plate is a solid block of 1/2" aluminum. If what you are saying is correct, it sounds like this could be a likely culprit for my problem. Maybe I can mount it on a block of a wood or plastic temporarily and see if I get the same issue.

[Jeremy Harris]

With hindsight I'd have been better fitting the Halls internally, as I've done on a few other motors.

That's awesome that you're running a milling machine off an outrunner. In regards to internal halls, do you lose the ability to adjust timing that way? I assume you mean placing the halls in between stator arms at 120 degree angles, which would mean you're stuck with no adjustment longitudinally around the motor, right?

TBH, running the milling machine on an outrunner wasn't my original idea, I pretty much copied the set up Matt (recumpence on here) uses on his milling machine. The power of these little motors is way more than the power that the standard fixed speed motors give, IIRC the fixed speed motor for my little milling machine is only about 1/4 hp. I can run at around 1 hp or more on the outrunner.

You're right, fitting the Halls internally means no timing adjustment, but in practice all the motors I've done this too have worked very well indeed like this, better than the one motor that I tried external Halls on.

[nieles]

You're right, fitting the Halls internally means no timing adjustment, but in practice all the motors I've done this too have worked very well indeed like this, better than the one motor that I tried external Halls on.

if you mount the sensors internally, you have the choice of mounting the sensors in 4 different slots, 2 of those options will give neutral timing (it will run the same rpm forwards or backwards) and the other 2 options will give you either 30deg advanced or retarded timing.

if you know the winding pattern of the motor, you want the sensors in the slot between two phases (eg beteween ab, ca and bc).

if you dont know the winding pattern you can run the motor with the halls not permanently installed and see how the motor runs both forward and backwards.
if it runs the same rpm(and no-load current) both ways you have neutral timing (with the correct phase and sensor combination ofcourse). if this is not the case, move the sensors over one slot (doenst matter which way) you will have neutral timing