Quote:
Originally Posted by Chris is me
I've heard from a team that tested such an idea that the gain was not big enough to counteract the magnet weight.
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57 discovered that a FP/540 flux ring fits nicely around the Tetrix motor. We thought we were geniuses and fitted out a pair to see if it made a difference, planning on modding the two Tetrix trannies into pseudo flux rings. We didn't see a discernible difference in performance, however. I'm surmising that the rotor is saturated and dumping additional magnetic flux in there isn't going to greatly improve matters.
Quote:
Originally Posted by eagle33199
We didn't do any real scientific tests to see how motor output changes, but we did try this with a Tetrix motor! Start by hooking up a motor and listening to it. Then add a magnet - you can hear the pitch of the motor change! Moving the magnet around, you can tell that the pitch increases if you're adding to the magnetic field, and decreases if you're subtracting from the field. It's important if trying this to find the "sweet spot". Using a multimeter, we tracked the input current while doing this... using a magnet results in a significant increase in current through the motor, based on our observations. Given the Tetrix motor's enthusiasm for burning out (and their ridiculously high cost), we stopped our experimentation there - no need to encourage them to burn out faster... but it's enough to convince us that you can significantly affect a motor's performance by adding magnets to the casing!
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You can certainly affect motor performance with magnets on the case. The question is whether you can significantly improve it or not. You were likely changing the orientation of magnetic flux in the motor as well as changing the strength of it. That would effectively change the brush advance of your motors, changing the performance at high/low speeds. You can tell if you're changing the brush advance of the motor because it will run differently in the forward vs the reverse direction.
The theoretical ideal brush advance changes with rpm and current draw, so it's going to be different at different points on the pole. It'd be really interesting if you could rotate the magnets around the motor as it climbed to change your brush advance dynamically as your bot climbed the pole. Or you could just go with a magnetic minibot + ramp and hit top speed before you even get to the pole.