motor(s) for very low speed operation

Hi Folks,

I'm trying to build an electric walker for my dad (see https://www.youtube.com/watch?v=1FSWf8vG0kI starting at 1:30 for what inspired this). Think of it as a very wide electric longboard with handrails.

Motor selection is becoming an issue - mechanically, the ideal would be a dual-hub motor skateboard truck (like http://diyelectricskateboard.com/diy-electric-skateboard-kits-parts/electric-skateboard-hub-motor-dual/) - with steering by differentially applying power across the two motors.

But... I can't seem to find any information on how these things behave at very low speeds (either torque/power characteristics or power drain). Does anybody have such information, or a pointer to it? Or does anybody have an alternative suggestion for a very-low-speed drive train?

Thanks very much,

Miles

Nice idea. Is there a reason why your looking at skateboard motors/trucks in particular? a better option might be to use the single sided hub motors readily available on sites like ali express (the kind that are used on those self balancing stand on scooters) - they're going to be better for low speed stuff and should have better torque.

to answer your question, the low speed performance would probably leave a bit to be desired. generally the motors you linked to are run using RC controllers... they're good for what they are but generally have no current limiting, they rely on the back EMF from the motor to regulate them (which comes from spinning the motor quickly) as such they tend to fail at low rpm with high loads, hence my suggestion of the larger hub motors. The other thing to note is that while the power of a motor isn't tied too closely to size/mass, torque usually is, and for your application, torque is what you want. Those little RC hub motors produce decent power, particularly for their size, but not that much torque (hence why they have a reduction stage, despite being used on tiny skateboard wheels).

edit
something else i forgot to mention is that the RC controllers are generally sensor less... so they're poor at starting from a standstill. You'll want a controller/motor combo with halls so that your dad can start from 0rpm without issue.

something like 1 or 2 of these
https://www.aliexpress.com/item/24V-36V-48V-350W-Wheel-Brushless-Toothless-Hub-Motor-E-bike-Engine-Wheel-Motor-Scooter-Kit/32811432372.html?ws_ab_test=searchweb0_0,searchweb201602_1_10152_10065_10151_10068_10136_10137_10157_10060_10138_10155_10062_10156_437_10154_10056_10055_10054_10059_303_100031_10099_10103_10102_10096_10147_10052_10053_10142_10107_10050_10051_10084_10083_10080_10082_10081_10110_519_10111_10112_10113_10114_10179_10182_10185_10078_10079_10073_10123_142,searchweb201603_9,ppcSwitch_5&btsid=f17870b1-4da8-4e20-97bf-7a896b39f15e&algo_expid=ffc6447f-819a-4698-a704-d45ed5970e8b-6&algo_pvid=ffc6447f-819a-4698-a704-d45ed5970e8b
will likely suit well. (search for 'scooter hub motor' if that link doesn't work)