High Torque, low RPM motor source or build

[simey_binker]

Greetings - I've lurked on here for years. Years ago I remember seeing a very good thread about DIY motor builds which included a spreadsheet with a matrix within it comparing pole winding and magnet counts for best performance. it was specifically for low speed, high torque applications with ~16-100+ pole windings - I'm a bit rusty on it. where is that spreadsheet?

I'm on the hunt for something in the 1kW range; ultimately I need 2400 Nm at 3.3 RPM, but I'd be ok to send it through a ~1:10 gearbox, so I'd be looking at closer to 240 Nm at 33 RPM which is more reasonable.

thanks,
Sim

 

[lnanek]

Doesn't Grin make a motor for that use case?

Geared Wheelbarrow Motor, No Tire

Electric Wheelbarrow motor with high 30:1 Gear Reduction Ratio, (3.1 RPM/V). Uses common 4.00-8 Tire size.

ebikes.ca

There's probably an upper limit to the magnet count, though, because for geared motors like that you multiply the pole pairs by the gearing and then that's your erpm, and many controllers can't handle very high erpm.

 

[Hillhater]

Why not just use a higher RPM motor and a planetary reduction gearbox ?

 

[simey_binker]

there's a requirement for no greater than 1000 in.lbs (113 Nm) of back drive force when the motor is shut off. so going with large ratio gearboxes is undesirable. There's also a general desire for reliability, and some would argue gearboxes aren't are great as direct drive. My advantage is that size is less of a constraint. I am entertaining hand-building a custom wound, large diameter motor, but I'd like to find that spreadsheet first.

 

[lnanek]

Lots of geared motor hubs have a clutch, so there's little resistance when overrunning. Sprag clutch, etc.. Mostly only direct drive hubs don't, or geared hubs with that clutch welded or shipped without to allow regen - but those are rare.