I'm trying to build a similar spec-ed robot to Ubiquity Robotics's Magni - Silver. Basically carry as close to 100 kg of weight on it and have a speed between 1 to 2 m/s. I'm having a hard time finding a DC motor with encoder that has the specs I'm looking for. I found 8" wheels (20cm) so to reach that 2 m/s it needs to have an RPM around 190 with a torque of 9 N-m based on robot shop's calculations. I set the inclination to 5 degrees and the efficiency to 75%.
If it's a little slower or carries a bit less then that's okay. I'm trying to reach the closest I can to the targets. I found a few powerful motors but don't have an encoder.
I’d look for the motor and encoder separately , as you or only want the encoder after any gearbox on the wheel-yes you’ll need to gear the motor down for best performance .
There's a good secondhand market for mobility scooter and wheelchair motors and
transmissions, which could be a reasonable source of suitable hardware. Bonus is the
motor controllers that are also available, built to be rugged and reliable.