dc motor - spindle / shaft drive

[dsc]

Thanks again for the replies gents.

Normal usage will be mostly short bursts, as I mentioned before, maybe 10-20s at a time, few times a day. Heavy usage would probably generate loads of heat, so would need additional vents + fans in order to cool it down. Not sure how much heat will be generated, so it's all guesses at the moment.

I don't really need to keep 3:1, I can even use 1:1 if the motor is up to it. Steppers would actually benefit from low ratio, as they provide rather high torques at the lower speed range that interests me.

I've stumbled upon Mark's (blackburn mark) spindle thread and also discussed the details with him. I've looked at this motor:

EMP C6354 KV250 Outrunner brushless motor 2450W for RC airplane match 90A ESC | eBay

which can be ran at 500RPM at 2V (which seems oddly low), but I'm not sure of the torques produced at that point. I can also run it at 1000RPM at 4V and then use 3:1 to drop down the speed to around 300RPM.

Regards,
dsc.

[blackburn mark]

with that motor i,m getting 2800rpm at 12v (bit of drag on the angular contact bearings)

I wouldn't get you knickers in a twist about voltages... use a 12v power supply and let the ESC take care of the speeds (just dial it in with the servo tester)
I think between 1500 and 2000rpm would be a better speed with this motor so if you could squeeze a 4:1 you may be getting closer to where all the grunt is

a problem you may have with this route is at startup the toque is pretty low, if the grinder is loaded up it may struggle to start (im not up to speed with coffee grinding procedure, I assume you would run it dry and then knock it off?)