dc motor - spindle / shaft drive

[dsc]

Hmmm all good stuff Jonathan, thanks for the info. Shame about the steppers not being up to the task, as it's dead easy to change their speeds and generally driver them via off-the-shelf drivers / components. Does it matter that the 9Nm torque requirement is only momentary ie. it's static torque needed to get the grinder moving sometimes. Once past that point the thing can be driven with anything as low as 1Nm (although it's prone to stalling from time to time). There's an existing grinder which uses a DC motor which only has 0.3Nm and is driven via a 30mm dia pulley : 90mm dia pulley (so effectively 1:3), which I thought would triple the torques and divide the speed by 3. That stalls from time to time but manages to do the job even with those low specs.

Duty cycles are low, say on for 20-30s a couple of times a day maybe. Although that would change of course in a busy environment.

Regards,
dsc.

[Jonathan]

Does it matter that the 9Nm torque requirement is only momentary ie. it's static torque needed to get the grinder moving sometimes. Once past that point the thing can be driven with anything as low as 1Nm

Yes, that helps a lot since you just need a motor with high starting torque, so again the motor with planetry gearbox is probably a good bet. The average power whilst switched on is now 1/9th, so about 32W which is more realistic for a stepper motor. The problem with stepper motors is in addition to the motor you'll need a driver which is probably quite expensive.