re: stepper sizes was re:re:Re: Stepper motors and increased Amps

Roman wrote:

>I have noticed some motor manufacturers have three sizes in the 23
>frame, the 42mm, 54mm and 76mm lengths.<snip> So the two smaller
>sizes are both one-stack?

42mm = 1/2 stack 54mm = single stack 76mm = double stack

>Do you have any info on which of these are better, like
>reliability or performance etc.

Reliability will be the same for all motors, IF they are sized
properly to the job... Performance also depends on suitability of
motor chosen.

>I have noticed also for the same official inductances these smaller
>motors have better torque at high speeds than the larger ones. Maybe
>less detent torque? Less magnetic drag?

Simple physics. Smaller diameter 'rotating' mass. Accelerates more
quickly than a larger diameter motor at the same force applied...
Also, differences in total mass (different lengths of a given
diameter).

Hope this helps.

Ballendo