On Fri, 12 Feb 2016 16:39:36 -0800 (PST), whit3rd
wrote:

On Friday, February 12, 2016 at 3:45:34 PM UTC-8, wrote:
On Fri, 12 Feb 2016 16:26:54 -0500, "Steve W."
wrote:

How about using DC to brake an AC servo? Higher the voltage the more
resistance to motion.

How would that work? How are AC servos made? I'll look online.

Most AC motors (the ones without brushes) will brake if you feed 'em
some DC. Steppers (but they cog), shaded-pole, or hysteresis types,
all have a rotor without driven windings, and DC on the stator makes
them into brakes.
I thoughty they only braked while spinning and once stopped there is
no braking force. I ordered some MR fluid and will try making my own
magnetorheological brake.
Eric