On Thu, 11 Feb 2016 19:33:18 +0000, David Billington
wrote:

On 11/02/16 19:31, wrote:
Everybody,
I'm working on a project that needs a slip clutch or brake or
something. I'm turning handwheels that need some sort of instantly
variable resistance to turning . Anywhere from 0 to 40 inch pounds. I
have been looking at magnetic particle clutches and brakes, eddy
current brakes, and disc type clutches and brakes. The magnetic
particle brakes would seem to be a good solution except that the ones
I have seen that can provide enough drag have too much drag when not
energized and have too large a diameter. About 3 inches diameter by
about 3.5 inches long is the space the clutch or brake must fit in. I
am considering rolling my own devices but am not sure how I would do
it. Maybe some sort of generator feeding a resistive load. By varying
the field strength the resistance to rotation would increase. Whatever
the solution is the resistance to rotation must be linear to the
current that actuates the device. That's one of the reasons I like the
magnetic particle barkes.
Thanks,
Eric
Have you looked at automotive aircon clutches. I don't know if they're
suitable and normally used for on/off operation but likely cheap to get
one from a breaker to test or play with.

A/C clutches aren't made to slip at all, David. This won't work.
Band clutch/brakes have been used in auto tranny setups and on old
emergency brakes for early vehicles.

Eric, band brake setups might work for you, with solenoid actuation.
Variable voltage to the solenoid could facilitate varied braking.
https://www.youtube.com/watch?v=fSRWf8PY_4Y Something like this.
But done a teeny bit more professionally? g
https://www.youtube.com/watch?v=RwVeIbRx7wE

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I would be the most content if my children grew up to be the kind of people
who think decorating consists mostly of building enough bookshelves.
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