On Tue, 08 Jul 2014 20:26:30 -0400, clare wrote:

On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott
wrote:

This is related to my dynamometer thread. We didn't find anything, so
I'm working on plan B, which is to roll my own.

The thing would need to work with an existing piece of equipment, which
has no solid external reference points to provide for good alignment to
the shaft on the device under test (or, for that matter, a really easy
way to get centered onto a shaft).

I'm visualizing getting something that can locate things to within an
inch, and within five or ten degrees, then having one of two things:

1: A foot-long shaft with U-joints (probably CV) at each end, to couple
the dynamometer to the device under test, or

2: A much shorter mechanical gizmo, which is currently labeled in my
mental sketches as the "magic coupler".

The important thing in all of this blathering is that when all is said
and done the coupling needs to transmit torque accurately -- it can't
just be efficient, it has to not have any severe differential gearing
effects that would mess up torque readings.

So, do you think #1 would work? Is there a name for #2, and could I
count on it, or should I just stick with #1?

As suggested by my foot-long shaft idea, space is not a huge issue,
particularly if the thing can be stowed away compactly when not in use.
#2 is called a belt.

Not if I can't easily mount it concentric to the axis of rotation.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com