Creating a strain gage coupling

So now I have to find some way of measuring the torque applied between the two shafts of the viscometer. Here’s my idea.

Strain Coupling Model View
Strain Coupling Model View

What you can’t see is that I plan to manufacture it out of plastic, that way the strain gage experiences the most out of the deflection of the part. I’ll use a flexible polyurethane bonding agent for the strain gages, allowing the forces of the strain to work without breaking the bond.

Here’s a through model view:

Strain Coupling Transparent View
Strain Coupling Transparent View

Of course, it only took me a few minute to make this model but it helped me see if what I was doing would work, I also used FEA to see if the forces would be transmitted where I wanted them. The FEA results were promising, nice even strain along the gage surfaces. (Those gauge surfaces are seen in light blue). You can see though that the hole through the side relieves some strain on the strain area, though, this shouldn’t be an issue.

Strain Coupling Strain Test view
Strain Coupling Strain Test view

Here’s an image of the stress as calculated by Cosmos

Strain Coupling Stress Test view
Strain Coupling Stress Test view

Well, hopefully this will work. First I need to get the strain gages to provide reliable results. By using two of them, temperature concerns should no longer be an issue and should help mitigate innacuracies. I’ll post pictures of the finished part, though I don’t think I’ll do it on the NC, I’ll just do it manually, it may look like ass 😉