Digitally measure angle of a rotating shaft.

[sammcc]

Hi all and hopefully this is the correct forum.
I need to design a test fixture whereby I will spin a 1/2" diameter x 10" long shaft at 2RPM

While the shaft is spinning I need to apply a force to the side of the shaft to achieve an angle between 3 & 3.5 degrees.
This is straightforward enough.

What I am wondering is there some piece of equipment available on the market that I could use to measure the angle of the shaft during rotation digitally, I could probably do it using some sort of engraved plate as a visual indicator but this is 2017 and I would like to do it digitally.

Thanks in advance for any help provided.

 

[AidanMc]

Is a rotary encoder what you're looking for?

Aidan McAllister
Metallurgical Engineer

 

[3DDave]

You are bending the shaft?

 

[IRstuff]

There are digital protractors:

https://www.mcmaster.com/#digital-protractors/=1991mv6

TTFN (ta ta for now)
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[sammcc]

Hi Aidan, I need to explore rotary encoders further- thanks

Hi 3D Dave, yes, sort of. It is fixed at the bottom and pulled from the top to a 3degree angle

Hi IRstuff, the protractor I do not think would work as the angle needs to be measured while the shaft rotates.

 

[IRstuff]

?? What is being "pulled?" Is that part rotating as well? There has to be something that isn't rotating that allows you to push on it without generating infinite friction; that part can be attached to a protractor.

TTFN (ta ta for now)
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[sammcc]

The shaft is mounted at the bottom It is then rotated at 2RPM, The shaft is then pulled from the top to 3 degrees, this is what I want to measure while the shaft is turning. I need to be able to measure it while it is rotating to ensure that the rotation at this angle is smooth and consistent. I am replicating how the part will work in service.

To perhaps add a bit of clarity, it is a partly thin walled fabricated shaft that has some flexibility, it is not a solid bar, this is what I might have given the impression of.

 

[IRstuff]

I understand all that. How are you pulling on the rotating shaft without causing all sorts of friction? Are you not using a bearing or bushing?

TTFN (ta ta for now)
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[sammcc]

Yes I am using a bearing as part of the device that pulls it.

 

[IRstuff]

OK, then you can attach one free end of the protractor to the bearing and the other free end to something that's fixed.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[sammcc]

hmmm- the inside of the bearing rotates but the outside doesn't so I may be able to potentially attach it as you suggest.
Thank you!