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# Digitally measure angle of a rotating shaft.

## Digitally measure angle of a rotating shaft.

(OP)
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.
Replies continue below

### RE: Digitally measure angle of a rotating shaft.

Is a rotary encoder what you're looking for?

Aidan McAllister
Metallurgical Engineer

### RE: Digitally measure angle of a rotating shaft.

You are bending the shaft?

### RE: Digitally measure angle of a rotating shaft.

(OP)
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.

### RE: Digitally measure angle of a rotating shaft.

?? 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)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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### RE: Digitally measure angle of a rotating shaft.

(OP)
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.

### RE: Digitally measure angle of a rotating shaft.

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)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

### RE: Digitally measure angle of a rotating shaft.

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

### RE: Digitally measure angle of a rotating shaft.

(OP)
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!

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