Experiment: method for applying and measuring torque

[Bicky22]

Hi all,

I was looking for some advice on setting up an experiment. I just am looking for something simple, compact and rigid.
I am looking to apply and measure torque (via DAQ system) to a small shaft. I have leeway with the shaft design, it will be attached to the female end of a ¼” socket drive. The torque applied and measured only has to reach 50 in-lbs or so.

Since I am using a DAQ system I have a wide variety of measuring options. Two types that stick out to me;
(1) Socket extension sensor:

http://www.omega.com/googlebase/product.html?pn=TQ103-600&gclid=CJrbkLiOrr4CFTMA7AodnVkAQg

I have used this in the past, loved it, it worked great… However I am looking for a much more economical method of this experiment… I need multiple of them.
(2) Strain gauge:

http://www.omega.com/pptst/SGT_Full-Bridge_Shear.html

Must be full bridge (temperature compensated). The cost is more in my range. I have used this exact type in the past, I don’t like this particular one for my application because my past experience: The ribbon leads are weak and broke on me often. I also have had some difficulty with the solder pads as well, the wires would occasionally break off on me. I guess what I am trying to say is that I am trying to find something slightly more ridged for this particular application.

I am open to any suggestions for applying the torque as long as it is economically and compact. It needs to reach roughly 50 in-lbs and only has to rotate bi directionally for 100 degrees (360 is fine though). It can be pneumatic, magnetic or anything you can think of as long as it is small, fairly inexpensive and can apply torque to a shaft.

Thank you for your help in advanced.

 

[racookpe1978]

Do you need to measure the actual torque being applied to the socket at every point in time, or need to ensure every socket receives the same torque everery time?

reason I ask is: If you know the force applied to a known length of the "wrench" trying to turn the socket, then you know the torque being applied. If so, then you can measure the force directly, and do not need to try to figure out the torque on the socket extension as it revolves.

 

[Bicky22]

I do not need it to measure every point in time. I just would like to monitor it every cycle the shaft turns 90 degrees. I plan to rotate this half a million times, so depending on what I am using to apply the torque, this may alter the torque applied over that time period. I have a similar set up to this right now where I use a friction brake to apply a torque on the shaft. Over time the brake pads heat up and it causes the torque being applied to the shaft to increase. Which for the most part is fine, I would just like to monitor it.

With that said, I am also looking for other method to apply this torque, this old set up I have is great, however is much too large and expensive for this new application. If there is a fairly compact way to apply the torque that we know will be consistent torque load over a long period of time, I am more than open to any suggestions that will allow me to not need a torque sensor.

 

[btrueblood]

You could get a very consistent torque from a pneumatic or hydraulic cylinder and scotch-yoke linkage or similar. Connect pressure gages or transducers to the cylinder ports to log the actual torque. You could even vary the torque/speed profile with suitable throttling valves. Alternatively, same idea but transmit torque via a vane or gear motor (vane/gear pump running in reverse) - but you said you only need 90 degree rotation.

What actuator manufacturer do you work for?

 

[Bicky22]

I am just working for the man and doing the grad school thing.

I really like that cylinder and scotch-yoke linkage idea. This would be consistent, rigid, and fairly compact; just what I am looking for. I will start playing around with a design. Thank you very much, I do really appreciate it.

To anyone else reading: I am always open to more suggestions.. there is never one right answer to a question like this.

 

[CoryPad]

A rotary torque transducer is another style to consider, although the price may not be to your liking. Here is one example:

http://www.pcb.com/Linked_Documents/Force-Torque/LT_RS_PC9000Series_Lowres.pdf