Torque sensors for a small system

[AdamJ2]

Hello All,

Is anyone aware of any torque measuring products or brands that are suitable to measure torque for a rotating 5mm shaft with only 100rpm and >30 N.m torque? I've been looking for a while but everything seems either prohibitively expensive (<$1000) or not suitable for my purpose (usually both). Any suggestions or alternative ideas to measure the torque would be very appreciated. I've attached a rough sketch to show what I mean.

Thanks!

 

[BUGGAR]

At least for ideas, you can look at car power steering valves. There's a little torsion bar in most of them. Could that be calibrated and used? They're cheap.

 

[Compositepro]

Slide a tube over your rod with an index mark on it that lines-up with a protractor scale on the disc you show. This will measure the twist of the rod, which is directly proportional to torque. If you need to read it while it is rotating use a strobe light.

There are many ways to solve your problem with some imagination and reasonable requirements.

 

[CWB1]

There are many ways to accomplish what you are trying to do, and several books on the subject. I'd recommend "Measuring Torque Correctly" by Schicker & Wegener.

 

[BUGGAR]

The trick is to to it for less than $1000! I suspect your torsional rigidity is relatively high such that torque deflections will be very slight and thus require very precise measurement. Can you build in a deflecting link to measure? This will require your thing to twist more. But then you could measure it.

 

[AdamJ2]

Cheers everyone for the replies and ideas. Do you recon there are any torque sensors that can be used be used given my parameters? or is my system too small? I have a reasonable budget of up to $800 if I can find a suitable torque sensor but for the life of me nothing in the market seems suitable.

 

[BrianE22]

Tough to find one that will bring the signals out from a rotating shaft. How much sensitivity do you need? Strain gaging the shaft might not be too expensive but then you would have to figure out a way to get the signal from the rotating shaft. If your sensitivity requirements aren't too tough you might be able to find an inexpensive 4 channel slip ring assembly. High sensitivity means low noise and slip rings for that get more expensive.

 

[BUGGAR]

What drives this thing? Can you measure the torque there? I'm thinking of the neighborhood "mechanics" that would calibrate their flexible motor mounts with a torque wrench, then read the torque output by the corresponding movement of a bar bolted across the top of the engine while racing up a hill with the hood off.

 

[BrianE22]

Can you mount the motor like a dynamometer?

 

[SnTMan]

Tacometer? Lunch anybody

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[AdamJ2]

Brain many thanks for both of your responses. I'll definitely have a look slip ring assembly to see if there's anything suitable. The dynamometer idea is quite interesting but I'm not certain if I can pull it off because the shaft has to be vertical.

Buggar, It's a small rotating mechanism, the purpose of the shaft is to make it easier to estimate the mechanical power coming from the mechanism. With regards to the torque wrench do you recon there's anyway it could be used to estimate the torque of the shaft in some way? I've attached an example product to shown what I mean. Thanks again for your interest in this problem.

 

[kjoiner]

Similar to what Brian mentioned, would a Prony brake work?

Kyle

 

[hydtools]

Whether the shaft is vertical or horizontal does not mater to a dynamometer. It measures reaction to system torque not reaction to weight (gravity).

Ted