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Measuring torque / power on a rotating shaft - quick and dirty?

apestate

Stainless
Joined
Mar 29, 2003
Location
Utah
Hello

I'm working with someone who is designing something and they want to figure out how much torque / power is needed to rotate a shaft in their assembly. The shaft is 1/4" diameter and accessible. They are turning a dozen cams which articulate these arms with paddles on the end for material handling.

We are trying to figure a way to measure the power needed to turn the shaft to determine motor sizing, and to see what parts of the assembly might need to be beefed up.

I went looking for the torque values of a DeWalt cordless drill with slip clutch. This would be -really- quick and dirty. They don't mention the torque amounts on the clutch in this screwgun.

I was thinking that a measurement of current in a motor would probably be the easiest and cheapest method. Any other ideas?
 
I'd suggest there are in fact two figures you'll be interested in, the torque required to initially rotate the mechanism, you could probably measure this successfully with a torque wrench. The other will be the power required to maintain the appropriate speed. It must be a very small mechanism if you can use a cordless drill!

For the latter I'd suggest you instead connect a motor you feel will be about the right size and compare the current draw between no load, and loaded conditions. You should be able to calculate the power requirements from that.
 
Some "other way" .-)

Wrap the shaft with fish line or similar. fix an adjustable weight to the free end of the line. Add weight until the mechanism is driven. Do the math!
 
I'm working on a similar issue. The clutch will slip on 18 on my Milwaukee 18v drill. I was thinking about hooking the drill up to the torque wrench and going from there. As I'm designing, building, and paying for it I want to get this right the first time.
 
Some "other way" .-)

Wrap the shaft with fish line or similar. fix an adjustable weight to the free end of the line. Add weight until the mechanism is driven. Do the math!
The acceleration moment is the hard one to get, as that method is just enough force to move. The acceleration rates will change the force dramatically
 
Some "other way" .-)

Wrap the shaft with fish line or similar. fix an adjustable weight to the free end of the line. Add weight until the mechanism is driven. Do the math!

I do some of this stuff for scientific instruments I make; this is the approach I'd use. Put a larger pulley or disk on the shaft because your measurement of the torque arm is critical; doing it on a 1/4" shaft you could have error from string wrap, etc. If you have enough height here you could get up to whatever speed and do power measurements. A bucket of water is a good variable weight.
 
I do some of this stuff for scientific instruments I make; this is the approach I'd use. Put a larger pulley or disk on the shaft because your measurement of the torque arm is critical; doing it on a 1/4" shaft you could have error from string wrap, etc. If you have enough height here you could get up to whatever speed and do power measurements. A bucket of water is a good variable weight.

additional pulley radius would be my choice as well, even if the inertia would change considerably if the overall mechanism is light.
 
There's a HF "electronic" torque wrench adapter that is pretty fun. In addition to beeping at preset torque, itcan be set to log highest torque after load is removed. About 30 bucks or so. You'll need to make some adaptors to and from 3/8" square...

Digital Torque Adapter

Chip
 
Put the 'gadget' on a base, and support that base on two points equidistant from the drive axis. Place ONE of the points atop a reasonably accurate bathroom scale, or a smaller-sized postal scale. Spin it with your drill, and observe the scale's reading, take good notes, then figure out how much torque you had to have applied, to get that reaction you see.
 
Reply

Hello

I'm working with someone who is designing something and they want to figure out how much torque / power is needed to rotate a shaft in their assembly. The shaft is 1/4" diameter and accessible. They are turning a dozen cams which articulate these arms with paddles on the end for material handling.

We are trying to figure a way to measure the power needed to turn the shaft to determine motor sizing, and to see what parts of the assembly might need to be beefed up.

I went looking for the torque values of a DeWalt cordless drill with slip clutch. This would be -really- quick and dirty. They don't mention the torque amounts on the clutch in this screwgun.

I was thinking that a measurement of current in a motor would probably be the easiest and cheapest method. Any other ideas?


Hey something like one of these can help with your project. Let me know if it helps!
Shaft-to-Shaft Reaction Torque Sensor TSS400 : FSH00281
Non-Contact Shaft to Shaft Rotary Torque TRS500 : FSH01646
 
Reply

Hello

I'm working with someone who is designing something and they want to figure out how much torque / power is needed to rotate a shaft in their assembly. The shaft is 1/4" diameter and accessible. They are turning a dozen cams which articulate these arms with paddles on the end for material handling.

We are trying to figure a way to measure the power needed to turn the shaft to determine motor sizing, and to see what parts of the assembly might need to be beefed up.

I went looking for the torque values of a DeWalt cordless drill with slip clutch. This would be -really- quick and dirty. They don't mention the torque amounts on the clutch in this screwgun.

I was thinking that a measurement of current in a motor would probably be the easiest and cheapest method. Any other ideas?


Hey something like one of these can help with your project. Let me know if it helps!
Shaft-to-Shaft Reaction Torque Sensor TSS400 : FSH00281
Non-Contact Shaft to Shaft Rotary Torque TRS500 : FSH01646
 
This may seem odd but I have measured force with one finger, two fingers, three fingers,four....
First I went to the market to finger(s) test on the produce weight tester. Yes, the device would have to be slow RPM or travel in your case to not get hurt.

also consider torque at one inch/one foot and the like.
 








 
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