Finding torque on a rotating disk.
Finding torque on a rotating disk.
(OP)
I need to find a way to measure torque on a rotating disk.
The input force is applied on the outer radius (R) of the disk. The disk then outputs a force to a shaft on the inner radius (r).
I cannot instrument the shaft because space is very limited and a dyno can in no way be used for this measurement.
I have some instrumentation ideas as far as using strain gauges goes but I don't know how to get from the strain measurements to torque accurately.
Any ideas?
The input force is applied on the outer radius (R) of the disk. The disk then outputs a force to a shaft on the inner radius (r).
I cannot instrument the shaft because space is very limited and a dyno can in no way be used for this measurement.
I have some instrumentation ideas as far as using strain gauges goes but I don't know how to get from the strain measurements to torque accurately.
Any ideas?





RE: Finding torque on a rotating disk.
TTFN
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RE: Finding torque on a rotating disk.
Maybe I should word it like this. I have axial and radial strain at some point on the face of a rotating disk. How do I go from the strain to the torque being applied to the disk?
RE: Finding torque on a rotating disk.
Is your torque due to acceleration, or steady state friction?
RE: Finding torque on a rotating disk.
Or, why not measure the 2D acceleration of the disc....this can then translate into a torque (using the inertia of all the rotating mass). (Of course this is not valid if the system is connected to a brake or is static) (also assumes negligible friction)
Fe
RE: Finding torque on a rotating disk.
radial torque sensor?
Mfgenggear
RE: Finding torque on a rotating disk.
Fe
RE: Finding torque on a rotating disk.
The only instrumentation option is the flex plate, or rotating disk. Any other location is either too involved (meaning days of labor) or will result in false results by not accouning for engine accessory power loss and bearing friction.
Oh, and the measurement will be taken at steady state. Well, steady RPM. Because there are two forces involved it will never reach a true steady state as one force will be lagging or advanced at any point.
RE: Finding torque on a rotating disk.
Stick an accelerometer onto the disk. zero the gage. Applya known torque to to the disk. Observe the new reading on the gage.
Draw a straight line.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Finding torque on a rotating disk.
RE: Finding torque on a rotating disk.
This is what has put me on the strain gauge path. I am thinking of a four gauge rosette placed on 45s with the radius. My initial thought is this will eliminate any strain due to flexure of the plate.
I made a quick drawing of the system and will upload it, along with a picture to see if it helps clarify the issues invloved.
RE: Finding torque on a rotating disk.
RE: Finding torque on a rotating disk.
As mentioned above, your best option, if you've got a few of these White-Superior units to test, is to buy or rent a coupler that will measure running torque.
There have been some discussions on here regarding measuring flywheel torque in real time, you may want to try searching these forums as well.
Brian Bobyk - Hoerbiger Canada
RE: Finding torque on a rotating disk.
Can you disconnect your shaft and generator, and do a dynamometer on the engine?
It is easy to rig up a brake. You need to monitor speed, fuel usage and throttle settings for a batch of torque values.
Connect the shaft and generator and monitor the engine settings again.
RE: Finding torque on a rotating disk.
Bribyk: The problem with the load cells is two fold. First, it won't account for other accessories and since the test will be on different engines with different accessories we cannot accurately estimate their power draw. The second is that the shaft is dialed in at 0.002in and any movement up could very well get it out of balance. I like the thought though.
RE: Finding torque on a rotating disk.
RE: Finding torque on a rotating disk.
RE: Finding torque on a rotating disk.
Walt
RE: Finding torque on a rotating disk.
Can you measure the reaction forces at the motor mounts? You should fairly easily be able to calculate motor torque from this.
RE: Finding torque on a rotating disk.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Finding torque on a rotating disk.
If there is a way to accurately monitor and record the speed in fine enough increments, you can get acceleration, thus torque.
RE: Finding torque on a rotating disk.
1) You can calculate the shear strain at your point of interest for a given torque and then use the gage factor to get the change in resistance of the gages. Go through the bridge balance equations and you will have volts/torque.
2) Apply a static torque and measure the output from the bridge. Can you lock up the output and use a crow bar of some sort to apply a known torque?
You've probably already figured this out, put the gages in a location that has the best combination of high torsional strain and low disk bending strains.
RE: Finding torque on a rotating disk.
Marks' Standard Handbook for Mechanical Engineers comes close, and Shigley's book throws in a couple of pointers, but nothing exactly correct. So I need to either find a solution to this problem or go in a different direction.
I don't have the stuff in front of me or I would throw some equations down. It seems as though I may have to measure deflection angle too according to one of my other books.