Torque-speed metering device

[daanh]

Hello,

I'm looking for a device with which I can measure the required torque at various rpm's. This way I could map the torque/rpm graph of various machines.

Is there some device for sale that can do this?

Thanks, Daan Haeyen

 

[Skogsgurra]

I have seen useful things from Dewetron. Possible to combine lots of different inputs. A Little like LabView, but easier to use and better price. Where are you situated?

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[daanh]

In the Netherlands. I emailed them with this question, thanks!

 

[Skogsgurra]

What a coincidence! Did you talk to Andries?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[daanh]

No, I literally just emailed them.

A colleague of mine had the suggestion to take a battery drill and just measure the current to the motor and the current, and determine the speed and torque with that.

 

[Skogsgurra]

That sounds interesting. I wasn't aware of load being so small - was thinking kW and up. But make sure that the drill isn't series wound. Most are, and then the torque isn't proportional to current any more. But there are PM DC motors where that idea could work.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Skogsgurra]

BTW, I am using this test rig for similar purposes. The DC motor in this rig (to the right, with chuck and pulley) has a very linear characteristic, both torque/current and speed/voltage.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[jraef]

How are you changing the RPM? I ask because some of the high end Flux Vector Control VFDs on the market will provide you with an output motor torque metering function. So if you have a test bench for your machines, just use the largest motor you would ever need for the tests, connected to a VFD with FVC (also called Field Oriented Control / FOC in some sectors). If you are using a VFD anyway to attain thedifferent speeds anyway, you already have most of what you need, so long as you don't go for the cheapest one you can find. The highest accuracy will come from using the "closed loop" FVC/FOC option, requiring a shaft encoder on the motor, but the level of accuracy you are looking for was not stated. There are several out there that can offer "Encoderless FVC" that might serve your purposes if the required accuracy of your torque values is in the neighborhood of +-1%.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[daanh]

I don't need high accuracy. +/-5% is fine. I just ordered this to measure torque of a moving shaft. Measuring the speed is easy, so I guess I'm set.

 

[waross]

Torque range: 29.5 to 147.6 ft. lbs. (40 to 200 NM)
and
A colleague of mine had the suggestion to take a battery drill and just measure the current to the motor
These statements may not be compatible.
29.5 Ft lbs is pretty high torque for a battery drill.
When you find a suitable motor you may just mount it on a pivot and measure the reaction with a spring scale.
Not the best accuracy but +- 5% should be no problem.

http://www.ebay.com/itm/NIB-Delta-H...745515?hash=item41be12506b:g:B3UAAOSwQupXWb2R

Or, if you need more capacity:

http://www.ebay.com/itm/Vintage-Cha...293897?hash=item25cf650449:g:67AAAOSw3mpXHTXW

Bill
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"Why not the best?"
Jimmy Carter

 

[daanh]

Thanks Bill. I thought I read somewhere that it can measure smaller torques, but that the beep function (beeping when a certain torque is reached) doesn't go lower than 29.5.

We'll see...

Gunnar, how does that device of you work?

 

[Skogsgurra]

Daanh,
It is mostly being used to demonstrate electrical discharge in Deep groove ball bearings at different speeds and temperatures and with different oil/grease qualities. But it is also used to show rolling friction when a bearing has been damaged by EDM. To that end, a DC current transducer is used to measure motor armature current and feeds one of the inputs in the PicoScope unit at the bottom. A temperature transducer (I use an NTC with scaling and linearization in the PicoScope) and whatever other things I need to measure are connected to other inputs.

The DC motor to the right (shaft and chuck visible only) is an old ElectroCraft 24 V motor with a very constant Nm/A (torque/current) relationship so I can measure friction in the bearings with good enough accuracy. I use only one belt and one bearing for those tests.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.