Dynamometers

That's pretty much it. I need to poke at it a bit, to find out just how much traceability they want -- they wanted a lab that would do it, but I think that maybe they just need me to whomp something up.

so, power upto about 1 horsepower but at slow rotational rates? water wheel? stationary bicycle?

that sort of precision is should be fairly easy with a de Prony Brake and a half-way decent force-meter (eg: electronic scale)

The idea is that if you mount the frame of the induction motor in some large ball race bearings and put an arm connected to the outer frame of the motor, with a force sensor (scale) on the end, then you measure the torque exerted on the arm by the outer frame of the motor, whereas you measure the RPM on the shaft of the motor. The shaft rotates at 80rpm, but the frame of the motor hardly moves at all in its outer bearings, only enough to actuate the force sensor which will be fairly stiff.

The assumption tht the shaft on the motor has the same torque in it as gets applied to the arm with the scale on the end of it, depends on the frame of the motor including the extension arm being well balanced around the axis of the large bearings in which the frame of the motor is mounted. If it is not balanced, you could take a torque reading with the shaft unconnected, and subtract that off future readings as a reasonably good correction, provided that the arm hardly moves when actuating the scale.

Chris

I think that if I do it I'll just use a geared motor with a suitable supply, mounted on bearings and with a nice flexible cable. Fix the rotation of the thing with a load cell, and -- voila! it works.

Years ago there was a guy posting here that made a Don Foreman inspired eddy current dyno for testing electric motors. I think his name was Gerry. I had some pictures of it.at one time. An eddy current dyno (also called an absorber) can be air or water cooled, has no motoring capability, and doesn't use a "load resistor". Take apart an elliptical exercise machine and you may find a version that has a band of magnets around a steel rotor.

With the proper drive ratio you could also use a gear pump (like a Brown and Sharpe 3S) as a loading device. I'd use an in line torque cell but that's because it's available to me.

Interesting request, good luck!

Probably cast iron...you could try experimenting with a brake rotor, those are designed to dissipate heat....

How about a regenerative DC motor controller and a DC motor? DC motor mechanically coupled to your source. Power is put back on the mains.

Dc onto the mains. Now THAT is a trick (unless you forgot the inverter)

The _regenerative_ motor controller does the trick.

Like this:

And how does that work?

Jamie

"Maynard A. Philbrook Jr." fired this volley in news: snipped-for-privacy@news.eternal-september.org:

"Electro-Majic DC". It couples directly to AC lines with no problems. No need for syncronous inverters, no voltage control, no nothin'. Just hook it up and pedal your bike for an instant reduction - and even payback - on your power bill!

Lloyd

I think you're going to be disappointed with your understanding of it.

Jamie

Well I am glad you straighten me out on that!

Jamie

"Maynard A. Philbrook Jr." fired this volley in news: snipped-for-privacy@news.eternal-september.org:

No, I think he's perfectly comfortable with his understanding of it. It would be entertaining to watch when "understanding" meets "mains".

Lloyd

Had a bunch of them at a previous job (225D and 240D) do not profess that I understand how they worked, but do why they were needed in our application. Large slowly spinning arms with molds attached which were never truly balanced. Regenerative drives help get back *some* of the energy used to raise the heavy side as it falls and the light side rises.

Also astounded by the difference in appearance between 20 + year old drive boards and there modern replacements. Old ones are absolutely crammed with components, new one look almost bare! Will try to get a picture the next time I'm down that way...

Oh, posting from rec.crafts.metalworking. Just noticed this is cross posted to two groups I am not following.

I can't believe it..

Ring the dinner bell and they all come out of the wood work!

Jamie

The only ones I've seen have been for battery operation - wouldn't be the first thing I missed.

That control does NOT put power back into the grid. It is a "plugging" brake that reverses the torque on the motor to stop it. Standard 4 quadrant control. They call it "regenerative" braking, but in reality it is "dynamic" braking.