Coupling misaligned shafts

Tim Wescott fired this volley in news:4o- snipped-for-privacy@giganews.com:

Tim, This sounds like it might be a bit out of your ken. First, a five or ten degree mis-alignment between shafts almost demands a CV joint, and they're not 100% efficient except when running perfectly axially.

If you can't joggle things to be within a degree or two, you're just not going to get what you want, unless you belt drive the sucker. Put a sheave on the driving element, and a sheave on the torque sensor, and do it that way.

Otherwise, a simple, cheap coupling for minor misalignments is called a "Lovejoy Coupling". It transmits torque effectively with only minor heat losses and also cushions any shocks in the train.

Lloyd

Belts would have more heat loss than a coupler.

This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own.

The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft).

I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things:

2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler".

The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings.

So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1?

As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use.

Lovejoy

cnc zero backlash coupler

What have you considered for the absorber?

electric motor/generator?

hydraulic pump?

magnetic clutch with scale and tach?

GglProd&003=18299132&010=990-4046&gclid=CJPGvbjRtr8CFSxo7AodjjsAqw

I'm probably going to use a motor. I need to drive as well as absorb.

Better than five degrees could be done, but with more fiddlin' and fussin'.

This doesn't have to be small for it's strength, so something outside the usual machine design box may do.

And, if this sounds interesting and you're within driving distance from Portland, Oregon, send me an email -- I can do all the work myself, but farming it out may be better for my customer, if you've got the right skill set.

#2 is called a belt.

A timing belt drive is extremely efficient

snipped-for-privacy@snyder.on.ca fired this volley in news: snipped-for-privacy@4ax.com:

Yup. L

Not if I can't easily mount it concentric to the axis of rotation.

you will also hace considerable side loading which may be important, whch will be avoided with a shaft coupling.

OK, spill the beans--- What is the application??? Picture or diagram, or at least a good description?? How about a hunk of hose the right size to fit the shaft, and a couple of hose clamps. Braided hose if required. Even steel braid. You are only talking

And I'm assuming you mean parallel to the axis of rotation.

It's for a customer, so I have to be all secretive. Which is a pain, I know.

Things could, in theory, be mounted dead center on a shaft on the device under test, but doing so would require some disassembly and reassembly to do the test. I'll go there if I must, but I'd much rather have something that'll work anywhere, anytime.

Perhaps a roller chain coupling would be suitable if the angular misalignment is not severe.

This is just a wild idea, but how about a hydraulic pump driving a hydrauli c motor. They could be sized so there is a speed up of the RPM's. It woul d solve all the alignment problems. Or just a hydraulic pump with a needle valve as the load. Use a optical tachometer from China to get the RPM an d a pressure transducer on each side of the pump to get the torque.

Dan

Hi Tim, I didn't chase down all the links others posted, so perhaps it's already been mentioned, but I used a bellows shaft coupler. (not cheap) Link to the first hit on google.

George H.

How about directly coupling the unit to the shaft? If that isn't possible how about a sprocket and chain?

The problem with any types of angles in the connection is that it will screw with your measurements.