Shaft Alignment

[69gto]

I hope is ok to ask this question within this forum. My question is about shaft alignment. I know the ideal way would be to align both shafts with a laser device connected to both shafts. But would you still accomplish the same results if one device is fixed to the coupling of the fixed piece of equiptment and the other is on the shaft of the moveable equiptment. There is not enought room to place the fixture on the fixed shaft.

Thanks

 

[Heckler]

I would say that using a coupling is a good idea as long as the shaft RPM and Torque are within the couplings rating.

 

[electricpete]

I would say it should work as long as coupling is true to the shaft, and as long as coupling has smooth true surface for mounting the laser device.

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[Tmoose]

Are both machines assembled in their bearings and ready-t0-run? Are you turning both shafts with the laser fixtures attached (as opposed to sliding one or both the laser fixtures around the stationary shaft)? If both shafts are rotating Then coupling hub (rigidly attached to shaft)OD runout has no influence. The shaft or coupling could be milled square, or have big offsets, or half the coupling fixture jacked up with a thick shim on one side of the shaft, and as long as the shaft turn together, and in their own bearings, then all is well.

The exception is coupling sleeves, which are NOT attached to the shaft, as shown here -

http://www.dahlbeckelectric.com/images/images_IND_1.jpg.

Don't forget to consider thermal expansion, radial forces and (sleeve) bearing clearance (gearboxes with sleeve bearings).

 

[electricpete]

What are the coupling sleeves attached to?

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[Tmoose]

-

http://www.dahlbeckelectric.com/images/images_IND_1.jpg.

In the above link the "sleeves" are attached to each other and have curvy gear teeth cut on the insides. Those gear teeth engage teeth cut on the outside of the hubs. The hubs are attached to the shafts. Like this.......

http://www.lovejoy-inc.com/images/Web Product Updates/F.jpg

The hub>sleeve<hub connection has 1 power transmission plane at each hub, so the sleeves pivot to "connect the dots" between transmission planes. Kind of like this.
-X------X-

Anyhow, if the alignment laser heads (or dial indicators) are accidentally attached to the sleeves they will report perfect alignment since they are effectively attached to a hunk of pipe. "Alignment" is meant to determine the concentiricty of the two shafts

 

[electricpete]

Thanks Tmoose.

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