Hollow Shafting

[TexasRotorHead]

If you were to make a hollow shaft with the following dimensions, how would you do it?

OD - 65.000mm/64.95mm
ID - 56mm/54mm
Length ~ 500mm

There will be no bearings directly run on said shafts. The shafts will be under approximately 50-60 MPa of stress and will be rotating at 2000 RPM.

I have thought about gun drilling a 7075 round and finishing it on a lathe, but is their a cheaper alternative? Nothing is touching the inner bore, it just needs to exceed ~52mm for clearance. I would like to use 7075 or 2024 if aluminum is available. 4xxx series steels are probably my next choice.

Thanks for your help guys.

 

[ornerynorsk]

For a one-off I would Gundrill and either barturn or centerless grind, depending on what is available locally.

 

[DanDwig]

You've probably considered this, but can you find anything with a stock ID in the range you need and just turn down the outside? It's a bit of an odd size I admit, but it looks like something with a 2 1/8" ID would be pretty close.

 

[unclesyd]

Check over sizes of different type Al tubes or pipe available from Argyle. Better yet give them a call and discuss your specific details.

I would 2024 only as the last resort.

http://www.argylein.com/extruded_shapes_search.php?profile=Round-Tubes

 

[GregLocock]

I'd consider getting an aluminium extrusion if you are doing many of these.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[desertfox]

Hi TexasRotorHead

Well I would look at standard tubing, however with an 0.05mm tolerance on the OD you would certainly have to do some machining, why is the OD so restricted? is it, so you can join it to other shafts or just to keep the stress within the range specfied?
I assume the stress range you quote is due to torsional shear stress and not anything else.
If your going to do a lot of these, then Gregs suggestion of an extrusion is the best way to go.

desertfox

 

[TexasRotorHead]

DanDwig, I have tried finding 2 1/8 ID tubing, but I have had no luck in anything besides 6061 with close to 65mm OD. I have found 4130/4140, but nothing in 7075 or even 2024.

Unclesyd, is there a reason you would avoid 2024? Does it not take well to torsional loads?

GregLocock, this is a one off part.

Desertfox, the OD will connect to a flange holding rotor blades. The tolerance is semi-arbitrary. I figured .05mm is tight enough to not get sloppy, but not insane. The stresses come from multiple sources, but mostly torsion. There will be axial lift force and bending moments as well as bolt concentrations, but all of the analysis has been done. The ID is set to just clear another shaft (coaxial).

We are leaning towards drilling with a deep morse taper drill (2 1/8 x 24" long) and then finishing the OD with the ID as a reference. The tolerances for the concentricity are not tight (the shaft just has to clear). We will probably clean up the ID to increase fatigue strength.

Good idea, bad idea???

 

[Compositepro]

2.5" Schedule 160 pipe is 2.875" x 2.125"