Tubular drive shafts for centrifugal fans 2

[spike]

I am looking for detailed information as to how to join a hollow circular tube shaft to solid smaller diameter journals. The completed assembly would consist of a long hollow tube joined at each end to a solid shaft journal.
The large shaft would support two to three centrifugal fans.

Any ideas would be appreciated.

 

[eg9arh]

Not sure if i understand fully, but i if do,
my only thoguht would be to machine the bore of the tube so as it was a light press fit onto the journals at both ends, then secure the journals at the set distance to stop it working out. That or machine a keyway into both journals and the shaft but thats even more costly. If the differance in dia is large, you could use a taperlock coupling, using the bore of the tube as the o-ring for the lock to compress against, locking it onto the smaller solid shaft

Al HIllery
Design Engineer

 

[Tmoose]

That construction is pretty popular in industrial rooftop HVAC units. The ones I recall seeing were press fit.
Failures of the press fit were rare, but not unheard of.

Issues of balance, critical speed etc depend a lot on uniform wall thickness, which is related to initial wall thickness from the mfg method, and straightness.