long drive shaft
long drive shaft
(OP)
Hello all.
I have a solid steel shaft driving a generator from the PTO output on a marine gear. It is rotating at 1820 rpm with max. power transmission of 800kW. The shaft is 5.188" diameter and 84" long.
It looks like critical speed is ok. I believe it is around 3100rpm. The static deflection is 0.0036". The shaft will be balanced - probably to AGMA 8.
Just wondering what else I should be concerned about. Is critical speed and deflection the only analysis that can be done - other than computer modeling which is big $$.
I want to be confident that when we power this up that no unforseen things will happen.
Cheers!
I have a solid steel shaft driving a generator from the PTO output on a marine gear. It is rotating at 1820 rpm with max. power transmission of 800kW. The shaft is 5.188" diameter and 84" long.
It looks like critical speed is ok. I believe it is around 3100rpm. The static deflection is 0.0036". The shaft will be balanced - probably to AGMA 8.
Just wondering what else I should be concerned about. Is critical speed and deflection the only analysis that can be done - other than computer modeling which is big $$.
I want to be confident that when we power this up that no unforseen things will happen.
Cheers!





RE: long drive shaft
Don
Kansas City
RE: long drive shaft
How is the shaft coupled between the gear and the generator? If bolted, which will fail first under torsion loads - the bolts or the shaft?
Are there any built in failure modes, such as a key-ways or shear-pins?
800 kW is over 1000 horsepower. Assuming engine speed is equal to the drive-shaft output speed, that translates to 3093 ft*lbs of torque. Probably not enough to twist off a 5" driveshaft. But in the case the shaft failed, are there provisions to keep it from whipping around? (like a drive-shaft loop used on high-horsepower automobiles)
RE: long drive shaft
Fatigue, SCF's, mat'ls etc., in there
RE: long drive shaft
RE: long drive shaft
Several things to look at:
1. static bearing load
2. shaft imbalance
3. shaft whip (frequently significant in a slender shaft)
4. loads and frequency response of the castings at either
end
5. shaft angles
Truck
RE: long drive shaft
Russell Giuliano
RE: long drive shaft
One end has a lovejoy rigid-flex gear coupling and the other a Spiroflex torsional coupling with spherical bearing option. The spherical bearing keeps intermediate shaft centred but allows angular misalignment.
The gear coupling only allows angular misalignement also.
I checked critical speed and is ~3120 rpm based on 0.0035" deflection. Combined stress (bending/torsional) looks fine also. Stress concentrations at both ends with keyways look fine.
The shaft balance will be AGMA 8. Can anyone comment on this spec.?
Thanks.
RE: long drive shaft
Russell Giuliano