Torque Rating of Gearbox
Torque Rating of Gearbox
(OP)
This seems to be a pretty basic question, but I have probably been over-thinking it. I am trying to clarify some torque issues with one of our gearboxes. Is there an equation for torque that the manufactures use to rate their gearboxes? I know that Power=Torque*speed or HP=torque*rpm/constant. For couplings, Torque=63000*Pnormal*SF/Nnormal (already has constant included?). I was wandering if this formula is applicable for gearboxes also? I am guessing that the gearbox manufacturers have the same gearbox for a range of power and they only change the S.F. to have an accurate nameplate. We have changed the driver power and I wanted to make a quick check to see what the gearbox is capable of handling. If I used a new gearbox I will probably have to put a new foundation in.
Background info:
Gearbox ratings
32hp
In RPM: 3402
Out RPM: 808
Ratio: 4.211
S.F.: 1.46
Steam Turbine Driver
Background info:
Gearbox ratings
32hp
In RPM: 3402
Out RPM: 808
Ratio: 4.211
S.F.: 1.46
Steam Turbine Driver





RE: Torque Rating of Gearbox
No, unfortunately, there is no "easy" method to do the job properly.
RE: Torque Rating of Gearbox
Then, if you want to have a well calculated gearbox,it is necesary to be working with it a very very long time, and there is not an easy way to do it
RE: Torque Rating of Gearbox
RE: Torque Rating of Gearbox
RE: Torque Rating of Gearbox
RE: Torque Rating of Gearbox
- higher tooth loads and slliding components;
- higher bearing and bearing support loads;
- higher gear pin or trunnion loads;
- higher mounting loads on the mounting means;
- higher heat load on the lube system whether grease or oil pressure.
The gearbox may be able to stand up to the new conditions, but you have to prove it. Run an exhaustive cyclic testing program.
Along similar lines, how do you test a product that requires continuous duty for a very long time? Challenge it with higher loads, degraded lube, less cooling, etc. The exact proportions of the challenges are according to your judgement as agreed by your peers.
RE: Torque Rating of Gearbox
constant, I think you would expect the heavier hp motor
to last longer.
If the speeds remain constant and the loads increased
your contact stresses would be higher. You might need
a better lubricant to handle the higher contact stresses.
If the failure is the result of higher contact stresses
having a dynamic effect on life, I think you would see
only 90 percent of the life of the gears in the gearbox
and this would assume the same gears as in the 32 hp
gearbox but maybe of a better material and quality.
There are so many variables that would have allowed the
increase in rated power or torque.
RE: Torque Rating of Gearbox
I think, but I will need to ask around, that the shafts on the gearbox failed when the clutch engaged and transfered the load. We don't have any run-up data or useful indicators on the turbine to see the torque during run-up.
RE: Torque Rating of Gearbox
However, if you do not have adequate scoring margin, your gearbox will fail in a matter of minutes. Scoring function can be slightly improved with a better grade of lubricant and by putting a better finish on the gear teeth. Both of these can be done to your existing gearbox without too much effort.
Also you haven't mentioned what type of gears these are. I'm assuming they're spurs or helicals?