Gearbox Wind-Up Torque/Force

[ScottQMiller]

On a gearbox for a pump, the torque should be higher on the low speed side (the pump shaft) than the high speed side (the motor). I'm sure this is true for a steady state system. On startup, shutdown, or anytime the system undergoes a transient response (say the pump shaft is quickly torqued while the pump is not running, is this still true? Take for instance the following example:

-Pump is not running. There is an anti-reversing clutch mounted on the motor shaft to prevent the motor from spinning backwards and damaging components.
-Something quickly torques the shaft in the reverse direction.
-Before the clutch will stop the reverse motion, all the free play in the gearbox must be removed, so the pump has the chance to speed up for a short time.
-Finally, after all slop in the system is gone, the clutch starts seeing torque and stops the pump from rotating.

If the clutch was mounted directly on the pump shaft, is it possible that the torque would be lower because there is not as much slop in the system that would allow the pump to accelerate?

 

[PersonalProfile]

1. Propose you would need to assess for the situation in question.
2. The following may be of use:

http://www.ringspann.com/files_db/1335332857_85__14.pdf

Regards,
Lyle

 

[MikeHalloran]

When you say 'the torque', you have to be specific about which torque you're discussing.

If you put a no-back clutch on the output shaft, then the motor would see little or no torque under circumstances that would engage the clutch. ... but the torque involved would be larger by the gearbox ratio, and you would need a proportionately larger clutch. ... which might engage more slowly because of its mass.

The _exact_ answer to your hypothetical question requires consideration of a lot of information that is not available to us, but that was probably available to, and considered by, the gearbox engineer.

Do you have an actual gearbox with a problem, or are you just ruminating?



Mike Halloran
Pembroke Pines, FL, USA

 

[ScottQMiller]

Do you have an actual gearbox with a problem, or are you just ruminating?

The discussion was a theoretical discussion on whether a no-back clutch (such as a Ringspann clutch) would see the highest loading if mounted on the output shaft, an intermediate shaft within the gearbox, or the motor shaft. I looked through the Ringspann article and it clearly is a complex problem that is often miscalculated. At this point I'm not trying to calculate actual peak loads, but just understand whether it is likely that the torque would be higher on the output shaft, or somewhere else in the system. I suppose it depends on a lot of factors, including gear ratios, stiffness of the components, clearances between gear teeth, and the profile of the load applied.

 

[desertfox]

Hi

I would say the maximum torque (peak) would occur at the point of loading, so lets say the pump impeller jammed instantaneously, then the motor via the gearbox would try to keep the pump turning and down stream from the pump impeller all the mechanical components like shafts and gears would suffer wind up until such time the brake or cutout/ slipping clutch kicked in.