Drivetrain analysis

[dlreed]

I am analyzing a drive train consisting of a motor, transfer case, driven load, and a flywheel case. The motor housing is directly coupled to the transfer case, which transfers the motor torque thru a belt to treadmill front roller, which is the load in this case. Directly coupled to the front roller is the flywheel assembly, which is also bolted to the motor housing. I am attempting to calculate shaft and bearing reactions and housing bolt reactions. I am assuming that the motor torque drives the system, while ignorng system inertia. I am not quite sure how to handle the torque transferred to the flywheel housing. Does this torque also load the flywheel housing screws, or am I counting this torque twice since the motor box is already rigidly attached to both the transfer case and flywheel case, which are both rigidly attached to opposite ends of the front roller. Any ideas on now I should handle this close loop system.

 

[Biggadike]

Reagrdless of the actual drive design, the same basic principals apply. For simplicity, lets ignore inefficiency:

1/ Power is always constant. You swap torque for rpm as the gearing changes.
2/ A torque is equivalent to a couple (a twisting motion about the center) and a side load. To determine the side load at a shaft, claculate the torque (from power and linear speed of the acting part of the drive. On a gear that would be the PCD/2). The force part of the torque can be taken as acting directly at the shaft centre. Add that force to any pre-load in the system.
3/ Standard equations exist for inertia of fly wheels. That will resist stopping and starting by imposing an opposite torque on the drive.
4/ You need a good margin of safety to avoid failure as no system runs perfectly and shock loads and vibration do damage.

If you want to add efficiency, you need to do it per drive interface (gear to gear etc.) - This reduces the power at the point in question in a cumulative way.