Torque calculations for logging winch

[Pkruse]

Yes. But put the crows foot at 90 degrees, and it stays the same. A U-joint will also seriously complicate the math.

 

[FeX32]

Agreed :)
The U joint will change the torque sinusoidally from input to output as the joint rotates.

 

[Pkruse]

Use 2 in line u-joints 90 degrees out of phase with each other. They will cancel each other out and give true torque. Lines of action must be parallel.

 

[FeX32]

Yes, just like the way they are designed in transport trucks.
The only reason why we are changing to CV joints for trucks (or trying to) is fatigue loads. Even though the input-output relation can be almost the same the intermediate shaft is subjected to repeated and reversed sinus inertial torque. This causes premature wear and eventual failure.
Anyways, this is way off topic LOL.

Cheers,

 

[Pkruse]

I always wondered about drive shaft fatigue. I figured that they just threw enough material at it for infinite design life.

 

[FeX32]

Engineers try to design these components for infinite life, particularly when lives are involved. However, if we designed everything to last very long periods of time no one would need a new transportation vehicle in 50 years. This is bad for business. Moreover, the typical engineering approach to design such components is a nonlinear optimization problem. Optimizing performance, life, and cost all in one shot.
You could imagine over engineering a shaft so that it can handle 2000ft-lbs of torque for 20000 hours and use it on a device that only subjects it to 500 ft-lbs peak torque would affect the inertial performance of the device. All that extra mass can significantly affect the performance.

In short, we don't design things for infinite life most of the time. Just as long as possible given a certain cost and performance criterion.

Cheers,

 

[FeX32]

To add a bit to that. New engineering methods can reduce inertial affect and simultaneously increase its fatigue life. This however, is expensive to engineer and manufacture. Some of this involves composite materials and extensive finite element analysis and experimentation.