[EricH]

Originally Posted by Gray Adams

I can't say that I recommend blindly following random posts on CD and expecting success. You could always either go through to math with the max torque seen on the shaft during a direction reversal at top speed, calculating the stress for a hex shaft, a churro, or a keyed shaft, and then selecting an appropriately strong material.

Or you could just test it and see what happens. Both are totally valid.

Why not do both? Run the math, then run the tests, and see how they stack up. Then if (when?) the test doesn't match the math, run more math and more tests to see which one forgot to take reality into account. There've been cases where tests showed a bit of a reality that doesn't show up at all in high school physics (or college physics, for that matter).