Quote Originally Posted by WESTERNAERO View Post
Yes, if everything stays linear.
ANY side load will ruin that.
And it is amazing, but the so called "whip" of a twisted shaft is pretty much mythical IMO.
Look at a tiny ass drill bit in a drill press. You can press to the point the bit bows, but it doesn't whip. The bow stays pretty much put. AS Westernaero says, so long as the shaft doesn't experience any side loading, the smaller shaft will absorb more angular twist under the same load without failure, but for a lower number of cycles.