If you pull a shaft in tension, it can have a 'strong' side and a 'weak' side, i.e. one side of the shaft has more material than the other. When you bend a shaft, however, the neutral bending axis shifts so that the shaft is equally stiff in both directions (in the plane of bending). You will get the same deflection in both directions. No preference. We can talk about variations in stiffness planes (bending planes), but not side to side (180* apart) of the shaft variations in bending stiffness.
Regards,
Alan Brooks
At 10:00 PM 10/5/2003 -0700, you wrote:
Dear Shoptalkers,
With regards to your discussions about Spines & NBP:
First of all, with the shaft resting (settled, if you will) in a bent position in a bearing type spine finder, NBP is on top, spine is on the bottom........Period.
Mark the shaft in this position.
If it is a steel shaft, determine the residual bend in the shaft. Roll it on a flat surface, use V-blocks and a dial indicator, but come up with a method of noting the residual bend.
Note the correlation of residual bend and the location of the Spine and NBP.
You will find that with the vast majority of steel shafts there is a direct correlation between the curvature of the shaft (residual band) and the location of the two planes in question. It will nearly always be the same correlation. I say nearly because I come up with some exceptions from time to time that defy explanation.
Best,
CB
