Losses due to bending a rotating shaft
Losses due to bending a rotating shaft
(OP)
I'm trying to find out how the bending of a rotating drive shaft effects the power output of a system in qualitative terms.
So, if we have a cantilever system with a rotating shaft and a load causing the shaft to bend - is there a formula for calculating the power required to rotate that shaft at a specific rate?
Many thanks
So, if we have a cantilever system with a rotating shaft and a load causing the shaft to bend - is there a formula for calculating the power required to rotate that shaft at a specific rate?
Many thanks





RE: Losses due to bending a rotating shaft
If your shaft is subject to elastic strain, all the energy you put into it should be recoverable. There should be no power losses, due to the elastic strain.
Your bearings and gears are another matter, and not as easily modeled with simple equations.
RE: Losses due to bending a rotating shaft
Have you patented this apparently hysteresis-free and entropy-free material?
RE: Losses due to bending a rotating shaft
RE: Losses due to bending a rotating shaft
RE: Losses due to bending a rotating shaft
You might have more luck finding an approach if you look in the literature for torsional harmonic dampers, where the rubber insert does absorb a useful amount of energy.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Losses due to bending a rotating shaft
Drivers report a significant difference in performance between axles with slightly different wall thickness. Generally we assume the stiffness of the axle has an effect on the overall flexibility of the kart chassis, but the deflection of these axles is very small under significant load so it doesn't seem plausible.
a typical axle would be in 4340 steel, 40mm x 3mm x 1040mm
Total weight of kart + driver 160kg.
So, I'm wondering if there might be significant efficiency losses due to complex harmonics, that can change with the stiffness of the axle.
RE: Losses due to bending a rotating shaft
The axle's torsional stiffness probably has a significant effect on the instantaneous traction distribution left to right. You might try putting a second axle across the chassis and see if its stiffness helps.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Losses due to bending a rotating shaft
thanks for your time
RE: Losses due to bending a rotating shaft
Vertical deflection would seem to be absorbed by the tire sidewalls for little overall effect. Torsional wind-up of the axle could affect instantaneous yaw, but because that effect is damped by the entire mass of the kart, it seems that this should be of little consequence.
If you arranged a test rig with a limber axle and then added supplemental outboard bearings near the rear wheels, and located those bearing via angle struts back to the chassis in a vertical and horzontal plane it might be possible to experimentally determine what factors are significant. With this rig, the compliance of the axle in the desired plane could be adjusted by substituting harder or softer steel, nylon, and various rubber washers to determine what is actually occurring.
RE: Losses due to bending a rotating shaft
RE: Losses due to bending a rotating shaft
Tmoose: Performance feedback from drivers and laptimes is what gives rise to the idea that different grade axles give different results.
I think my next step will be to do some track testing, and see if a data logger on the kart can quantify the reported differenes, and report back here.
Thanks again for your input everyone