NS Dev
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| posted on 31/8/06 at 07:06 AM |
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The drag racing comparison is very relevant as grasstrack cars have a suspension setup almost enbtirely devoted to getting to the first corner first,
and develop enormous traction even on very slippery surfaces.
Cars with lots of power and locked diffs (i.e. most top grassers) tend to snap shafts at the startline with some regularity, and gundrilling prevents
this, as does making the shafts as long as possible and of not too great a diameter.
Just chatting to a fellow engineer at work and coming to the conclusion that the benefit if gundrilling is probably a combination of REDUCING
torsional rigidity of the shaft so reducing shock loading by enabling increased "spring" of the shaft, coupled with removing any stress
raisers left in the centre of the bar during production (which is where nearly all bar impurities end up)
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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NS Dev
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| posted on 31/8/06 at 07:08 AM |
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................however we are still guessing, and the next question is........why is an annulus a better torsional spring than a solid bar????
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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ned
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| posted on 31/8/06 at 07:41 AM |
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for anyone else like me who doesn't know what annulus means:
http://en.wikipedia.org/wiki/Annulus
beware, I've got yellow skin
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MikeRJ
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| posted on 31/8/06 at 02:28 PM |
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quote:
Originally posted by NS Dev
................however we are still guessing, and the next question is........why is an annulus a better torsional spring than a solid bar????
IMO it isn't necessarily a better spring, but maintaining a shafts diameter by gun drilling is going to give a more rigid shaft i.e. less liable
to whip than a slimmed down solid shaft.
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JoelP
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| posted on 31/8/06 at 05:56 PM |
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quote:
Originally posted by 02GF74
I cannot see how removing material from an object can make it stronger than the original no matter where it is remove from.
Wont make it stiffer but can definately make it stronger. If part of an item is too stiff, all the stresses and twisting/bending are forced onto the
weakest part, hence if you can spread the stress out, it will last longer. This is why wishbones can be made stronger by removing some of the shock
mounting plate, the bend is spread over several inches rather than being focused by the plate onto the weak part where it ends.
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C10CoryM
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| posted on 1/9/06 at 03:30 AM |
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Man, I searched through a pile of books and could not find the info I wanted.
I did find this which is similar enough to the article I remembered.
http://instruct1.cit.cornell.edu/Courses/virtual_lab/chalktalks/theory/1.shtml
Page 8 shows solid VS hollow.
Cheers.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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leto
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| posted on 1/9/06 at 06:08 AM |
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At some conditions you can get a stress concentration at the center of a round bar. IIRC, typically if you press the bar between two flat surfaces. I
don't know if/how this in anyway applies to a drive shaft.
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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mcerd1
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| posted on 1/9/06 at 09:44 AM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by RazMan
Heat treatments only affect the 'skin' of the metal don't they?
Not always, you are possibly thinking of case hardening which does just affect the surface. Steel is a very complex metal, heating it to various
temperatures and letting it cool at different rates can significantly change it's properties.
when I mentioned heat treatment I was thinking of 'annealing' or 'normalizing' processes where the steel is heated to a given
temp. then allowed to cool slowly
this helps to relieve internal stresses from the manufacturing process (removing the centre of the shaft could setup an unbalanced system of internal
stresses that could accelerate fatigue cracks etc - can't remember much about this stuff though)
any other form of heat treatment is an attempt to get the best balance between a shaft that has a high yield point (but is brittle) and one that has a
low yield (but will deform rather than fracture) and all this depends of the alloy used and where the week point is on the shafts (you could have a
shaft with hard ends and a soft middle)
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