02GF74 Posted August 29, 2006 Share Posted August 29, 2006 question posted on another forum: ---------------------------------------------- Why do gundrilled driveshafts not shear off in conditions that cause solid shafts to shear? I know all the theory behind tubular shafts being lighter and obviously that a thin walled shaft of the same cross sectional area as a solid one will be much stronger in torsion BUT experience (not just by me of course) shows that gundrilled solid shafts will withstand vastly higher loadings that solid shafts of the same diameter, why is this? -------------------------------------------------- assuming this ^^^ is correct, then anyone have an explanation as to why that would be? Quote Link to comment Share on other sites More sharing options...
Astro_Al Posted August 29, 2006 Share Posted August 29, 2006 God, not this again. Does he give any references? Al. Quote Link to comment Share on other sites More sharing options...
02GF74 Posted August 29, 2006 Author Share Posted August 29, 2006 again? must have missed it the last time. presumably is it bo77ox then? (can't see how it cannot be myself). Quote Link to comment Share on other sites More sharing options...
GBMUD Posted August 29, 2006 Share Posted August 29, 2006 'cos you could case harden the inside too? Chris Quote Link to comment Share on other sites More sharing options...
Bush65 Posted August 30, 2006 Share Posted August 30, 2006 'cos you could case harden the inside too?Chris Can't see it myself! Consider the torsional shear stress distribution from the outside fibre to the inside/centre, then try to prove how case hardening the inside will make any difference. Quote Link to comment Share on other sites More sharing options...
GBMUD Posted August 30, 2006 Share Posted August 30, 2006 Can't see it myself!Consider the torsional shear stress distribution from the outside fibre to the inside/centre, then try to prove how case hardening the inside will make any difference. That was a guess. I would have no clue how it would work, never mind be able to prove it! Chris Quote Link to comment Share on other sites More sharing options...
Daan Posted August 30, 2006 Share Posted August 30, 2006 I does not make a difference if you leave the outside diameter the same, in fact it makes it worse. However, if you start with a bigger diameter and drill a hole through the centre, the strength to weight ratio is much better. Any race car or rally car Which is allowed to spend money on has gundrilled shafts. Problem with landrovers is that you cant up the outside dia of the shafts without changing a lot of other parts, so probably not worth the effort. Daan Quote Link to comment Share on other sites More sharing options...
simonr Posted August 30, 2006 Share Posted August 30, 2006 Thanks Daan - I was about to jump in with that (or something like it!) As you move towards the centre of a solid shaft, the material makes pregressively less difference to the overall torsional strength. While it is the case that a solid shaft is stronger than a tube, it is not by a staggering amount. By taking the same mass of steel and making it in to a bigger diameter tube, you can gain a significant amount of strength. Si Quote Link to comment Share on other sites More sharing options...
02GF74 Posted August 30, 2006 Author Share Posted August 30, 2006 experience (not just by me of course) shows that gundrilled solid shafts will withstand vastly higher loadings that solid shafts of the same diameter, why is this? yep - I think he/they are deluding themselves. personally I cannnot see how removing material from the centre thus reducing cross sectional area cna make anything stronger. Quote Link to comment Share on other sites More sharing options...
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