The thing is a hollow tube CAN be stronger from the standpoint of weight in tosion. Here is why. Torsional stress for a solid or hollow rod/tube is:
S= T*r/G*J Where J is the polar moment of inertia for a tube is: J= (PI/64)*((DO^4) - (DI^4)) For a rod it is: J=(PI/64)*(DO^4) Since most of the stress is in the outer fibers, removing the inner part of the rod, to make a tube and increasing the outer diameter gives a hollow tube that is stronger in torsion than the rod. It will however, have a larger outside diameter. The same is true in bending. Understand there are more things at stake here than just the bending and torsional stress and deflection. Using welded or seamless tubing can affect the load capacity of the tube, and there is always the issue of buckling under load. Sometimes people draw vast conclusions from half-vast data. The bottom line is that a hollow tube CAN be stronger, by weight, but not by size, than a solid rod of the same material. ________________________________ FormulaCar Magazine - A Proud Supporter of Formula 500 The Official Publication of Junior Formula Car Racing Subscribe Today! www.formulacarmag.com or 519-624-2003 _________________________________ _______________________________________________ F500 mailing list - [email protected] To unsubscribe or change options please visit: http://f500.org/mailman/listinfo/f500 *** Please, DO NOT send unsubscribe requests to the mailing list! ***
