Hollow torsion bar equivalent as solid bar.

[motowaz]

Cheers all,

I am currently using a hollow torsion bar (splined on both ends) with an OD of 1.125" and an ID of .875". What dia. solid bar would give me equivalent performance.
I know this formula is in Shigley somewhere, but I cannot find it.

Thanks in advance,
Jason Miyamoto

 

[boo1]

If u recall the elastic torsion formula relates to the polar monent of inertia:
J=1/2*Pie*c**4
Equating the solid J (Js) to hollow J (Jh)
Js=Jh
1/2*Pie*Rs**4=1/2*Pie*(Rhouter**4 - Rhinner**4)
Rs=1.004 inch

 

[motowaz]

Thanks for the post boo1,
The fact that going to a solid bar will require an increase in dia. was not what I was expecting.

Thanks

 

[sreid]

The answer should have said that the new OD was 1.004 inches for the solid torsion bar. Note, however, that the solid torsion bar has twice the area (and twice the weight) of the equivalent hollow torsion bar.

 

[mloew]

Boo1,

What kind of Pie? I suppose you were meaning [π] or pi, right?



Best regards,

Matthew Ian Loew
"I don't grow up. In me is the small child of my early days" -- M.C. Escher

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[boo1]

How do you add the special char to posts?

 

[mloew]

Boo1,

Click on the Process TGML link and scroll down to the Special Characters section.



Best regards,

Matthew Ian Loew
"I don't grow up. In me is the small child of my early days" -- M.C. Escher

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.