Torsion Bar 1

[MECH8T4]

I have a torsion bar we use in our product that now is 2"x2" with 3/16 wall in HSS, hollow tube.
We need to change this to 1.5"x3" with the same wall thickness. Everything else to remain the same.
Will this be a safe change from a torsional strenght point of view?
What chart figures could I check to ensure we are not making the product weaker?
Any expertise on this would be much appreciated.

 

[desertfox]

Hi MECH8T4

Look at this site, although you will need to convert to metric you can compare the torsional constants J for both sections:-

http://www.roymech.co.uk/Useful_Tables/Sections/steel_section_index.htm#tables

 

[MECH8T4]

Hi Desertfox-thanks for the replay. I ahve a chart for this, and I just wanted to confirm that the "J" figure is what I should be looking to compare and get assurance on this. I thought it was but not having actually used some of this for a hwile, wasn't confident.

 

[rb1957]

for a closed tube torsion stresses are a function of the enclosed area ... 1.8125" * 1.8125" = 3.26in2 ... 1.3125*2.8125 = 3.69in2

all other things being equal, the new section has lower torsion stresses.

 

[MECH8T4]

Thanks rb1957, sounds like all should be good then. is the J figure also an indicator of the alternate being acceptable?