Re: torsion bar springs

[William and Melissa Johns <gizmology-at-gizmology.net>]

If they're too soft, shorten them!  Of course, you'll hit the elastic limit 
sooner.  On the flip side, if they're too stiff, lengthen them!  By 
adjusting the length, you can get any stiffness you want.

Bill


At 10:02 AM 11/6/2003 -0500, you wrote:

>Randy,
>
>At 05:47 PM 11/5/2003 -0600, "randall b reynolds" <reynoldsrk-at-msn.com> wrote:
>>I was thinking of torsion bars for the tank I'm building. Ace Hardware 
>>has spring steel rods 36" long , in 1/8" and 3/16" dia. They also have 
>>cable ends in these sizes with clevis ends to make attachment easy. The 
>>rod fits nice and snug in the cable end so loctite should be plenty 
>>strong to hold them. The cable attaches by swaging into this end so I 
>>guess this could be done also.
>
>The 3/16 may be a little too stiff and the 1/8 may be
>a little too soft based on my calculations below.
>The target value for my M1A1 is 68 in-pounds/radian
>torsional stiffness.
>
>round steel torsion rod 3/16 OD x 8 inches long
>r = 3/32
>G = ~ 11.5 x 10^6 psi for steel
>J = J = pi * r^4 / 2 = 121 x 10^-6 inches^4
>K_theta = J * G / L = 174.4 inch-pounds/radian
>
>round steel torsion rod 1/8 OD x 8 inches long
>r = 1/16
>G = ~ 11.5 x 10^6 psi for steel
>J = J = pi * r^4 / 2 = 23.97 x 10^-6 inches^4
>K_theta = J * G / L = 34.5 inch-pounds/radian
>
>I would give the 3/16 a try.  It depends on the weight
>of your tank, the number of road wheels and the swing
>arm radius.
>
>Good luck,
>Joe
>
>
>
>**********************************************
>Joe Sommer
>2378 Nantucket Circle, State College, PA 16803
>814.234.4773     anvilus9-at-adelphia.net
>http://users.adelphia.net/~anvilus9/
>
>

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