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Re: Chassis stiffness

From: Philip Dingle
Category: Technical
Remote Name:
Date: 15 Sep 2002
Time: 12:26:32


I think a better way, and not too difficult to undertake, is to anchor the chassis to the ground rigidly and then apply a torque to the other end: -

I visualize two short lengths of RSJ (I-beam) bolted to your garage floor using concrete anchors. The rear of the chassis sits on these. A close fitting tube runs across the chassis through the lower chassis rear trailing arm trunnions (attachment points), and that tube is in turn anchored to the RSJ using U-bolts. This will make a rigid attachment, although it would be more correct to use the upper trailing arm (torsion bar) trunnions since this is where the force feeds into the chassis. It is however difficult to make the firm connection there, unless you U-bolt to another chassis tube close by.

At the font, the chassis sits on a single central fulcrum which keeps the frame horizontal. A simple wire pointer is attached to the center of the front crossmember, and indicates rotation on a large protractor which is supported on the garage floor. Another tube is U-bolted across the chassis adjacent to the front suspension lower arms. Known weights are suspended on this cross tube at a known distance from the chassis centerline (say 1 meter), and the chassis twist measured on the pointer in Nm or foot/pounds.

Try this with and without the body on the frame and see what difference there is. It may be possible to identify where judicious strengthening could be applied. It is a pity that Jowetts did not use oval tube for the main chassis side members as utilised on the very similar (but not very successful) G-type ERA.

Last changed: November 19, 2008