Traction or “ Anti-Tramp” bars were fabricated to limit the wind-up of the rear leaf springs, mainly during braking. Each bar is fabricated from ¾ in. OD steel tubing with welded 3/8 in. L/R hand inserts for rod ends. One end attaches to the axle through a pair of vertical brackets of 3/16 steel which are welded to the top of the axle housing and positioned so the bar is in-line with the leaf spring. The other end attaches to a bracket on the on the chassis. Two sketches and a photo follow the text.
The upper sketch shows how the chassis mounting point was determined. A masonite panel was clamped to the chassis with a 90 degree corner snug against a crossmember and the lower chassis flange. The corner was the origin of an X-Y coordinate system to transfer measurements from the axle movement to the chassis (point O). A wood mock-up of the axle housing bracket was clamped to the top of the axle and a pencil-sized hole drilled at the attachment for the bar. With the rear shocks removed, the chassis was carefully bounced, causing the pencil to scribe an arc on the masonite. The center of the arc was identified (point P) and transferred to the Roll Bar Structure.
This procedure was initially done during the 1970-71 Conversion to a Race Car, and again with the new Roll Bar Structure during the 1999-2003 Major Upgrade.
The lower sketch shows the chassis attachment consisting of a bracket welded to the Roll Bar Structure and a fitting that allows both pivoting and a small degree of fore-aft compliance using shock absorber rubber mounts.