Roll Bar Structure

In Spring 1963 a roll bar was fabricated. It was a bolt-in design consisting of a main hoop and a forward brace from the top to the passenger side foot area. There were no rearward supports. The forward brace bolted to the hoop, and feet cut from angle iron were welded to the bottom of the tubes for bolting to the frame. The roll bar was installed for races and removed for street driving through 1969.

SCCA had updated the rules, so a new roll bar was designed and installed in the 1970-71 Conversion to a Race Car. It had a main hoop with a diagonal and a lower crosstube, a forward brace to the passenger footwell, and two rearward supports that attached to the chassis side rails. Angle iron feet were welded to the lower end of the tubes for bolting to the chassis and their upper ends were welded to the main hoop in the car. This was run until the Major Upgrade, 1999-2003.

The current roll bar structure was designed and installed in 2004. It  consists of a Main Hoop, Rearward Supports, Cowl Hoop, Cockpit Side Members, and Forward Supports. The lower parts of the Main Hoop, Rearward Supports and Cowl Hoop have welded-on feet that were bolted to the chassis, and their upper parts then welded together, along with the Cockpit Side Members. Details are described below, including a few photos.

 MAIN HOOP consists of 1 ¾ in. diam. x 0.095 in. wall DOM 1026 steel tubing and a diagonal brace of the same material. Tabs for the headrest are welded on the diagonal brace. The legs of the hoop are joined near the bottom with 1 ¼ in. x 0.065 wall square tube, which is redundant with the chassis rails, but serves as a mount for aluminum panels behind the driver and also to support the brackets to mount the traction bars. Horizontal sections of 1 in. x 0.065 tube are welded between the hoop and diagonal behind the driver and hold upper mounts for the seat and the shoulder harness.

REARWARD SUPPORTS of the same material as the Main Hoop,
straddle the Fuel Cell and attach to the rear crossmember. This protects the Fuel Cell and transfers loads from the rear spring mount to the roll structure. These tubes mount 6 inches below the top of the Main Hoop, meeting SCCA guidelines. Tube shock mounts are welded to these supports, and triangulated to the main hoop with 1 ¼ tubing. A bracket for the upper Watt’s Linkage pivot is also welded to one support.

COWL HOOP consists of 1 ½ in. diam. x 0.095 wall steel tubing and bolts to both the lower flange and the vertical portion of the frame rails. Mounts for the Forward Supports are welded on the front of the hoop, near its top.

COCKPIT SIDE MEMBERS of the same material as the Cowl Hoop are welded between the Main and Cowl Hoops. They bow slightly outward for elbow room, and their height is even with the top of the doors. These members and the 5 inch deep frame rails contribute to side impact protection.

 FORWARD SUPPORTS, consisting of 1 ¼ in. diam. x 0.095 wall steel tubing, run from each side of the Cowl Hoop, through the firewall, to the lower Front Frame. Rod ends (1/2 inch) are fitted to each end of the tubes which allow the Front Frame to twist slightly during cornering, but resist bending the front portion of the chassis during braking. The Front Frame section shows details of the lower attachment.

The tubing was obtained from Midwest Steel Supply Co., Minneapolis, MN, and the tube bending was done by Creative Metal Works in Blaine, MN.

DSC_0015.JPG

Cockpit Side Members, Etc.

DSC_0007

Cockpit Side Members, “Top View”.

DSC_0008

Main Hoop, Diagonal, Etc.

 

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