Building a roll bar that’s period-correct and vintage racing legal

Update by Tim Suddard to the Elva Mk VI project car
Sep 19, 2024 | Restoration, roll bar, Vintage Race Car, Elva Mk VI

Photography by Tim Suddard

Somewhere along the way, our Elva sports racer lost its original roll bar. It wouldn’t have been tall enough, anyway, nor made from the correct tubing. We needed to start from scratch.

Our job was to build a roll hoop that would be legal for SVRA and HSR competition yet still retain the car’s vintage looks.

Small dose of reality: Short of completely caging the car and, for that matter, rebuilding the flimsy tube frame, there is no way to make our Elva Mk VI as safe as a sedan with a full cage.

This forces those running vintage formula cars and sports racers to make compromises, and we faced a big one ourselves: The SVRA rule book tells us that we should, but don’t have to, link the main hoop to the bottom of the chassis, but on an Elva Mk VI, the trailing arms are in the way. To satisfy this request, we would literally have to put trailing arms right through the middle of the hoop.

Linking the main hoop to the bottom of the chassis would also cause interference with the engine, water pump and alternator pulley.

To overcome this issue, we figured that we’d mount our main hoop to the top part of the chassis and reinforce everything as much as possible. We welded a pair of 1/8-inch plates to the top of our chassis to accept the roll bar hoop and then added extra support bars underneath to help spread any load down to the bottom of the chassis.

Next, we needed the hoop itself.

We purchased a stick of 1.5-inch, 0.120-wall DOM roll bar tubing. According to the rules, a car of this weight only requires thinner, 0.90-wall tubing, but a bit of extra thickness, and thus safety, is not a bad idea. Always consult the rules–and the experts–when building a roll cage. A larger car, for example, would require 2-inch tubing.

We then went to Harbor Freight and purchased a $150 tubing roller. A tubing bender will not work as it kinks the tubing, something absolutely not allowed on race cars.

We wrestled with not one but two of these benders, with the first one breaking. In frustration, we ended up going down to a local race shop that, in minutes and with real equipment, bent a perfect hoop.

To meet SVRA rules, this roll bar hoop needed to sit 2 inches above our driver’s helmet. The rules also said that this roll bar needed two support bars going forward or backward that mounted within 6 inches of the roll bar’s crest.

This is essentially impossible on an Elva Mk VI. We looked at pictures of similar cars, and they all had just one bar.

Again, we talked to both SVRA and HSR tech officials and were told that one support bar would suffice. Our support bar would head toward the back of the car.

Now, where to place the mounts for that support bar? Thanks to the Elva’s engine cover, this bar would need to be easily removable.

At the top of the roll bar, we formed a boxed mount out of 1/8-inch plate to accept a quick-release pin.

The lower mount, the one that attaches deep in the engine compartment, would be a little trickier: We didn’t have a lot of placement options, and we wanted the bar to enter the engine compartment through its access lid.

After considering the various options, we settled on a point near a mount for the transaxle’s cradle. We would again use a boxed mount that we’d weld to a frame tube and also bolt to the transaxle’s cradle. This mount would then accept a 7/16-inch bolt. Before calling this complete, we needed to further strengthen this area of the frame.

We also had to slightly cut the body so this diagonal support could fit.

We then welded in a harness bar. While the bar should ideally place the harness 15 degrees below the driver’s shoulders, HMS Motorsport, our harness provider, and HSR Technical Director Jack Woehrle both told us that an inch or 2 either way would be okay.

Mounting the belts below the shoulders would have required attaching them to a crossbar inside the engine compartment. Doing that would have required slits in the fiberglass body.

Not only could this cause rubbing of the belts on the fiberglass body, but unless you figured some way to box in the slits, flames could pass though those slits. Generally speaking, no slots, slits or holes are allowed between the engine compartment and the driver compartment. Plus, the heat of the engine wouldn’t have helped the lifespan of the belts.

The final step was to add a ¾-inch horizontal bar for a padded headrest.

Finishing this project represented another major milestone in our project. Our goal was to add as much safety as possible without destroying the vintage look and feel of the car.