The roll cage
I took a trip over to Must Weld Motorsport on Monday 4th July to carry out a few minor jobs on the Coupé to allow the cage builder access, to discuss the required spec in person and to get measure dup for seat fitting. Jamie likes to build the cage around the seat / driver to ensure everything works together.
Although a ‘belt and braces’ approach to building a roll cage would be the best way to maximise torsional rigidity, it would also make the car heavy. As I wanted to strike an efficient balance between rigidity and weight, before getting into diminishing returns, we had a lengthy discussion on what was and wasn’t required. After discussing just about every brace I’d seen online and what it was for, we went full circle and eventually settled for a fairly straightforward 6-point cage.
The spec then:
• It’s a custom-made, weld-in cage in CDS with 2.5mm wall bars
• The main hoop and harness bar is in 45mm, while all other bars are in 38mm
• The rear struts are mounted to the boot floor above the subframe is mounted. As Jamie points out, there seems to be no sense in mounting it to a wheel tub if suspension isn’t mounted to it. Best to put it where the load will be to make the cage take the weight and not the chassis.
• It has an ‘X’ in the rear stays to prevent lateral movement in the main hoop, but won’t have gussets.
• It features double door bars in Jamie’s ‘easy access’ style – I asked him if he could line these up with the slashes on the door. When I asked for this, he gave me exactly the look you would imagine he would…
but did it anyway – I think it really sets it off! Two bars are used to maximise side impact protection but there is no X that can result in a bar pointing into the cabin if notched against the first diagonal. You can bend two bars to make an ‘X’ but then access is restricted.
• A harness bar is installed on the main hoop (as opposed to between the rear stays) to keep the harnesses as short as possible, and they line up exactly half way up the harness holes in the seats to ensure they hold the driver in place and put no pressure on the seats in the event of an accident.
• The cage is super tight to the shell and welded to it wherever possible. This ensures that it functions with the chassis (rather than moving about within it!) and also keeps it as far aware from the occupants as possible.
• FIA spec seat mounts have also been fitted. This means the original seat mounts and box section are no longer required – they’ve been cut down for now but I’ll have to drill the spot welds to clean it all up. Jamie measured me up for fitting for the best placement of these but I will have a degree of adjustment using the Sparco FIA Steel Side Mount Brackets. Annoyingly, there is little to no adjustment in height with these brackets in combination with my seat, so I may have to look elsewhere if this is an issue.