Gavin gives his Mk1 Cortina project some Lotus-style bracing for the rear.
Hoping to prevent some rear-end droop, Gavin channels the spirit of Lotus with some extra bracing courtesy Bishop’s Bespoke Builds.
Every day is a school day, but when I started out I didn’t realise just how much I’d learn when building a car. My Cortinas have taught me so much over the years, the latest regarding some of the modifications made to the Lotus Cortinas.The Lotus has never really been my thing, I’d prefer to utilise modern tech rather than be constrained by 1960s originality, but now I’m thinking I should have paid a little more attention to the modifications they made and the problems they were solving.
I knew that they fitted bracing to the rear of the car, but I thought this was to add some strength to a road car without the intrusion of a roll cage. They fitted diagonal bars from the base of the B-post to the top of the wheelarch, then another tube down to the chassis in the boot. I’ve only recently learnt that this was added when they found that the rear of the car could crease following the replacement of the leaf springs with the Lotus A-frame set-up on the early models. It seems that the springs were to a certain extent holding up the rear end of chassis/boot. I guess the bending of the rear probably happened in extreme circumstance — rallying or racing — but I figured I should take heed anyway.
The link
The previous owner of my two-door had five-linked the rear — not quite the suspension set-up used on a Lotus, but it does have the removal of the leaf springs in common. So I figured there was a risk that the rear of my car could be afflicted by the same droop, and I should do something to prevent it now, before it
hits the road. At first I thought the obvious solution was to buy some Lotus reproduction bars but this thought changed with a conversation with Rich at Bishop’s Bespoke Builds. Firstly we weren’t sure how easy it would be to access and weld them in place between the inner arch and the outer wing. Secondly, I haven’t got a Lotus, so why be constrained by a design originating in the 1960s? So Rich started with a clean sheet and fabricated bracing running from the damper towers (revised when the car was five-linked) down to the rear chassis. Rich builds a lot of roll cages so used his experience to fabricate a much stronger connection to the chassis than the Lotus bracing — a welded joint allows a vertical tube to pass through the chassis. This is welded to the underside of the chassis rails, a much stronger detail than the Lotus tab welded to the top. It also seemed unnecessary to add the bracing from the bottom of the B-post up to the arch given that I already have a rear roll cage fitted, and we figured adding a firewall would tie everything together and give improved rigidity to make a the rear end stronger. So while Rich was there he also welded in a detailed firewall. That was another lesson — I said there was no need to add detail as the firewall would be covered, but evidently adding some pressing gives more rigidity and will prevent the firewall flexing while driving.
The new bracing has also resulted in the swirl pot needing to be relocated but that was simple with it now sitting over the driver’s side on a new platform.
I’m more than happy: inspired by Lotus but not a copy, I now have modern day bracing which should prevent my Cortina having a droopy rear end.