rubber infusion for fuel tank bladder?

I’ve been thinking about an internal bladder when I make my fuel tank, and one thing struck me – infusing aramid with viton rubber (very low viscosity) – wouldn’t that get the best of both worlds – really strong bladder and fuel resistance to boot. then sling the entire thing in a CF/Aramid tank.

I can’t see anyone selling VITON compound on its own though – seems to be as a finalised product.

Any thoughts?

Aramid floor tray is in

Here’s the floor tray, all nicely bonded in.

IMG_3334Here’s the floor-tray all nicely bonded in. You can see on the right of the picture how the floor-tray now replaces the cross-member I removed. I put several extra layers in there as well to pass even more force forward (than the 6 layers of 300gsm that’s already in there).

There’s also extra reinforcement, like a lardy-blokes truss, to take engine mounts if I decide to do that.

So Mark – tell us how you did it

IMG_3316 2


Here’s the part as it came out of the mould – all sharp edges and over-sized. Next job was to put it on the car – mark it up and trim it. That’s the boring bit and I don’t have any photos to document.



IMG_3324This is the chassis before the part is bonded to it. It had been blasted before powder coating, and I used the right high-temp non residue leaving breaker-tape to mask off the mating areas. The blasting heaves a fantastic key. I was worried originally that the tape wouldn’t make a brilliant barrier to rust after coating but it’s worked out fine. The reason being, the coating forms a seal against the tape so there’s nothing to get in – no air or moisture so no rust.

I marked the part up after clamping it down, and drilled for rivets. The rivets were just soft-ally headed ones to provide clamping force rather than to be anything structural.




Here I am as Clampy-McClamp-Face. I had every surface clamped before I drilled rivet-holes. If you drill-rivet as you go along the part, it starts to creep and your holes don’t line up. Clamping the entire thing before drilling keeps the accuracy.



IMG_3325Here’s a close-up of the rivet holes – I’m pretty pleased with how accurately the holes line up. Structurally it’s not really important, but attention to detail matters.








One post-trimming, bonded, riveted part in place. I used an epoxy two-part adhesive. It’s the slightly flexible stuff for parts under a lot of vibration.

Once the adhesive set (24 hours for full cure at 20C) it feels rock-solid.


First Pedal In

Jake the Peg

Here’s the first pedal in, with the box fully bolted down. This is the modified OBP pedal box I made a while ago. OBP were great about what I’d done, especially after I emailed them and jokingly asked if my warranty was still valid.

After I’d bolted everything down, it then dawned on me that I didn’t have clearance to get the clutch-pedal pivot bolt in, so it all had to come out.

I also greased the bolt shank as well (copper grease) just for good measure. The bolt half way up the pedal is for the clevis, so care needs to be taken not to over-tighten or else the pedal won’t move as smoothly as it should do. I’ll get the rest of the pedals in this weekend. Speaking of clevises, the clutch master cylinder is a 0.72 bore, which is

It’s a great feeling to take parts I modified a while ago, and be bolting them into the car for good. Having them fit is even better. The only mistake I made is not allowing for the extra 0.75mm either part has for powder-coating. However, whilst snug, it fits.

There is no try, only do or not do

So, there’s always a short cut, and a proper way to do something – what you can see here is the top diff-cradle bracket. My problem was the clearance between the bracket and the chassis wasn’t sufficient for a lock-nut and using two thin nuts jammed against eachother isn’t a good solution.
imageSo, given that, I’ve cross-drilled it and used a split pin. I’m also pretty pleased that the bolt shank to thread transition happens just through the bracket on the right, which you can see here. According to Carrol Smith, this is exactly the transition point.

So, I engineered it properly.