Homemade CFRP mid engine sports car

[Paul Bristo]

Hi all, a few updates

Mostly been fabricating little bits here and there from my big box of carbon fibre fabric offcuts and using up my left over epoxy resin before it goes out of date. The main new thing to share is the pedal box;

I need to swap out the accelerator pedal spring with a stiffer one when it arrives, but aside from that its done.

The pedal box will slide along the aluminium rails to adjust position. Ignore the white plastic bars, they are just temporary spacers i printed to hold the rails the correct spacing. The rails will be bonded and bolted to the tub floor.

I made the pedals and frame and footpads from the same process I have shown before .. print a two part mould on the 3D printer, chop up a load of carbon fibre into 50-100mm long strands, mix it with epoxy into the mould .. compress it all over getting all the mould filled (I jab it all over with wooden sticks, add a bit more fibre and resin, then jab some more). Then close the top of the mould and compress the whole thing tightly between clamps, let the excess resin bleed out. The mould needs to be printed quite strong to take the pressure.

my 3d printing booth / spare bedroom toilet, printing a mould for one of the pedals;



some photos before assembly;



I've also been making a steering column and i'm about to start making a steering wheel. More on those in a future post !

 

[Nicolas]

Impressive job!!!
Chapeau

 

[Garth]

Fantastic build! I just discovered your thread, but will follow with anxious anticipation! Keep the updates coming!

 

[Paul Bristo]

thanks guys,

Winter update .. last few weeks i've been manufacturing the steering, designing some brake cooling ducting systems, and shopping for braking system parts and trying to decide on wheel rims.

here's the steering parts. I decided to try and make my own steering wheel, i 3d printed a hollow core for the steering rim, tightly wrapped it in 2 layers of continuous +/-45 degree carbon fibre strip and used spray adhesive to keep it all stuck in place. I used chopped strand carbon fibre (from my large box of offcuts) for the rest. I used a 2 part 3d printed mould, generously added a load of chopped fibre and wet resin onto one side, then added in the wrapped core rim, then a load more chopped fibre on top and then closed the other side of the mould. Then put it in a plastic bag to catch the resin run off and clamp it all tight with as many clamps as i can find. The clamps need to be re-tighted every so often to maintain pressure as the excess resin bleeds out. The demould, sand, paint in a surface coating resin, sand and polish.

Next was the steering column, in UK IVA you need a system which is collapsible, since my column is short and straight i can't do this via offset multi-link joints, so i needed a collapsible column. I struggled to find one that i liked and was short enough, so i manufactured one from two box section aluminium profiles, with one that slides inside the other. I chose box section rather than round so that even once collapsed it will still steer. I used solid carbon fibre for the rest of the column, moulded directed around and into the aluminium tube. The column is designed to collapse at approx 1kN force via clamp friction from two M5 bolts and i left 90mm of travel.

I made an instrument panel beam for steering mounting. The beam is carbon fibre over a 3d printed core, I moulded in two M8 threaded inserts to mount a steering bracket. The steering bracket is moulded from chopped carbon fibre in a 3d printed mould. The only way of adjusting up/down of the column is with a different bracket so i might make a few of these. I need to get a rubber gaiter to seal the column to front bulkhead hole. I'm going to try and print one from rubbery TPU filament.

 

[Paul Bristo]

wow two updates in two weeks! this time, ducts for front brake cooling. Made the design in CAD and then 3D printed a multi-part mould, then used a wet layup approach and vac bag. I made it super thin, only 1 ply of 600gsm 0/90 twill and 1 ply of 300gsm +/-45 NCF. Then glued and riveted in place.

The corresponding wheel-side parts were also made today (same process), once cured i'll bond and rivet them to the upright and connect up the hose. Once all done i plan to cover the exposed surfaces near the disk on upright/wishbones/duct with some zircotec self adhesive reflective thermal shield

 

[Paul Bristo]

Bought some more bits in recent weeks, radiator, braking system and wheels (wheels are delayed though waiting on stock, can't wait to test fit those!)

Mounted the radiator on rubber isolators. I've connected bleed lines to the tops of both tanks which T together and then run down the tunnel, I used 3/16 brake lines/hoses for the bleed lines. While messing with the tunnel i also ran a copper cable for earthing front to back (can't ground things to a CFRP body!). I Also made a bracket for the hydraulics reservoirs and fitted them too. Still need to fit the front bulkhead brake/clutch lines and sort hoses inside the cabin to the moving pedalbox.

I have cooling fans arriving this week, once they are test fitted i'm going to mould a CFRP shroud / cooling duct to direct air from the radiator up and out, while also covering/shielding the plumbing on the front bulkhead.

I've also test fitted the brake discs and calipers using some 3d printed placeholder brackets, just to check my maths is correct and everything actually does fit together properly

 

[Chris Kouba]

Paul,

I feel like all I do is fan-boy post on this thread, but I have massive respect for this project and your execution looks phenomenal. This is one of the most interesting threads/projects on this forum for me. Please keep up the efforts and share your progress, I always look forward to the updates! Things are looking great!

Chris

 

[Brian]

Same here. I really appreciate your sharing techniques most people could cobble together in the garage. I really like leveraging 3 D printing to make cores and molds. I got one wanting to use it to make cast aluminum forms.