Auto Union Type C. No 6.
I chose the Auto Union type C as it is probably one of the most Iconic early G.P. race cars of our period.
The Inspiration Car
I chose the Auto Union type C as it is probably one of the most Iconic early G.P. race cars of our period. Dr Porsche made many ground breaking innovations with the machine, some of which are still seen in principles of design in modern F1 racers. I also think it is one of the most beautiful designs of the era too. I wanted to stretch myself with this build after completing the BSA. I knew I had taken on a task from the off with the front suspension and I wanted to try and include a differential into this build. I would say the whole process was twice the job of the BSA.
The Chassis
The steel rear chassis sub frame is joined to an aluminium front chassis with mounting points added for the front suspension in steel. The aluminium floor pan is bonded to the front chassis with MMA adhesive and riveted. This gave a strong chassis that in testing was stiff enough to drive without bodywork. Like the original, the engine is mid mounted behind the driver and in front of the rear axle. I went to college and learned to weld so the chassis is TIG welded -new skill unlocked!
The Body
The challenges with this build were many, the body has many compound curves so I chose to make it in fibreglass, and that is another new skill as I have not done any fibreglass work before. I also made a home made dimple die and that worked out well for the dashboard and seat surround/firewall too. The front grill is actually a grill from an Indesit grill pan.
Running Gear & Engine choice
The chassis has a peerless differential unsprung on the rear chassis frame running in 5 bearings and connected to long and short half axles, the brake disc and sprocket are mounted to the differential. The front suspension is four parallel trailing arms with the lower arms transmitting the force to a reaction arm against a conical rubber bump stop. Think hybrid Beetle/Mini mk1 technology. The handbrake is mechanical from an old Kart calliper and the main brake is a hydraulic four pot caliper. Engine wise, I have a Hyundai 212cc 7hp X series engine in with governor removed, 18lb valve springs and a Honda clone bored out (16,5mm) carburettor and large air filter, the exhaust is bespoke 1" tube to 1 1/4" flared tube into a home made baffled can made from a double walled stainless steel drinks bottle. The drive is through a TAV30 torque convertor with a Juggernaut driver pulley.
How long did it take to build ?
I built it over the course of a year from first concept late July 2023 to completion of body and paint late August 2024, over twice the build time of the BSA. But as we all know, a CycleKart is never finished.
What’s the least and most favourite part of the build?
The least fun bit by some margin has to be working with fibreglass. Itchy, splintery, dusty stinky stuff that has a mind of its own and a necessity to work quickly in warm conditions. I cannot see myself ever considering a career in it :-) My favourite part of the build was seeing it all come together at the end when the body was mated to the chassis and the first few coats of paint were added.
The little details
Using "found" bits and re-using old items always brings me a little joy in a build. The aluminium front chassis frame was a £5 purchase from a part complete tower scaffold staging rated to 250kg. The steering wheel that Mark Underdown provided is remarkably similar to the original and the home made aeroscreen is a reasonable representation of the model used. I did not go for the 44 curved inward louvres of the original or its shaped side panels but opted to get the lines of the car somewhere near to suggest the original. The suspension is the big innovation on the CycleKart that was a big worry until I had tested it a few times and tweaked it.
How does it drive?
Pretty good now. The front suspension went through three stages of improvements along the way after testing the chassis at a local club car park, Whilton Mill, Malvern and Santa Pod. The rear axle was improved and strengthened after fatiguing to near failure at Santa Pod. I dare say ongoing modifications and repairs will always be necessary, that's part of the fun.
Ongoing changes and tweaks
I have only done minor stage 1 mods to the engine so watch this space if I get bored. It seems to keep up with the other karts so I am not in a rush to do much more. I am considering switching to an electric start as getting the engine cover on and off is a bit of a faff.
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