AUSTIN SEVEN ULSTER. No 34.
One day early in 2022, a friend said “Do you know what a Cyclekart is ?”. I said “
No, never heard of it, what is it ?”. He said “ I think you should Google it”. I did,
and I’ve been hooked ever since !!
The Design Process
I did the entire design using Solidworks, 3D CAD. I started by building a basic CAD model of the engine, the wheels and a manakin to represent me. Then I set about designing a chassis and suspension around those key elements. I didn’t actually make anything until I was confident that it would work and I would be able to drive it.
The Inspiration Car
When I started I didn’t really have an inspiration car, I just had an image in my mind of a pre-war racing car. Then as the design progressed, and I started looking at pictures of old cars, the Austin Seven Ulster caught my attention and I added features to enhance the similarities.
The Chassis / Body
The chassis is fabricated from 75mm x 25mm x 1.6mm and 25mm x 25mm x 2mm box section steel with a few parts made from 3mm and 5mm steel plate. The side rails are tapered in towards the front with raised sections for the engine and front suspension mountings.
The bodywork is mostly made from 18mm plywood clad in 1.2mm thick aluminium. The curved rear engine cover is moulded from fiberglass, as is the front radiator surround. I bought a cheap electric sewing machine so that I could make the seat cushions. Many of the detail, non structural, parts are 3D printed using PETG.
Running Gear & Engine choice
All the steering and suspension parts are made from scratch from bits of steel I had lying around. The front transverse spring, I found on a scrap heap and did extensive modifications with an angle grinder until it “felt about right”. The Hartford style dampers were added later, and do seem to make a difference. I was lucky to find a Peerless differential on EBay and built the rear axle around that. I’ve used a Vespa scooter brake disk and caliper and 219 chain & sprockets. The engine is a Chinese (no name ) 212cc clone which I’ve removed the governor and fitted a Mikuni VM22 carburettor. After a few meetings I noticed that the magnet was starting to part company with the flywheel so I fitted a cast aluminium flywheel for peace of mind.
How long did it take to build ?
I started designing around the Spring of 2022 after a friend suggested that I should Google Cyclekarts. Initially, I was just sketching out a few ideas but it soon developed into a full blown design exercise and I was soon sourcing and buying the various bits and pieces. I finished building just in time for the inaugural meeting of CKGB which was held at the National Motor Museum in Gaydon in the Spring of 2023. I was invited to exhibit the cart at the meeting.
What’s the least and most favourite part of the build?
I really enjoy the design process and all the mechanical engineering involved in fabricating the structural parts. I also like finding and repurposing cheap everyday items. My least favourite part is the fiberglass, which is very messy and seems to take forever.
How does it drive?
It is certainly a lot of fun, with the skinny tyres providing very little rear end traction. After nearly two years of refinement including many changes to steering geometry and lowering of the seat it drives reasonably well now and is generally very predictable.
Ongoing changes and tweaks
There have been many. My first race outing at Stretton revealed that my steering geometry was completely wrong and I had seriously underestimated the forces through the steering components. This was beefed up for my next event at the Star& Garter where I realised that the engine was running very lean and overheating.
That was resolved by re-jetting the carb and adjusting mixture. As the engine performance improved I found the direct steering more challenging so changed to a rack and pinion system. After seeing a Cyclekart roll over at Stretton I fitted a roll hoop. I have also made side bolsters for the seat to stop me sliding about and, more recently, lowered the seat. Too many minor changes to list them all and I’m sure there will be many more.
