Its chassis time!
Well the concept was simple enough - grab a heap of steel tubing and follow the plans in Ron Champion’s book to build a space-frame chassis for your Locost. The reality is that the process is not that simple and there are many decisions to be made and problems to solve before you have a useable chassis.
First step is to decide on the mechanical components that are to be used, especially the engine, as they determine a lot of the final design. For my donor vehicle I purchased a complete 2006 Mazda MX5 NC and then organised a selection of steel tubing. With that done I was then ready to begin my project.
First challenge was to rethink the chassis design because Ron Champion’s original chassis will not pass the torsional rigity testing required for road registration in Australia. With minimal additional bracing and triangulation my completed chassis had no problem passing the testing by an engineer.
There are many different ideas floating around on how to build the best Locost and I believe that no two cars are really identical. I obtained a great set of detailed plans from Formula Motor Sport in Queensland and incorporated many of their ideas into my chassis. Unfortunately they no longer sell their realistically priced Locost chassis plans due to the high cost of public liability and professional indemnity insurance.
The original Ron Champion “book” design is also a bit on the narrow side, therefore, like many other builders, I added extra width (130mm in my case) and also extended the length by 100mm in the cabin (for adjustable seats), 50mm in the footwells and 50mm in the engine bay plus 25mm higher sides from the scuttle forward and increased the size of the rear “boot” area. My Locost is very individual and designed to suit my needs.
I built a solid timber build table with steel legs to provide the level surface required for the space-frame construction, which also gave me a chance to practice my cutting and welding skills before launching into the serious construction stuff. The top was 20mm chipboard with 90mm x 30mm pine supports glued on the long edges and a steel tube frame underneath.
I haven't written a detailed build diary as the many photos below show how the chassis developed. I have included some notes with the photos where appropriate. So take a look at the photo album and follow my project as it grew into a home built, road registered sports car.