Car Construction 101

Today I had a chance to go through some of my old email… which pretty much felt like opening a short-term time capsule. It turned out to be worthwhile, as I came across some photos of my Lotus project that I had sent to one of my CAD professors in college.

I had started this project after I finished High School. The goal was to get first-hand experience building a car from the ground up… and to use the product of these efforts as a ‘drivable resume’. I picked the Lotus Super Seven because there was a nice book written by Ron Champion called ‘Build Your Own Sports Car’, which walked you through the process of creating the chassis for a car Mr. Champion dubbed ‘Locost’ (Low Cost). I later found a book more relevant to the American market called “How to Build a Cheap Sports Car” by Keith Tanner.

The car was to be built using square section mild steel tube, and welded together to form a space-frame chassis. The thing I appreciated the most about the book was the fact that it gave you enough information to fabricate the chassis… but left the rest to your imagination. It would be up to you to pick the engine, transmission, rear end, suspension components, brakes, etc.

So I decided that I would make an attempt at building the chassis… and if I was pleased with my work I would continue on to finish the car. I bought a MIG welder, enough steel to finish the job, and then set to work chopping tubes and tack welding them together. It took about 3 months to complete about 80% of the chassis. The hardest part was ensuring that all the frame angles were exact and all the tube lengths perfect.

'Locost' Frame

'Locost' Frame

In the photo above you will notice the ‘build-table’. The purpose of the table is more than just a place to build the frame. It is perfectly flat, level, and square… and the first step in building the chassis was to create this surface to serve as a ‘datum’ or reference plane for chassis measurements.

 I am sure the sound of metal-cutting drove my neighbors crazy… but it also brought some of them over to see what I was building.

 The plans for the chassis could not be exact to the plans Colin Chapman penned for the original Seven for obvious copyright reasons… but that did not stop me from making my own personal modifications to my version. The original Seven had a slight angle on the chassis tube that runs next to the drivers arms on the outside of the car. To simplify things and avoid any design infringement… the book plans called for this tube to run flat across and eliminate this angle. I chose to go the authentic route and include it.

Custom Modification

Custom Modification

 I wound up picking the 4 cylinder 2.0L Ford Zetec engine as a powerplant since Caterham was using it for their official version of the Seven at the time. It was supposed to be mated to a Ford Type 9 gearbox… but I ran into some issues. The Zetec engine was pulled from a 2001 Ford Focus…which of course is front wheel drive… and the Lotus is a rear wheel drive vehicle. This meant that for me to use such a setup it would require a custom bellhousing to join the engine and transmission… and that bellhousing was a bit too expensive. Plus, it would lead to further issues down the road. The biggest issue was a lack of Type 9 gearboxes in the US. The other issue was finding an appropriate rear end for the vehicle. A simple option should have been to use a solid rear axle, but there are not many U.S. vehicles that have an appropriately sized rear axle. The rear ‘track’ (distance between the two wheels) on a Lotus seven is not very wide at all, and most of the axles I found were far too wide. I did not want to dive into the hassle of making modifications, so I went is search of another solution.

In 2007 I bought a 2001 Mazda Miata. It was a better fit for me than my ’84 Ford Bronco since I like to carve my corners at a brisk pace. The test drive won me over in less than a mile… and in my opinion the Miata has looks to kill. As it turns out the Miata happens to be the perfect ‘donor’ vehicle for the Seven. The rear track is about the right width, and it has a compact 4 cylinder engine in a rear wheel drive  setup. As a bonus it would not be too difficult to modify the rear of my chassis to accommodate the independent rear suspension (IRS).  It was in essence the complete solution.

Now this should be the part where I dive into details about buying a junker Miata and transplanting its guts into the Seven. Unfortunately that’s not the case. You see… building a car is expensive and time-consuming. We all have those periods in life where you have zero ability to focus on what you want to do… and can only focus on what needs to be done. The Lotus was a luxury, and the project went on hold.

This year I have vowed to revive the Seven project. The chassis needs to be fully welded, the rear end modified to fit a Miata IRS, and mount points for the suspension must be added. Soon I will be swapping the engine in my Miata for one with fewer miles on it… and at that time I will use the pulled engine for the Seven. I would imagine I am a few years away from completion. My only real limiting factor at this point (and always) has been financial. But if I do a little at a time I think a 2015 completion should be reasonable.



Of course all the work I do regarding the Seven will be discussed here… and new car sketches will be added soon.




~ by ddmotorsports on January 27, 2012.

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