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Pembleton Ecosse Build Bulletin

by

Ade Colmar

The trouble started when I bought a shiny new TIG welder!

Up until that point, it had been a fairly straightforward journey. The search for another car project had been ongoing for a couple of years and more recently I was inspired when watching a historic hill climb event. Down in the paddock I was really drawn to the lightweight, small engined machines built in the 1930s and 50s. The minimalism and sense of purpose tweaked something inside my head.

A part built Brooklands came up for sale in Glasgow and that got me onto the Forum asking the all usual silly questions, which everyone answered like true gentlemen. My nearest owner (and gentleman) is Mr Rae who easily persuaded me that less is more, and so in the end I ordered a Grasshopper chassis last October. The engine would be a Guzzi 750, both for the vee engine aesthetic and greater reserve of power. PMC were not keen on supplying the chassis with extended rails for the Guzzi engine (as pictured on their website for the completed car) and so began the idea of doing a bit of my own welding.

By the time I picked up the chassis and many other bits from PMC in January, the list of welded extras and alterations was growing. I had learned to weld during my apprenticeship, but in those days a TIG welder was way out of the reach of any 'Garagista'. Now armed with my new purchase, I got back into the swing of welding by making a frame for a set of free standing shelves for the workshop. This frame gave me an idea. Why chop and change a perfectly good chassis when it could be uses as the template for a new chassis? The extension of the chassis forward to pick-up the Guzzi engine mounting points was straightforward, but a more serious challenge was the roll-over hoops. In order to stop them looking too prominent, the profile of the car needed to be raised so that the driver sits deeper inside the car – also handy for keeping out more of the Scottish weather.

The basic chassis was created as four sub-assemblies; front end, dash hoop, roll-over hoops and rear suspension mounting. These were threaded onto two longitudinal base rails, followed by two longitudinal curved waist rails. All very recognisable so far. TIG welding machines are wonderful things and by now I was really getting carried away. Next was extension of the fulcrum arms on the 2CV suspension arms. The standard ratio is 3.5:1 and by making it closer to 2.5:1 the standard springs can be used but, more importantly, the dampers are given more travel. The track has also been increased by using rear suspension arms on the front (which also have bigger fulcrum arms). In order to work out the optimum spring rate and suspension leverage ratio, I used something called 'Wheel Frequency'. This may be of wider interest when choosing from the various standard or uprated springs and so will the subject of a separate article.

In the meantime, I would like to thank everyone on the forum and those who I have met so far. Without them, I would not have had to courage to get myself in such deep trouble. Let's hope I finish this machine and it all works!

front engine mount
roll bar
front hoop
partial chassis built
panel fitting
installed engine
front suspension

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