McArlus Cars - 24 - radiators etc.

On the yellow car the cooling system was always marginal.

Initially it was fitted with one small radiator from a 250cc bike fitted in the right hand side of the car and fed cooling air via the wheel arch and duct in the top of the door. This quickly proved inadequate. The solution was to add a second similar radiator to the left hand side of the car, so doubling the radiator surface area and at the same time I fitted some aluminium paneling to provide some extra sealing so that more air would find its way through the radiators rather than around them, but the complicated pipe work was always a concern.

At this point the cooling was OK for one driver to run sprints, but would still struggle with two drivers on anything but a coolish day.

On the new cars I sourced a new larger aluminum motorbike radiator.

Initially the plan in this project has always been to use as many unmodified proprietary parts as possible, and once again in this instance it was possibly not the best option.

I sourced some late model Yamaha R1 radiators that were almost exactly the right size to fit in the side of the car, under the door and in the sill. These would provide around 1.5 times the surface area of the combined two radiators used previously.

This time there would only be a single radiator on the left hand side of the car, and I hoped to fit it with no modification.

Unfortunately this would not end up being the case. Firstly the radiators were turned 90 degrees, changing them from side tanks to top and bottom tanks, then the old radiator cap hole needed to be filled, the pipe connections weren’t ideal and so it goes on!

In the end I think that I may have been better off getting a couple of custom made radiators made that were the right size with outlets in the right place, and it may have been cheaper in the long run too!

I have made a new swirl header tank for these cars too.

Although heavy, I make these tanks out of copper plumbing fittings as they are easy for my mate Ray to solder for me! As I had to make two this time I needed a way of making two identical tanks. I first made a dummy swirl tank out of 100mm steel tube and tack welded the necessary inlet and outlet on it with 25mm steel tube. This was made with everything positioned in the chassis some time ago, and was done this way as it is relatively easy to tack these pieces together in situ in steel (at least with the equipment I have).

Once the dummy tank was made, I then set about making a jig that would allow me to duplicate it in the copper pipe. The jig has to be able to be dismantled to get the finished tank out of it.

The filler necks are then solder in as well as brass fittings for the temperature gauge. Before painting I check the whole assembly with a radiator pressure gauge to make sure it holds pressure.

In the pipe work that connects the radiator, swirl tank and engine together I also have used copper pipe fittings, connected with straight pieces of rubber hose. The copper fittings allow you to may tight bends that would otherwise be impossible in the rubber. I have however doubled the thickness of the copper, by soldering in a 20mm long piece of pipe wherever there is a hose clamp connection. The hose clamps can apply enough pressure to distort the copper pipe, particularly if tightened when the system is hot.

A few soldered “tits” on the outside of the copper where the rubber hose is connected will also help to stop the hose slipping off under pressure.

Although it is not yet done in the pictures, the radiator will be sealed with foam to the aluminium sill and the bodywork (door) to make sure that all of the high pressure are to the front of the radiator goes through it and not around it. If there is still a cooling problem there is still the option of fitting a fan or even an electric water pump.

The whole assemble comes up quite well with a coat of paint.

Radiator Fitted.

Swirl Tank Fitted.

Dummy Swirl Tank.

Dummy Swirl Tank In Jig.

Swirl Tank Jig.