McArlus Cars - 19

For a while I have had some concerns about the fuel tanks, but because they hadn’t been needed, they were typically out of sight and out of mind.

Now that we are getting well into the final assembly stage, it is time to address the concerns.

The tanks were made with short pieces of aluminium tube welded in to connect to rubber fuel line. There are two at the top of the tank, which act as 1, a breather and 2, a potential return line, and two on the side that are the fuel pickup, and a spare in case a second pickup was required in case of fuel surge.

These pipes were supposed to be 10mm ID tube, but somehow ended up as 8mm OD, resulting in a far smaller opening. They also had 90 degree bends in them, and the breather ones that I could see looked dangerously crimped, so I was concerned about the pick ups that were also bent 90 degrees, but that was invisible within the tank. (Unfortunately I don’t have good pictures of this so you will need to bear with me!), but you can just see the old welded up holes in the end on picture of the welded tank.

There was also a mismatch in the alignment of the fuel pickup in the tank and the fuel filter (which is only 75mm from the tank) and pump that I was not happy about, although in retrospect I could have made a loop in the rubber fuel line that would have solved that problem, there is really no need for it to go the absolute shortest distance that I can see.

Anyway, after must procrastination I decided to modify the tanks, especially as they had never had fuel in them, so now was the time. When I cut off the fuel pickups that had been welded in I was very glad that I did. As they were welded, obviously the aluminium has melted into the tube, partially blocking them. I apologise for the fuzzy pictures, but this problem was impossible to see until I cut the old pickups off.

The way I wanted to do things meant that each step required welding in stages, which I can’t do.

I started by machining some bushes that are tapped ¼ BSPT one side and take the 10mm aluminium tube, bent, not crimped 90 degrees on the other. This is the first welding process.

Next I made a plate that the bushes and tube fitted into. The bushes, complete with welded tubes are then welded to the plate. This plate is then welded into the tank complete. By doing it this way, I was able to be sure that the pickup tubes were both in the bottom of the tanks and that the outlets from the tank were in the correct place.

I made a similar tapped plate for the top of the tank to take similar screw in fittings.

In retrospect, the tank design could have been better.

I could have created a sloping base and/or a “sump” that would have helped with fuel surge problems. I could have used screw in fittings from the outset, and always will in the future.

The outlets could have been positioned better to allow for better alignment of the fuel line.

But as always, we live and learn!

Regards

Simon

Fuel Tank Blocked Tubes.

Fuel Tank Parts to Weld In.

Fuel Tank Welded.

Fuel Tank Installed.