FH fuel tap

The Owner's Manual for the FH describes, in several paragraphs, how to operate the fuel tap and makes it very clear that the tap specified was not the usual two-plunger tap used by Ariel since before the war. In fact the manual tells you to pull the plunger to turn on the main supply, and then to twist and pull it again to get reserve. It took me a few eBay mistakes before I found the right one, courtesy of John Mitchell of the AOMCC. 

The tap John sold me was in great shape, but it was missing the filter and the main supply pipe which draws the main supply from a point above the water in the bottom of the ethanol-laden fuel. Since I have other taps with this pipe, and I have made several filters, it was no problem to make the missing parts.

I started with a bit of 3/16" copper tube which I annealed with the wonderful Rothenburg Superfire torch. I set the tube up in my cable nipple swage:

Using a centre punch & a pin punch, I belled out the tube until it was a tight fit in the register machined in the tap.

Next step was to make a little cylinder on the lathe to position the pipe within the filter. This is machined internally to fit the tube and externally to the same diameter as the filter, and soldered in place at the top end of the tube:

So there we have it, the components of the tap:

To assemble the tap, I pushed the swaged end of the tube into the register machined in the tap body - I didn't attempt to solder it in. I then pushed the tube into the filter, and applied some flux to the tap body where the filter sits and around the cylinder I made earlier, through the filter gauze.

When soldering the filter onto the tap body, you need a fair bit of heat - I use my kitchen blowtorch for those sort of jobs.

You'll notice the tap has a fibre washer - I usually use Dowty washers in this application, but there was no way the plunger was going to 'fall easily to hand' with a Dowty washer on the tap - so a thinner fibre washer it had to be.