Charlie's Shed - Lining a petrol tank

Regular readers will know that in the past few months I have made weld repairs to two petrol tanks, one of which still has a weep in a very inaccessible place.

Today I'm going to line the tank with Slosh, from Rustbuster. This is a polyurethane sealer, resistant to Ethanol, that cures in air. I've cleaned this tank already with their SP10 Tank Kleen and a selection of nuts and bolts:

Those bolts came out a lot cleaner than they went in!

The sealer comes in two bottles, for two coats. You have to pour it in, rotate it around, wait twenty minutes and repeat twice more.

You let it drain from the tap connection to avoid it pooling in the bottom of the tank.

The reason you don't want it pooling is that it gases off a little when setting, and you don't want voids in the lining:

Three hours later, or when the sealer is dry but still tacky, you do the second coat in the same way. Then you let it cure for five days. Easy peasy.

This 400 ml kit is supposed to be sufficient for a 10 gallon tank, and I'm sure it is. My plan was to seal both the MZ tank and the Huntmaster tank in one sitting, but obviously two tanks have a greater metal surface than one tank (though the two together totalled less than 10 gallons) and I wasn't confident I'd have enough for both, so I ordered some more sealer for the FH.

Now that son Tom has his MZ sparking, he's clamouring to get his tank back...

W/NG - Cleaning the fuel tap

 One embarrassing thing that happened last year was a shortage of fuel - or rather not. I ran out of fuel out in the wilds of Norfolk having given son Thomas a lecture about coming out without checking the tank, discovering a little while later that not only had I run out of fuel but that the reserve tap wasn't working.

Emptying the tank, I pulled the tap off to check and found the filter torn and the reserve port full of paint chips:

A few minutes poking around soon had that clear, and I fitted a new filter:

I realised later that this one is of a coarser mesh than I would have liked - I'll have to replace it again...

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.

QR50 - Petrol Tank: renovating plastics

Like most of the QR50, the petrol tank had received more than it's fair share of poster paint but it is at least intact and comes complete with its tap. The cap is unfortunately missing (like the oil tank cap) and has been replaced by a green plastic one from a Derbi:

The poster paint comes of in the sink, but the green acrylic underneath needs paint stripper:

With this gone, we can survey the damage. There are a few dings, the deepest of which pushes out with heat; other damage can be trimmed with a knife to remove it completely or make it a bit less obvious. Next, the whole tank is rubbed down with 240 grit wet and dry to start on the removal of the scratches:

When we've gone as far as we see fit, we'll move up though the grits to get it looking a bit better.

More later.

Charlie's Shed - Fuel Tap Plungers

If you find yourself short of plungers, or the shaft of your adjustable plunger is damaged, they are quite easily made if you have access to a lathe.

The brass centre of the adjustable plungers, which is often short from having the slotted end broken, can be made from a bit of 3/8" round bar. Chuck this in the lathe and turn a suitable length to 5/32" - the best way to do this is to turn an 1/8" or so to exactly the right diameter, then use this short length as a guide to turn the rest in one pass. With a sharp tool this shouldn't be too much of a problem and it avoids the tiny bar bending away from the tool, which will result in the outside diameter being over size.

Chamfer the end and cut the thread - it's 5/32" BSW. Make sure you use a tailstock die holder or back the die holder up with the tailstock to keep it square - you don't want that thread wandering off.

Give it a polish and part it off:

Assemble it into the plunger and you are done:

The shaft I have made here is a bit over-length compared to the old one - maybe I will adjust it a tad. Notice the diamond knurl. I don't have the cutters for that - straight and diagonal knurls yes, but not the 'inverted' diamond knurl. Rather nice, and easier on the hands...

Post war plungers, as I mentioned in my other post on the subject, are non-adjustable unlike their prewar forefathers, and because of this I think it makes sense to update them with an O-ring seal.

The hexagon reserve plungers are made from 0.600" 303 stainless steel hexagon bar. You'll need a decent length for chucking and for the milling operation. Chuck the bar with a couple of diameters showing beyond the jaws, to give you enough space to part off when you are done:

Turn the shank to the required diameter - a little over 5/16". This needs to be a loosish clearance fit in the tap body you just reamed.

Use a thin parting tool to form the O ring grooves. Space them so that they are at either end of the equivalent length of cork:

For those, like me, without a mill you can use the toolpost or a milling attachment to mill a 3/32" slot, about 1/16" deep in the tap shank. Since the loads involved in this operation are tiny, I didn't bother to set the lathe up for milling. I cut the slot at about 1500 rpm in two passes, with a 3/32" slot drill.

Once you have completed the milling, test the plunger in the body and make sure the plunger slides freely with the retaining screw in place. Next, put the bar back in the chuck and polish up the shank; then, before you part off, turn the shallow chamfer on the inside of the head. You can then part off.

Turn the plunger in the chuck, and skim the outside face of the head, cutting the shallow chamfer in the same setting. Polish the head and you are done.

And watch out - the reason that slot looks slightly ragged is because I broke a cutter in it. Go easy.

Next thing - you will want to smooth the edge of the ports in the tap. look at this:

See the sharp edges? Remove that with a burr in the Dremel, or a tiny grinding tool. If you leave it, the O ring will be damaged. Look:

That nick will cause a leak. You are not really supposed to use O rings in dynamic applications like this.

Thanks for reading, and I hope you found it useful.

Shields Up, Mr. Scott...

In the everlasting challenge to keep heat away from my carburetter, I have added a heat shield to the previous insulating gasket.

I know from test rides that the radiated heat from the engine is as significant as the conducted heat, so I have attempted to deal with that with a stainless steel heat shield, mounted on the front float bowl screw. Petrol boils at 95 C, and we have seen temperatures in that region on the float bowl - and we have heard the fuel boiling. So, with some spare time and in 'metal working mode', here it is:

It's bent up from a piece of 0.9 mm stainless steel I had knocking about in the shop, cut to shape with snips:

This notch is to clear the starter jet on the front of the float bowl:

Here it is in position:

It's only mounted at the top, so we should expect some vibration and potentially a fatigue failure. We'll see how effective it is tomorrow.

Oh, and by the way if you are wondering why it says 'Meyer' on the side, have a look in your kitchen cupboards. It's the bottom of a stainless steel casserole. Waste not want not!

Time to admit I made a mistake...

This, I have to admit, is a KH tank. It is a shame that I painted and lined it but it does look very nice!

This however is a Mk1 Square Four tank, which I bought from Jorgen Andersen of the AOMCC; it too will be very nice once it has had some treatment from a nice man with a welder and a can of Sureseal - oh, and a gritblaster, some lead, and some paint in various colours

 It has the bonus of being fitted with a better filler cap than my one

But it does have some dents, a mounting that is full of either weld or chemical metal, some holes around the edges, and some rather dicey looking threads. Its got the right tap (though it is in poor shape) and it has the crossover pipe.

It has some original red paint underneath, which happily looks very like the red I used on the wheels.

This is not so nice but it will add to the experience!