Sunday, 18 July 2021

W/NG clutch repairs

July has been a month of tinkering with little bike jobs. I use the W/NG a lot, because it's an easy bike to ride around the little lanes and to thread through busy holiday traffic - unlike the Square Four, which is much heavier, less nippy but is also more suited to the open road - faster, more comfortable and with a much lighter clutch. 

Talking of clutches, the W/NG's clutch was starting to trouble me a bit - it felt notchy, gear changing was getting more difficult to perform quietly and it was obviously starting to drag. I knew the plates, basket and centre were in good condition because I had pulled them apart when I rebuilt the engine late in 2020, but the operating mechanism had not been touched.

Here's the first observation. See the pushrod? It's not supposed to be dished like that, so that was obviously knackered. The little bronze bush wasn't in too bad condition, but it was very loose in the gearbox cover:

Next - the arm is not supposed to pivot on an M5 bolt. This gave rise to a lot of lost lever movement as the larger of the two holes in the arm is threaded 1/4" CEI:

The pushrod was dished at the other end as well, as someone had fitted a ball in the pressure plate:

I looked around for a new pivot pin for a while. These came from AOMCC Gearbox spares:

The bush is held in place with Loctite 603 Retaining Compound:

All back together and feeling a lot better. I just need a road test now, though I think I may need a new set of clutch springs. It's been difficult to get the pressure plate level without one of the springs ridiculously loose....

Wednesday, 14 July 2021

W/NG horn repair

The W/NG has had a rather nice military Altette for years, which I found I think on eBay. It's always worked, but never very well - not very loud and with that strangled parrot sound common to Altettes with shims missing or loose parts.

One idle moment I tinkered around with the adjuster, which is quite easy to get to in these early Altettes being hidden under a big cap nut on the front of the horn. I could get it to sound a bit better, but I was puzzled by the adjuster moving out of position after I had tightened it. I realised eventually that the armature, which is held to the diaphragm by a large nut and which contains the adjuster, was loose on the diaphragm.

No matter! Says I, I will tighten it up. Weeks of soaking in various solvents followed as these are notoriously tight and being out in the weather, will corrode up. I eventually loosened it with a big tube spanner, only to find that it wasn't loose on the diaphragm at all but that there was a nice ring of diaphragm material held tightly by the nut but that was no longer attached to the rest of the diaphragm. A fatigue failure after 80 years of service!

Now, you can't buy these parts. I had another Altette to cannibalize, but I also have a TIG welder. After a few attempts (during which time I realised my Tungsten tip was contaminated, hence the mess on the left) I got a decent weld all around and re-fixed the broken ring in its original position.

The Dremel made short work of the excess weld:

In adjusting the horn, I was messing about with the screws on the back. It's important that the internal contact breaker assembly is level:

The two screws on the right fix the contact breaker; the one on the left adjusts the level. Once you have it level, leave the screw alone!

Here's the diaphragm reassembled with the armature and the adjuster. I assembled the rest of the horn and tested it - it didn't work, but the coiled pulled the armature in. Why? Because the diaphragm is upside down in this picture...

With it turned over, it worked beautifully and sounded better than it ever has.

Friday, 2 July 2021

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 tapped 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.

Friday, 18 June 2021

SQ4 gets a new tank

A long while ago, I confessed that I had realised the tank that my SQ4 kit arrived with, and which I had painted at vast expense was not a Square Four tank at all, but one which had once belonged to a KH Hunter twin. It did look good though:

It looked even better on the bike:

I started to look for another tank and after a short interlude with a very rusty tank from Denmark I found one in original paint at Yeoman's Motorcycles. When they are on the bench together , you can see how different they are:

So now, with a new tap (actually a refurbished original) and a balance pipe, here is Amelia in her latest incarnation:

Tuesday, 15 June 2021

SQ4 - bushing the saddle nose

Since I've had it on the road, the Square Four has felt a bit wayward around the rear end. Since I had rebuilt the rear suspension and knew that it had no wear, I suspected the tyre and wheel though they were both new and rebuilt - until I realised the problem was closer to home. Literally much closer, to my backside.

The saddle nose bracket on an Ariel frame is quite small, giving little bearing area. Coupled with a bolt with an over-long thread, used as a bearing surface produces this effect after a few years:

This picture shows the saddle removed, but with the bolt in position. The red circle shows a portion of the thread used as a bearing - a very poor idea:

So, the first job is to make those worn holes round again. The bolt is 5/16" (0.312", or around 8mm), and they are both worn to over 0.350". I used an adjustable reamer on them to remove the ovality.

Ovality in the frame holes is not the only problem - the holes in the saddle frame are also very large. I have another problem in this area in that the fuel tank has very little clearance around the saddle nose bolt and I have solved both these problems in one go. In this picture, the original bolt has had it's head thickness reduced to produce a shoulder which fits in the saddle frame hole with very little clearance, and the full nut used at the other end has been reduced to the thickness of a half nut, again with a shoulder. This enabled the bolt length to be reduced, to get more clearance for the tank, and removed the whole assembly to the right to move the thread out of the bearing area.

Next job was to make two shouldered bushes to fit in the holes:

The bushes pass right through the fixed frame lugs, to provide maximum bearing area; there is a minimal shoulder to allow the bush to be retained in place (or removed).

This repair has removed virtually all the play from the saddle nose bearing.