Charlie's Shed - W/NG Dynamo Repairs

 Some while after fitting the new headlamp and instrument panel, I became aware that the ammeter rarely showed a charge. At the time, I assumed it wasn't centring properly and resolved to pull it out and adjust the needle. However, obsession being what I'm known for, I kept an eye on it and eventually realised the needle intermittently showed a charge. There had to be something wrong.

Following the usual checks (voltmeter on the battery, linked D & F cables with voltmeter to earth, connectivity checks) I realised the dynamo was struggling to go past six-point-something-small volts.

I went inside, and here is what I found:

That's it - goop and copper dust. I sprayed it with brake cleaner and put it back on the bike, with the brushes now sliding in their holders. A few trips showed a steady improvement, but it still wasn't right. Waiting until I had a few hours I could dedicate to it (it's in daily use, more or less), I took it off again and stripped it down to find the shims that one of the previous owners had fitted (and I had re-fitted) to accommodate the non-standard bearing had moved and cut into the commutator, shorting out the segments intermittently.

I resolved, after much deliberation, to bring the bearing arrangement back to standard. As part of the process, I cleaned up the commutator on the lathe:

The bearing came off after a few minutes with a grinding wheel in the Dremel. It wouldn't budge for a puller, but the Dremel cut through the outer race easily so that I could split it and pry off the ball cage without damaging the segments. I ground the inner race tangentially until I was almost through to the shaft, when it cracked and came free. The shaft was in good condition underneath, measuring a hair under 7 mm - odd, because the Lucas parts book suggests the internal diameter of the bush at this end is 8 mm. This must have been enlarged post war - this dynamo is marked 1943.

These are the culprits - two pieces of thin steel:

I made a drift to knock out the old bush:

I turned the new bush out of a bit of SAE 660 phosphor bronze I had. This is a bearing bronze that is considered the standard bearing material for light duty applications. It is easily machined and the bronze alloy is hard, strong and resistant to wear. Apparently it also conforms well to journal irregularities and is less dependent on lubrication than other alloys.

I drilled it 6.5 mm and reamed it 7 mm:

The old bush measured 11.2 mm outside diameter and pushout out easily. I made mine 11.3 mm and whilst it went in with no trouble, it was considerably tighter than the old one. I reamed it again when I had it fitted and deburred the ends.

The clean armature journal fitted beautifully and I reassembled the dynamo, pausing to look at the drive end which seemed to have a lot of end float, though in fact it was around 0.5 mm.

I attempted to motor the dynamo on the bench, but unfortunately the only loose 6V battery I had was completely flat. I refitted the dynamo to the bike, and started the engine to find the ammeter kick over to the 'charge' side with a few revs. Job done, except for the felt washer around the bush which I don't have at the moment.

Another small job I wanted to do was bush the end cover retaining screw hole (3/16" BSW) which has stripped. Unfortunately there is not enough room to fit my preferred M8 bush, which is plenty big enough to tap 3/16" or even 1/4" BSW if you have to, so I re-tapped the hole M5 which is a little bigger than 3/16". I'll have to think about that some more - perhaps go for an M6 brass bush which I can drill and tap 3/16" BSW.

FH -Seat Base Repairs 2

 Following the repair of the FH seat base fixing screws which I wrote about recently, I found a bit of time to finish the repair of the rear end.

You can see how the seat is constructed here. The large shaped pressing that you sit on (Ariel were making more use of steel pressings in the late '50's) is spot welded to two angled sheets which sit on the frame rails and carry the mounting holes. Those angles are closed with two quadrant shaped pieces which rot away.

I cut them out:

Using a bit of cardboard, I made a template to get the shape right:

This pale blue metal was an old bread bin, which has given me the air box for the QR50 amongst other things. It's about 0.9 mm thick and is easily cut with the Wiss snips, followed by clamping the two together and shaping with the linisher.

The paint burns off easily and it's remains are cleaned on the wire wheel. They just need tacking into place:

With both done, you can see how the back of the seat is closed off. The cover will actually come down over these plates, but more of that when it is painted.

I mustn't forget to smooth off those welds before painting!

W/NG - Field Stand Springs

 Whilst the field stand on the W/NG is a fine thing, I don't use it very much as it's a bit of a nuisance to get it down and back up again. The stand is not quite as shown in the factory parts books and is probably not original.

The same could be said of the spring clip, which looks a bit like the earlier type but is too short - it’s not only stiff but now that I have the panniers fitted, it allows the stand to foul the pannier frame bracket.

So, inspired by fellow W/NG owner and YouTuber Alan Moore, who compiled an excellent instructional video on this subject, I resolved to make a pair. You can buy these clips now from various sources (including the AOMCC Singles Spares) but I decided carry on with the plan to make my own to prove that I could.

I started with a simple bit of wire to develop the profile of the spring:

That gave me the length and the shape I would need and I used this to make a card template. Following Alan’s example, I bought a couple of lengths of CS95 spring steel from eBay, and used the Rothenburger MAPP torch to normalise them, by heating to cherry red and cooling in air.

This process left the hard spring steel soft enough to drill and to cut to shape with the snips.

With the blank cut and drilled I could bend them to shape. The first one took a bit of faffing around with bits of round bar in the vice, pliers and swearing; for the second one I welded up this little tool which made the bending much easier. I left the sharp bend near the mounting holes until last.

Using the tool, it was easy to make those reverse bends. It’s the fact that they are so close to each other that makes bending the spring difficult without a bars fixed close together.

Once I had both springs bent up, I could fit them to the bracket on the bike and ensure that:

• The stand would be gripped adequately
• The ends of the spring would be open enough to allow the stand to be pushed in

I messaged Alan through YouTube to ask if he had had any problems with the bends opening during heat treatment - he hadn’t (and nor did I).

I built a little barrel furnace out of a 5 litre beer keg, some ceramic insulation, a fire brick and some fire cement. The first step was to heat the springs cherry red; you can see the torch is low on gas in this picture as the shroud is glowing. I swapped gas cylinders after this and used the almost-empty cylinder for tempering.

Next, quench in oil:

After cleaning the oil off, you can test the hardness with a file. The file just skates off the hardened steel and will not mark it. Next, you clean the oxide off with Scotchbrite so that you can see the colours form during tempering:

Next job is to temper the whole spring to 350°C, which is the blue colour you see here and quench in water to stop the process. One of these springs is polished post heat treatment, the other is straight out of the water bath. They certainly sound springy after tempering!

Here's a rather hasty picture of it in place - in fact this is the first fit though it took a while to get it there. The old springs were fitted with some oddball screws and wing nuts, possibly 3/16" BSW - I think I must have done my previous, pre-heat treatment trial fit using these screws, because the springs don't fit with the 1/4" CEI bolts I have in there now as the holes are tight on the bolts and are not quite in the right place. Silly boy. 

So, having spent ten minutes with a grinding wheel in the Dremel moving those holes a little inboard and opening them to about 7 mm had the springs fitting easily - or more easily. If I have to make another pair of springs, I would allow a bit more space for the nuts & bolts - the one closest to the camera is a bit tricky to get to.

And it works! The spring is much, much easier to use than the old one which means the field stand will get used more often - currently you have to align the stand with the spring and kick it to get it in, which is tricky if you are on the bike. Right now, with only a couple of tests the spring temper looks to be acceptable - though I wonder if I have overheated it - it's springy but not overly strong. Lastly, you can see from the picture that the field stand is now clear of the pannier frame.

So that's it - all done for the moment. I will but a safety chain or perhaps a zip tie around the field stand and the pannier frame, to keep the frame clear of the road should the spring break or the stand bounce out of it. We'll see how it goes.