Model A - dynamo drive

 I have been wanting to sort out the dynamo drive for a while - not having it in place leaves a lot of parts laying around on the bench that I want to clear up. It was hindered by having to make a special puller for the dynamo bearings, something that I use infrequently but is very necessary if you're going to rebuild one of these dynamos.

Having finished the puller, I spent a little while turning up a short spacer. For some reason the replacement armature is a little shorter than the original though it fits where it needs to!

And I needed to file up a Woodruff key for the dynamo drive sprocket. It actually took me a long time to get to this place because I had inadvertently assembled the dynamo and fitted it with the dynamo body the wrong way round which caused the sprocket to be something like a half an inch out of line!

Here's the drive in place

That was a chain in amongst the past that came with the bike - it's the correct 3/8 inch pitch but the width is way too much. I'll have to look at Simply Bearings and see if I can find another one, but it really needs to be endless.

You can see here that this over wide chain will rub on the crankcase.

The thickness of the drive sprockets is 1/8" - so that tells us what chain we need -  50 links of 3/8 x 5/32 chain, readily available with soft links from Draganfly:

Magneto bearing puller

 With these old bikes every new job is a challenge. I suppose I could have sent the dynamo away to be refurbished like I do the magnetos but they're not that complicated so I do them myself. 

The E3 fitted to the Model A is a little bit different to the later E3Ls and E3HMs that I've worked on in that it uses magneto style bearings with separate races, cages and balls. Simple enough you might think - well yes, if it all goes to plan. 

What I discovered was that the reproduction armature that I bought for the E3 on the Model A, the first three-brush dynamo I have worked on, wasn't quite the same dimensionally as the old bent armature that came out and I found when I fitted the bearings for the first time that I had far more endfloat than I could cope with. To fix that you need to remove the bearing again, put a spacer in behind it to take up the end float, and fit the bearing back again - and you might end up doing this two or three times.

You need a special puller to remove the bearings and I found the details for one here:

https://www.kynoch-douglas-parts.com/html/articles/magneto%20bearing%20extractor.htm

The main tube part of the puller is made from a bit of old handlebar which I've turned internally to make the hemispherical form that will fit into the bearing race.

I turned up a plug to go in the end of that with an M8 female thread in the middle and welded it into the end of the tube. The six slots were cut with a hacksaw - you could make a much better job with a slitting saw but frankly I didn't want the work of setting it up.

There are a couple more details - the end of the threaded rod has a small disc welded to it to bear on the end of the armature shaft to reduce the likelihood of damage and the other end has a t-piece to allow you to turn it easily.

Here it is in action. Initially I used a regular worm drive jubilee clip to hold the six legs into the bearing, but they are just not strong enough and will pop out. The worm drive does not allow you to put sufficient force into the legs so I have used a much better quality hose clip - this trunnion type clip:

It works very well but you do need quite a lot of force to remove those bearings.

W/NG - maintenance

 Amidst a couple of days of routine maintenance, greasing, oiling, checking stuff, chain adjustment, cables etc. I finished a couple of outstanding jobs on the dynamo.

One was the missing felt pad from the commutator end bearing;

The other was fitting the missing cable boot.

It's starting first time, though there seems to be a lot of piston slap and it's quite rich. 

There's also a lot of oil around. On the drive side it's clear the primary case is leaking; on the timing side we have oil coming from the back of the magneto chain case. I suspect it's not pulled up tightly enough...

Model A - Lucas E3 dynamo

So what's next? With the kickstart done and the gearbox back together, my plan is to reassemble the primary drive to get the bits off the bench, and move on to the front forks - a big unknown. They didn't have bushes in 1930, so we are looking at a machining job at home or away. To get there though, I have rebuilt the clutch and next is the primary chain and covers, which just need paint. I'd like to reassemble the dynamo and it's drive, but it's toast. I could either:

1. leave the dynamo in a box for a few months and get on with other things
2. reassemble it mechanically (the body needs replating)
3. Fully restore the dynamo

I've got no nickel plating chemicals, and I have a long list of FH bits that need plating which I don't really want to get into right now (and as of this afternoon, my son has taken the Huntmaster and left me with the Square Four which won't idle...); I don't want to leave the dynamo bits in a box for months, so we will go for option 2. I've also seen at least one picture of an E3 dynamo with a painted body - and I've seen another picture of a 1929 bike which made me realise that you can't really see the body when it's mounted on the bike!

Here's a photographic survey of the dynamo:

In the picture above you can clearly see the damage done to the armature - it's thoroughly bent and unrepairable. Notice that this early E3 has the magneto type open ball bearings and the taper fit for the driving sprocket along with the male thread for the retaining nut. Characteristically, the armature is 157 mm long. Putting all this together enables us to purchase a new armature for this 36 watt dynamo.

I've ordered this repair kit from Rex's Speed Shop which will include the proper bearings:

As I may have mentioned, this is just going to be a photographic survey for future use. Here are some views of the dynamo body and the commutator end casting:

Close up, we can see that the other dynamo and casting has been a victim to the side swipe that this bike has suffered - there is a crack in this end as well. It looks repairable though:

Model A - dynamo engine plate covers

 There's a lot of splits in sheet metal components on this bike - not surprising after 95 years of corrosion & vibration. This is the top engine plate cover over the dynamo, and one of the bolt loops is missing. I'm replacing it with a bit of sheet cut from the side of a dead dishwasher - 0.5 mm thick:

One of the benefits of having quite a small TIG welder is that you can do tiny little things like this - this was set at 15 amps:

This is the front engine plate cover. Despite the fact that the one in the parts book is slightly different (it has four bolt loops) it appears Ariel modified this part without reflecting the change in the parts book illustration - I'm saying this because others I've seen are the same as mine - go and look at the one in this post, about the dynamo clamp.

Model A - dynamo clamp

 As I may have mentioned, one of the first parts I found missing was the dynamo clamp, shown here in this screenshot from the parts book. I have a couple of bits missing including the stud, bridge, and the clamp itself. I have no idea what they look like.

Or rather I didn't until I kind club member pointed me at this set built up some years ago by a Czech member Karol. None of this is available now unfortunately, these things tend to get built in small batches and then sold and remain unavailable until demand rises again.

Another member sent me this picture - this is an original clamp I believe so I can use this as a pattern to make my own.

This is folded up from a piece of 3 mm thick 25 mm flat bar. It's supposed to emulate what I believe is a Mazak casting. I shall file it to shape.

Metalwork almost complete - just requires some form of finish, probably chemical blacking...

Like this:

Model A - work faces

 The Model A has been on the bench a while now and I've been spending time investigating what I've bought and reminding myself of the parts I've made or acquired over the last few years. 

As a man who likes to tinker in his workshop - who doesn't - various work faces have opened up as I've investigated the machine. 

One is the broken dynamo and it's clamp. Removing the dynamo I realised that I didn't understand how it was held in place with only half a strap - pleas to other club members soon yielded a few photographs showing the bits that were missing. 

Taking the dynamo off showed me quite how bad the damage was. Both of the end castings appear to be broken - the drive end is in two pieces and I had to drill out one of the screws, but worse, the armature is actually bent. It looks like it's been dropped on the floor or had a whack from something at some point.

For the record, the armature is 157 mm long and you can get new ones - Feked have them.

The secondary of investigation is all of the tinware on the drive side. I started with the clutch dome but I have various repairs to do to the primary cover and the dynamo chain cover. 

This led to me looking at the clutch and the gearbox because of course the aperture in the primary cover dictates the movement of the clutch to some extent during the tensioning of the primary chain.

Thinking about the gearbox and it's range of adjustment led me to the gear controls, most of which I have already made. This leads naturally to the fixing of the fuel tank because of course unless the fuel tank is firmly bolted down (and I have new rubbers for that) the gear controls can't be set up. 

If that wasn't enough I've been looking at the front wheel and loosening the spoke nipples. I'm not going to go any further than that though - I was trying to establish whether the front wheel rim could be used or whether it was too far gone. 

The other area I've been looking at is the Lucas H52 headlamp, it's shell, and the mountings. The shell was quite bent and whilst I had the hammers and dollies out to sort out the clutch dome I knocked the dents out of the headlamp shell. It still wouldn't sit straight - it's aligned to the offside - because the mounting bars are also bent...

I think that's enough for now. I promise that I won't take anything else to pieces except perhaps for the gearbox outer cover - the kickstart doesn't seem to work and I can't get first gear!

FH - dishonourable discharge

 So after a few weeks on the bench, dealing with the wet-sumping and the fact that I seem to have forgotten how to start the Huntmaster, it now seems to run ok. Only problem is that it won't charge.

First suspicion was some wiring problem, or a failed regulator - crazy really, as in all the years I have used these regulators and wired my own bikes I have never had a problem. With the bike idling I had a look at the dynamo to see if there was anything coming out of it. I saw nothing. Zero volts. Nada.

I had a bit more of a poke around with the multimeter and eventually realised that the problem was a bit more fundamental than even the wiring of the dynamo - it wasn't actually turning! If I turned the armature by hand from the commutator end it was clear that there was actually no resistance - mechanical resistance I mean.

Next step is to turn to the other side and have a look at the drive chain. Normally this is suspended between two sprockets, one on the idler spindle and one on the dynamo - it's not supposed to be lying in a heap at the bottom of the timing case.

I poked around in the grease and pulled out a chain which still had the broken link on the end. Fortunately a bit more poking around found the side plate so I could be satisfied that I had all the broken bits and nothing was going to disappear into the engine and cause some monumental failure.

I bought this chain from Draganfly - and of course I mailed them to say that it had broken after 250 miles. They were excellent and had a new one in the post the same day.

The expert opinion from the AOMCC FB pages is that the chain was probably too tight. There is a recommendation in the Owner's Guide that it should have an 1/8" to 3/16" play - I've always had a bit of a problem with determining chain play and thinking about it I am undecided as to whether the measured play is stretch, with the links tight, or play with the links loose. I am going to try and fix this with that play being given by looseness in the links rather than by forcing the chain to deflect by the given amount. 

The little puller makes short work of removing the idle pinion dynamo sprocket, and attempting to replace the chain without moving the dynamo suggests the chain was way too tight.

It's charging merrily again now and we'll see what happens - if it fails again I might buy a belt drive kit from SRM.

Charlie's Shed - polarising the dynamo

 The need for this post arises because I have wired the Huntmaster negative earth. The dynamo that came with the kit is probably the original dynamo which of course will be expecting a positive earth system.

What's a dynamo 

A dynamo is an electrical generator that provides a direct current using a wire wound armature moving in a magnetic field following a principle discovered by Michael Faraday in 1832. It needs a mechanical commutator to turn alternating current into direct current since the rotating armature generates a current which changes direction as it moves through the magnetic field. An important principle as far as we are concerned is that the faster the armature rotates, the more voltage and current is generated by the machine. Similarly if the magnetic field strength is increased, the voltage and current will also increase.

How does it work 

In the motorcycle dynamos that we are looking at, the armature consists of a number of coils of wire wound around a stack of sheet metal shapes. The wires are terminated in a number of copper strips at the end of the machine arranged into a cylinder. The magnetic field is provided by a coil of wire wound around a suitably shaped metal structure fastened into the inside of the machine. The engine rotates the armature and a current is generated providing a magnetic field in the field coil. 

You will note that the magnetic field is provided by an electrical coil, and consequently you can imagine that the machine will not work unless that magnetic field is present when the engine starts. This is one of the issues we have to address. 

When the dynamo starts it is disconnected from the rest of the electrical system by the cutout in the regulator box and consequently won't start to generate electricity. In practice the field coil pole piece remains magnetized at least partially, after the machine was last used and we call this residual magnetism. This residual magnetism provides sufficient field strength to induce a current in the armature as it starts to revolve. Of course as the armature starts to revolve it generates a voltage which raises the field current which in turn increases the magnetic field, which allows a higher current to regenerated - and so it goes on. The voltage will carry on rising and in practice is limited by an external voltage regulator which takes effect by limiting current to the field coils.

Why do you re-polarise it

In a world where a motorcycle dynamo is perhaps not used every day, or the dynamo is moved from one machine to another perhaps having been bought at an autojumble or perhaps having lain around for a very long time since it was last used, it's functionality maybe compromised by a residual magnetism that is in the wrong direction or is so weak that it is virtually non-existent and the machine will not work. 

Therefore we need to have a method of generating that residual magnetism or changing its direction. Changing the direction of the residual magnetism might be necessary because you wish to rewire the machine for negative earth or perhaps because the machine for which your dynamo or specified rotated the dynamo in the other direction than that for which you wish to use it.

How do you re-polarise it?

Repolarizing the dynamo is quite straightforward and is just a matter of providing a current in the appropriate direction through the field coils. If you disconnect your dynamo, and provide a temporary cable from the battery terminal (that is not earthed) to the field terminal on the dynamo, you can repolarize the field coil by touching the wire on the field terminal momentarily. That should be sufficient to change the polarity of the residual magnetism or to generate it if it has seeped away. 

The temporary cable is not really necessary. Disconnecting the wires to the regulator reveals the green field coil cable and a brown and white cable from the ammeter. This brown and white cable is actually a battery cable, passing through the ammeter from the battery. Therefore, touching this cable to the field coil cable will polarize the dynamo correctly.

FH - dynamo chain

 In 60 stolen minutes (home early from a turn on the railway) I had an opportunity to do something on the Huntmaster. My initial thought was to set up the tappets and I had a look at the tappet cover locating pins to see what was going on with the inlet side, which doesn't fit. This job was going nowhere without a bit more time so I looked for something else to do and settled upon the dynamo chain. 

I removed the dynamo driving sprocket successfully with a small puller but I couldn't remove the driven sprocket at all; however, that was enough to allow me to put the new chain on.

For the record the cork gasket behind the driving sprocket is definitely there:

The new chain looked a bit larger in width than the one that was originally fitted; I've kept the old one just in case. The new one went on without any problems followed by the driving sprocket with a new tab washer - folded up here again for the record:

I'm a bit puzzled about the driven sprocket, which is a castle nut and has a hole for a split pin in the shaft. However, the slots in the castle nut don't fall in alignment with the hole due to the width of the sprocket and since it is fitted with a tab washer per the parts list, this is obviously correct. The tap washer is bent up correctly:

I really ran out of time to put the timing cover back on, but we'll do that tomorrow.

In the meantime, there's a curious little puddle underneath the oil filter - perhaps it's loose. Another little problem to take a look at!

FH - various jobs

 There's lots of little jobs around the bike to be getting on with. This one is the dynamo cork gasket which I bought from eBay. It was a little big and needed 3/8" taking out of the circumference.

That's the dynamo chain in place. I had one with a split link which I think is unusual - but I think that this is the original chain. I replaced it with an endless one from Draganfly. It's very difficult to tension because whilst you can turn the dynamo to tension the chain, as soon as you do up the clamp it pulls the dynamo back into the crankcase and loosens the chain again...

These are the clamps for the head steady. I've fitted them in place with some leather shim between the clamp and the frame to protect the paint. I'll leave these here for the moment until I have made the new studs for the rock box, and then I can fit the head steadies.

I bought all the cables as universal types from Draganfly. When I unwrapped them I was pleased to find the air and throttle cables were complete with their nipples fixed in place at both ends. Whilst the throttle cable fits ok, the choke inner cable is much too long so I will have to move the nipple.

These two pictures show the routing that I have adopted for the clutch cable. I've shortened the outer to suit this routing, and when the gearbox is back together I will fit the nipple.

I've made up two gaskets for the carburettor and the heat shield. 

Perhaps inevitably, the throttle stop is missing from the twist grip. As soon as you slacken the cable these loose stops fall out and can be easily lost. I'll make one on the lathe later - perhaps two, one for the toolbox as a spare.