W/NG - Lucas DU42

 Originality creeps closer with every passing blog post at the moment, this time with a genuine Lucas DU42 headlamp. The bike has worn an Indian replica since I've had it, and since one came up within the club a while back I've had a plan to replace it, with a bit of help from Wali Taylor who came up with the proper flat glass.

This picture comes from the W/NG workshop manual and shows the BA15 bulb holder, with adjustable focus (C), held in place with the long spring clip and the early rim clip (A) my bike would have worn:

The long spring clips (B) are retained to the reflector with two little sheet metal clips, riveted to the reflector. One of mine was rusted away, so here is the replacement made from a scrap of 0.5 mm sheet steel:

Here's the beginning of a rivet made from 2.5 mm² annealed copper wire:

The next thing we need is the gasket and the glass, shown in this later diagram from a 1944 parts book where the ammeter has been deleted and the headlamp switch moved to under the seat, with the new hi/lo pushbutton in the headlamp panel:

I've decided to use round section foam strip for the gasket; the glass is original, from Wali Taylor of the AOMCC.

The clip came from eBay, but didn't fit until I gave it some attention. The rim was full of dents too, but with a panel beating hammer and a dolly I soon had that smoothed out.

The clip is retained with a bit of piano wire - this is about 2 mm in diameter:

Onto the bulb holder. This is a military pattern bulb holder - there is only one contact for the main bulb, and I guess I will make another. Also very visible here is the clamping screw that allows the bulb holder to move backwards and forwards to position the filament at the primary focal point of the reflector.

Here's the view from the other side. Needs a clean but it is in good shape - it's not distorted at all.

Next is the instrument & switch panel. This is the illustration in the manual:

This is the one that came with the shell: it's a bit early for the W/NG as it has the fitting for the half charge resistor - that little casting between the ammeter and the switch hole:

This switch panel would be 1932-36, as the earlier H52 headlamp is quite different and the half-charge resistor disappeared with the introduction of the MCR1 mechanical charge regulator in 1937. I might use this or perhaps the repro one that is fitted to the bike at the moment.

This is the only original Lucas shell I have with the holes for the rubber string seal. Here it is in place - it’s a 2 mm sponge EPDM round section:

There will be a bit of wiring to do as the repro ammeter currently on the bike has terminal posts and ring terminals, and the headlamp is wired up with Japanese bullets:

I've chosen a CDRC Double Dipper Pro projector headlamp bulb:

This is the beam it produces, in a picture taken on my phone using the 'night' setting.

With the camera set for daytime you can see the bulb is using the high beam LED and the low beam LED:

The completed headlamp:

Installed:

Updating the Lucas MCR1 Voltage Regulator

The little Lucas MCR1 is used with the short Lucas E3 dynamos, like the one fitted to my W/NG.

I like my bikes to look period, but I don't mind updating them to improve performance if there's no visible sign of it externally. The MCR1 was not working, and since I have a similar electronic regulator on my SQ4, which has been looking after my charging system for years, I have no qualms about updating this one.

The update to the SQ4's MCR2 Regulator is shown in a previous post. Today we are looking at the MCR1.

I am going to fit a modern V-Reg 2b dynamo regulator which is designed to replace the mechanical regulator with modern, reliable semiconductors, can handle up to 100W at 6V and even more for the 12V version provided the dynamo is capable of delivering this power. This device is proven and reliable and is available in Positive or Negative earth. 

New features of the 2b include: 

• Current limit to the field winding, allows excellent performance when using a 6V dynamo on a 12V system while not straining the dynamo. 
• Tougher electronics, with the introduction of higher energy spark suppression to reduce spikes generated by the dynamo. Improved "thermal foldback" which progressively reduces output power if the regulator gets too hot, indirectly limiting the dynamo from excessive current. 
• Better servo loop stability, with new electronics which 'predict' when the output voltage is nearly correct and control the field current earlier.

Mine came from AOServices, who manufacture the V-Reg. You can buy them from a number of other suppliers, but Alan Osborn at AO provides a fine customer support service here in Norfolk. When you order your regulator, you must specify the polarity - a positive earth regulator uses different components to a negative earth regulator, and you cannot convert them. However, the same V-Reg 2b will run a 6V system or by cutting a simple wire link will run a 12V system.

Here it is, with the original 1942 MCR1 quaking in the background. That little green wire is the 6V/12V link.

To get inside, undo the wire clip and remove the cover to reveal the coils & terminals. We'll be removing those coils in a moment:

Here's the underside, showing the two screws holding the bobbins in place:

The cover is stamped with the month and year of manufacture:

Now to start work. The original D terminal screw is soldered in place - peel the solder away and remove both of the visible screws:

The coils will now be loose. Cut all the wires to each of the terminals, being careful not to damage the terminals:

Lift the coils away:

Remove the clip. It's going to get in the way:

Clean up thoroughly. This is a glass brush - it's quite abrasive and does a fine job of cleaning the terminals and the muck around them. Clean the rest down with a spirit wipe.

Take a small soldering iron (this one is a variable 60W iron) and remove the solder and any remaining strands of original wire from the terminals. You can use a solder sucker if you need to.

Then clean the terminals with your glass brush or a sharp knife. Make sure the holes are clear.

Cut off the eye underneath the regulator. It's connected to the D terminal - you don't want charging voltage escaping into the rain. It easier to do this from above, unlike my picture:

Now, the MCR1 is a lot smaller than the MCR2 we upgraded for the SQ4, and the mounting for the V-Reg 2 needs to change. Here I'm using four adhesive pads to stick the V-Reg to the Tufnol insulated base of the MCR1. Don't stick them down yet.

So here we have bared the wires and carefully threaded them through the holes in the correct terminals. BE CAREFUL! you don't want to get this wrong and destroy your new regulator. Bend the bare ends to align with the terminal and increase the strength of the joint.

Now solder the wires in place. Make sure you have heated the terminal effectively, so the solder flows cleanly and wicks into the conductor strands. Don't melt the solder directly with the iron, but let the work heat the solder - that way, you know the wire or terminal is hot enough to make a good joint. I'm using electricians cored solder here:

Coil the wires above the regulator such that they stay within the MCR1 cover, and retain with a small tie-wrap. We don't want to introduce a fatigue failure or have these wires trapped somewhere.

All done:

Finished, with no visible changes:

And the bike is charging:

E3HM Dynamo

Well, the charging system is not working. Hardly surprising after an indeterminate period of laziness under the Italian sunshine, but the problem must be in the regulator, wiring or dynamo. The wiring is very simple and it's brand new; the dynamo needs inspecting anyway and is first up.

Removing the Dynamo

The dynamo is removed by releasing the clamp holding it onto the magneto and removing a nut drawing the drive end of the dynamo into the magneto drive cover. Suspicion is immediately raised by this screw:

Conspicuously shiny and really shouldn't be there!

There should be a little sleeve nut on a stud there. There is nothing too much wrong though - it motors when connected to a battery

View of the drive from the magneto. It was at this point I realised the whole magneto rocked slightly on the engine plates - not loosely, as though the mounting nuts were not tight, but as though something was bending.

The reason is that the fourth mounting is broken - we will have to invent a way of getting to that.

Broken 5/16" hex screw

Dismantling the Dynamo

This handy diagram comes from the W/NG workshop manual.

The manual is also useful to show us how to take the dynamo to pieces.

Starting to look over the dynamo on the bench, we can see the drive end bearing retaining plate (Item V in diagram H13) is loose.

Stud and sleeve nut missing

Removing the commutator cover band by releasing the clamp screw on the cover band (F), we find the cork gasket looks like a tired bit of cardboard. New gasket required.

Greasy brushes:

Mucky scored commutator:

The next thing we do is remove the brass screw (H) securing the end cap (I). Next, we can remove the nuts (J) securing the D and F wires to the end cap terminals

Brass screw H back in place for safe keeping

Next, disconnect the wiring in the commutator end of the dynamo to allow you to continue dismantling.

Disconnect the earth side with this screw

Disconnect the D brush with this screw

Remove the wire link between the D brush and the D terminal on the end cap.

Wire link, D brush to end cap D terminal

Remove the brushes by pulling back their springs with a wire hook, small screwdriver or a small pair of pliers. Pull the brush out gently.

One of the brushes

With the brushes out, you can see the commutator.

Dirty commutator

The next job is to remove the armature. Grip the drive gear in the soft jaws and remove this screw, starting by knocking back the tab washer (if it is still there).

Sometimes the drive gear is a tight fit on the armature. Remove it with a small puller - watch out for the key:

Drive gear dismantled

Next you can remove the two long screws (K) running through the yoke (S). Grip the nuts (L) at the commutator end as you undo the screws.

With the screws out, the armature will pull out of the yoke. I didn't expect to see this ball bearing on the commutator end.

The next step is to free the drive end bracket (O) and the drive end bearing retaining plate (V) from the armature. We'll need to remove the armature shaft nut (M) for this. This has two slots in the top and needs a special tool which I cut from a damaged box spanner:

After some filing and a dose of case hardening it is ready for use:

With the armature in the vice in soft jaws, the tools, equipped with a tommy bar makes short work of the slotted nut.

Rebuilding the Dynamo

Drive End Bearing

Someone has mangled the drive gear journal with a punch - that will clean up easily. The bearing is held in place with these screws. Unfortunately, that fine thread is a poor choice in this soft alloy and one of them has stripped. It's only 73 years old as well...

The bearing is very rough. We'll measure it up and get a new one.

Like this:

It's a double sealed bearing, so that it will retain its own grease and prevent oil coming into the dynamo.

The bearing retaining plate (V) is, as I said, loose. We'll need to repair those tiny stripped screws - I have decided to replace them with 4 BA screws which are slightly larger and will be stronger, especially as I will run the tapping size drill right through the driving end bracket (O), so the screws will be longer. Countersunk 4 BA screws will still fit in the original holes in the plate.

Recutting the drive end bearing threads

The result is quite neat:

New 4BA csk screws in brass

With the drive end bearing assembly complete, we can refit the armature with its nut.

Armature reassembled into the drive end bearing

Next we need to look at the other end.

Commutator End Bearing

The commutator end is still a problem. This is the journal for the bush - the bush ID is 0.318"; this journal is 0.275" OD, which is very undersize...

The rolling bearing should not be there on an E3HM; it maybe home made - there is a journal machined in the end bracket and as previously noted, the journal for the oilite bush is undersize. The bearing is 22 mm OD;

Unfortunately, the journal diameter in the commutator end bracket (Q) is larger.

It's actually 22.5 mm ID. I'm wondering if this was meant for a 7/8" bearing, which is around 22.25 mm OD. They are cheap, and I could order a double sealed (2RS) bearing which would last a while but these bearings will be too large on the ID. Whoever modified this, and it is non-standard, ground the armature to suit the 22 mm bearing. I have no choice but to shim the journal to suit the bearing, which works fine.

I can refit the through bolts and nuts (K) and (L) and move on to the commutator. These are fitted with shakeproof washers both ends - I must remember to fit them when I find some!

Commutator

Once the bearings are sorted, the next step will be to rebuild the commutator. The first job is to thread the field coil leads through the fibre plate on the commutator end bracket (Q)  and fit the plate with the three tiny screws:

I have a set of NOS Lucas 200290 brushes, all the way from Australia:

Holding the springs back, slide a brush into each holder, checking that it is free to slide. Mine are a bit tight and will need a polish. Let the free end of the spring rest on top of the brush:

Wiring Up

The link connecting the D brush to the terminal on the end cap was horrible, as shown earlier. We need a short piece of wire and a couple of small ring terminals to fix it:

Crimped and soldered

Connecting the wires back up is simple, but it pays to be careful with the routing. Try the wiring with the end cover loose:

Its quite tight in there, and the D wire passes closed to the F terminal:

Testing

Quite the easiest way to test the dynamo, re-magnetising it in the process, is by causing it to 'motor' - that is, driving it from a battery and causing it to behave as a DC motor.

To do this, connect the D and F terminals together (I use a small crocodile clip to span the terminals - one jaw in each hole). Connect the case of the dynamo to your battery's earth terminal (negative in the case of the W/NG) and the other terminal (positive in my case) to the crocodile clip. The field coil and the armature are thus both exposed to 6V, and the dynamo should smoothly turn, relatively slowly, in the direction that it will run on your bike. In the W/NG's case this is anti-clockwise when viewed from the commutator.

End Cover

The commutator end will need a new cork gasket. The originals were riveted in place with the bifurcated rivets still remaining in this band:

I've cut some holes with a wad punch to allow the band to fit in place without removing the original rivets:

Drive Pinion

Refit the key and slide the pinion into place. The pinion is retained with a 1/4" BSF screw with an oversize shallow hex head; this is retained with a tab washer. Pimple the tab washer into one of the pinion keyways, and when the screw is tight fold up the tab washer against a flat on the hex head.

A 'before' picture of the drive pinion

Refitting the Dynamo

Once the end cover is back on and the sleeve has been tightened down, you can refit the dynamo. Grease the magneto drive pinion by turning the engine on the decompressor, then slide the dynamo into the retaining strap. Draw the dynamo into place using the sleeve nut.

The sleeve nut whose absence started it all

You can then tighten the strap screws with the special dynamo spanner and refit the yellow and green dynamo and field wires.

Dynamo spanner

Dynamo & field wires