FH - Ammeter rebuild

Way back in the dim & distant past, when I was still working, I rebuilt an ammeter for a friend and blogged it as ‘Tim’s Ammeter’. This is another one, a similar 0-8-0 amp CZU27 from the Huntmaster kit. It’s not in bad shape.

It’s a bit grubby and scratched as you might expect, so I will pull it apart for a clean. There isn’t much glue on this one and it comes apart easily.

All in bits with nothing broken:

Here’s a curiosity - it’s dated January 1960. It must have been replaced at some time, though it’s correct for 1958.

It cleans up nicely:

This is interesting. The power supply is set up for constant current:

These aren’t hugely accurate! This is actually at full scale deflection, but as you can see it’s only passing 7 amps.

FH - Ammeter identification

 Despite concerns to the contrary, the 1957 Lucas Parts Catalogue confirms that the ammeter should be a Lucas model CZU27, PN 36084:

It looks like this:

And here's the one from the FH:

Tim's Ammeter

This is Tim's CZU27 Lucas ammeter, from his Matchless single - the very common 8-0-8A instrument that's found on many of our bikes, and it doesn't work. The bike doesn't charge, and the ammeter is off centre. Tim has a repro replacement but this is the original one from his bike, and so it's important that it's repaired and goes back to the hole it's been living in for the last 60 years.

Here's Tim's bike - a G3LS that looks about 1957 to me, still has the pressed steel chain guard but has the new Girling shocks that replaced the jampots in that year:

Checking the ammeter with the multimeter shows that it's showing open circuit, so we are going to have to take it apart.

These meters are made with an acrylic plastic housing that forms the lens and the body, and the separate back is glued in. The glue goes quite hard and brittle and can be scraped out - but there is often some case damage around the edges:

I use a tool ground from a small screwdriver to scrape the glue away:

The dial usually gets caught up in the glue frenzy. It has four feet which clip to the base of the ammeter and these get glued down as well. Here are all the bits separated; notice how the dial has faded. There is a shadow of the needle on it:

Here's the whole thing dismantled (dial is not in this shot), and there is a couple of washers missing:

Closing in on the problem, we can see that the coil connection has broken - a fatigue failure, probably:

Here's the coil removed from the back plane:

The other eyelet:

Easily repaired, we can open the swage on the loose eyelet, clean the end of the coil and re-swage. We'll solder this joint and then re-lacquer the coil.

Soldered up:

On to the back. It's straightforward to repair the break with a suitable medium-viscosity cyanoacrylate, but using a technique I picked up while repairing guitars we can drop-fill the missing bits as well.

While I repaired the base, I noticed the part number stamped into the back plate:

So this ammeter was made in August 1966. Fifty-two years service is not too shabby!

For reassembly, start with the coil, the large Tufnol plate and the two domed screws. assemble them with the small Tufnol washers like so. Make sure the magnet is in its recess in the back plate:

The two large Tufnol washers isolate the terminal with their brass nuts from the backplate:

Remove this lot again and assemble the backplate to the repaired base:

Add the backplate, terminals and coil:

Assemble the Tufnol washers through the base and tighten the brass nuts:

Use a watch oiler to lightly lubricate the needle pivots

Assemble the dial onto the backplate assembly and add the needle. Screw down the needle pivot until it just moves freely, with no shake

Test the ammeter in both directions. This set up is just a 9V battery driving an H3 halogen bulb - which draws quite a lot of current and serves to show the ammeter deflecting:

Reverse the polarity to drive the ammeter in the opposite direction:

Make sure the dial has no damage to the legs. if the dial catches on the case, it will bend the needle when you remove the case.

Seal the dial legs to the case with a suitable weatherproof glue, preferably one you can easily remove:

Glue the top of the case in place and clean off the excess

Seal the needle pivot thread with nail varnish and you are done.

Brightspark have some useful information on these ammeters here:

http://www.brightsparkmagnetos.com/...Ammeters.pdf

As do the Vincent Owners Club:

https://www.voc.uk.com/net/docs/tl/lucasammeter.pdf

And I've rebuilt my Red Spot ammeter:

http://ariel-square-four.blogspot.com/search/label/Red%20Spot%20Ammeter

Ammeter Finished

So, here is the finished article. The ammeter has been stripped & cleaned inside & out and is now working happily.

The chrome on the rim is good, and the case has been repaired.

This is the new ignition light. The design & material selection is inspired from the genuine ones I have seen on eBay and the various forums, particularly the C10/C11/C12 forum. It's not an exact replica of anything but it looks the part.

I've made a carrier from 2 mm Tufnol which is a little thick, but all I had. The lamp bracket is made from 0.5 mm brass sheet, with insulation gaskets as necessary, riveted together. The one thing I would like to find now are a couple of 2 BA thumb nuts to replace those steel hex nuts.

Almost a red spot ammeter

Well, here is the first of the post-Christmas presents!

This is the kit of parts that I have, now that I have stripped a Lucas red spot ammeter that I bought on eBay from a member of the AOMCC, for a lot less than one can spend on such things.

It is a bit of an oddity. It seems genuine, it has a Lucas part number and is made of parts of approriate 'quality'. It is marked '1980', and I guess it was a replacement part for vehicles still using red spot ammeters. It is marked 'Lucas' on the dial, but it does not have a window in the back, like the earlier versions that would have graced Amelia's curves when she was new, and it has no facilities for an ignition lamp internally so it could not have functioned as the red spot ammeters were intended to do.

The plan is to replicate the parts used for the ignition lamp and to cut the window through the ammeter, so that we end up with a suitable white faced ammeter with the functionality that we need.

So, starting the work. Here is the back plane of the meter, with it's insulator. I've marked out the holes I need, and I've drilled a pilot hole in each. Then I have taken my piercing saw with it's V-table and carefully cut the shape we need for the ignition lamp aperture. I've cleaned the hole up with needle files.

Here is the back of the ammeter, the back plane and the insulator, all assembled and showing the aperture lined up. Not quite right yet.

Here's are the prototype parts for the ignition lamp. Following the style of the original ammeters, I have used a plastic card to replicate the tufnol insulator that is used to mount the lamp holder, just to get the shape, and the position of the lamp correct in relation to the aperture on the back of the meter.

The lamp holder is mounted on a small piece of 0.5 mm aluminium sheet, pop riveted to the insulator. There is a plastic insulator between the centre terminal of the bulb holder and the mounting bracket.

So for now, the lamp is in the correct place. We will reassemble and see if it looks OK from the front, when it is illuminated, then we will make some nicer parts.

Here it is, put back together with the ignition lamp off...

And here it is with the ignition lamp on! Isn't it exciting!

Parcels still wrapped - more electrics

Well, the eBay parcels are still under wraps. Christmas is coming and sometimes it isn't wise to buy too many present for other women, however much shiny paint & chrome they will have when they are finished!

So in the meantime, let's get on with the headlamp. We've got a nice original SSU700, no repro bits here!

The instrument panel looks like it is off a WD bike; it's in great nick but the ammeter is wrong - it's not the white face one with the ignition light that should grace a Square Four headlamp.

Also, there are some flaky bits. The edges of the pilot light aperture are rather ragged - it's an aluminium casting and I'm not sure how to repair it yet. Then there is the rim:

The picture is not too hot but it's bent and it looks like it has been thrown down the road. I'm going to see if I can straighten it before I give up and buy a new one.

Here's the inside of the switch panel from the inside. All right & proper, apart from the ammeter I mentioned before. A new one will have to wait though - the proper ones will be like hens teeth!

Lighting switch, cleaned up nicely.

Here's the pilot light mounting plate. It was missing, but I made this one from some photos & dimensions provided from the fantastic people on the AOMCC forum. It's designed to hold one of these in the underslung pilot lamp:

And here is the ammeter, with the steering damper knob lurking in the background. I'm going to tackle the rim and the headlamp fasteners with a Plug 'n' Plate chrome plating kit, and see how much of the original stuff I can save.

More later.