Ammeters

[RogerSB]

Hi all. I’m considering changing my ammeter because the needle on my Lucas ammeter is not in the middle when it’s ‘at rest’. It may seem a minor thing but it bugs me beyond belief because it’s not as it should be and as a consequence it’s very hard to see if it’s actually showing a slight charge or discharge from the riding position (see pics).

Secondly, it’s 8-0-8 and originally for 6v. My GF is now 12v.

I know ammeters only measure the current flow and are not fussed about being wired 6v or 12v and my understanding is, that with a E3L dynamo with an output of 60w combined with a 12v battery = 5 Amps, so an 8 Amp ammeter is up to the job but has anybody got any idea if the 12-0-12 versions brought in for the later alternator models show any significant difference in the deflection of the needle with 12-0-12 as opposed to the 8-0-8 ammeter?

Also anybody got any recommendations on decent ammeters currently available based on their recent experience?

The hole in the 1960 GF nacelle is to take a 1 3/4” (45 mm) diameter ammeter, so a Miller type isn't an option as I don’t want to file the hole bigger.

[chaterlea25]

Hi Roger,
Gravity ??

John

[RogerSB]

Thanks for your reply John, yes I know and at one time I had the needle pointing down (see photo) and it did help a little.

Edit: I'll probably end up turning it again.

[RichardL]

Roger,

Is there a centeting adjustment screw on the back of the ammeter? Not saying I'm the best source on this (despite my E.E.degree), but I would stay with the 8A version. As you note, cureent is what is being measured.  In the 12V system you'll draw half the cureent for the same wattage. With the 12V system  and 12A meter your needle deflections will be notably smaller, making it trickier to judge charging rate and changes in charging rate.

Richard L.

[RogerSB]

Hi Richard, thanks for that. I knew 6v (with its thicker wiring) carries twice the current of 12v but I couldn't fathom out what the effect would be on the needle. There is no adjusting screw on mine, it's a completely sealed unit in a metal case.

[Greybeard]

Roger, are you able to check that the ammeter is at fault, rather than an electrical problem? I imagine if you put a low wattage light bulb across the ammeter connections you should see it glow when current flows either way through the meter. More accurate would be a multimeter set to amps/milliamperes.

[RogerSB]

Hi GB, thanks for reply. Ammeter is working ok, it's just that I don't like the needle being off centre. Absolutely silly, I know, but it contantly causes me some irritation.

I know if I replace it I could easily end up with the same problem!

[Greybeard]

You might try placing a small magnet near the ammeter and see if you can influence the needle position.

[morris]

I would kindly offer you a swap with mine but that won’t help much because it’s showing exactly the same deflection as yours...
Still don’t know why it does that but decided to live with it. Gives me the feeling that there is some charge when the pointer is on zero

[Greybeard]

My ammeter is aligned with zero at the top.

[morris]

Forgot to mention but mine is a new one I bought a couple of years ago. It looks exactly like yours with the “LUCAS” and “Made in England” print.
It may be of the same batch/manufacturer?

[KiwiGF]

Hi all. I’m considering changing my ammeter because the needle on my Lucas ammeter is not in the middle when it’s ‘at rest’. It may seem a minor thing but it bugs me beyond belief because it’s not as it should be and as a consequence it’s very hard to see if it’s actually showing a slight charge or discharge from the riding position (see pics).

Secondly, it’s 8-0-8 and originally for 6v. My GF is now 12v.

I know ammeters only measure the current flow and are not fussed about being wired 6v or 12v and my understanding is, that with a E3L dynamo with an output of 60w combined with a 12v battery = 5 Amps, so an 8 Amp ammeter is up to the job but has anybody got any idea if the 12-0-12 versions brought in for the later alternator models show any significant difference in the deflection of the needle with 12-0-12 as opposed to the 8-0-8 ammeter?

Also anybody got any recommendations on decent ammeters currently available based on their recent experience?

The hole in the 1960 GF nacelle is to take a 1 3/4” (45 mm) diameter ammeter, so a Miller type isn't an option as I don’t want to file the hole bigger.

An 8 amp ammeter should be fine, but for the record it is generally accepted the e3l can provide more than 60watts when working at 12v 

See http://dynamoregulators.com/documents/improved%20charging%20for%20BSA.pdf

I think the technical reason may lie in the fact the “waste” heat created by the dynamo is directly proportional to the current going through it, and the voltage does not affect the amount of heat generated, and it is this waste heat that limits the dynamos output capability.

[Rex]

Some years back it wasn't unusual to hear of 6V-12V dynamo conversions that had got so hot that they'd melted the soldered connections on the commutator.
To get any near approaching those sort of temperatures is cruelty to old machinery.

[RogerSB]

You might try placing a small magnet near the ammeter and see if you can influence the needle position.

Thanks GB, I've already tried that. It does pull the needle well over to the plus side but when the magnet is taken away it just springs back and it would be a right old bodge to have to permanently stick a magnet in place inside the nacelle.

Forgot to mention but mine is a new one I bought a couple of years ago. It looks exactly like yours with the “LUCAS” and “Made in England” print.
It may be of the same batch/manufacturer?

Maybe be a 'last day of term' batch from Lucas . The ammeter was already on my bike when I bought it and it's always been like it - and gradually driving me paranoid . Bike is pretty much original but no doubt it is a replacement. Maybe an Indian fake?

[RogerSB]

Here's a sequel which definity explains my dodgy ammeter.

Look at the photo carefully and you will see that the Lucas face has actually been overprinted on one that originally was printed Royal Enfield. My camera showed it up as it's not visible with the naked eye (well, not mine anyway). It puzzled me at first and then it dawned on me and I went looking and came across this horrible cheapy one for under £8.00 which shows the exact design that I can see underprinted on mine  .

My conclusion is that my ammeter stamped Lucas and Made in England is anything but - and is a fake.  The manufacturer (probably somewhere in India) has even used up surplus bits or offcuts to manufacture a batch of fake Lucas ones.

It goes without saying I'll be replacing it.