Classic cars forum & vehicle restoration.

DM · Joined: 21 Dec 2008 Posts: 212 Location: North Cornwall

If there is enough thread on the ammeter connections I would ditch the Lucar connectors and use crimp ring connectors to connect all your existing harness wires directly to the ammeter.

You would be risking any warranty if you disturbed the red paint locking the lower nuts and could damage the ammeter if you let the studs spin but would have a more reliable fitment.

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

DM · Joined: 21 Dec 2008 Posts: 212 Location: North Cornwall

Ok read the label and saw what I thought was there.

PIggy back connector but I don't think you can get them for 3/8 Lucar connectors

https://www.autosparks.co.uk/electrical-components/terminals/spade-terminals/male-to-male-piggy-back-spade.html?

Or if you have the space you could use a junctin box like this to combine the wires and take only one wire to the ammeter.

http://polevolt.co.uk/acatalog/Power-Cable-Jointing-Box-2-x-8mm-studs-PJ1.html#SID=120

Peter_L · Posted: Tue Jun 23, 2020 12:24 am Post subject:

I can hear purists reaching for their keyboards. I am not saying this is the way you should do it. This is the way I would do it and have done so more times than I can count, from Vehicles, Trailers, High Voltage. May I add that in my past I have perhaps spent thousands of hours soldering. I know that there are those who avoid it like COVID-19.

Line tap without cutting main line.

Remember: Note: Slide on appropriate size shrink tubing. Add a few so as to have a couple of layers when finished.

Wire strippers at correct diameter. Create two cuts through the insulation approx. 1/2 inch apart for this application. Sharp as in New craft knife blade slide along between the two cuts and peel off that bit.

Wrap the tap wired around the main line, making as tight a wrap as possible.. Solder the joint !!. If you have flux then let it at least have a look at the joint, it will make the solder run that bit easier. Under heating is enemy number one. over heat will "crozzel" the insulation. Happy hour is when the solder just starts to run into the wire under the insulation but the insulation doesn't turn black.

Now for the really fussy - fussy bit. The soldered area may/could/has been know to benefit if the flux is removed. Use cotton buds to apply.
Methylated Spirit, Brandy or Whisky, or good old WD 40, spray and wipe.

If you are really really fussy, bind the joint with a couple of layers of insulating tape. Now pull the first piece of Shrink Tubing over the joint and give a quick blast to pull it down enough to get the second over... Allow the first one to cool a bit otherwise the second will have premature shrinkilation.

If all has gone well there should be a fairly small, aesthetically pleasing cable tap.

As it happens and purely by coincidence I have used this process in the last few days on a couple of boat trailers. The only difference being the use of adhesive lined shrink tube, and a final binding of "paint on insulation" Aesthetics was not on these particular work sheets..

ukdave2002 · Joined: 23 Nov 2007 Posts: 4104 Location: South Cheshire

I'd use a piggyback Lucar, AES should stock them, I presume they will be the heavier 3/8" (9.5mm) spades? Make sure its on the otherside of the ammeter to the battery connection else the ammeter reading will be incorrect.

I'm confused about the ammeter mod, possibly I have misinterpreted things !, I understand why they have put a shunt in so that the ammeter can read a higher load, but by keeping the face the same the reading will be very inaccurate?

Dave

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

alastairq · Joined: 14 Oct 2016 Posts: 1950 Location: East Yorkshire

Sorry, Ray..posted, then shut down computer for the day!
Piggybacks have been very well illustrated by dave...
The advantage of piggybacks [do be wary of vibration cracking the connections, however?]....is that each wire can be separated as the need arises.

Not easy with a permanent joint as with soldering.
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
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Ford Pop chassis, Ashley 1172 bodyshell, in pieces.

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

Thanks to everyone for the advise given. Should come in useful.

ukdave2002 · Joined: 23 Nov 2007 Posts: 4104 Location: South Cheshire

petelang · Joined: 21 May 2009 Posts: 442 Location: Nottingham

Ray,
I personally would not use a piggyback connector on the back of the ammeter even if it's possible to get one for larger 3/8 size Lucars.
The only loads on the battery side of the ammeter are small wires for the clock and inspection sockets. I would add here that such items unfused are always a risk. You plug something with a short on it into the inspection socket and potentially your whole loom could go up in good old Lucas smoke.
The better option would be a separate single wire, taken from the solenoid switch terminal (Battery positive-unfused) through a single line fuse rated at say 20 amps and route to the dashboard to join to the back of the clock and piggyback with a small 1/4 Lucar there to the inspection socket.
In this way the system is safely protected and means a less bulky connection on the back of the ammeter.
I think it's a real shame that the instrument supplier didn't provide you with a dial scale that properly represents the actual current flow as I'm sure a 50-50 scale must exist in white. It just seems a bit unprofessional. The other alternative, when alternators became the norm and high current was flowing through the ammeter, was to ditch the ammeter altogether (saved volt drop over length of cables and kept the fat wires in the engine bay) and fit a voltmeter which gives you a very clear indication of charge status. This notably on later Daimler DS420's where space behind the dash for the thick cable was limited.
Peter

petelang · Joined: 21 May 2009 Posts: 442 Location: Nottingham

https://www.smiths-instruments.co.uk/documents/dials/magnolia/classicmagnoliawatertempamp-451.png

petelang · Joined: 21 May 2009 Posts: 442 Location: Nottingham

Like this:
https://www.smiths-instruments.co.uk/documents/dials/magnolia/classicmagnoliawatertempamp-451.png

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

If there has been a mistake then it is probably my fault. I have commissioned John Marks of 'Vintage Restorations' to rebuild my instruments to look exactly as they would have done originally with the "British Jaeger" logo and correct "green" hue.

As it happens, John owns the Brand and he is generally regarded as being amongst the best in the business; if there is a problem he will happily correct it or give me a full refund or whatever I want.

Peter_L · Posted: Wed Jun 24, 2020 5:11 pm Post subject:

May I suggest that Dave's comment is slightly flawed. As in the actual meter part does not show the amount of current flowing through it's own circuit, which Dave correctly says is a % of the whole, but the total current flowing through the shunt + the meter. The needle will not go past 20A because it is physically prevented from doing so and aesthetics required 20A to be the maximum. If a larger scale meter was inserted, in series, into the circuit then the full current would be displayed on that. On for example large switchgear or generator sets, the Ammeter's are fed with relatively small cables while the greater portion of the current passes through a shunt.

Simple Ammeter and Shunt diagram.

I avoided the words, millivoltmeter and voltage drop. All I was attempting to do is show how Ray's Ammeter will be providing him with a reading in Amperes.