9-0-9 DC Ammeter (Application?)

[The Philpott]

Some years ago i was given this Ammeter and am curious about the precise application/s.

(Legend reads 'AD6586 Made in USA By US Gauge Co NY')

Assuming a linear response it is of around 9-0-9 Amp range, and the clamp on the rear, it appears, originates from elsewhere. (probably a cad. plated capacitor clamp)

The meter is brass, with a hefty glass which has an angled edge. The flange has 3 holes, and has traces of paint similar to what you might call 'Allis-Chalmers Orange'.

The zeroing is best when the meter is set horizontal, and i suspect it may have been used in early tractors. They have changed hands on ebay in the past, but i can't find any good lead as to the machinery which they were used on...Can anyone can shed any light on this?

Thanks
Dave

[broadgage]

Almost certainly for some type of vintage motor vehicle, and quite probably a stock item fitted to many different vehicles.

9 amps is rather small by todays standards but would have been ample back in the day.

The dynamos fitted to early vehicles were not regulated but did often have three different current settings, low, medium, and high.
The dynamo control was often interlocked with the main lighting switch.

Lights off=low charge rate selected.
Marker lights only in use=medium charge rate selected.
Headlights in use=high charge rate selected.

An additional control permitted the driver to select a higher charge rate if the battery was suspected to be low, due perhaps to frequent starts or low speeds.

With a pair of 6 volt 36 watt headlight bulbs, and perhaps 4 marker lights each of 6 watts, and a few small lamps for the dashboard, the total demand would be about 18 amps and the High dynamo setting would be about 20 to 22 amps, so as to give a slight charging current.

Note that the actual current was not sensed, only the position of the lighting switch.
Prolonged running with the lighting switch set to "headlights" but the lights unlit due to failed bulbs, could cook the battery.

[G6Tanuki]

I'm thinking an 'industrial' application, like a tractor, domestic lighting-set, well-water pump or such.

Or maybe a motorcycle?

Something whose electrical load was probably only the ignition-coil and maybe a very low-powered set of lights - and where the engine once started would run for a long time so a low-powered dynamo could still produce enough output to recharge the battery.

[MotorBikeLes]

8-0-8 and 12-0-12 centre zero ammeters were regularly used on 6v motorcycles certainly from early '30s to even the '70s.I have 8-0-8 versions on two of my bikes, a 1935 New Imperial, and a 1954 Velocette.
I think the one shown by OP would be off a tractor or bulldozer. They usually had limited equipment, lights and maybe a heater, and running usually 12v, 9 amps would be plenty.
Les.

[AC/HL]

Flat panel mounting, American manufacture, low current, and that thick orange/red paint suggest machinery of some sort.

[The Philpott]

Thanks for contribs. While a sensible range for a m/c it feels agricultural from its weight and build so at this point it looks like tractor/'dozer/dumper. I have dipped a toe in a tractor forum to see what comes up. I have a feeling it suffered an internal malady in the past, as the 3 bezel holes aren't lined up with the casing holes. The brass would have had to have been peened back over the casing following the repair, and I am not tempted to interfere as any attempt to re-align would surely result in embrittlement and break-up.

[hannahs radios]

Have you ever tried it with say a sidelight bulb from a car in series with a 12 volt PSU and a modern multimeter to see if it works at all and how accurate it is? I think I'd be tempted to try.

[Herald1360]

A headlamp bulb would give a more meaningful deflection.......

[The Philpott]

I have indeed guys, from memory I ran a 12v 36w bulb through it and got 1 'notch' of deflection, that's what led me to think it was nominally 9-0-9.

There is silence thus far from the tractor people so it may end up being mounted in the lid of a wooden box and used in conjunction with my little Impax generator, which has a 12v DC @ 4A facility for charging car batteries when out and about.

Dave

[Biggles]

Could it be from an wartime airfield portable charging set? The orange paint would steer it towards a vintage tractor or bulldozer though, in my opinion. My experience of vintage motorbike ammeters is that they weren't much use due to the vibration of the single cylinder engine or whatever making the pointer swing across about 80% of the meter dial at all times. I suppose you just had to hope that it showed positive slightly when the engine was running.
Alan.

[pmmunro]

Tractor dynamos were often totally enclosed to avoid dust and chaff entering the machine. This resulted in a derating to around 50% of the equivalent ventilated dynamo. The standard dynamos in the UK were rated at 19A, later 22A, so that tractor versions would be around 9 to 10A.

This however was on 12V systems. Standard US practice was to use 6V systems on cars long after current demand created difficulties with dynamo commutation.

My impression is that American tractor manufacturers did not fit any more electrical equipment than absolutely necessary and I would not be surprised if many tractors had only a single headlamp.

PMM