50 amp (yes, 50!) gauge

Great Lakes Greg

Great Lakes Greg

Well-known member
I can only guess that this is some kind of industrial application. Must be a heck of a generator to push this much.
 

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What do the terminals on the back look like? If they're the same old thumb-screw jobs, at 50 amps that thing will be smokin'! So will the wiring.
 
Just because the gauge says 50 amps, doesn't mean you can or will put that much thru/across it. My 32 coupe had a 160mph stewart warner speedometer in it but I couldn't get that much out of it.
Paul in CT
 
The wires going to the ammeter are almost moot. You could simply have a large high wattage resistor parallel to the meter under the hood. Not sure if the 50A one for the A does this? Sometimes the resistor is right up against the back of the meter, or internal. And sometimes its remote.

You could easily have a +-100A ammeter with 26AWG wires going to it :)
 
Mitch,

I'm wondering what your concept was for using such a meter. You had it and it fit, and have a fuse in the line that will save your fanny if need be? My 30 amp gauge often pegs and sticks (until tapped), and I can see where it would be handy to have a bit more headroom, so to speak. I assume you're not really planning on having a steady 50 amp draw or charge in or out of your battery; I believe you would want to have 6 gauge wire for anything longer than momentary 50 amp flow.

Mike,

Can you explain to me why people who have, say, 60 or 70 amp alternators don't seem to need the super heavy wiring coming out of it that the charts would suggest?

Thanks.

Steve
 
MrTube said:
The wires going to the ammeter are almost moot. You could simply have a large high wattage resistor parallel to the meter under the hood. Not sure if the 50A one for the A does this? Sometimes the resistor is right up against the back of the meter, or internal. And sometimes its remote.

You could easily have a +-100A ammeter with 26AWG wires going to it :)
Click to expand...

What you say makes half sense to me. Even if the meter is shunted/wired/calibrated to carry only a fraction of the current, SOMEWHERE there's got to be really heavy wiring to carry the 50 amps, right?

Steve
 
MrTube said:
The wires going to the ammeter are almost moot. You could simply have a large high wattage resistor parallel to the meter under the hood. Not sure if the 50A one for the A does this? Sometimes the resistor is right up against the back of the meter, or internal. And sometimes its remote.

You could easily have a +-100A ammeter with 26AWG wires going to it :)
Click to expand...

Yes, it's called an external meter shunt. Not really a resistor, although it does have some ultra low resistance, as do all conductors. A very small current will bypass the shunt through the meter. The one pictured will show a 50 millivolt drop across it when 100 amps pass. If your meter reads 125 millivolts, you have 250 amps. I seriously doubt the meter pictured in this thread has an external shunt.
17298.jpg
 
Steve S, of course. I think the current carrying wire in the A is 12AWG stock. Should be good for 30-40A at the absolute most and thats going to be making some heat with a fair amount of voltage drop. I have a 25A fuse in our A at work.

Keep in mind, the head\tail lights in the A come right off of the generator or alternator and are separate from the battery and interior light and ignition.
 
steve s said:
Mike,

Can you explain to me why people who have, say, 60 or 70 amp alternators don't seem to need the super heavy wiring coming out of it that the charts would suggest?

Thanks.

Steve
Click to expand...

Three reasons: 1)All wire (except supercold 'superconductors') has some internal resistance. The amperage squared times that resistance gives you the wattage (resistance heating) that the wire needs to get rid of. In house wiring where wires are often buried in insulated walls a 10 gauge wire carrying 25 amps may get extremely hot. The same gauge in a car with air circulation will be able to dissipate more heat, permitting higher amperage. Wiring size/amperage charts are actually application specific, but few people know that. 2)Alternators rarely put out high amperage for sustained periods of time. If you take the typical 63 amp 10SI or 12SI alternator and put it on a test bench, run it up and load it to 60 amps, the thing will go up in smoke after about 30 minutes. Alternators are tested at full load for less than a minute. Running any alternator constantly at an output more than 50% of it's rating will shorten it's life. 3)If you do have a vehicle with a big load (bus with three AC units comes to mind, 225A brushless truck alternator, always a 100A load) there are usually multiple takeoff wires directly from the alternator output stud, not one giant lead.
 
of course i am not running 50 amps . lol. my car came with that 50/50 amp meter when i purchased it and before restoration. i am running a stock setup and the meter works great never sticks so i just left it there. the only difference is it goes by 5 amp increments. works as good as the other ones
 
MrTube said:
... Keep in mind, the head\tail lights in the A come right off of the generator or alternator and are separate from the battery and interior light and ignition.
Click to expand...

unless, the motor is off or the generator is not generating for some other reason, then all of the current for everything comes from the battery and through the ammeter.
 
Re: 50 amp (yes, 50!) gauge MINE is Shunted

:)I have a 6 volt converted alternator in My Model A ...Works so nice I would not go back to a generator it never overcharges or undercharges just does its job like in your mordern car ..It also charges at Idle ...The 30 amp gauge always pegged when the car was first started
Then after a few minutes it goes down to just a few amps ...I did not like the gauge ******* so I experimented with a simple "meter Shunt" mine is 10 feet of #14 stranded electrical wire wound in a small coil with crimp on connectors and fastened across the two terminal box screws ...I arrived at the 10 foot length by trial and error if you use wire that is different from what I used it will have different resistance and you will have to do the same experimenting to get the shunt right ...Anyway This makes the 30 amp gauge in my car NOW into a 60 amp gauge so when I see 10 amps current I know it is actually 20 ...My ammeter no longer pegs ...Of course I can remove the shunt very easy in a couple of minutes any time I want to thats why it is on the terminal box in the engine compartment ...By the way the 50 amp gauges were sold By J.C.Whitney years ago I bought one when they had the MODEL A section in their catalog ...The 50 amp gauge was for us guys who changed the Model A generator to a larger one with a regulator on it I had a 1954 Chrysler generator on My Model A then and a 6 volt regulator installed on the firewall ...That was 1959 and I was in hi School :D... B0B
 
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