Ground 6-Volt Battery - 1936 Ford Sedan

Based on the 38 jail bar I used to own, I'd say negative earth.

In fact I can't think of a single positive earth 6 volt (common make) vehicle.

Although there's bound to be one.

Check the markings on the Generator, if they haven't been painted into oblivion.

Chrysler FH sixes were positive ground.

They also had left hand threads on the left side wheels

I had a 41 ford that was a positive ground.

Have a look here,

http://www.vanpeltsales.com/FH_web/flathead_drawings_electrical.htm

http://www.vanpeltsales.com/FH_web/FH_images/FH_electrical-pics/Flathead_Electrical_wiring1936.jpg

The battery is drawn as negative earth.

I've done a bit more research and yes they are actually Positive ground, which means the circuit diagram I found is wrong..

My Jail Bar must of been converted over at some stage in its life, I acquired it as a rolling meccano set, bought it because the motor started and ran..

The Flathead V8 we had in a skiboat was 12v and negative earth, but then you can do that with generators and the right regulator..

GA and GI (Good Idea!)

Come on now own up to it. You've done this before haven't you.

The first automotive related job I had involved road service work in NYC. Back then we had 58 through 61 Chevy pickups with Mitchell tow booms on them. We would just charge up a bunch of old batteries, and join two together to make 24 volts. And like you said, just hold the jumpers on the battery while cranking the car. But, every once in a while, there would be this 6 volt car with a very fast starter.

Positive it is positive

Penttijp

Ford 'messed' with a positive ground for a time during the 1930s. The quickest why I can think to check for polarity is to (for positive ground) connect a jumper from the negative side of the battery to the starter connection, and the positive jumper to ground. Check which way the engine turns. If it turns the proper way its a positive ground.

Sorry but the starter motor is a 'series' type which runs the same way regardless of the supply polarity.

penttijp

Australia

And a vehicle of that age probably has an inertia-type starter pinion, so it wouldn't engage (and turn the engine) if the starter went wrong way.

Cheers........Codey

Usually starters are serial DC motors, that is the field and the armature are in series, when the polarity to them changes, the motor STILL turns in the same direction!!!

As does a DC shunt motor which also has wound fields.

There are two reasons for the motor to reverse with a polarity change:-

1) Permanent magnet motor

2) Swapping polarity of ONLY the commutator OR the fields......not both.

Remember swapping the polarity of both will always cause the motor to turn in the same direction!!!!

Its a point many never understand!

But, if you know what an AC "Universal Motor" is, it has wound fields and brushes/Commutator, it turns in one direction only with AC or DC supplied to it!!

Most vacuum cleaners, mains electric drills, hair dryers etc are all of the Universal AC/DC type.......

I know, all I meant was that even if the starter motor somehow managed to turn the wrong way, it wouldn't engage with the flywheel. Thinking about it again, it wouldn't if the starter were pre-engaged either, as these have a one-way clutch to prevent over-revving of the starter by the engine. On an inertia type, of course, the pinion flicks out automatically if the engine tries to drive the starter.

Cheers...........Codey

That will as good never happen in the real world.......

But as I have never examined EVERY type of starter motor, there could be one with a permanent magnet somewhere.......or one designed to start an engine in one of two directions, so I never say "never!"

In earlier times, a reverse gear was sometimes more expensive than restarting backwards. Old tractors or similar I believe.......

I've heard of cases of diesels, probably big marine ones, which would be run in one direction for a few 1000 hours, then reversed, to get maximum total life. It would need to be cranked either way, I assume via a reversing gearbox, as reversing direction of the motor (if this were possible) would not work due to the one-way clutch. But I daresay a solution could be found, one being to have 2 starters, 1 each way. Or perhaps the starting method is quite different for these big diesels e.g. compressed air.

Cheers.......Codey

I agree, the big diesels I have seen in marine applications all used compressed air, some to blow an air motor (small ones around 100 liters capacity, the very big ones were "run" using compressed air in the cylinders.....

I looked here:-

http://en.wikipedia.org/wiki/Diesel_engine#Starting

and found these comments (well down the page):-

Large and medium marine engines are started with compressed air directly applied to the pistons. Air is applied to cylinders to start the engine forwards or backwards because they are normally directly connected to the propeller without clutch or gearbox, and to provide reverse propulsion either the engine must be run backwards or the ship will utilise an adjustable propeller. At least three cylinders are required with two-stroke engines and at least six cylinders with four-stroke engines to provide torque every 120 degrees.

As far as I am aware, almost all (if not all!!) vehicles were positive earth till around the end of the 50's both inEurope and everywhere.....

I do believe that it was discovered that with a negative earth, that corrosion was somehow reduced.....though that might be urban legend.....

If I was the owner of a 6 volt vehicle (any earthing), I would convert it to 12 volt negative earth, as its easy to do nowadays, possibly with bits from a scrapyard......

Ed Weldon did a really GREAT post......I GAed him for that!!!

I did it (conversion) with a '50 Studebaker. Went from 6Vpos, to 12V neg....

Robbed a '57 Auto for the Generator and regulator, changed bulbs, swapped wires on ammeter. Only thing I didn't get to work right was the gas guage. Radio will never work If I install one.