Positive Ground

[rfitzpatrick]

What's the Story why Ford went positive ground? What did the industry consider common, not just Ford Motor Company, during the Era?
Tks

[old ugly]

model T is negative ground, i don't know why he switched to positive ground.

electrons travel from negative to positive direction, maybe he thought it was the natural order of the universe.

lets hope someone has the correct answer.

[Bob Bidonde]

The advent of solid state electronics drove the change from a positive ground to a negative ground. The opportunity for the ground polarity switch arose with the change to 12V electrical systems in the mid 1950s. In development at that time was an alternator which used transistors and diodes dependent on a negative ground. By 1960 the 12V alternator design was mature enough for production, and it first appeared on the 1960 Valiant.


Original thinking was that a positive ground would minimize corrosion because it made the frame a positive anode instead of the car body. The anode corrodes and the thick metal frame was able to loose some of its thickness without consequences whereas the relatively thin body metal could not cope with corrosion.

[rotorwrench]

The model T didn't need much for a battery and folks didn't drive at night as much as they did with later cars that were better equipped and ran faster on the crude roads of the time. Some folks even run there Ts on 12-volts. The old 3-brush generator would have a hard time charging any battery but the starter and the coils will work on 12-volt. The magneto on the T likely put out more than 12-volts anyway.

Ford's electrical system was taxed more on the model A when they decided to use a battery type ignition. Coupled with this and a full complement of lights, they needed all the help they could get to keep the system reliable. A positive ground system follows the natural flow of electrons so it makes the system more efficient. Ford kept it this way till 1956 when they changed to 12-volt systems. 12-volt systems have twice the voltage so the efficiency level of the current flow was no longer relevant by that change. Modern designers were all using negative ground and more electrical accessories were becoming polarity sensitive so they went the normal way of the industry at the time and changed to negative ground.

[nkaminar]

I worked for a while for a solar company that had very high efficiency solar panels. The systems used negative ground and the voltage built up to high values because it was more efficient for the inverters. We started having mysterious reductions in panel output. The negative charge on the frames relative to the positive charge on the cells was causing the problem. (Technically the panels were operating as a programable memory device., PROM) We switched to positive ground which solved the problem. We had to search for inverters and other equipment that could be used with positive grounds.

I don't think anyone is positive why Ford made the switch (pun intended). Best reason i heard is the anode argument.

[hazelhoff]

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I think Bob is right. Compare kathodic protection for shipd, steel underground gas pipes etc.
Related question ? Does the positive part of the car attract dust more ?
Henk

[TomInCologne]

Originally Posted by rotorwrench

<snip>


A positive ground system follows the natural flow of electrons so it makes the system more efficient. Ford kept it this way till 1956 when they changed to 12-volt systems. 12-volt systems have twice the voltage so the efficiency level of the current flow was no longer relevant by that change.

<snip>

Whooooooooot? Would you care to elaborate on that? I am a physicist and i cannot for the life of me think of any physical explanation...

[nkaminar]

As an engineer, I am with Tom on this. There is no physical reason why a positive ground would be more efficient. The electrons complete a path and it does not matter which direction they are going.

[rotorwrench]

The current only flows one way in a DC electrical system and that is a fact. It flows from positive to negative. The ground path generally has less resistance to flow unless the cars is all crusty and rusty like many are after 90+ years. Same with the copper conductor wires but they are at the end of the circuit path in a positive ground system so the galvanic transfer of materials may have been thought to be an issue. The battery ignition was new territory for Ford in late 1927. They had used the Magneto for many years in the model T which is AC in nature but the battery, distributor, & coil was not something that Henry trusted as much until they started testing it. The thought was that the high tension spark would be more efficient with positive ground. Ford wasn't the only company to use positive ground so there was likely an industry wide consensus on this at the time. The model T had been negative ground so it was a change for Ford.

Another thing that is affected is the starter circuit in these old cars. This is the heaviest current draw in the system and also the most prone to problems in the 6-volt systems. With the body of the system already positively connected through the ground path. The flow only has to travel back to the battery when the starter switch is applied but that is where most of the deterioration would take place if that power cable was attached to the positive terminal. They felt that this would cause more arcing at the switch terminals when the starter was engaged. Maybe they were wrong but this was the early 20th century and folks had a different way of approaching things back then.

[TomInCologne]

Originally Posted by rotorwrench

The current only flows one way in a DC electrical system and that is a fact. It flows from positive to negative. The ground path generally has less resistance to flow unless the cars is all crusty and rusty like many are after 90+ years. Same with the copper conductor wires but they are at the end of the circuit path in a positive ground system so the galvanic transfer of materials may have been thought to be an issue.

<snip>

i think you wanna speak to those pesky electrons, they are all negative about this... ;-)


But let's agree to disagree...

[Badpuppy]

Conventional current positive to negative.
Electron flow negative to positive.
Go figure.

[nkaminar]

Electrons were not known when electricity was first being learned about. The plus and negative was arbitrarily assigned. Later electrons were discovered and it was determined that they were negative charged.

[redmodelt]

Dodge Brothers went from 12 volt negative ground to 12 volt positive ground around 1921/22 when the horn button was moved from the door, to center of the steering wheel. The reason given was, had to do with degrading contacts in the horn button.

[Ted Duke]

Electricity=Magic
No one REALLY knows. LOL

[Crankster]

In Shop Manuals or engineering papers what information was provided? They doubtless had to 'splain themselves or provide justification when they completely changed from one way to the other.

[rotorwrench]

I was taught conventional theory but electron flow was there too but not taught in basic electricity at the time. For the purpose of calculating Ohms law it is irrelevant as to what moves where.

The other school of thought is that when a free electron moves away from its atom to another then there is a positive charge build in the proton due to the loss of the electron and that positive charge can move as a force to another proton that loses an electron.

Science is still tinkering with any way to manipulate the tiny atom to make it do what they want. There may still be other possibilities that haven't yet been discovered by science. Semi conductor technology puts things to test on a regular basis and progress will march on as new discoveries are made in the future. When I was young, I never would have thought that I'd be carrying a mini computer around as a communication device. I hated pagers when they came out because they called me out to do things I didn't want to do at all hours of the day and night. It took me a while to get used to a cell phone.

[noboD]

Originally Posted by redmodelt

Dodge Brothers went from 12 volt negative ground to 12 volt positive ground around 1921/22 when the horn button was moved from the door, to center of the steering wheel. The reason given was, had to do with degrading contacts in the horn button.

Yes, they did. If you want to mess with someone with the current flowing from negative to positive on a DC system ask them what happens when you hook up the coil backwards. It was explained to me by someone way smarter then me that the current actually flows from the block BACK through the spark plug to the points.

[woofa.express]

I had hoped I’d learn from this thread but have ended up quite confused. I have concluded with-
1. I no longer care and
2. What does it matter.

[Crankster]

Originally Posted by noboD

It was explained to me by someone way smarter then me that the current actually flows from the block BACK through the spark plug to the points.

Ignition coil polarity. This is a different matter and strangely enough, it has nothing to do with whether a car is positive or negative ground. The coil will work when connected either way, but the spark output at the plugs will be attenuated by about 25% if not hooked up correctly. Electrons "like" to jump from a hot surface to a cold surface, so the strike voltage required to initiate a spark is lower. There are a couple easy methods to check for correct ignition coil connections regardless of the markings on the coil itself, or whether engine is (or was) positive or negative ground.

https://mgaguru.com/mgtech/ignition/ig104.htm

[rotorwrench]

The spark is a product of a high voltage step up from the reversal of the magnetic field in the coil. The secondary winding in the coil is connected to the primary very near only one of the two terminals of the primary coil so it doesn't have a complete circuit to it. The polarity of the COIL depends on which side of the primary is connected to the "power" from the battery.

Back in the day, they marked coil terminals with abbreviations for "switch" and "distributor" so that folks knew how to connect them. After the change from positive ground to negative ground they started marking then + or -. This is confusing to some when using a modern coil in an old positive ground system. To further confuse things, some coil manufacturers get the markings wrong. Polarity of the coil depends on them being connected correctly to get the best spark from the other end of the secondary coil.

It takes high voltage to ionize the air enough for a spark to jump. A lot of that spark is voltage and very little is amperage or whatever you want to call it.

Electricity is a lot easier to explain if a person sticks with the conventional way of describing it.

[Tom Endy]

Originally Posted by Crankster

Ignition coil polarity. This is a different matter and strangely enough, it has nothing to do with whether a car is positive or negative ground. The coil will work when connected either way, but the spark output at the plugs will be attenuated by about 25% if not hooked up correctly. Electrons "like" to jump from a hot surface to a cold surface, so the strike voltage required to initiate a spark is lower. There are a couple easy methods to check for correct ignition coil connections regardless of the markings on the coil itself, or whether engine is (or was) positive or negative ground.

https://mgaguru.com/mgtech/ignition/ig104.htm

When I was in high school back in the days of iron ships and wooden men our auto shop teacher, Mr. White, demonstrated how to tell the polarity hook up of the coil with a lead pencil. You insert the tip of the pencil into the spark stream and the direction it flashed tells you if it is correct or not. Then he would hand the pencil to the class clown to try it and watch how he would get a high voltage shock.

Today you can buy a device from any of the suppliers that hooks to the coil and an LED will tell you if it is correct. I bought one years ago and at a club event we tested about 20 cars. About half were incorrect and the owners were not aware of it.

Tom Endy

[Crankster]

Originally Posted by rotorwrench

Back in the day, they marked coil terminals with abbreviations for "switch" and "distributor" so that folks knew how to connect them. After the change from positive ground to negative ground they started marking then + or -. This is confusing to some when using a modern coil in an old positive ground system. To further confuse things, some coil manufacturers get the markings wrong.

Or an old coil in a modern system, or .. Yeah, I was going to mention this but you explained it way better than I ever could.

Just check it with analog voltmeter and reverse the primary coil wires if necessary. I think Jim Linder at Bubba's Ignition services or somebody said something about an ignition coil being permanently damaged by this defect, if ran for a long time, as the iron core is magnetized? Something like that. I like the neon or LED tester idea, should be easy to make one.

[J Franklin]

Originally Posted by woofa.express

I had hoped I’d learn from this thread but have ended up quite confused. I have concluded with-
1. I no longer care and
2. What does it matter.

I agree, if someone doesn't like the polarity they have, change it. There is too much polarity in the world now anyway.

[nkaminar]

Most lightening is produced when the ground is negative and the clouds positive, so the electrons travel up from the ground. Tell that to Thor next time he tosses down a thunder bolt.

The latest theory about everything is that matter is just forms of fragments of energy. These fragments are long strings that flow through the universe. The math behind this theory has shown to calculate gravity according to general relativity and how particles behave according to quantum mechanics.

[rotorwrench]

Lightening is a form of static discharge energy which has it's own rules with energy levels high in the megajoules. It has no conductor but can make ion pathways that allow for the discharge to move any way it wants to. The potential energy is way off normal electrical scales.

A coil works with half wave DC current so it shouldn't have any effect on magnetization similar to AC current. With the power applied to a completed coil circuit, it will build a magnetic field in the core if it is connected either way but the pathway to the breaker points is important to get the most efficient reversal of the magnetic field when the circuit is broken. The reverse flow has to take a very long pathway to create a discharge of high energy. This link has a good coil diagram so you can see the normal pathway.
https://mgaguru.com/mgtech/ignition/ig108.htm

In the Magnaflux inspection procedures, DC current is used to magnetize steel parts for inspection. It takes a lot of amperage to magnetize a part. Coil shots give a lengthwise gauss field and straight through head shots give circular gauss field in a steel part. After magnetization, the steel parts are slowly passed through a big AC coil to demagnetize the parts. Complicated shapes sometimes take a few passes through the AC coil but it will remove all magnetism from the parts. AC has a full wave current flow with constant reversal of the polarity. DC can only be manipulated to half wave to make a polarity reversal as in ignition coil, horn vibrator, and radio vibrator circuits.

[Crankster]

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Yeah, I was going to mention that, instead of power being generated in the coil by the relative motion of conductors and fluxes, it is produced by the modial interaction of magneto-reluctance and capacitive diractance. The coil primary winding was of the normal lotus-o-delta type placed in panendermic semi-boloid slots of the core, with every seventh conductor being connected by a non-reversible tremie pipe to the differential girdle spring on the “up” end of the grammeters. Simple, really.

[Jemelton#]

Smoke don't care! You let the smoke out, and the beast won't work. Keep the smoke in!

[katy]

Originally Posted by Crankster

Yeah, I was going to mention that, instead of power being generated in the coil by the relative motion of conductors and fluxes, it is produced by the modial interaction of magneto-reluctance and capacitive diractance. The coil primary winding was of the normal lotus-o-delta type placed in panendermic semi-boloid slots of the core, with every seventh conductor being connected by a non-reversible tremie pipe to the differential girdle spring on the “up” end of the grammeters. Simple, really.

That makes sense, I never thought of it that way.

[nkaminar]

rotorwrench, Doesn't the capacitor and coil set up a resonance ringing that causes multiple sparks at the spark plugs, in a really short time. The first spark is the big one, of course.

[rotorwrench]

The condenser catches the back flow from the reversal of the magnetic field when the points open and does have a bleed off that delays the complete induction process so it does keep the spark discharge going for a very short period of time. The scope illustrates that effect.

The condenser or capacitor is sized to match up with the resonance of the inductor coil so that the cycle will be as efficient as possible. The resonance is like the ring of a bell when struck.

The back flow of energy would jump the open breaker points if the condenser was not in the circuit to catch it which would quickly ruin the points and reduce the spark discharge to near nothing.

[Crankster]

The way it was explained to me years ago, the condenser acts as a kind of "shock absorber" and ensures most of the energy occurs between the plug electrodes where we want it, instead of arcing at the points.

I've seen in some of the forums people say they've been able to run a motor without a condenser installed for whatever reason. I don't think they are lying, so I wonder how that works. Theoretically it shouldn't run at all without a condenser? I'm sure it didn't run very well.

[Bob Johnson]

Boy there is a lot of interesting explanations here.


One of the reasons for using negative ground is corrosion. Many people use electrolysis to remove rust from iron or steel parts. The part is connected to the negative wire and a sacrifice piece of iron is connected to the positive wire. Rust is removed from the part connected to the negative wire and the sacrifice piece becomes rusty. A positive ground vehicle will rust much faster than a negative ground one.



I did my Master Thesis on proton conductivity. This is a rare phenomenon. It only occurs is certain crystals with loosely held protons. By definition protons have a positive charge. They do not transfer their charge. We use the term electricity because it is the movement of electrons. The electrons move from the negative source to the positive.



Bob

[Crankster]

Originally Posted by Bob Johnson

A positive ground vehicle will rust much faster than a negative ground one.

Sounds like just the thing, if you're selling new cars! That's why I'm skeptical ... lol

[Bill Cilker]

This question has been asked for a long time.
Here is an article on it from the August of 1931 Automobile Digest.

[TomInCologne]

Originally Posted by Crankster

Sounds like just the thing, if you're selling new cars! That's why I'm skeptical ... lol

But it does make sense when you think about it... in a corrosion process, the metal will pass its electrons to the oxyidiser, which will gladly accept it. If you have a negative ground system, the metal will find an abundance of electrons and therefore cannot pass its electrons to 'whoever'. But i agree that this effect may be miniscule...

[nkaminar]

Bill, good research. Thanks. I guess this is a good argument for using electrical grease to protect the cables and connectors. I see the auto parts stores have different grease and pads for the negative and positive sides of the battery.