6V electrical theory questions/help

rockfla

rockfla

Well-known member
Why....OR what difference does the polarity of the ground make in our 6V systems OR why a positive ground over a negative ground.....AND THEN to carry this further, HOW can you test or verify which ground a system is??? I went to look (and help) at a friends newly acquired 35 Convertible Sedan and he thinks its been converted to negative ground (that's how he as been connecting it since he got it AS well as that's how he got it)....HOW can I 100% verify that....OR my question to that would be IF it had been changed would the ammeter read backward since the polarity changed??


ALSO, I was told the generator was getting very HOT after a very short period of run time....COULD that be because it could possibly be positive ground and its running now as negative ground??
 
Whatever battery lead that is connected to chassis is condsidered ground. As for the meter it depends on if the person that converted it changed the leads on back of the meter. Should have reversed stock position.
 
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To answer your first question, I believe 12 volt cars are negative ground because of convention. Negative is usually ground in electrical circuits, and the automakers just "went with the flow" and stayed with convention. The question is why are most (not all) 6 volt cars positive ground? Positive ground circuits are slightly less susceptible to corrosion problems than negative ground systems. When the automakers went to 12 volts, technology had evolved enough to provide superior resistance against corrosion (better insulators and plastics) so that slight advantage was eliminated.

And to your second question, ALL cars are both positive AND negative ground. It depends how they are wired. Given the mess your friend has inherited, he would be much better deciding what polarity he wants (probably positive ground for 6 volts and negative for 12) so he can be sure what he has. It's obvious the previous owner or builder had no idea.
 
As for the generator getting very hot. First check that the charge rate is not set too high. Polarity neg or pos ground would have no effect here. If the car has its original three brush generator fitted then the third brush should be set to about 6 amps maximum for normal day time running. It can be set to about 15 amps for night time running but that is way to high for extended day time running. Another reason for heat could be the armature hitting the field pole shoes due to worn bushes or bearings. If the car is fitted with a later generator and voltage regulator then the regulator voltage setting should not be higher than 7.5 volts. When checking generator output some engine revs are required here as generators do not charge at idle speed. Regards, Kevin.
 
The ammeter is the "loop" style back so NO connections to the actual meter, just the wire running through the loop.
 
The direction the wire enters and exits the ammeter loop can determine if the polarity has been changed. Ford - ground the wire entered from the harness through the bottom of the loop and exited the top of the loop and then went to the left side of the fuse block.
 
One of the "other" mysteries, surrounded in secrecy wrapped in an enigma is the wire to the coil is running through the ballast resistor BUT its an early 21 motor, been converted to a crab with a "Blaster" aftermarket coil (which ANY of the info decal on the coil is ALL but rubbed/smeared Other than the "Blas") SO not sure about IF that is ALSO internally resisted too??? AND If so, what issues does that cause?
 
Robert there’s more to the positive/negative ground theory and it makes a difference but I am not person to explain. I believe 6 volt needs to be Positive ground and it’s to do with the direction of current travel and spark strength. I also remember Bubba saying that if polarity is changed you must change coil as the change affects the coil. Sorry I’m not more help but there’s more to the story.
 
Found this AI synopsis:

"Ford used a positive ground system for its 6-volt flathead engines primarily to extend spark plug life and reduce electrical corrosion. By grounding the positive terminal to the frame, the majority of damaging heat from the spark was directed into the spark plug body rather than the center electrode, which had limited heat dissipation.

Corrosion Reduction: Positive grounding minimized electrolysis and corrosion on the vehicle's frame and undercarriage, which was critical for the reliability of low-voltage systems.

Ignition Points: It helped reduce metal transfer and deposit buildup on the stationary contact of the ignition points, keeping the contacts cleaner for longer.

Electron Flow Theory: Early engineers believed that with the frame grounded to the positive terminal, the flow of electrons provided a more efficient current to the spark plugs during cranking.

While some theories suggested a "hotter" spark, the primary benefits were durability and reliability in an era where battery capacity was limited and maintenance intervals were longer.
 
glennpm said:
Found this AI synopsis:

"Ford used a positive ground system for its 6-volt flathead engines primarily to extend spark plug life and reduce electrical corrosion. By grounding the positive terminal to the frame, the majority of damaging heat from the spark was directed into the spark plug body rather than the center electrode, which had limited heat dissipation.

Corrosion Reduction: Positive grounding minimized electrolysis and corrosion on the vehicle's frame and undercarriage, which was critical for the reliability of low-voltage systems.

Ignition Points: It helped reduce metal transfer and deposit buildup on the stationary contact of the ignition points, keeping the contacts cleaner for longer.

Electron Flow Theory: Early engineers believed that with the frame grounded to the positive terminal, the flow of electrons provided a more efficient current to the spark plugs during cranking.

While some theories suggested a "hotter" spark, the primary benefits were durability and reliability in an era where battery capacity was limited and maintenance intervals were longer.
Click to expand...

Exactly what I thought Bad internet here in Ireland. Thanks Glenn.
 
I'm not sure what was going on with the technology in 1927 but Ford decided to switch to positive ground which was common with most other manufacturers of the period. The model T wasn't set up that way but they had only had electric starters for 8 years by that time.

Some of it was due to the way current flows versus they way electrons flow in the copper conductor which is still rather perplexing to try to explain to folks even in the modern era. Electrons flow the opposite direction of current and the flow of free electrons is at a snails pace compared to current. Anyway, I imagine that they felt there was a tiny bit of advantage to setting systems up with positive ground. As most folks know, a lower voltage like that is not the strongest mover of electrical current. Doubling it to 12-volts in 1956 actually saved money in the lesser amount of copper needed for those systems to function normally, ie 18-AWG instead of 16-AWG for normal copper wire. Twice as much electrical pressure was a big advantage over the 6-volt set up. Ford used 12-volts late in the model T era. I'm not sure why they didn't go that way but some engineer talked them out of it. 6-volts was the common voltage in the US at that time so that's the way they went.
 
Doubling it to 12-volts in 1956 actual 6-volts was the common voltage in the US at that time so that's the way they went.[/QUOTE]

That was a good thing. Trying to find good 6 volt ANYTHING is a challenge now!
 
Electrons move extremely slowly. I like this mechanical analogy:

"Mechanical analogies

It's like dominoes that fall. The energy wave propagates through the falling dominoes, but the dominoes don't translate much.

Remember energy is the charge of the electron times the force applied to it (voltage). It is (overwhelmingly) the forces that are moving through the metal lattice, not the charges (electrons).

Just like in this picture:

qfY5s.jpg


The forces transfer across the balls, but the balls stay largely in place. Unlike the mechanical balls, which are balanced by gravity, with electrons in metal wires from galvanic cells (batteries), there is a slow overall drift of the electrons (like cars stuck in traffic) to the other end."
 
Okay


STILL from my previous post...It is looking like I have the power to the coil, running trough the ballast resistor (OR from) inside on the firewall TO a blaster coil, WHICH, from what I read ALSO has an internal resistor???? WHAT are my issues/problems with this set up???
 
Measure the total resistance with a VOM from the dash resistor inlet to the outlet of the coil going to the distributor.
 
Coils are made up of coils of wire with the secondary winding of fine wire being approximately 100:1 ratio of the number of larger gauge primary windings. This makes the primary a resistor of sorts. For a 6-volt system, the resistance should be around 1.5 Ohms.

Ballast resistors are external insulated wire wound types that bleed off excessive amperage and heat from being drawn by the primary coil. They were more common when 6-volt systems changed over to 12-volt but they were still using 1.5 Ohm ignition coils. Eventually, modern materials allowed for 3.0-Ohm coils to function without damage from the ravages of internal heat. The 3.0-Ohm ignition coil needs no ballast for 12-volt systems.

Early Ford V8s with Mallory design front distributors that incorporated the integral coil mounting, were found to need a ballast resistor to give higher reliability. These ballasts were around 0.8-Ohm types. The model A & B types didn't have a ballast resistor since it had a normal can type ignition coil.
 
Robert why would you not put it back to stock with correct coil ,wiring and polarity. Trouble free.
 
KiWinUS said:
Robert why would you not put it back to stock with correct coil ,wiring and polarity. Trouble free.
Click to expand...
Not my car....just trying to help a fellow church member at my Dad's church with it....One of the major set backs for him IS its a crab with a 2 bolt front timing cover and he's not wanting to get into swap it back to a three bolt cover........YET!!!!! I have a feeling the time spent on trying to sort this car "might" change his mind!!!
 
Robert no problem. Keep the crab the rest of the ignition system is same for either, get correct replacement coil for a crab and the rest back to stock and all should be grand.
 
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