I have always wondered why almost all the old tractors, cars & trucks used a positive ground electrical system. I'm sure not an electrical expert but it just always seems backwards to my way of thinking for positive to be ground. If I understand electrical therory correctly, doesn't current flow from positive to negative? Why then would they have made the positive ground? I have asked many good-ole-boys and good mechanics that question and have yet to get a viable answer. Some say it went back to magnetos, most just shrug their shoulders and say,"Guess they just didn't under stand electricity that well back then." I'm curious what some of you guys think.
- Thread starter 2+2 Guy
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James Williams
Well-known Member
I had a old mechanic told me there reason was there was less arc on the contacts,A lot of the old boom trucks were wired the same way were I used to work.
jimmy
jimmy
Bob M
Well-known Member
I asked the question many years ago in an electrical engineering course in college. A couple explanations:
1 - Positive grounding was simply the early engineers' arbitrary choice.
2 - Oxygen molecules (the key element involved metallic corrosion) tend to be more attracted to the negative side of any circuit. By making systems positive ground (ie wiring is negatively charged relative to ground), wiring and connections tend to be less affected by corrosion.
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My experience after 40+ years of fooling with both + and - grounded systems has me leaning toward #1. I suspect the designers had to agree on a "standard" ground polarity. Someone tossed a coin and positive ground was the winner.
(Then I'll bet they all adjourned to drink beer by a fire on a cold winter day - just like I'm doing now...)
1 - Positive grounding was simply the early engineers' arbitrary choice.
2 - Oxygen molecules (the key element involved metallic corrosion) tend to be more attracted to the negative side of any circuit. By making systems positive ground (ie wiring is negatively charged relative to ground), wiring and connections tend to be less affected by corrosion.
---
My experience after 40+ years of fooling with both + and - grounded systems has me leaning toward #1. I suspect the designers had to agree on a "standard" ground polarity. Someone tossed a coin and positive ground was the winner.
(Then I'll bet they all adjourned to drink beer by a fire on a cold winter day - just like I'm doing now...)
RedRoundhead
Member
I think of it like this.
On an automotive ECU, the ECU turns the "grounding" of any given circut on and off. Which turn the electron flow on and off. Which would pulse, say, a fuel injector. The voltage is always at the fuel injector; it just need a path to complete the circut, and fire the injector. So the ECU "grounds" it.
As was stated, less arcing, because you are switching less energy, post-load.
Not that what I said answers your question.
On an automotive ECU, the ECU turns the "grounding" of any given circut on and off. Which turn the electron flow on and off. Which would pulse, say, a fuel injector. The voltage is always at the fuel injector; it just need a path to complete the circut, and fire the injector. So the ECU "grounds" it.
As was stated, less arcing, because you are switching less energy, post-load.
Not that what I said answers your question.
I believe it was completely arbitrary. Electron flow is from negative to positive - electrons are the charged particles - charged negatively - they "flow" towards the lack of negative charge on the positive side -
So positive ground might have sounded like a logical choice.
(however current flows from positive to negative... so..)
The bottom line is - it really doesn't matter.
I think auto/tractor manufactureres happened to chose positive - other electronic manufacturers happened to chose negative. The two had very little to do with eachother in the beginning, and no need to worry about standards when they started out.
I would suspect (but I do not KNOW) that it was the radio that probably prompted the change to a negative ground in the auto world (which would carry over to the tractor world) - I would assume that's when the auto world really merged together with the electronics world.
.
Owen Aaland
Well-known Member
As long as the electrical circuit is a series circuit and not a parallel circuit, the current flow is the same at any point in the circuit.
Tom Fleming
Well-known Member
Well, if it goes back to magnetos, I did find out why IHC was a stickler for the horseshoe magnet to have the IHC logo on the serial number side.
It was all due to the flow of current and which direction the spark would arc to on the points. IHC did that as a design point to have the stationary contact burn out faster. It was the cheaper one, so they minimized the farmer's cost. The stationary point is also easier to replace.
Reason I know that is because I have an original IHC mag book, and it explicitely calls that out. So, when they went to battery ignition, I wonder if that was the same reasoning.
Just a thought.
It was all due to the flow of current and which direction the spark would arc to on the points. IHC did that as a design point to have the stationary contact burn out faster. It was the cheaper one, so they minimized the farmer's cost. The stationary point is also easier to replace.
Reason I know that is because I have an original IHC mag book, and it explicitely calls that out. So, when they went to battery ignition, I wonder if that was the same reasoning.
Just a thought.
Janicholson
Well-known Member
The current in amps in a series circuit is in every part of that circuit. Electrons must get back to the positive terminal of the battery.
Other than lucas wind shield wiper motors, and some fuel injectors, most switching is done on the supply side, not ground side. Jim
Other than lucas wind shield wiper motors, and some fuel injectors, most switching is done on the supply side, not ground side. Jim
SadFarmall
Member
In 1927 Riley Motors Ltd published the following sheet, explaining the change from negative to positive Earth on all their vehicles.
SadFarmall
SadFarmall
Sad,
That's some really interesting information there. Kinda sounds like maybe the udnerlying reason for +ground systems was an atempt to reduce corosion and/or arcing problems. Ya know, the more I learn about old tractors the more respect I have for those old engineers. They did some pretty amazing things with the technology they had available back then.
Especially the IHC guys. :lol:
That's some really interesting information there. Kinda sounds like maybe the udnerlying reason for +ground systems was an atempt to reduce corosion and/or arcing problems. Ya know, the more I learn about old tractors the more respect I have for those old engineers. They did some pretty amazing things with the technology they had available back then.
Especially the IHC guys. :lol:
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