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Old 09-06-2019, 06:48 PM   #1
ericr
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Default Stupid Question #2: how does an iron frame act as a ground on our cars

-or any car, for that matter. but I'll bet some of us have wondered about this.


our cars are DC of course, meaning, apparently, that there is a constant flow of electrons through the system when some application is using electricity. how can a frame of iron/steel act as a successful conductor for one pole of the battery?


We don't associate iron/steel as being a significant conductor in other contexts....how can it be successful in electrical transmission on a car?
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Old 09-06-2019, 07:02 PM   #2
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

The structure is so big there is very little losses. No reason to use silver or copper. It’s just another big wire.
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Old 09-06-2019, 07:32 PM   #3
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

One thing is for sure,a ground strap from the battery to the frame and from the frame to the driveline is critical if you don't have splash pans.

if you don't believe steel is a good conductor then you haven't had a full childhood..
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Old 09-06-2019, 07:35 PM   #4
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

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if you don't believe steel is a good conductor then you haven't had a full childhood..
Hah, that's pretty good!
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Old 09-06-2019, 07:35 PM   #5
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

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if you don't believe steel is a good conductor then you haven't had a full childhood..
Or peed on an electric fence.
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Old 09-06-2019, 07:39 PM   #6
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

No problem according to Myth Busters.

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Old 09-07-2019, 12:00 AM   #7
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

Steel and iron are excellent conductors of electricity. The frame is used instead of running a "common" grond wire. It was a pretty common practice back in the day and was part of keeping the cost of cars down. Separate ground wires are better, and used a lot more on modern cars because so much of new cars are made using plastic parts which don't conduct electricity.
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Old 09-07-2019, 01:27 AM   #8
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

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Steel and iron are excellent conductors of electricity. The frame is used instead of running a "common" grond wire. It was a pretty common practice back in the day and was part of keeping the cost of cars down. Separate ground wires are better, and used a lot more on modern cars because so much of new cars are made using plastic parts which don't conduct electricity.



Not just "back in the day" but even today. imagine the cost, weight, and complexity of running two wires to every single part of a car that needs electricity. I'm not saying there are no components that use two wires but there are a whole bunch that do not.
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Old 09-07-2019, 03:06 AM   #9
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

this is fun site for checking voltage drop and resistance https://www.rapidtables.com/calc/wir...alculator.html
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Old 09-07-2019, 05:24 AM   #10
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

AH, so thats why I feel all tingly whenever I get in the car !
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Old 09-07-2019, 09:22 AM   #11
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

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Originally Posted by Railcarmover View Post
One thing is for sure,a ground strap from the battery to the frame and from the frame to the driveline is critical if you don't have splash pans.

if you don't believe steel is a good conductor then you haven't had a full childhood..

Not so....you know what they say about Dad and Mom being in the iron and steel business.
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Old 09-07-2019, 07:29 PM   #12
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

Don't look on it as a "ground", look at it as a big conductor hooked to one side of the battery. The critical factor in completing a circuit that works lies in the quality of the connections to the conductors between the battery and the component to be powered. Clean connections will make good contact, dirty or corroded connections may not let the current through.
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Old 09-07-2019, 08:07 PM   #13
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

Steel works pretty good, that is how power gets to your house
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Old 09-07-2019, 11:05 PM   #14
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

'Sand Pebbles" with Steve McQueen.. Master Chin,head coolie of the engine room said there are wizards,wizards in the engine....

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Old 09-08-2019, 07:29 AM   #15
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

well gang, I confess I fibbed a little bit. I read in my book about Henry Ford and the D T & I that when he bought the line, it had iron telegraph wires, but they had corroded significantly.


But if iron is an acceptable conductor, I don't see why it doesn't replace copper, which the US is not well-endowed with.
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Old 09-08-2019, 08:48 AM   #16
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

I'm not sure I would want a frame of iron, I prefer steel. I really don't think I'd want one of copper, even if it could be afforded
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Old 09-08-2019, 09:25 AM   #17
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

Note to ericr, Arizona and a lot of other states have abundant supplies of copper. EPA and OSHA and other agencies have made it difficult to mine cost effectively. Smelters put out a lot of undesirable byproducts. Cant get a mine open near Superior, AZ as it is on a sacred site per the native americans.
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Old 09-08-2019, 10:17 AM   #18
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

The perceived dearth of American copper was magnified during WW2,all copper available was diverted to the war effort. Some interesting things about that...we all know about the zinc penny in '43..but did you know the calutrons used to enrich uranium for the bomb used electromagnets wound with pure silver? it was 'borrowed' from the Treasury,and had to be accounted for to the ounce..


Mining and smelting capacity increased by the end of the war,we began using our vast reserves of copper ore..we are currently 4th in the world in production.

A German would appreciate that,they were on the receiving end of most of our copper..


Last edited by Railcarmover; 09-08-2019 at 10:30 AM.
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Old 09-08-2019, 10:44 AM   #19
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

Steel or iron isn't used as wire for the reason stated, it corrodes, rusts, easily.
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Old 09-08-2019, 11:17 AM   #20
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

A lot of metals can be used as conductors but some are definitely better than others. It's all about resistance or the need for very low resistance levels. The longer a conductor the higher the resistance. Steel and other ferromagnetic related alloys do OK but corrode easily as already mentioned. Aluminum and copper are the least expensive of the metals that make good wire. Silver and gold are much better but obviously much more expensive. The alternate is to plate wire with tin, silver, or gold to reduce contact resistance. With gold being so very expensive, it is limited to plating for terminal pins and sockets so as not to break the bank. Aluminum wire has to have a larger cross section gauge to replace copper but it is used a lot in power transmission wires we see on the side of the road every day. Aircraft wire is available in silver plated copper for better conductivity or tin plated copper for better corrosion resistance. Copper is king in the automotive business with tin plated copper as a more expensive alternative to bare copper.
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Old 09-08-2019, 08:56 PM   #21
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

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The perceived dearth of American copper was magnified during WW2,all copper available was diverted to the war effort. Some interesting things about that...we all know about the zinc penny in '43..but did you know the calutrons used to enrich uranium for the bomb used electromagnets wound with pure silver? it was 'borrowed' from the Treasury,and had to be accounted for to the ounce..


Mining and smelting capacity increased by the end of the war,we began using our vast reserves of copper ore..we are currently 4th in the world in production.

A German would appreciate that,they were on the receiving end of most of our copper..

I am sure you are correct but I thought I read in grade school that our copper came from some South American country....
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Old 09-09-2019, 04:38 AM   #22
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

See https://www.tibtech.com/conductivite.php?lang=en_US

Copper is almost ten times as conductive as steel. The steel frame makes up for it by being more than ten times the cross sectional area.
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Old 09-09-2019, 05:03 AM   #23
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

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Note to ericr, Arizona and a lot of other states have abundant supplies of copper. EPA and OSHA and other agencies have made it difficult to mine cost effectively. Smelters put out a lot of undesirable byproducts. Cant get a mine open near Superior, AZ as it is on a sacred site per the native americans.
Here's something fun, at least one of those mines is now owned by Mexico. So they are mining our copper, and selling it back to us.

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Old 09-11-2019, 11:59 AM   #24
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

When I was young, 14 or so, I pee'd on an electric fence wire which was surounding our horse lot. It was steel wire, and conducted electricity quite well. Will never foget it.
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Old 09-11-2019, 12:13 PM   #25
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

Comparison of square cross-sections of materials having the same conductivity (measured in IACS)
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Old 09-12-2019, 07:08 AM   #26
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

Current is carried on the outer edge of the material. That is why larger power lines are hollow to reduce weight. In the end it is just surface area. This is something you get to do the math when you get physics or engineering courses.

With the A it is not the iron that is a problem. It is in understanding the ground paths as they are complicated. When we restore the car we do a lot to cover what would be the ground paths.

So from the engine to the frame you travel from the driveline up through the springs (spring bolts to be exact) to the frame as one major path. You also have the often not installed engine shields. Of course you have to be sure that the various bolts have bit though the paint to make a path.

So in restoring my car. I tinned the area where the pos strap attached to the frame and then put tape on the area so no paint is put there. I made grounding contact paths from the frame through the fender brackets into the headlamp bar and put tape in the sockets for the headlamps before paint.

If you used a thicker paint on some areas then you need to be extra certain the lock washers cut through or maybe cut through the paint first. A little extra care goes a long way to a more reliable car.
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Old 09-12-2019, 08:07 AM   #27
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

Ditto what Kevin said, electrical current travels on the surface of the conductor. There's a bunch of different paths for the current to get from the engine to the frame and battery but a heavy gauge ground strap does it best.
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Old 09-12-2019, 08:15 AM   #28
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

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Current is carried on the outer edge of the material. That is why larger power lines are hollow to reduce weight. In the end it is just surface area. This is something you get to do the math when you get physics or engineering courses.

With the A it is not the iron that is a problem. It is in understanding the ground paths as they are complicated. When we restore the car we do a lot to cover what would be the ground paths.

So from the engine to the frame you travel from the driveline up through the springs (spring bolts to be exact) to the frame as one major path. You also have the often not installed engine shields. Of course you have to be sure that the various bolts have bit though the paint to make a path.

So in restoring my car. I tinned the area where the pos strap attached to the frame and then put tape on the area so no paint is put there. I made grounding contact paths from the frame through the fender brackets into the headlamp bar and put tape in the sockets for the headlamps before paint.

If you used a thicker paint on some areas then you need to be extra certain the lock washers cut through or maybe cut through the paint first. A little extra care goes a long way to a more reliable car.

Kevin sounds like you have the best-grounded Model "A" in America JK.


More seriously, I think it is acknowledged that the Model "A" frame, as it came from the factory, did not really have much of a paint job on it, surely not the thick glossy enamel we like to use.
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Old 09-12-2019, 08:37 AM   #29
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

Auxillarily grounds can make a surprising difference in the amount of power that gets to the starter. I was always hearing "Ya need an 8 volt battery!" No, I needed a good ground! I put a second ground on it. The old ground cable bolted to the top flange of the frame. Using the same bolt, only the underside. I changed the bolt to a 3/8 brass and ran the cable to one of the starter bolts. The starter spun over with new life, who needs 8v or 12v for that matter. We generally can't get to the ground paths and they've been rusting away for 90 years. Naturally they slowed the current down somewhat.
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Old 09-12-2019, 08:39 AM   #30
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

the engine pans were the ground path to the engine/driveline.
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Old 09-12-2019, 09:00 AM   #31
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

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Auxillarily grounds can make a surprising difference in the amount of power that gets to the starter. I was always hearing "Ya need an 8 volt battery!" No, I needed a good ground! I put a second ground on it. The old ground cable bolted to the top flange of the frame. Using the same bolt, only the underside. I changed the bolt to a 3/8 brass and ran the cable to one of the starter bolts. The starter spun over with new life, who needs 8v or 12v for that matter. We generally can't get to the ground paths and they've been rusting away for 90 years. Naturally they slowed the current down somewhat.
Terry

My car has the main ground cable running right from the battery to the top starter bolt. A 7 year old neglected 6V battery still spins it over like it was new. I use the stock ground on the frame for an auxiliary ground.
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Old 09-13-2019, 10:19 AM   #32
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Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

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Current is carried on the outer edge of the material. That is why larger power lines are hollow to reduce weight. In the end it is just surface area. This is something you get to do the math when you get physics or engineering courses.
The skin effect only applies to alternating current. Direct current flows equally through a conductor. This is why DC is used a lot for magnetizing ferromagnetic objects for magnaflux inspection and for welding.
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