Earths...

[Jack]

I may be stupid but...

 

How the hell can a vehicle be earth when it is sat on rubber tires????:confused::confused::???:???

[Marmite!!]

Earth (Ground) is another name for the Negative side of the battery..

[fv1609]

Jack, the term 'earth' (or in the US they say 'ground') can have several meanings, literal or not.

 

In this context it is the point in the circuit that has zero potential. The chassis is the most convenient place for this to be.

[Degsy]

Come on Clive , thats far to technical for Jack, just tell him it completes the circuit, thats near enough:-D

[Marmite!!]

I think Jack was hoping to just hang a chain off his truck thinking that would sort his Earth problem out:nono:

[ian2b]

Earth (Ground) is another name for the Negative side of the battery..

 

But not forgetting the "Possitive Earth", just to confuse Jack more.

[radiomike7]

Earth (Ground) is another name for the Negative side of the battery..

 

Not quite Lee, many older vehicles were wired with positive earth and the feeds were negative. Posh vehicles such as mine have insulated (wired) return rather than using the steel chassis.

Edited February 16, 2009 by radiomike7

[Marmite!!]

Not quite Lee, many older vehicles were wired with positive earth and the feeds were negative. Posh vehicles such as mine have insulated (wired) return rather than using the steel chassis.

 

I know that, I was just trying to keep it simple for Jack...:-D

[Jack]

Not quite Lee, many older vehicles were wired with positive earth and the feeds were negative. Posh vehicles such as mine have insulated (wired) return rather than using the steel chassis.

 

Yea! Come on Lee - keep up :coffee:

[Degsy]

Yea! Come on Lee - keep up :coffee:

 

Crikey you still here..... thought it was long past your bed time:-D

[N.O.S.]

For example your indicator problem may be a poor earth - i.e. the wrigglies might be getting to the bulb but there is no path for them to get from there back to the battery negative post via the steel wing/chassis and an earth strap.

 

You are relying on good elecrtrical metal-to-metal contact on each panel joint (e.g. wing-to-chassis then chassis-to-cab then cab-to-gun ring mount and then to your crocodile clip :-D) in order for your indicator return/earth circuit to be complete.

 

You might find it is earthed ok to the chassis, so with a new earth strap the problem might go away.

 

A simple multimeter will enable you to check - by putting one end on the negative side of the bulb holder (if there are 2 wires going to the bulb) or direct onto the metal bulb holder (if there is only 1 wire going to the bulb) and the other end on a known good earth (like your jump lead :-D) you should get pretty much zero resistance (i.e. no ohms).

[Tony B]

Except of course lads, we are considering 'Conventional flow', not 'Electron flow'. The electron being a partical the carries a negative charge, as you know.

[AlienFTM]

Also don't forget that Negative Earth, a track by Barclay James Harvest on the album Everyone is Everybody Else was a tribute to Apollo 13 (according to the blurb on the CD - I only discovered this a few years ago when I updated my music.

[radiomike7]

Except of course lads, we are considering 'Conventional flow', not 'Electron flow'. The electron being a partical the carries a negative charge, as you know.

 

Yes, absolutely correct Tony, current flows in the opposite direction to electron flow.

[antarmike]

And in some vehicles of WW2 and after eg Matador, Foden etc. They had 24v starting and charging and 12v lighting. half the lighting load coming from one battery, half from the other.

 

The centre point of the two systems connects to the chassis, so when considering one battery you have negative earth, but from the other battery's perspective it is a positive earth system... ie one set of lights runs 12 volts below chassis potential, the other lights run at 12 volts above chassis potential... Okay Jack?

Edited February 16, 2009 by antarmike

[N.O.S.]

And the Autocar uses 12V starting and 6V everything else. The starter switch momentarily changes batteries from parallel to series for starting. :trustme:

[antarmike]

And the AEC Blue steel missile transporter had electically conductive tyres so the chassis was literally Earth potential.

[R Cubed]

Ahh yes but the electrons in the wiring flow in the opposite direction...

 

He he he :-D :idea:

[Tony B]

That explains the problem then! Don't know if their coming or going. :idea:

Of course the other important factor in a earth strap is surface area. More surface more curent can be coped with.

[Enigma]

Come on Jack, come down to earth..

[Chrisg]

Jacks going to be realy happy he asked this question. :-D

[Guest catweazle (Banned Member)]

So why did it all change to Negative earth from posotive:-D

[Marmite!!]

So why did it all change to Negative earth from posotive:-D

 

I was told because it because it reduces the likelihood of corrosion forming from electrolysis:confused:

[fv1609]

To fit in with the rest of the worlds automotive industry!

 

Although it was claimed that we used positive earth as some components corroded less readily. Although I'm not sure if that is true as it is usually the positive terminal that becomes more corroded than the negative.

 

Not a major point but, at the time of the change, it saw the reduction in the use of PNP transistors which were most conveniently configured in a positive earth circuit. Whereas the new NPN transistors lent themselves to a negative earth arrangement.

Edited February 16, 2009 by fv1609

[radiomike7]

Come on Jack, come down to earth..

 

I think he has gone to ground:)