Earth strap question

[Slow]

While doing turbos my engine earth strap decided it likes snapping off.

Are they fairly universal or is there a reason I should go to Land Rover to get this?

[dvs_dave]

Nothing special about them. Just make sure it’s at least the same gauge or larger and you’ll be good. You could also double them up if you can’t find a thick enough one.

[Slow]

Perfect, is there a way to tell what it needs to be or just take a piece down to some shops and ask?

Trying google to find the strap part number or even a listing is impossible.

[100SRV]

https://www.durite.co.uk/s/c/wiring-accessories/ba...

[Baldchap]

Make sure the replacement is attached to clean metal. A dodgy earth can make for all sorts of weird and wonderful problems.

[Sensibleboy]

Even Halfords sell such things.

[finishing touch]

I'd bet most earth straps aren't even copper any more.

1 thou of copper plate over some recycled steel tin cans is about it.


When I made my Homebuild I used 240amp welding cable, same for the positive to the cut-out switch.

[Slow]

Thanks guys

Going to take it off and take it down to town to find something similar in length.

When ordering some others bits off land rover I asked the price as if it was £10 or so its worth it to save the hassle. £50!

[tapkaJohnD]

Manufacturers use that awful metal braided stuff as an earth cable. Must be cheap. But it lets in water and road muck, and corrodes away.

That cable has to carry the highest current that goes to the engine - IE starter current, 300Amps or so! So, use starter cable, same size as what you have. Such cable is available as cut lengths, or made up with swaged terminals to almost any length you wish. Protected by a PVC cover and, if you wish you can grease the ends, so waterproof and last for ever.

See: https://www.vehiclewiringproducts.co.uk/c-1-home/c...

John

[gazza285]

tapkaJohnD said:

Manufacturers use that awful metal braided stuff as an earth cable. Must be cheap. But it lets in water and road muck, and corrodes away.

You could cover it with heat shrink.

[tapkaJohnD]

Zulu 10 said:

I agree that it's rarely adequately protected, but the principle of using braid is justified because of its reduced impedance at higher frequencies compared to the type of cable which you are suggesting.
This is due to the skin effect, and if noise is, or might be an issue, then using the cable you recommend may not end well.

Impedance is a feature of AC. How is this important in a 12V DC vehicle?

[rustednut]

Have replaced countless earth straps over the years and never had any issues.

Decent copper braided, highly flexible and a clean connection is all that has ever been required. Never had a replacement fail or cause issues.

But happy to be educated more.

[Slow]

Bought one from a local parts place. They do parts for trucks and just asked them for a "big one" about a foot long. Cost me few quid.

[tapkaJohnD]

Thank you, zulu10!
But is a 10-20cm length of braided cable going to reduce interference when the rest of the loom is entirely the other sort?

John

[GreenV8S]

Zulu 10 said:

This is one reason why many people, myself included, only ever tie down one end of an outer screen on a cable, for to tie both ends down in different places would risk the introduction of earth loops by stray currents travelling in screens around the very cables that were supposed to be protected from noise.

The reason earth loops are a problem is not due to differing earths being at differing voltages. If the screen is grounded at both ends then it forms a physical loop which can act as a generator in the presence of a changing magnetic field. This will induce a current along it, which can then induce a voltage on the wire it encloses. In other words it's an electromagnetic problem, not just a differential voltage problem.

[rustednut]

I think the OP has replaced his strap (with a non braided type) and appears to have no more problems.

Which leads me to think, and concurs with my experience of replacing them, that a new earth strap is far less of a problem than an old braided one that was failing.

[LimSlip]

Braided earth straps are not used for any slight reduction in skin effect. To significantly reduce skin effect each strand has to be insulated from the rest as it in in Litz wire (a type of wire designed to reduce skin effect at high frequencies).

An earth strap needs to carry a lot of current and it also needs to be flexible if it's bonding the engine to the chassis, more so than the starter cable as they tend to be much shorter. Insulation reduces flexibility (particularly under cold conditions) and without insulation you have to braid the strands to prevent it becoming a copper hairball.

[ChocolateFrog]

Just make your own using battery cable, a couple of ring clamps and some heat shrink.

Better than new.

[Penelope Stopit]

LimSlip said:

Braided earth straps are not used for any slight reduction in skin effect. To significantly reduce skin effect each strand has to be insulated from the rest as it in in Litz wire (a type of wire designed to reduce skin effect at high frequencies).

An earth strap needs to carry a lot of current and it also needs to be flexible if it's bonding the engine to the chassis, more so than the starter cable as they tend to be much shorter. Insulation reduces flexibility (particularly under cold conditions) and without insulation you have to braid the strands to prevent it becoming a copper hairball.

Tell the kids of today that and they won't believe you

Went very quiet in here after you posting the above

[tapkaJohnD]

Wow! Once again, a simple request for advice turns into an arguement between well informed and erudite contributors.
Professor FK Lewis knows all about this:

https://www.youtube.com/watch?v=aEQcsuXnnnc&ab...