Jump to content

Recommended Posts

Guest catweazle (Banned Member)

I remember the terminal fured up a lot more,but thought there must be other reasons.but doesnt a pos earth fit in better with the theory of it all.

Share this post


Link to post
Share on other sites

From th RR Owners Club...

 

 

 

With the S Cloud series and all models since, the Company reverted to negative pole of the battery to frame although their reasons had nothing to do with the radios. Let me quote from the RREC 1978 Technical Manual:

 

"...it has been found that cars wired positive earth tend to suffer from chassis and body corrosion more readily than those wired negative earth. The reason is perfectly simple, since metallic corrosion is an electrolytic process where the anode or positive electrode corrodes sacrificially to the cathode. The phenomenon is made use of in the "Cathodic Protection" of steel-hulled ships and underground pipelines where a less 'noble' or more electro-negative metal such as magnesium or aluminium is allowed to corrode sacrificially to the steel thus inhibiting its corrosion. Also the radiators of post war cars wired positive earth have a tendency to become blocked due to electrolytic deposition of metallic salts, particularly in hard water areas. For this reason it is important to bond these radiators to the chassis and bodywork with flexible copper braiding so that they are at 'earth' potential"

 

Share this post


Link to post
Share on other sites
Guest catweazle (Banned Member)

Thats interesting,but we noticed on L/rover esp militarys the body mounts etc had rubber insulaters sometimes but still corroded.

Share this post


Link to post
Share on other sites
Thats interesting,but we noticed on L/rover esp militarys the body mounts etc had rubber insulaters sometimes but still corroded.

 

Yes but wouldn't the bolts go from body to chassis & the chassis a body earthed together:confused:

Share this post


Link to post
Share on other sites

A bit more..

 

The RR Service Sheets dated 1960 detail the problems of radiators being choked by silt (mostly iron oxide from the block) being deposited by electrolytic action. A system of braided bonding straps was developed from the generator to the radiator to try and reduce this problem and finally the generator was electrically insulated. The cause of these problems was, of course, the positive frame so that is why the company changed polarity to negative frame.

 

Share this post


Link to post
Share on other sites
Guest catweazle (Banned Member)

They did but the bolt hole was a lot bigger than the bolt and the insulater pad hole was small so keeping it insulated,i dont know if this was on maybe radio vehicles etc,it wasnt on all vehicles maybe some experiment but have never seen mention of it before ,maybe Clive knows.Oh yes there was nylon washers under the bolt heads.

Share this post


Link to post
Share on other sites
They did but the bolt hole was a lot bigger than the bolt and the insulater pad hole was small so keeping it insulated,i dont know if this was on maybe radio vehicles etc,it wasnt on all vehicles maybe some experiment but have never seen mention of it before ,maybe Clive knows.Oh yes there was nylon washers under the bolt heads.

 

 

Wouldn't things like the steering column, brake pipes etc. of earthed the body & chassis though:confused:

Share this post


Link to post
Share on other sites
They did but the bolt hole was a lot bigger than the bolt and the insulater pad hole was small so keeping it insulated,i dont know if this was on maybe radio vehicles etc,it wasnt on all vehicles maybe some experiment but have never seen mention of it before ,maybe Clive knows.Oh yes there was nylon washers under the bolt heads.

 

 

As they would be dis-similar metals, body in alloy and chassis steel, it might have been to stop erosion at that point. I recollect having to use a special marine paint to the locality when bolting up suspension mountings to Fox hulls, again, dis-similar metals.

Share this post


Link to post
Share on other sites

That's just great. Thank you very much for the clarification.

 

IT IS SO STRAIGHT FORWARD THAT I AM SO AMAZED THAT I DIDN'T FIGURE THIS OUT FOR MYSELF :help::iamsmiling::computerrage:

Share this post


Link to post
Share on other sites
Guest catweazle (Banned Member)
As they would be dis-similar metals, body in alloy and chassis steel, it might have been to stop erosion at that point. I recollect having to use a special marine paint to the locality when bolting up suspension mountings to Fox hulls, again, dis-similar metals.

Thats exactly it Richard,i have seen the body allmost detatched at the rear x member due to this action,needs belzona :rofl:

Share this post


Link to post
Share on other sites

earthing is an art in itself, on the more modern military field (post ww2) you need to look at earth return systems (saves money in build and can help protect equipment), rust and the prevention, Radio frequency supression, RF signature (so the enemy can't here you) EMC (compatibility so you power systems dont muck up data) and finally EMP, Electro Mangetic Pulse (A-bomb or pulse weapon)

 

for catweasle the big LR problem is Alli and steel, you get the electrolytic at contact points (including any dissimilar metals bridges by water) and the alli works as a big sacrficial annode)*** too late again ***

 

the change from + to - to slow down the chassis rusting.

 

a good point but off topic some what - if you use those nice shiney stainless steel bit on you rebuild, those original (rare) plain steel bits will corrode like billyoh, even if they are not touching (this is a big problem we have at work big black plain steel sausage with a nice shiny stainless and err very heavy metal steam generation plant.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...