Guest catweazle (Banned Member) Posted February 16, 2009 Share Posted February 16, 2009 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. Quote Link to comment Share on other sites More sharing options...
Marmite!! Posted February 16, 2009 Share Posted February 16, 2009 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" Quote Link to comment Share on other sites More sharing options...
Guest catweazle (Banned Member) Posted February 17, 2009 Share Posted February 17, 2009 Thats interesting,but we noticed on L/rover esp militarys the body mounts etc had rubber insulaters sometimes but still corroded. Quote Link to comment Share on other sites More sharing options...
Marmite!! Posted February 17, 2009 Share Posted February 17, 2009 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: Quote Link to comment Share on other sites More sharing options...
Marmite!! Posted February 17, 2009 Share Posted February 17, 2009 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. Quote Link to comment Share on other sites More sharing options...
Guest catweazle (Banned Member) Posted February 17, 2009 Share Posted February 17, 2009 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. Quote Link to comment Share on other sites More sharing options...
Marmite!! Posted February 17, 2009 Share Posted February 17, 2009 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: Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted February 17, 2009 Share Posted February 17, 2009 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. Quote Link to comment Share on other sites More sharing options...
Jack Posted February 17, 2009 Author Share Posted February 17, 2009 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: Quote Link to comment Share on other sites More sharing options...
Tony B Posted February 17, 2009 Share Posted February 17, 2009 Just a quiet smile and slightly raised eyebrow. Quote Link to comment Share on other sites More sharing options...
Guest catweazle (Banned Member) Posted February 17, 2009 Share Posted February 17, 2009 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: Quote Link to comment Share on other sites More sharing options...
rbm Posted February 27, 2009 Share Posted February 27, 2009 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. Quote Link to comment Share on other sites More sharing options...
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