[AT] Tractor batteries

[rlgoss at twc.com]

Steve, I'm old enough to have lived through the heyday of positive grounded systems and the changeover to the system we have now. It was very confusing in things like physics books where they indicated that the actual flow of electrons went opposite to what we consider as correct today.  In the 50's, I think the 6 volt systems were mostly positive ground, and it was commonly thought that electrons flowed from the negative battery terminal to the positive one.  The result was that we hooked up the battery the wrong way on the grand electo-plating experiment in high school and instead of getting a nice copper coating on a key that was suspended in copper-sulfate solution, it disintegrated instead.  Then again, we may have just neglected to take the ionization of the solution into account.    :-)  It DOES make a difference on ignition systems when owners don't pay attention to the polarity markings on the coil.  More than once, I have worked on an engine that had no spark, and correcting the problem was as simple as exchanging the ignition and ground wires.

Larry



---- Stephen Offiler <soffiler at gmail.com> wrote: 
> I recall hearing that positive ground was related somehow to a corrosion
> issue.  Something to do with minimizing an electro-chemical corrosion
> mechanism, if positive ground was used.   Google found this writeup, which
> sounds pretty plausible to me:
> 
> http://www.daviescraig.com.au/POSITIVE_AND_NEGATIVE_EARTH_CARS-news.aspx
> 
> SO
> 
> 
> 
> On Fri, Jan 17, 2014 at 12:06 AM, Greg Hass <ghass at m3isp.com> wrote:
> 
> > Was looking at some old tractor stuff online and was reminded of
> > something I  have know for years but have never, at least in my failing
> > memory, seen a plausible explanation as to why most 6 volt tractors have
> > positive grounds whereas 12 volt tractors have negative ground.  At
> > first I thought it could be because 6 volts had generators, however, our
> > first 12 volt tractors had generators and later models had alternators
> > so that doesn't seem to be the reason. Any and all answers would be great.
> >       Greg Hass
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> >
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