Posted by Gerald J. on January 26, 2010 at 09:23:08 from (70.219.126.63):
In Reply to: Positive Ground posted by mss3020 on January 26, 2010 at 07:08:34:
The question of polarity was debated from the beginning of electric starters until some time in the 1960s when SAE put out a new standard that required negative ground. Search out posts on this topic and you'll find where I posted the number of that SAE standard. I'm still wanting to look up more history and I have some older SAE standards books but some have been packed up and moved already. Some haven't appeared while packing yet.
I think the corrosion arguments came from the corrosion experiences with water pipes and DC trolley systems. Turns out that no matter how big a grounded conductor you use, so long as you have contacts to earth the large cross section of earth, though not a great conductor, will carry a significant portion of the power (something called Carson's theory). In a DC trolley feed, then depending polarity of the trolley wire and distance from the power plant a metal water pipe will either be eroded or will have metal added. One polarity is better for pipes near the power plant but worse for pipes away. So the trolley runs with the polarity that gets the fewest water company gripes.
Fact is, on a vehicle, either polarity works for starting and ignition, and in the early solid state days radios came with a way to set the polarity to match the power source. Reversed polarity usually means destruction of the solid state device. Often with striking visual results (a cloud of smoke)! Alternators are among those very polarity sensitive products and for convenience is probably why the SAE demanded negative ground, long about 1968.
Deere fuel gauges in the '20 era are polarity sensitive, why I don't know.
We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]
Today's Featured Article - Restoration Story: Fordson Major - by Anthony West. George bought his Fordson Major from a an implement sale about 18 years ago for £200.00 (UK). There is no known history regarding its origins or what service it had done, but the following work was undertaken alone to bring it up to show standard. From the engine number, it was found that this Major was produced late 1946. It was almost complete but had various parts that would definitely need replacing.
... [Read Article]
Latest Ad:
1964 I-H 140 tractor with cultivators and sidedresser. Starts and runs good. Asking 2650. CALL RON AT 502-319-1952
[More Ads]
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy
TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.
