[AT] Tractor wiring

[charlie hill]

Phil,  a 1 inch pipe will flow 4 times as much water at a given presure than 
a 1/2 inch pipe ( if you assume laminar flow).  Does that hold true with 
wire size or is the difference smaller?   Does the cable for a 6 v battery 
need to be twice the diameter of that for a 12 v or ?

Charlie
----- Original Message ----- 
From: "Phil Auten" <pga2 at hot1.net>
To: "Antique tractor email discussion group" <at at lists.antique-tractor.com>
Sent: Thursday, November 18, 2004 8:30 PM
Subject: Re: [AT] Tractor wiring


> It's the current capacity of the wire that determines the gauge needed. 
> More current, bigger wire. It's that simple.
> The bigger wire has less resistance so it "drops" less voltage over it's 
> length. A 4 Ga. wire might drop 2V over a 4
> foot length at the current drawn on a 6V starter. Changing to a 0 Ga. wire 
> will decrease the dropped voltage to less
> than 1V. More voltage applied to the starter so it can get the full 
> current needed to spin it and the engine up to
> starting speed.
> Another analogy is pipe and water flow. A 1/2" pipe can only flow X amount 
> of water at 25 PSI. If you double the
> size of the pipe, you get more flow at 25 PSI.
>
> Phil
>
> At 08:51 PM 11/17/04, you wrote:
>>Here is my question on this subject.
>>
>>Why are battery cables for 6 volt systems heavier than those for 12 volt 
>>applications?   Assuming both are powering a starter to turn a similar 
>>size engine (similar load), why would the 6 volt cable need to be bigger. 
>>It flows more amps but less voltage and should flow roughly the same 
>>wattage in both applications.
>>
>>Charlie
>
>
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