[AT] Project Updates '49 A, '51 A, and '47 B (STEVE ALLEN)

[szabelski at wildblue.net]

In order to prevent the points from burning you would need some heavy duty contacts, both in material and size, that adds highly to cost. 

The contacts we specified for the relays used in military vehicle required thick nickel contacts to prevent burning from the arcing that happens when you open on a large load or dead short. The contacts on the Prime Power Interruptor used on the Abrams are about 1/4 thick and are about the size of a nickel. They were two pole contacts with dual contacts on both sides. So there were four sets of contacts that opened and closed together.

Carl


----- Original Message -----
From: Kurt Musgrave <rvar at plainstel.com>
To: 'Antique Tractor Email Discussion Group' <at at lists.antique-tractor.com>
Sent: Mon, 11 May 2020 14:16:13 -0400 (EDT)
Subject: Re: [AT] Project Updates '49 A, '51 A, and '47 B (STEVE ALLEN)

 

>>You are correct Carl.  A 12V system takes a 12V coil with an internal resistor or and external 1.4 ohm resistor commonly called a ballast resistor can be used with a 6V coil.    These are available at most auto parts stores.   This is to avoid burning the points as you say.<<

 

I never really understood why the ballast resistor, always seemed to me it would have been just as easy and probably cheaper to have just made points capable of handling the 12 volts, instead of the ballast resistor and the associated hassles.