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Fat Wires & Brass vs. Copper

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george(at)georgejenson.co
Guest

Posted: Mon Apr 07, 2008 12:42 pm Post subject: Fat Wires & Brass vs. Copper

Bob & Listers,



I'm finishing up the contactor mounting/wiring on my RV-7 firewall and 

about to make and mount the ground busses and ground pass-through.



I'm planning on 2AWG welding cable for both battery cables, the starter 

cable, and the engine to firewall ground bus. Is this OK or should I use a 

braided strap for the engine to firewall ground?



This leaves the Alternator B-Lead. 2AWG is overkill but convenient to buy 

and use. However, would I be better off downsizing it to a smaller gauge 

welding cable? I'm planning on a 60amp Plane Power alternator.



I can get brass plate and bar easily and cheaply. Is it practically / 

functionally equivalent to copper for the main contactor to starter 

contactor bar? Same for the bar to connect the current limiter? Van's specs 

out .125 x .5 for the first and there is no spec for the second but I plan 

on .063 x .5 for it. Will those work in brass?



I've already sourced two copper bars that are a bit thinner (.050) that are 

perfect size for each side of the firewall for the ground busses. I'm 

planning on soldering brass tabs onto them and mounting them with brass 

bolts through them for the fat wires? Is this OK?



I've summarized these 5 questions below, and I appreciate the help. Other 

questions following in separate threads.



George Jenson

Tucson, AZ

RV-7



Summary - 5 questions:

1. 2AWG welding cable OK for engine to firewall ground in lieu of braid?

2. 2AWG welding cable OK for 60amp PP alternator b-lead or should I downsize?

3. .125 x .5 brass bar OK for contactor to contactor run (Van's specs same 

size but Copper)?

4. .063 x .5 brass bar OK for contactor to current limiter (no starter 

current)?

5. .050 x .75 x 5 copper bars/straps on either side of firewall, each 

soldered with brass tabs, with 3/16 brass bolts as ground setup OK?

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nuckolls.bob(at)cox.net
Guest

Posted: Mon Apr 07, 2008 1:38 pm Post subject: Fat Wires & Brass vs. Copper

At 01:36 PM 4/7/2008 -0700, you wrote:



 	  Quote: 	
		  

<george(at)georgejenson.com>



Bob & Listers,



I'm finishing up the contactor mounting/wiring on my RV-7 firewall and 

about to make and mount the ground busses and ground pass-through.



I'm planning on 2AWG welding cable for both battery cables, the starter 

cable, and the engine to firewall ground bus. Is this OK or should I use a 

braided strap for the engine to firewall ground?


	




    The welding cable is sufficiently fine/flexible to

    serve well as a crankcase ground jumper.



 	  Quote: 	
		  This leaves the Alternator B-Lead. 2AWG is overkill but convenient to buy 

and use. However, would I be better off downsizing it to a smaller gauge 

welding cable? I'm planning on a 60amp Plane Power alternator.


	


    In an RV . . . 4AWG is fine for all fat wires.

    2AWG is indicated on plastic canard pushers and

    some rear-battery installations in metal airplanes.



 	  Quote: 	
		  I can get brass plate and bar easily and cheaply. Is it practically / 

functionally equivalent to copper for the main contactor to starter 

contactor bar? Same for the bar to connect the current limiter? Van's 

specs out .125 x .5 for the first and there is no spec for the second but 

I plan on .063 x .5 for it. Will those work in brass?


	


    .063 is plenty good and brass is easier to

    work with than copper which is exceedingly

    soft and hard to drill.

 	  Quote: 	
		  I've already sourced two copper bars that are a bit thinner (.050) that 

are perfect size for each side of the firewall for the ground busses. I'm 

planning on soldering brass tabs onto them and mounting them with brass 

bolts through them for the fat wires? Is this OK?


	


   Sure . . . but go with brass. Check out local

   hardware/hobby stores for K&S Engineering

   displays like:



http://www.ksmetals.com/HobbyMerchandisers/metal_center.asp?Title=Hobby_Merchandisers



   They will stock some .032 brass sheet that is

   fine for crafting the short jumper straps between

   contactors, limiter mounts, etc. Make the 5/8" wide

   or so and thinner. Easier to work with . . .



 	  Quote: 	
		  I've summarized these 5 questions below, and I appreciate the help. Other 

questions following in separate threads.



George Jenson

Tucson, AZ

RV-7



Summary - 5 questions:

1. 2AWG welding cable OK for engine to firewall ground in lieu of braid?

2. 2AWG welding cable OK for 60amp PP alternator b-lead or should I downsize?


	


   Go 4AWG throughout . . .



 	  Quote: 	
		  3. .125 x .5 brass bar OK for contactor to contactor run (Van's specs same 

size but Copper)?

4. .063 x .5 brass bar OK for contactor to current limiter (no starter 

current)?

5. .050 x .75 x 5 copper bars/straps on either side of firewall, each 

soldered with brass tabs, with 3/16 brass bolts as ground setup OK?


	


   Go .032 brass for all and at LEAST 5/16 or better

   yet 3/8" brass bolts for fat-wire terminals. Torque

   to 80+ percent of maximum for the materials and thread

   sizes. Check AC43.13 for values.



   Bob . . .

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grjtucson

Joined: 07 Apr 2008
Posts: 7
Location: Tucson, AZ

Posted: Mon Apr 07, 2008 10:59 pm Post subject: Re: Fat Wires & Brass vs. Copper

 	  nuckolls.bob(at)cox.net wrote: 	
		  At 01:36 PM 4/7/2008 -0700, you wrote:



 	  Quote: 	
		  



Summary - 5 questions:

1. 2AWG welding cable OK for engine to firewall ground in lieu of braid?

2. 2AWG welding cable OK for 60amp PP alternator b-lead or should I downsize?



	


   Go 4AWG throughout . . .



 	  Quote: 	
		  3. .125 x .5 brass bar OK for contactor to contactor run (Van's specs same 

size but Copper)?

4. .063 x .5 brass bar OK for contactor to current limiter (no starter 

current)?

5. .050 x .75 x 5 copper bars/straps on either side of firewall, each 

soldered with brass tabs, with 3/16 brass bolts as ground setup OK?



	


   Go .032 brass for all and at LEAST 5/16 or better

   yet 3/8" brass bolts for fat-wire terminals. Torque

   to 80+ percent of maximum for the materials and thread

   sizes. Check AC43.13 for values. 	




Fantastic Bob, thanks for the help and for the work you continue to do. Simply extraordinary.



George

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_________________
George Jenson - http://www.georgejenson.com
Tucson, AZ - RV-7 Standard Build
Empennage Completed 1/06
Wings Completed 11/06
Fuselage in Progress

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