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 Post subject: Buss Wire Stretching and Fabrication
PostPosted: Jun Thu 23, 2022 5:34 am 
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Location: Panama City Florida
This post shows how I changed a #12 AWG copper residential wire into a straight, tinned wire suitable for antique radio buss wire.
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The Process
To make the buss wire, you’ll need either #12 AWG or #14 AWG copper wire. I used #12 AWG copper wire from 12-3 residential wire bundle. You will need a way to stretch and straighten the wire. And lastly you will need to tin the wire with solder.
The Wire Stretcher
Some antique radio enthusiasts recommend straightening the wire using a fencepost and a long pipe for leverage to stretch the wire. This approach didn’t work for me so I made a wire stretcher out of a wood 2x4, a lashing winch, some 5/16” lag bolts, and two 5/16” wire grippers. I used a 60” length of 2x4 just because it fit my work bench and because I figured I didn’t need to stretch any wire longer than about 40 inches. The below graphics show my setup.
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Lashing Winch I bought at Amazon for about $18
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5/16" Bolt Wire Gripper with small hole for the wire
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I used a short loop of 550 parachute cord to hook the gripper to the stretcher
Take up the slack using the winch and adjust the grippers so they have a straight pull on the #12 AWG wire to prevent breaking the wire. Next measure the wire. The wire needs to be stretched 5% to 10% so multiply the length of the wire by 1.1 to determine when you are done stretching. (I found that stretching the wire past 15% tends to break the wire). In my case my length of wire between the gripers was 38 inches, so my stretch was done when the length reached 42 inches. (Although I used nylon rope that stretches, it did not cause things to fly across the room if the wire breaks). Next use the winch to stretch the wire to the appropriate length.

Wire Tinning
Now that the wire is stretched, for aesthetics, the wire should be tinned to look authentic. I leave the wire on the stretcher while tinning the wire. To make sure the solder adheres to the wire, it must be buffed with sandpaper and coated with solder flux.
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I used 220 grit sandpaper
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I have a 120W Weller soldering iron and I set the temperature to 600F to get plenty of heat to melt the solder to the wire. When applying the solder, go slow to allow the copper wire to get hot and move slowly with the soldering iron top/bottom/front/back to make sure the wire is 100% coated with solder. Don’t use too much solder or the wire will turn out lumpy
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After coating the entire wire with solder, let it cool and clean off the excess solder flux. I found that alcohol works well. The end product will be a straight and stiff length of shiny #12 AWG wire suitable for your antique radio.
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Hope this helps. I had to use trial and error to develop this procedure. There may be a better way but this is what worked for me.


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 Post subject: Re: Buss Wire Stretching and Fabrication
PostPosted: Jun Thu 23, 2022 3:25 pm 
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Location: S. Dartmouth MA 02748-1225 USA
Well done Tim!

Far better, bench-top approach than using blocks and tackle as well as half the back yard as I did :lol:

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 Post subject: Re: Buss Wire Stretching and Fabrication
PostPosted: Jun Thu 23, 2022 5:36 pm 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 11382
Location: Santa Rosa, CA
Impressive.

I simply clamp one end of a #12 bare wire in my vise. I use "vise-grip" pliers on the other end and pull until I can feel some "give." It might be helpful to anneal the wire with a propane torch before stretching.

Once the wire is stretched it will be "work hardened" and you may need to anneal it again to stretch it further or to make tight bends or loops.

Rich

PS: I have also used bronze brazing rod to make very straight runs of buss wire. Since you won't be running a lot of current through it, the difference between copper and bronze is not meaningful.

Or get it from K&S: https://ksmetals.com/collections/brass/products/brr-1-32

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 Post subject: Re: Buss Wire Stretching and Fabrication
PostPosted: Jun Thu 23, 2022 10:37 pm 
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Joined: Apr Sat 17, 2021 5:24 am
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Location: Panama City Florida
Rich,
I don't have any experience with metal work. I first tried to grip with a vise-grip but the wire frequently broke and really had to pull HARD which sent me flying across the room when it broke. (Plus I got some insulting and degrading comments from my wife) So I made this stretching contraption and had more control on the length of stretch.

It seems to me that annealing with a propane torch (which I don't have) would be counter-productive because you want the wire to be stiff. Doesn't annealing soften the wire?

I looked at brass welding rod but I needed longer lengths that 12". Will brass rod accept solder tinning?

Voltman


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 Post subject: Re: Buss Wire Stretching and Fabrication
PostPosted: Jun Fri 24, 2022 12:03 am 
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If you need square buss wire, you can use a drawing die like this: https://www.amazon.com/Drawplate-Wire-D ... B000RB212W Just tap a flat spot on 4 sides with a hammer to get started and use beeswax as a lubricant. It's amazing how much longer the wire gets after a few draws. Annealing is required in between draws but you can leave the last draw hard for support.

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 Post subject: Re: Buss Wire Stretching and Fabrication
PostPosted: Jun Sat 25, 2022 3:12 am 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 11382
Location: Santa Rosa, CA
Quote:
It seems to me that annealing with a propane torch (which I don't have) would be counter-productive because you want the wire to be stiff. Doesn't annealing soften the wire?


Anneal first to soften the copper. Do your stretching. That will work-harden the copper. It should stay straight after you stretch it.

Rich


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 Post subject: Re: Buss Wire Stretching and Fabrication
PostPosted: Jun Sat 25, 2022 2:48 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1596
Location: Bristol TN 37620
Great job Tim.


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