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Murphy's friend

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Joined: 04/10/2019
Location: Australia
Posts: 648

Posted: 09:36am 12 Feb 2024

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I used to do this using the expensive 3mm rosin cored solder wire and a gas blow torch.

It was very wasteful with the solder so I thought of a better way.

There are lots of solder pots on Ebay but they are all too shallow for this job, so I made my own:

For heating I used the inner ring of a two ring gas burner but any camping gas stove will do as well.

It is important that the base is heavy and big enough to prevent tipping over. I used a 6mm thick steel disk, this was tapped M6.
From the hardware store I got a 150mm long galvanised pipe with an inner diameter just big enough to accommodate the busbar (the bars are 20 x2 x250mm). I also got a brass screw on endcap which was also tapped M6.
The reason for tapping is that liquid solder can escape through the tiniest hole so the two parts tightly screwed together hopefully avoid that.

The pipe also has to be sealed to the endcap, I used muffler and tailpipe sealer from the auto store. (not shown on the picture).

That pipe section took three 60/40 solder sticks to fill, the price of them was a bit of a shock.

Once everything was ready, the busbars had to be scrubbed spotlessly clean which I did using 150 grit wet and dry sandpaper under a running tap.
It's important to wear gloves for this job as any fingerprints on the bare copper ruins the tinning.
The bars need to be dried immediately and coated with solder paste, I used one I got from Ebay but I see that Jaycar has rosin solder paste in tubs for sale.

Then the gas was fired up and the tinning began. I did this with 1/2 length of bar at a time, wiping the solder smooth with a rag. Use non synthethic rags, I used an old flannel shirt rag. This process splatters solder drops around, so wear suitable clothing and shoes and do it where the floor can take those solder splats.

As soon as one half was tinned the bar was gripped on the tinned end and the other half was tinned. For a first timer that might have to be repeated until the wiping part is turning into first class job

.

A tip here, if there is an un- tinned spot place the bar back into the pot and, once hot, use that 3mm rosin cored solder to tin that spot.

Here is a pic of the final result, apologies for the light reflections on the bars.

I hope this may be useful for some, if its old news just ignore it.

Solar Mike
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Joined: 08/02/2015
Location: New Zealand
Posts: 1138

Posted: 10:20am 12 Feb 2024

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Great result.

Another way to get your copper bars nice and shiny is go to your local electroplaters and get a liter bottle of silver plating solution from their bulk tank, rub it on the cleaned copper with a rag, leaves a nice shiny silver coating without any electricity, so simple displacement reaction; the layer is extremely thin, but stops the copper corroding. Would not be as robust as tin-solder dipped.
I used to do this over 40 years ago when making custom copper parts to fit inside high power RF transmitters.

Cheers
Mike

Godoh
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Joined: 26/09/2020
Location: Australia
Posts: 458

Posted: 08:28pm 12 Feb 2024

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When I was an apprentice we used to tin our bus bars and lugs with a paste.
I think it was called Tinsolflow.
We would clean the copper parts, then paint the tinsolflow paste on, heat it with a blow torch and presto, they would be tinned. Oh and also we wiped the bar with a rag to make sure the bar had a smooth coating.
I don't know if there is a product like that around these days.
Anyway your bars look good, I too have been shocked by how much solder costs.
Pete

Godoh
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Joined: 26/09/2020
Location: Australia
Posts: 458

Posted: 08:32pm 12 Feb 2024

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https://www.fribesco.com.au/product/solderin-s-tinning-paste

Pete

Godoh
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Joined: 26/09/2020
Location: Australia
Posts: 458

Posted: 08:36pm 12 Feb 2024

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I also spent a while as a bench fitter, making contacts for ancient traction machines.
I made the contacts from copper. To keep them clean and bright, I dipped them in Nitric Acid first. Then in a bucket of water while they were hanging on a piece of wire. Then into a solution of brightener that protected the surface from oxidisation. They stayed looking clean and bright for a long time.
Nitric acid works fast to clean copper, just make sure to take all the normal precautions. These days when I have old copper cables that have gone black on the ends and I still want to use them, I dip the ends in Hydrochloric acid then rinse. Works a treat.
Pete

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