Hot box

It is often convenient to be able to put tools away while they are still hot. To make this safe, I keep my soldering irons and hot air guns in metal cases but it is necessary to keep the hot ends away from anything else, including their own leads.

Having added a rework station to my collection, I needed a different box. For this, I have used a large army style ammo crate.

I've added divisions inside to separate the hot ends from the other items in the box.

I got carried away. I've sprayed it a gun metal colour...

and stencilled some lettering.

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Car wiring harness best practice... or not?

What inspired me to write up some notes was a question posted on Facebook. The answers to which were conflicting. How do you know which answers are the correct ones and which are wrong or just not the best solution.

That got me asking, what is best practice for car wiring harnesses?

It proved more difficult than expected to get a satisfactory answer.

Apparently racing teams use aeronautic or boating standards.

This is one of the most commonly quoted references that I found:

http://www.sailangle.com/articles/details/id/6

I fairly regularly come across people fixing car wiring with a soldering iron. Even my local garage was going to solder on some bullet connectors. They did admit that at the time they were lacking an auto-electrician. You can probably tell that I think solder, for this use, is a bad thing.

I want to be clear at this stage that I am perfectly able to solder a good joint, probably better than I can crimp but I believe that, for car wiring harnesses, a good crimp joint is the better choice.

I was taught that solder on stranded wires was a bad thing if the cable was likely to move. Mechanical vibration causes the wire just before the solder joint to crack because it can no longer flex freely. If the stranded cable is free to move it would be undamaged. That pretty much applies to the entire loom in a car, by my thinking.

I tried to find some on-line electrical training manuals but I could only find the odd extract from old paper books. A few of these repeated what I had been taught but I would not class any of them as definitive.

My best evidence for not using solder joints is that all car looms I have seen in the last few years have been exclusively crimp connectors.

I am sure there are cases, even within a car harness, where solder joints are a better choice. To further water down my comments, a properly secured cable will not vibrate much, so again, a solder joint would work well.

So I have not found the definitive answers I was hoping for. Therefore I am left to draw my own conclusions.

In my opinion, for wiring harnesses, I prefer to:

• Avoid solder joints (except for special cases)
• Use crimp connectors (securely applied with a correctly fitting tool)
• Use butt splice crimps to join wires

Where a solder joint is required, ensure the connection is mechanically secured from movement.

If I come across any more definitive answers I'll update this article.

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References:
http://www.colorado.edu/physics/EducationIssues/podolefsky/electric_motorcycle_howto_wiring.html#FAQ
http://www.fsae.com/forums/archive/index.php/t-4570.html?s=2f4ac3793225a1cc9fb6f05198249449

Suppliers of automotive (and other) connectors:
https://www.polevolt.co.uk
http://www.vehicle-wiring-products.eu
https://www.autoelectricsupplies.co.uk

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Solder tiny brass roll cage

It's probably been 30 years since I last did anything similar to this. I solder electrical wires and components fairly frequently but soldering 1mm solid brass wire to make a frame is a different skill.

I had forgotten the techniques for using a gas torch and had to experiment. After a few failures I watched some YouTube videos.

The bit of information I needed was the flux. As far as I could see, everyone uses a sticky paste flux.

The solder only flows and sticks where the flux is applied. That little bit of knowledge made all the difference. I bought a choice of flux but started with the one that claimed to be less poisonous. I got a near perfect joint first time using that flux.

I used the same flux cored solder I use for electrical work.

I also had to buy a new torch because the pen style torch I was originally using started to leak. I ordered a posh looking but very low cost butane torch. Easy to use but a bit messy to fill. I like the piezo self igniter and the push and hold button to use.

It has a lock to hold on the flame, if necessary but for soldering small joints you only need the flame for a few seconds so I didn't use the lock. There are separate gas and air flow adjusters so I could get the flame exactly as I wanted, about 10mm to 15mm (0.5") long to the centre blue flame point but it would reach over 50mm (2") if necessary.

While looking at the YouTube videos I came across other tips. Cleaning the joint area with sand paper, I already knew. One suggestion I tried was cutting a small bit of solder and laying it on the joint, stuck in the flux. That was handy on a few joints but with some practice I found it unnecessary.

My end technique was to apply the heat to the joint. Move the flame away momentarily to add the solder, move the flame back to melt the solder, wait until it flows then remove the heat. Ideally the heat should be applied on the opposite side to where the solder is to be put on but sometimes that was not possible.

The next issue was supporting the joints while soldering. That can be tricky but pretty much anything that won't catch fire can be used to keep the bits of metal together prior to applying the solder.

Being so tiny I also had a few cases where heating up one joint melted the solder on a previously finished joint. Frustrating but using a pair of tweezers as a heat sink usually solved that problem.

The model, shown in the photos for the roll cage, is a failed 3D print I had used for practising smoothing the surface. As you can see, that was handy to offer up the metalwork without worrying about damaging the paint on the work in progress.

The last job was to tidy up the joints. That was done by filing and sanding away the excess solder.

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