Fat Wire Test

I initially thought i would go with pre-made cables for the 'fat wires', so went ahead and ordered some 35mm2 cables from a local supplier - these were ok, but i soon realised that the length on these cables is very critical. If they are even a few mm out in length, they put pressure on the terminals you are connecting them to. Also, they don't twist very well, so if the connectors need to be 'clocked' with reference to each other, the supplier is not able to do this. 

So i got stuck into some research and seems i had a few options - one was 'welding cable'. This is a cable made up of many thin strands of copper, and is fairly flexible. It can be obtained with a silicone sheath according to the forums, but i was unable to find this in Australia.

The next option was 'marine cable' - this is also made of many strands of small copper wire, and is very flexible, but is tinned - so offers superior corrosion resistance. It is coated in a V90HT PVC coating which is suitable to temperatures up to 105c. I ordered 3 metres of each color (red / black) in 32mm2 (equivalent to 2 AWG) from a local supplier.

I also ordered a bunch of lugs with M6 and M8 holes, as well as red/black glue-lined head shrink. 

Test Cable

I decided to make up a test cable, to work out the process for the manufacture of these, including how to use the hydraulic crimper. The first issue was cutting this massive cable - that's ok - NEW TOOL DAY!

This is why the cable is so flexible - it's made up of many small strands. Each strand is tinned along it's length.

The cable must be stripped enough so it seats against the end of the lug.

Next up was the hydraulic crimper. These are fairly simple to use - you just select the proper die size. In this case, the one with the "35" marked on it (for 35mm2 cable). My dies don't have the "35" embossed in them for some reason.

After i shared some photos of the below crimps online, someone shared with me a process document showing the proper crimp locations. You are not supposed to overlap crimps, so the crimp below is not techincally correct. This is why we do a test article when learning a new skill! #EXPERIMENTAL 

In the future i will make the crimp like the examples below - either a single crimp, or two seperate crimps if the lug is long enough (it probably won't be). 

The next test was to install the cable - you can see here that this cable is a tiny-shade too long! I have learnt to install the cable into the lugs first (cut marginally long) with only one end crimped. You can then adjust the length as required, as well as mark the clocking of the cable ends. You can also see how i applied the glue-lined heat shrink here.

To make the cable head in this direction over the battery, i had to use a stack of washers. It was pointed out to me when i shared this photo on a facebook group, that a stack of washers is not the best idea. So i send off to the eBay Aviation Machining Shop and had some brass spacers made up. 

eBay Aviation Machine Shop for the Win!

Testing the Crimps

I thought it prudent to test the crimps - so made up a quick jig to allow me to use my luggage scales to test them. One end was held by a bolt pushed into a hole in my workbench, and the other to the pull-jig. I was able to pull over 50kgs before the scale maxxed out. I would say this is enough! I will test each and every cable i make like this. 

So that was a good learning experience - i will leave the actual fabrication of the cables until i have all the contactors installed for good on the firewall, and the engine in position.