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Concentric Twisting

Practical Harness Construction - Club Level

Discussion and questions related to the course Practical Harness Construction - Club Level

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I know the 'race wiring package' is not available yet but I still have a question.

Excuse my belligerent language. I was doing some engine building from 11pm to 5am, and then went to work. Hopefully this is cohesive, but i'm a bit delirious from the lack of sleep.

I've read in some spots that its best to have my shielded wires as part of my core. Fine. I can probably work around that (even though the shielded wires aren't necessarily the longest), but in general I was thinking about how to do branches/breakouts from a concentric twisted harness. How do breakouts/branches work into planning? Do I just make sure my longest wires are in my inner most cores and then work my way outwards so that my outermost layers are those that'll feed the shortest leads, and thereby easiest to breakout? When they break out, how do I continue the rest of the concentric twisting wire-counts?

Pretty please? Does anyone have any tips here?

G'day Trey.

The transition points of a concentric harness usually end up being a little messy. This mess gets contained with Kapton, or Teflon tape for strain relief, and then booted with a molded shrinkable boot that will become quite rigid when recovered, keeping everything strain relieved.

I plan my layers from the largest wires (usually the shielded wires, as you've mentioned) outwards to the smallest. If those shielded wires need to branch out somewhere, they'll do so, and the twist will get a little interrupted, and its possible that layers might need to change twist direction. It is just a case of managing this all as best as possible, keeping it as tidy as possible, and strain relieving it all.

Zac, If your main trunk splits into 2 sub branches, (example: 50 wire main trunk line branches into a 30-wire branch and a 20 wire branch.) Would you simply start your twist over again on each branch? So basically use a zip-tie on the main bundle, then unravel all the wires and begin 2 separate concentric twisted bundles from that transition. Then tape and boot the transition.

I ask because the Subaru EJ engine I'm wiring has 1/2 the devices on one side of the engine and 1/2 on the other side. My plan was to exit the firewall with a Deutsche AS 61-pin firewall connector, travel about 18 inches to the back side of the motor, then T-split into 2 to feed both sides of the motor - rather than having one bundle circle around the front of the motor. This keeps the heavy wire bundles a bit more hidden from sight (ricer motives haha)