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concentric twisting of wiring harnesses - howto
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joe90



Joined: 19 Mar 2013
Posts: 382
Location: under the car

PostPosted: Sun Dec 29, 2013 5:12 pm    Post subject: Reply with quote

Concentric twisting and telephone cables........it's so that you can bend the cable around corners. Plus you have to be able to wind it up on a drum. Big cables are made out of bunches of 25 pairs usually, the 25 pair bunches are wrapped with a coloured tape and twisted together. Some old cables were 1500 pairs or even more.
If it was only 1 layer then it would try to untwist. Twisted pairs is something totally different. The best example of that is data cable where you've got 4 pairs in the cable twisted at different rates to minimise / cancel crosstalk.
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racespec



Joined: 11 Sep 2013
Posts: 10

PostPosted: Sun Dec 29, 2013 6:36 pm    Post subject: Reply with quote

Technical Concentric/Contrawind/Handlay Benefits:
-Reduced overall bundle diameter
-Serves as strain relief on any crimp to the same conductor
-Ensures no conductor has more tension than another
-Excellent flexibility

There is no noise suppression that a handlaid bundle will provide. When working with unshielded twisted pairs in a harness, it is extremely important that while you handlay the harness you do not create quads of multiple twisted pairs.

The only 'cosmetic' reason is that it looks neat!

You will not be able to do this with a drill, however a small battery powered drill can prove useful for 2, 3, and 4 wire leads to sensors/components. The process is very time consuming, and really just requires practice - and lots of it.

It's actually not all that difficult with the same size conductor, jacket, and layout. When you start adding shielded cable, various conductor types/sizes, breakout locations, etc is really when the fun stuff starts.

Some will just not see any of this as being useful or beneficial for their project, but when you are creating a professional product that will withstand what a racecar will go through; it's just part of the process.

I'm going to try and give the OP a step-by-step to go off of; while pretty basic I hope it helps!

1) Get yourself a nice, clean work area. Terminate as need and pull your most centered (7) common sized conductors.
2) (1) of these wires will be your core, while the other six will helically cover it. Begin at the base point and work your way down until the length needed is met, ensuring you have no crossovers and the finished product is an evenly spaced and tight layer.
3) Take your previous layer's total wire count (6), and +6. Your next layer will now consist of (12) total wires. Repeat the above in the opposite direction.
4) Each subsequent layer will require +6 wires to the previous layer's count, and must be done in alternating directions for each layer.
5) Bind with Kevlar lace or equivalent.[/i]
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Steve Arndt



Joined: 07 Jan 2005
Posts: 74
Location: Idaho

PostPosted: Mon Dec 30, 2013 10:06 am    Post subject: Reply with quote

I really enjoy seeing the wiring pics you post to your facebook page. Quality work!

https://www.facebook.com/racespecus
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joe90



Joined: 19 Mar 2013
Posts: 382
Location: under the car

PostPosted: Mon Dec 30, 2013 4:19 pm    Post subject: Reply with quote

Everything that I've built has always had extra things added on at later stages over the years. It's great when you've got a proper plan and you're doing it for a customer as a one off.
For a project car of your own, adding things later on always ends up with a mess.

racespec wrote:
Technical Concentric/Contrawind/Handlay Benefits:
-Reduced overall bundle diameter
-Serves as strain relief on any crimp to the same conductor
-Ensures no conductor has more tension than another
-Excellent flexibility



The bundle diameter doesn't actually change, if anything it's a bit thicker when twisted.
The strain relief.....so long as the terminated wires are all exactly the same length.
Flexibility, yes, that's the main reason.
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racespec



Joined: 11 Sep 2013
Posts: 10

PostPosted: Mon Dec 30, 2013 4:55 pm    Post subject: Reply with quote

Steve Arndt wrote:
I really enjoy seeing the wiring pics you post to your facebook page. Quality work!

https://www.facebook.com/racespecus

Thanks! I really appreciate the support :)

joe90 wrote:
Everything that I've built has always had extra things added on at later stages over the years. It's great when you've got a proper plan and you're doing it for a customer as a one off.
For a project car of your own, adding things later on always ends up with a mess.

racespec wrote:
Technical Concentric/Contrawind/Handlay Benefits:
-Reduced overall bundle diameter
-Serves as strain relief on any crimp to the same conductor
-Ensures no conductor has more tension than another
-Excellent flexibility



The bundle diameter doesn't actually change, if anything it's a bit thicker when twisted.
The strain relief.....so long as the terminated wires are all exactly the same length.
Flexibility, yes, that's the main reason.


That's the point in planning WAY ahead, past your client's current configuration in order to make additional wiring of components/sensors a walk in the park. Measure three times and cut once.

The bundle diameter does change, proof is in the pudding. This is pictured at the first breakout. I am comparing diameter without cranking down 80+ conductors in place; more or less how the wires will now naturally lay.


The strain relief will occur whether one is 70" and one is 170". If the lay is done properly, you are adding a portion of material with every wind that is not under tension as it would normally be; which is why you will always use more wire in a layer than what the total length of the portion of the harness works out to be. In doing that, you are adding strain relief for both the terminating contacts of the wire, and for the wire itself.
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C. Ludwig



Joined: 29 Sep 2006
Posts: 354

PostPosted: Tue Dec 31, 2013 4:53 am    Post subject: Reply with quote

Race-Spec, stole this from your FB page to illustrate why the concentric twists are important. Very nice work!


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Tomak



Joined: 20 Apr 2008
Posts: 612

PostPosted: Tue Dec 31, 2013 9:35 am    Post subject: Reply with quote

I've noticed a trend over the last 10 or 15 years that efi wiring is getting smaller In gauge.

Curious what wire diameter guys are using for:
High impedance injectors
Low impedance injectors
Power and ground to Individual coils
Coil trigger
General sensor
Vr sensor
Hall sensor

Typical automotive applications.

Thanks
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haydenw



Joined: 18 Dec 2008
Posts: 80
Location: New Plymouth, New Zealand

PostPosted: Tue Dec 31, 2013 2:17 pm    Post subject: Reply with quote

racespec wrote:
Technical Concentric/Contrawind/Handlay Benefits:
-Reduced overall bundle diameter
-Serves as strain relief on any crimp to the same conductor
-Ensures no conductor has more tension than another
-Excellent flexibility

There is no noise suppression that a handlaid bundle will provide. When working with unshielded twisted pairs in a harness, it is extremely important that while you handlay the harness you do not create quads of multiple twisted pairs.

The only 'cosmetic' reason is that it looks neat!

You will not be able to do this with a drill, however a small battery powered drill can prove useful for 2, 3, and 4 wire leads to sensors/components. The process is very time consuming, and really just requires practice - and lots of it.

It's actually not all that difficult with the same size conductor, jacket, and layout. When you start adding shielded cable, various conductor types/sizes, breakout locations, etc is really when the fun stuff starts.

Some will just not see any of this as being useful or beneficial for their project, but when you are creating a professional product that will withstand what a racecar will go through; it's just part of the process.

I'm going to try and give the OP a step-by-step to go off of; while pretty basic I hope it helps!

1) Get yourself a nice, clean work area. Terminate as need and pull your most centered (7) common sized conductors.
2) (1) of these wires will be your core, while the other six will helically cover it. Begin at the base point and work your way down until the length needed is met, ensuring you have no crossovers and the finished product is an evenly spaced and tight layer.
3) Take your previous layer's total wire count (6), and +6. Your next layer will now consist of (12) total wires. Repeat the above in the opposite direction.
4) Each subsequent layer will require +6 wires to the previous layer's count, and must be done in alternating directions for each layer.
5) Bind with Kevlar lace or equivalent.[/i]



If u were doing a engine loom with VR position sensors would u use the shielded twisted pair as a core? Typical engine installations with twisted pair for vr cam and crank position sensors would u use both as a core?
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racespec



Joined: 11 Sep 2013
Posts: 10

PostPosted: Fri Jan 03, 2014 1:10 pm    Post subject: Reply with quote

Tomak wrote:
I've noticed a trend over the last 10 or 15 years that efi wiring is getting smaller In gauge.

Curious what wire diameter guys are using for:
High impedance injectors
Low impedance injectors
Power and ground to Individual coils
Coil trigger
General sensor
Vr sensor
Hall sensor

Typical automotive applications.

Thanks


As people really begin experiencing real world amperage characteristics of associated components, gauge size will always be questioned. The most important thing here is the type of wire being used. What you can 'get away with' in regards to higher quality material is worth it's weight in gold. M22759/16, /18, and /32 are all great conductors for motorsport use, and are really the standard for good reason. Better conductivity, higher ampacity, higher temp ratings, etc.

An important part of the gauge size consideration must also be the environment the harness will be subjected to, as well as the end user. You'll chase a smaller and lighter finished product, yet it's more delicate. In a professional race application, this is understood. However in many of the drag cars I wire - I tend to jump up in gauge size to give a bit more rigidity and allowance of mistreatment.

A meter will only tell you so much, and it's tough to compensate for in-rush which is in my opinion a more important deciding factor in gauge size. From my own experience:

High impedance injectors 22AWG
Low impedance injectors 20AWG
Power and ground to Individual coils 20AWG Smart Coil, 18-20AWG Dumb Coil w/ CDI or Igniter
Coil trigger 22AWG
General sensor 26-22AWG
Vr sensor 26-22AWG
Hall sensor 26-22AWG

Interesting aspect of this too is planning your layers, splices, and sizing to obtain proper lays.

haydenw wrote:
If u were doing a engine loom with VR position sensors would u use the shielded twisted pair as a core? Typical engine installations with twisted pair for vr cam and crank position sensors would u use both as a core?


I almost always tend to keep any shielded or twisted sets in the core, in some cases as many as (4) pairs.
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