Knowledge Boost:</br> Tackling Your Wiring Nightmare – Part 1
The Real Mil-Spec

As our cars have become more complex, the wiring ‘birds nest’ that goes along with them continues to grow, and this is one area that many enthusiasts have an inexplicable fear of. Many home enthusiasts for example are more than happy to crack into rebuilding their bottom end, perhaps fitting aftermarket cams or a turbo, but when it comes to picking up a set of wire strippers or a crimping tool they’re suddenly frozen with fear.

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I get it though – wiring diagrams can be scary, and in this age of social media one-upmanship it’s easy to jump on Instagram and see intricately-constructed harnesses, all carefully pinned out into expensive Deutsch Autosport connectors complete with service loops and Kevlar lacing cord (hashtag mil-spec). Based on this, one might assume this is the only way to build your harness, and therein lies one of the problems. The term mil-spec is now all too often misused, misrepresented and misunderstood, and perhaps dare I say – even unnecessary.

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So what does mil-spec mean, and should you care? Most people can figure out that the term is a shortening of ‘military specification’, which is a set of specifications that define operating standards for components destined for the US Department of Defence. With reliability and light weight being key considerations in the world of motorsport, it’s no surprise that we have borrowed from the military and aerospace industries and that the term mil-spec has started to become used and abused.

In this story we’re going to look at what’s available when it comes to automotive wiring options for the average guy or girl who doesn’t want to blow a weeks salary on a single connector, but still wants a professional and reliable result. This isn’t meant to be an all-encompassing guide to building a wiring harness, but it will address some of the most critical areas I get asked about.

No Solder. Ever
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Wiring problems suck. They can be very time consuming and frustrating to track down, and if you want to ensure the best reliability from your harness you’re going to want to leave the soldering iron in the draw. That might sound controversial and I know there are thousands of people out there that firmly believe that solder is the most reliable way of joining wires together. Unfortunately those people are wrong. Solder is something you’re not going to find much of in a professional motorsport wiring harness.

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The problem with solder is not so much in the actual solder joint itself, but rather where the solder joint ends and the wire continues. This becomes a weak area that is brittle, and through vibration or movement the joint could eventually fail right at the edge of the solder joint.

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The preferred technique is to crimp your connections. This is the same technique that OE manufacturers as well as those working in the likes of Formula 1 use. While I know many enthusiasts’ first thought is that crimping couldn’t possibly be as reliable as a soldered joint, the exact opposite is true. In fact, a properly crimped joint is stronger than the base wire, which is to say that if you pulled on a crimped joint hard enough, the wire strands would snap before the crimp fails.

A Reliable Connection
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Remember those expensive Autosport connectors I mentioned? if you are building a high-end harness, then these are definitely the most reliable option when it comes to connectors. They offer the ultimate in reliability and light weight, while acting as a barrier to moisture and dust. Another advantage is ease of installation. The entire engine harness can remain installed on the engine and a single bulkhead connector links everything up to the rest of the chassis with a simple 1/2 twist. They are also great for your Instagram game.

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If you’re not working on an F1 car at home in your garage and you don’t want to mortgage the house to build your wiring harness, there are other options though. The Deutsch connectors pictured above are a favourite of mine. These are available in a wide variety of options to suit different gauge (thickness) wire, as well as 2 through to 12 position options. These connectors are well-priced and offer a reliable connection that is environmentally sealed and up to the rigours of motorsport abuse.

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Assembling a DTM connector (pictured) starts by stripping the wire to the correct length. If you’re working with a proper mil-spec wire, even this requires some care as the insulation is very tough and it’s easy to damage the conductor strands if you’re too enthusiastic. Here we are using an Ideal Ergo-Elite wire stripper which uses a blade set specifically for mil-spec wire. This stripper also has a convenient adjustable stop that lets you achieve consistent strip lengths. That might not sound too relevant, but it’s a big help when you are terminating a lot of connectors.

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Once the wire is stripped it can be inserted into the terminal. If you’ve got the right length of insulation stripped, you should be able to see the conductor strands through the small window in the terminal to confirm the wire is fully inserted. At the same time though we also want a small gap between the insulation and the back of the terminal. This ensures that there will be no stress placed on the wire due to movement between the wire and terminal.

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Now the terminal can be crimped onto the wire. While there are expensive professional-grade crimp tools that suit these connectors, for the home enthusiast you don’t need to go crazy. The crimp tool we’re using here should set you back no more than about US$50 and is very quick and easy to use. It positions the terminal correctly to ensure the crimp is properly located, and they are available to suit different gauge wire.

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With the terminal crimped we can finally install the terminal into the connector before placing the locking wedge into the connector to prevent the terminal coming out. There you have it – a reliable connector that won’t break the bank.

It’s A Twisted World
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If you follow anyone in the motorsport wiring industry on Facebook or Instagram you have almost certainly seen a wiring harness all bare and naked before the protective heat shrink tubing is shrunk down over the top. The technique used to create these masterpieces is called concentric twisting and again it’s not well understood. This method involves twisting the wires in layers around a central core wire. Each layer of wires is twisted in the opposite direction to the previous layer, and as the layers increase we add more wires. Actually, to be precise, each time we add a layer we increase the number of wires by six.

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Of course, things become more complex when we start dealing with multiple wire gauges and shielded cable too. It’s not all about creating pretty pictures for Instagram though. The concentric twisting technique creates a wiring harness with a very small cross sectional area, as well as a harness that offers great flexibility.

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If you’re working with Raychem DR25 heat shrink tubing as a final protective layer for your harness, concentric twisting will also make it much easier to do a tidy job of installing this rather than trying to pull it over a bunch of haphazardly-tangled wires underneath.

To Be Continued…

So far I’ve discussed a few of the common questions I get asked about motorsport wiring techniques, but it’s hard to do justice to the topic in one story. Next month I’ll continue and we will cover shielding inputs, the importance of proper grounding, and how to protect your harness from the elements and ensure reliability.

Until then though, if you have any wiring-related questions ask them in the comments section below and I’ll be happy to answer them for you. Also, if you’re interested in learning more click here and sign-up for a series of  lessons about tuning and wiring. I consider these lessons the bare minimum any car enthusiast should know.

Andre Simon
Instagram: hpa101
Website: www.learntotune.com

Images by Ben Silcock

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1

Very good write-up for starting a wiring guide. I personally do not do wire harness work, but I work with people who do, and you are spot on with techniques so far. Glad to see a different approach to wiring nowadays then butt splices lol.

2

As an USAF Avionics Specialist, wiring is the bane of my existence. although it is very easy once you learn how to properly read schematics and learn some basic theory of operation.

Plus automotive wiring is very basic compared to some of the ridiculous setups on fighter jets.  Car wiring might look scary, but with a little research anybody with decent mechanical skills should be able to tackle it.

3

This post is way too pertinent to me right now. Looking forward to the next installment.

4

state of art

5

state of art

6

What do the pros use to shrink the DR25 (or any protective wiring coating)? I've had trouble getting uniform heat onto shrink tubing using a torch or heat gun.

7

another nice article!  the use of proper tools can never be emphasized enough - it'll make your life easier and produce quality results too.  

that being said, i'm still scared of wiring, only going as far as wiring the radio to the harness.  lol.

8

another nice article!  the use of proper tools can never be emphasized enough - it'll make your life easier and produce quality results too.  

that being said, i'm still scared of wiring, only going as far as wiring the radio to the harness.  lol.

9

MikeDonnelly Cool job.  If I so much as look at wiring I will short circuit myself :(

10

I work as an engineer in the naval defense industry and wiring is an elemental part of my daily business.Nice article but there are a few more things that should be taken in account. Twisting wires is a common method to reduce noise on your signals. Especially when their are close to power lines or electric machines. Take a minute to think about proper shielding and flame retardent jack material. Regard voltage and current rating of wires and pins. Cables have a mininum bending radius. Think about fixation to mak eit shock and vibration proof. Mil-connectors might be a bit of an overkill. They are a 1000-pieces puzzle with multiple shell and insert options. They take up a lot of space. Not even talking about price and time to deliver. Sorry for the long post but those are a just a few things that give me a headache everyday ;)

11

Id rather rewire a car from scratch than have to repair some one elses mess. Like anything, if you take wiring step by step, put some thought into layout, proper fusing/relays etc and install it cleanly...theres no need to be scared

12

@chris chabre I couldn't agree more. It's not as scary as many people think. If you're able to take a slow and methodical approach to wiring, and you've good good attention to detail, then there is no reason a home enthusiast can't do a great job.

13

@Johannes I will be addressing many of the points you mention in the second instalment - Trying to fit everything in one story would have resulted in a novel of crazy proportions so please don't think I'm trying to overlook any important details :)

As I said in the story, Autosport connectors are probably overkill for many. I'd disagree though on their size - They are probably one of the most space efficient methods of providing a solid, light and reliable connection. This however comes at a hefty price.

14

nugundam93 agreed, the right tool is essential if you want quality results!

15

@Joe for professional use something like a Steinel heat gun is a good option. The heat gun doesn't have to be anything flash though and we used a $80 cheapy for the shrinking on the harness pictured. You can usually get a reflector that clips onto the end of the heat gun and this does a better job of applying heat all the way around whatever you're shrinking.

16

MikeDonnelly I couldn't agree more. If you're at 30,000' you really don't want a problem with your wiring harness too!

17

I'm so lost but at the same time I'm enjoying trying to absorb new knowledge. Thankyou Andre!

18

Jagdroach I just about finished mine up then decided to add a couple of more sensors -- But those damn guys at AEM sure do talk their own brand of Geek-lish -- and still haven't got a good answer from AEM on how to hook up a Tach output -- guess I'll go back onto their forum and ask again while I'm thinking about

[URL=http://s586.photobucket.com/user/Fiatdude/media/Ghia/20150909_153910_zps4vwe4vnu.jpg.htmlIMGhttp://i586.photobucket.com/albums/ss306/Fiatdude/Ghia/20150909_153910_zps4vwe4vnu.jpg/IMG/URL]

19

Great writeup Andre i enjoy reading your tech articals

20

This might be a bit simplistic for most, but I would love to see a guide for rewrapping a stock harness with braided sleving. I plan on doing this but don't want to use the split loom type wrap rather full tubular witch means de pinning connectors.

21

Speedhunters now you tell me solder is wrong. U0001f623 I am a soldering boss, so I'm going to remain confident in my work. Great write up! U0001f44dU0001f3fbU0001f44dU0001f3fb

22

Speedhunters https://twitter.com/_fly_by_night/status/492304383087239168
Non-insulated but connectors are the bee's knees. They make for a clean job. Great write up! U0001f44dU0001f3fbU0001f44dU0001f3fb

23

I built a few harnesses, but I didn't have information on how to do it, so I just went ahead. So thanks for the writeup, it will be very useful in the future!
But I still have two questions:

I built the harnesses mostly without soldering. But sometimes I had to combine many little ground wires into one big wire, so it could be attached to one single pin at the ECU/battery. Is that also possible with crimping?
And regarding concentric twisting: Isn't the harness getting heavier, because the wires have to be longer when you twist them around a core?

24

I built a few harnesses, but I didn't have information on how to do
it, so I just went ahead. So thanks for the writeup, it will be very
useful in the future! But I still have two questions: I
built the harnesses mostly without soldering. But sometimes I had to
combine many little ground wires into one big wire, so it could be
attached to one single pin at the ECU/battery. Is that also possible
with crimping? And regarding concentric twisting: Isn't the
harness getting heavier, because the wires have to be longer when you
twist them around a core?

25

I work in motorsport, and everything is Autosport connectors (Deutsch and Souriau) and some industrial Deutsch for test and R&D use.  I understand that everyone wants pretty motorsport harnesses for their street cars, but it really is overkill for a street car, especially considering the high cost.  You're not always getting something more reliable either, and don't know how much engineering or development work went into something that you bought from a wire tuck company.  Removing a very well engineered OEM harness and replacing it with something different isn't always the best thing to do unless you have a very good reason (like the OEM harness isn't compatible with your needs, requires too much modification, etc).

There is really nothing wrong with the OEM connectors if they function properly.  Also, for the average person who is doing some minor wiring mods, I would suggest getting TXL wire instead of mil-spec, because it's cheaper and easier to find in small quantities, and there is no requirement for special strippers.  If you're going to use Autosport connectors, the proper wire is very important.  If you're using OEM connectors or industrial Deutsch connectors (the gray/orange connectors in the pictures), TXL wire works great.

26

@grf Yes, there are types of crimps that can combine multiple wires into one.  That's what OEMs use to combine power to multiple injectors, multiple grounds, terminate a braided shield to a ground wire, etc.  They are crimps that start out as a "U" or "V" and get crimped into a "B".  They are an uninsulated crimp and need to be covered obviously.

The contra-wound wiring does make the harness slightly heavier, but it's a tradeoff in terms of better reliability with increased flexibility and decreased harness strain.  Thin, high temp insulation and the smallest possible wiring gauge is the normal solution, so you run with a pretty small safety factor as well as higher temperature rise based on wire resistance.  On the flip side, making a large, multi-layer harness is also bad for heat dissipation in the middle of the harness, so that has to be taken into consideration when selecting insulation and wire gauge as well.

27

Kinda of special timing with this article- my buddy in aerospace engineering helped me score a literal ton of these connectors from a weird boeing NOS donation/tax write off thing. After a lot of sorting and figuring it out for myself i bought a used set of those crazy geared crimp guys off ebay for $15 and it was on like donkey kong! I found enough pins to last my life time and plan on using a couple 22-55s and 22-41 plugs for an extension harness on my little 2JZ pickup. Mine are real MIL spec i guess, amphenol and aero parts mostly. I find the stuff very pleasant to work with! Not scary at all

28

Damn you setup is way prettier than mine haha. I'm sure you'll figure it out though!

29

Hun'er MANtz good work on that score! Nice work. The key to using these connectors is having the correct crimp tool to suit the terminals and the gauge wire you're using.

30

@fabrik8 I agree that mil-spec is overkill in many situations - That's really one of the points of the story. OE harnesses are more than sufficient for any OE installation and the bean counters have done a pretty good job of balancing cost vs reliability so they seldom result in any real issues. Of course if you're performing an engine swap or building a race car then you might need to get creative.

31

@grf it's quite common to splice multiple wires into one single wire and yes, you are best to do this with a crimp. A barrel crimp over the wires and then protected with glue lined heatshrink is the normal way of doing this.

Yes a concentric twisted harness will have more wire in it and hence the weight will be slightly greater than if the harness wasn't twisted. Since we are usually talking about milspec wire though, the weight of the wire is already small, and the other advantages of concentric twisting definitely overshadow any weight deficit.

32

Brentonmartian no problem! Glad you're enjoying the articles :)

33

Mason Lockyer thanks Mason, appreciate the support :)

34

Andre Simon Hun'er MANtz thanks! Yeah, i've got that sorted. the 42's accept a larger diameter wire. Most annoying bit was actually understanding the clocking system, I didnt at first realize they can be rotated in the housing, and while mating properly while empty, would be rendered completely useless when you pinned them. Doh!

35

Andre Simon Brentonmartian Just do what I do and re-read them six times haha

36

Slappy_Pistons MikeDonnelly Ditto...

37

I was going to ask the exact same question about doing 4-to-1, 3-to-1, etc. I get the idea, but I can never find what I think is the right terminal. Can one of you guys link to an example ?

38

This is the kind of article that makes me feel like an 8 year old kid who's found his dad's old stack of Playboy magazines. It excites me greatly, but I'm not really sure why, and I still don't have a clue what to do with it.

39

This is the kind of article that makes me feel like an 8 year old kid who's found his dad's old stack of Playboy magazines. It excites me greatly, but I'm not really sure why, and I still don't have a clue what to do with it.

40
Carl Oskar Oestergaard

I'm working with creating custom autosport, and street car wiring looms myself. And was wondering what brand that inexpensive crimp tool was? We have always been using the DMC crimp tools, which you might know is a bit expensive. 

At last you might want to talk about the importance of terminating your CANBUS wires, when going longer distances.

41
Carl Oskar Oestergaard

I'm working with creating custom autosport, and street car wiring looms myself. And was wondering what brand that inexpensive crimp tool was? We have always been using the DMC crimp tools, which you might know is a bit expensive. 

At last you might want to talk about the importance of terminating your CANBUS wires, when going longer distances.

42

MikeDonnelly  I agree on the complexity; despite looking really daunting, car wiring is actually not that bad if you just take your time with wiring diagrams and carefully trace the harness from sensor to controller, etc.

I've moved the fuse panel in my 200sx from the front wing to the transmission tunnel, and also junking about 10kg of excess harness, and I reckon I did about 200 solder joints... all of which I am now worried about thanks to Andre's excellent article!

43

You guys have an uncanny knack of writing articles in time with sections of my current builds, can you do one on painting engine bays next? Like it, a large bulkhead connector is a big consideration for what I'm doing atm.

Its a very scary thing though, I'm rewiring my classic mini too whist also tidying the wiring on my Fiesta RST after its ECU install last year....

Its painful, but I'm determined.... may bin the soldering iron though

Looking forward to part 2!

44

fRunco  one little tip, use a hot knife to cut your braid lengths. it helps keep the braid together when you push it over connector pins.

45

nice to see a decent write up with the various do's and dont's on vehicle wiring. there are a lot of tips and guides out there which teach a lot of bad habits which doesnt help people when learning to work with cable/electrics. i do quite a few engine loom conversions on old wiring, will be nice to put some of these tips into practice. and youve totally opened my eyes to soldered joints! just a shame crimps arent that slim.

46

Awesome write up!!!  Cant wait for part 2.


I love wiring ... when im left alone in peace to work at my own pace and frame of mine.
Here's my current project

47

This is great. If you could do a little more detail on the steps that would be even better. Like that Deutsch connector you left out how to put it together. To a professional that's easy but I managed to do it wrong the first time and and fixed it. And you forgot to mention the brand and model of that red deutch pin crimper. I have that same crimper as I recently made a harness for my coil on plug conversion on my legacy.
Something I'd really like to know is where can the average Joe DIYer get oem or better quality and style wiring in bulk? Not that crap they sell at AutoZone. Where do all these wiring harness builders get that stuff? It would be nice to be able to buy the same wires in the same colors and stripes as the oem manufacturers use so we can repair or add/modify harnesses and keep things uniform with the factory harness. I guess that could be asking a lot but who knows, maybe it's available somewhere.
Thanks for the article. Looking forward to the next part.

48

Man can you hook me up with that deal? Lol

49

"Leave the soldering iron in the draw" is that like a drawer? Or like saying drawer but with a souther accent? :p

50

"Leave the soldering iron in the draw" is that like a drawer? Or like saying drawer but with a souther accent? :p

51

KimoKalihi Hi Kimo, without knowing where you are located, I would suggest Digi-Key for the single conductor cables. You can buy most of what you are looking for there, and while you can get medical or aerospace grade connectors there, these are typically special order for them, so expect longer leadtimes for those parts.

52

KimoKalihi Hi Kimo, without knowing where you are located, I would suggest Digi-Key for the single conductor cables. You can buy most of what you are looking for there, and while you can get medical or aerospace grade connectors there, these are typically special order for them, so expect longer leadtimes for those parts.

53

This is something every DIY'er should know. Wiring is certainly my weak point and based on how many hacked up project cars I've witnessed in the past, everyone else's too.

54

Whens the DIY wiring : Poverty edition?

55

@Lou No, it's a Northeast thing.  Southern accent would look more like "dror."

56

Great post. Wiring is my weakest point and seeing this article makes me want to yank the engine out of the race car I just finished building and re-plumb and re-wire it.

Would you mind posting links or part numbers to the tools you used? Namely the wire stripper and crimper.

57
JMax Paint Garage LLC

I love wiring. Tucking a wiring harness that looks like the ones above (aka wired right) makes me sad. I love to see a nice clean wiring job in a car.

58

Twisting wires like that is complete bollocks and unnecessary

59

Thank you sir for the awesome knowledge! Electrical work is black magic to many of us and having someone simplify certain base things really goes a long way. 

Speedhunters, these articles are the best idea you've had in years. Any chance we can get Mike Kojima on board for a couple questions? Or Syd Mead? or a Falken/Yokohama/Hoosier rep?

60

Andre Simon No worries, you're doing a good job, I think.  Some just don't consider it to be a major issue. It can be essential when it comes to safety, reliablility and performance. I actually appreciate someone writes about proper wiring.

61

I have made a lot of looms for classic cars. I'm amazed by the concentric twisting and the simular gauge wire used througout. Especially the twisting would freak me out. My photo show the basic loom, nothing twisted and everything neatly taped up. Flexibility, reliability and a new look compliments a full on restauration. 


Great article, love the detail and can certainly see the need for a clean build. The choices made are all very personal and great fun to read. Good tools define the work you deliver. It's great to custom build these one-off looms.

62

Great to see stuff like this, especially as an apprentice auto electrician! have never seen it done so intricately in the wrapping etc though! (buses are alot more simplistic) 

also, what crimping pliers are those? never seen a set like that before!

63

Great to see stuff like this, especially as an apprentice auto electrician! have never seen it done so intricately in the wrapping etc though! (buses are alot more simplistic) 

also, what crimping pliers are those? never seen a set like that before!

64

scottb28 looks like I got beaten to it. If you search 'deutsch crimp tool' you should be able to find a local supplier for those cheaper crimp tools.

65

scottb28 looks like I got beaten to it. If you search 'deutsch crimp tool' you should be able to find a local supplier for those cheaper crimp tools.

66

Giulia2000ts that's a tidy job you've done there. Nice work and thanks for the kind words!

67

D1RGE glad you enjoyed the article. Watch out for more to come ;)

68

@Barry mac thanks for your constructive comment, I'll be sure to inform the F1 engineers right away. 

In the article the reasons for concentric twisting in a motorsport harness are listed - You maintain a small bundle size that maintains exceptional flexibility, while making it easy to fit the completed harness into DR25 heat shrink tubing.

69

@Doug if you search 'Deutsch DTM crimp tool' and 'Ideal Ergo Elite wire stripper', you should be able to locate a local distributor. Good sources for wiring supplies include http://www.milspecwiring.com and prowireusa.com.

70

@Lou good spotting ;)

71

KimoKalihi thanks for the kind words. It's a balancing act with how much detail we can go into without the majority losing interest.

Wiring supplies are very dependent on your location. Online you can try milspecwiring.com or prowireusa.com although both are US based, they will ship world wide.

72

scibO that's looking great! Good work separating the CDI from the ECU. Many make the mistake of mounting these together and while it wont always end in disaster, it can easily cause interference that can be frustrating to track down.

73

@norfy I'm glad the article helped!

74

TurboHippie we aim to please ;) Painting however is not one of my strengths sorry :(

75

Carl Oskar Oestergaard search 'deutsch DTM crimp tool' and you should be able to find a local supplier of that crimp tool. Generally your CAN bus should have 100 ohm terminating resistors at each end although if your bus is less than 2 metres long, you can use a single terminating resistor at one end.

76

CJC_Matty haha that right there is some gold. Thanks for making my morning :)

77

CJC_Matty haha that right there is some gold. Thanks for making my morning :)

78

@Dave E There is a lot of great information on this page - https://www.rbracing-rsr.com/wiring_ecu.html. In particular here is a picture of a splice from that page. Obviously it's already had heat shrink added though.

79

@Dave E There is a lot of great information on this page - https://www.rbracing-rsr.com/wiring_ecu.html. In particular here is a picture of a splice from that page. Obviously it's already had heat shrink added though.

80

scibO Will have to have a chat about a wire job ScibO for my 1300 :) BO0557

81

Andre Simon scibO Thank you Andre. And yes i know all about RF noise from CDI's. Ive never had one cause me drama but i know the day i do put it somewhat close to an ECU it will give me grief.

82

Andre Simon scibO Thank you Andre. And yes i know all about RF noise from CDI's. Ive never had one cause me drama but i know the day i do put it somewhat close to an ECU it will give me grief.

83

BO0557 scibO  Any time Damo. ECU technology has come a long way since you did you car lol

84

Could you show with concentric twisting how youd lay it out if you split it from one to two, not sure if this will make sense or not

85

LeathanE not sure I follow your question? Are you talking about how we make a transition when using concentric twisting?

86

Speedhunters butt*

87

Andre Simon please do inform the f1 engineers on how to add extra needless weight to there already perfect looms. 

Not really sure why flexibilty in a loom is a factor as the loom should be tied up and secured to a secure mount, otherwise your "flexibility" will add stress to your plugs and receptacles potentially pulling on the pins and damaging insides of plugs. Speaking from experience as i use these plugs everyday at avionic modifications on behalf of Airbus.

Surely if you run the wires straight the bundle size will already be small without further adding to the length and weight with this superficial nonsense. 

Fitting a loom into heat shrink tubing is also not an issue as the hint is in the name "shrink". So the loom will fit into the tube and then it shrinks down and wraps around the loom, but hey, you knew that already.

88

@Barry mac Andre Simon The thing is, your going to be moving a harness about quite a lot when doing engine changes etc which are regular in motorsports. Thats why you need flexibility and durability in a motorsport harness. Do you honestly think they would add in needless weight if they didnt think there was a good enough reason to? bringing up airbus or any aerospace as a comparison is just stupid. I work in aerospace sector too and its is completely different businesses, completely different design specs.

89

@Barry mac I'm sorry you feel so strongly about concentric twisting but it's not a technique I've invented, nor am I making up the reasons it's used. You can choose not to believe that but it doesn't make it any less true.
You do understand that concentric twisting is the technique used to construct an F1 harness? Or for that matter harnesses used in WRC, LMP1 and basically every top level professional motor racing category? The guys building these harnesses don't do it for their instagram fame - Everything is done for a reason.

Flexibility is a pretty big consideration unless you expect your harness to be completely straight - Perhaps that's possible in an Airbus but there are plenty of tight turns to negotiate in an engine bay.

The flexibility has no effect on connector reliability as strain relief techniques are used to ensure no stress is placed on the terminals. Working in the avionics industry I'd assume your familiar with techniques such as service loops though.
Good luck trying to jam a bunch of haphazardly arranged wires into a length of DR25. It's typically an exercise in frustration that ends up resembling a wrinkly scrotum. You'll also lose all flexibility in the harness so refer to my point above ^^

But here's the good news Barry - Nobody is going to force you to concentric twist your own harnesses. Feel free to use whatever technique you're comfortable with. We won't judge.

90

@Barry mac I'm sorry you feel so strongly about concentric twisting but it's not a technique I've invented, nor am I making up the reasons it's used. You can choose not to believe that but it doesn't make it any less true.
You do understand that concentric twisting is the technique used to construct an F1 harness? Or for that matter harnesses used in WRC, LMP1 and basically every top level professional motor racing category? The guys building these harnesses don't do it for their instagram fame - Everything is done for a reason.

Flexibility is a pretty big consideration unless you expect your harness to be completely straight - Perhaps that's possible in an Airbus but there are plenty of tight turns to negotiate in an engine bay.

The flexibility has no effect on connector reliability as strain relief techniques are used to ensure no stress is placed on the terminals. Working in the avionics industry I'd assume your familiar with techniques such as service loops though.
Good luck trying to jam a bunch of haphazardly arranged wires into a length of DR25. It's typically an exercise in frustration that ends up resembling a wrinkly scrotum. You'll also lose all flexibility in the harness so refer to my point above ^^

But here's the good news Barry - Nobody is going to force you to concentric twist your own harnesses. Feel free to use whatever technique you're comfortable with. We won't judge.

91

Andre Simon Hey mate, great write up!! I build large mechatronic machines for a living and cars/bikes for fun. The wiring techniques look and sound like they'd be perfect for me where I run 15m of cables through a bunch of energy chains. Also can testify, trying to fit multiple wires through a decent length of heatshrink is a massive pain if they're not arranged properly.
I'm dead keen to give these methods a go on my next build, cheers for the info!

92

KimoKalihi Hi Kimo, buying in bulk will depend on your location. I use a lot of electrical whole salers to buy rolls of cable (100m) and bags of connectors but if I need a specific cable that's not easy to get I have to buy direct from a manufacturer who usually ask for a minimum order of >2kms.

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Great job, look forward to next month

94

I've considered this as I work on military aircraft one weekend a month.  My only concern was the weight.  If you where interested I might be able to dig up some Air Force training manuals for rebuilding wiring harnesses.

95

his has been an awesome write-up Andre, massive props! Cant wait to see the next article. You have made some good points too, but nothing is more rewarding then neat, durable, serviceable wiring and a minimalist/tucked harness at the end of the day. I thought my wiring was neat, but not quite on the same par as your work. I better lift my game, pull my car apart and wire it again! My next loom will endeavor to include the techniques depicted in this article, i can definitely see the reasoning behind all this. The people that shoot the idea down are just jealous and or incompetent Crimpers out! Soldering Irons away!  I know its hard to see but, this is my first attempt at wiring...

96

his has been an awesome write-up Andre, massive props! Cant wait to see the next article. You have made some good points too, but nothing is more rewarding then neat, durable, serviceable wiring and a minimalist/tucked harness at the end of the day. I thought my wiring was neat, but not quite on the same par as your work. I better lift my game, pull my car apart and wire it again! My next loom will endeavor to include the techniques depicted in this article, i can definitely see the reasoning behind all this. The people that shoot the idea down are just jealous and or incompetent Crimpers out! Soldering Irons away!  I know its hard to see but, this is my first attempt at wiring...

97

Very interesting article.  I've been wiring for the better part of 23 years and learned it while in the AirForce.  I do find that there are practices listed that I have never used and contradict what I was taught by the AirForce, but that's not to say it's wrong.  Each application requires different methods. I am really interested to read more during you next installment.

98

Very interesting article.  I've been wiring for the better part of 23 years and learned it while in the AirForce.  I do find that there are practices listed that I have never used and contradict what I was taught by the AirForce, but that's not to say it's wrong.  Each application requires different methods. I am really interested to read more during you next installment.

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ToddHix I remember T.O.s, but cannot remember what the study guides where called.  Where they SKT's?

100

ToddHix I remember T.O.s, but cannot remember what the study guides where called.  Where they SKT's?

101

somgaet ToddHix They gave us troubleshooting manuals and how to's in 7-level if I remember right

102

Andre Simon LeathanE He's talking about how you'd break out a group of wires from the main concentric twist to run to a connector/terminal/etc.

103

scibO BO0557 drop me a email or pm on ausrota scibo for chit chat about wiring up !!

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Thank you!

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Great write-up for beginners but I had a few additional points. Soldering isn't bad, it's just that the novice usually doesn't solder a splice correctly. NASA uses soldered wire splices in the looms on spacecraft. Its also been done in Motorsports harnesses to repair or modify an existing loom. Also there is an image of solid core wire used to demonstrate the anti solder message. Solid core wire should rarely (never) be used in Motorsports, or any high vibration, or stressed wiring.

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