How to build a professional motorsports quality wiring harness

[Dan G]

Gotcha! You probably thought this was a how-to thread. Maybe it can be, but for know I'm the one asking how-to.

Does anyone know of any motorsports biased wiring how-to books or websites? If not motorsports, then a decent airplane or aerospace focused substitute? I want to improve my own wiring abilities and figured this crowd might know of some good resources, while others might also be looking for the same thing.

I'm interested in subjects like:
<UL TYPE=SQUARE><LI>strain relief loops
<LI>proper power/ground distribution
<LI>loom routing strategies
<LI>noise isolation
<LI>insulator/sleeving tips
<LI>connector theory
<LI>everything I don't even know is important[/list]

Basically everything that wouldn't be obvious to a mechE in a sparkE world. Heck most sparkEs I've met don't even know this stuff.

[Dan G]

Ok, I'll post up one link I've found with some good stuff. Details on quality crimp tools, and links to videos on how to use them properly...

http://www.heli-chair.com/wiring_101.html

Also the Motec AUS and Megasquirt sites have some good info buried within. But I'm hoping to find a "motorsports wiring harnesses for dummies" type resource.

[exFSAE]

Connector theory? I didn't know there was such a thing.

[AJoshi]

This has proved useful in the past:

NASA Wiring Standards (http://workmanship.nasa.gov/wkstds_nasa.jsp)

[Dan G]

Originally posted by exFSAE:
Connector theory? I didn't know there was such a thing.
Well answers to things like "how heavy duty for different applications", "should I use a bulkhead connector or not", "split the harness into two branches or leave it all in one connector". I realize these are pretty obvious questions and probably just a matter of preference in some cases, but I'd like to find a resource that addresses them in some way.

That NASA link has some cool stuff in it. Thanks.

[screwdriver]

Well I don't think that there's such a ressource. If you're talking about a reference-text on these topics, I think your chances of finding it are close to zero.
You will much more likely find the answers by trusting in your own engineering common-sense and in asking the field application engineer of the connector manufacturer or reseller of your choice.

Let me give you a few examples from our car.
We've split our harness in half, because our car splits in half. We've got an "easy-disconnect flange (TM)"(1) that connects the monocoque and the engine-compartment. The car will be split each time we need to get at the engine, so we need a great big connector to easily separate the two parts of the harness. That's what I call engineering common-sense.

The question which connector to use remains though. Well we know a few things:
* number of contacts
* we want a proper attachment for the conector
* (splash-) waterproof
* we want crimp contacts
* may not vibrate itself loose
Finding them is again down to engineering common-sense and finding out which connector to order can be done by talking to your reseller or the manufacturer of your connectors or simply going through some catalogs.


(1) the easy-disconnect part is a joke, obviously

[Erich Ohlde]

I'm a fan of the four-prong crimper that the deutsch connectors use.

dual wall heatshrink for strain-relief of connectors

i'll type up a nice big list here in the near future but right now i'm prepping the car for an autocross...GO APRILIA's HAHAHA!

[Bazanaius]

I know the majority of F1 teams follow aerospace standards so that's probably a good place to look. At least adverts for F1 sparkE's specify knowledge of Aerospace standards.

also, somebody has put together a loom that integrates the wiring into a fibre (carbon I think) loom, with connectors integrated into the ends, making it light stiff and circular, plus easy to move about. Not necessarily on topic but might be interesting, I'll try and dig out the link.
B

[Prohet][]

I work with cables in defence (aerospace) and use MIL-STD codes and equipment. Some crimp tools can easilly cost $1k and alot of the small splices and terminators cost like $30 a piece so to have a truely professional cable for Formula SAE I think it out of the question unless you have some really good sponsors.

We factor in that something like a 25pin D-Sub connector on each end with each pin connected to a cable will cost around $2000US to design and manufacture.

[Julian Choquette]

For next year's car, we will be doing the wiring harness layout in CATIA. We already use high quality components, but the wiring could be better. And depending on the feasibility of it, we actually might pass the wiring through the walls our monocoque. Right now, we have a big 30mm OD loom that passes in the interior of the cockpit. One of the judges didn't really like that.

I'd love to see more documentation on professional aeronautics wiring (or F1).

Here's what we use:

Raychem (Tyco) SPEC 55 aeronautics cable.
Souriau aerospace connectors (MIL-DTL-38999 series III)
Astrol Tools crimper
CATIA Wiring Harness:
http://www-03.ibm.com/solutions/plm/doc/content/bin/plm...rical%20flyer_LR.pdf (http://www-03.ibm.com/solutions/plm/doc/content/bin/plm_05-PLM-001610_P2_Electrical%20flyer_LR.pdf)

[Igor]

Even though spec55 wiring is the best stuff, it's quite expensive for teams on a budget. I think FlexLite is a good alternative. Easily available through Farnell in Europe.
Also if you don't have enough time to completely plan your wireloom ahead of time, one made using adhesive lined shrink sleeve is a nightmare to rework. Thus it might be easier to use non-split corrugated tubing and the special junctions that come with it. It's also dirt cheap.

I also think there would be very few books going deep into autosports wiring, people are making tons on money on the racing looms and don't want others to know how to :-)

Some other tips:
Use crimped connector terminals and buy the proper tools ($$$). This is worth fighting over.
If using Faston connectors, use a ratchet crimper. NEVER EVER the sheet steel cheap tool.
Turned connector terminals survive more abuse than stamped.
Don't use terminals that are too small, they'll bend and break under mating abuse. (and are hard to work on)
Use waterproof connectors
Use enough connectors, you'll be happy you did later.
Don't use solder on a wire before crimping, it makes the connection worse.
Use strain reliefs and use them in the right places. (on the wire not closer than 5cm to the connector)
Don't use gold plated terminal for anything carrying high current. (you can for signal wires)
Do calculate the temperature rise above abient due to the electrical current for big loads.
Don't use wires that are too thin, even if they carry little current. They need some mechanical robustness as well.
Use firesleeve (don't remember the exact name) for wiring close to the exhaust.
Get tie-wraps that you can also undo
Ask a practical EE for his judgement on noise, shielding and ground layout.
Etc...

Sorry to rant in your post Dan, you probably already know most of this, but there are still too many cars breaking down due to electrical issues.....

Igor

[Rickertsen2]

The Question is, are 'autosport'/aerospace quality harnesses necessary in FSAE or will a production car quality harness do just fine?

Sure a full out harness with autosport connectors, mil spec Teflon coated wiring, and DR-25 covering looks cool, but can you justify a wiring harness that costs $1000 on the cost report? Does it make you go any faster? It might be a little but lighter but not by much. You can build a cheap harness that is reliable and durable enough from production car grade connectors, wiring and sheathing if you put some thought into it.

Just because its done in F1 or airplanes does not mean it should be done in FSAE. Our competition has different problems goals and objectives. We are not dipped in money.

[Mike Cook]

A lot of things are possible. Doesn't mean they should be done, asshole.

[Erich Ohlde]

this isn't club racing. we are trying to be professionals. We do things the correct way and we like to know how to do things the correct way and leave out the redneck engineering if at all possible.

[Dan B]

Some good info here
http://corner-carvers.com/forums/showthread.php?t=34419

[Erich Ohlde]

one way to clean up the messy fusebox/relays that are typically used is the power distribution box that motec came out with also the Ole Buhl Racing box is amazing and is used by a number of ALMS and LMS teams.

one huge thing is the current sensing technology that allows limits to be set and the power will switch off if the current exceeds the limit.

[mjdavidson]

I think Rickertsen and Flat Black have a point. Formula 1 level equipment doesn't fit in an inexpensive prototype. You have to consider the big picture.

Does your team have enough money to build such a wiring harness? If your team is 100% dedicated to performing well in the competitions there are definitely better places to spend money. A light, inexpensive, functional wiring harness is possible with some thought and ingenuity.

On the other hand, if your priority is to learn about 'professional/aircraft/F1' wiring go for it. "Because I'd like to learn how to do it" is a decent justification to do something. Just don't sacrifice the rest of the car if you want it to succeed.

[Superfast Matt McCoy]

We're really talking about a spectrum, with F1 cars on one side, and Flat Black's piece of shit Camaro on the other.

FSAE is a harsh environment with a lot of heat and g's and things that make bad connections break, wires melt, and overheated electronics not carry enough current to restart after 11 laps. If you're aiming for 40th place, you can probably build your harness at the auto parts store.

If you're aiming for 1st, your wires need to be lightweight and heat resistant, connectors need to be lightweight and reliable with good conduction and well sealed, and the harness has to be laid out with foresight and care. If you've accomplished that, you are going to be much closer to F1. You don't need to be at F1 quality, just closer to that than the alternative. Mil/aerospace spec allows you to trust the part quality is at least what you need.

Also, It's my opinion that the only connectors you should have fall into two categories 1) sensors, injectors, coils and others that use existing engine connectors and 2) One connector for all engine wires, one for all dash wires, and one good one for the brake over-travel switch. Two big connectors, and one small important one that you can spend a little extra on. Think Deutsch. I don't think you need expensive crimpers and individual wire connectors.

[jdstuff]

Well said Matt. A large amount of the entry-level motorsports jobs out there are DAG positions, whoes responsibilities include maintaining the integrity of the electrical systems. I think that the knowledge we're talking about here is quite valuable to any ME looking to break into a racing career. In general, I think it's also something your average ME graduate is lacking.

A full-blown Atlantic/ChampCar/IndyCar harness will range in the tens-of-thousands of dollars, which obviously exceeds any FSAE budget. But the principles used in its construction can (and should be!) easily carried over to FSAE application. Even if your team absolutely cannot afford anything from Raychem/Deutsch/Autosport/etc, just knowing their products and how they should be used would be a bonus!

[Wesley]

I think most engineers are retarded when it comes to solving a problem that has already been solved.

In that regard, a little 'backwoods racer' isn't a bad thing to have in you. While Engineer A is finding the best way to sketch up a set of wires in a cockpit to minimize weight and avoid heat sources and make a solid model with proper mass properties, Racer Joe A has put some wires in based on previous experience, noticed they were getting a little hot, rerouted them, and run for a month in the time the Engineer decides on a loom color in the modelling software. Wires are cheaper than software, and who says the designed version will work out of the box anyway?

Just because the testing was done without an engineering degree doesn't invalidate it. I see too many uppity engineers who think you can't do anything without a degree, and look down on people who consistently go faster than they do because they don't do the mental masturbation. Being a good engineer is knowing when to calculate and when not to reinvent the wheel.

Math is great, and computer software is terrific. But you're building a car, not a simulator. Look at what's been done, regardless of who's done it, and choose an appropriate compromise to suit your needs.

[Brian Evans]

I think the point you may be missing, Wesley, is that FSAE is far less about building a race car than it is about learning how to design and build a race car. You can either buy a harness from one of about three guys I know who build top notch ones, you can just buy a car loom and dash/data logger from Pi or similar, or you can learn how they did what they did and do it yourself. I have a nice Pi Pro dash system sitting on my desk, with beautiful Lemo connectors, and in my three race cars I use 1/4" spade lugs. Two ends of a spectrum. FSAE could use either - if it was jusifiable and it made sense!

Brian

[Chris Allbee]

Its the same old argument: Do you want to learn as much as possible, or do you just want to go fast on the track?

the same old argument is also off topic....

[Mike Cook]

You can learn a lot and still go fast on the track. It takes good preparation, good notes from year to year, good leadership/mentors, and most importantly attention to detail. Building a good harness doesn't necessarily take a long time. It usually will if you don't know what your doing which is why I think a lot of people come here and ask for help.

[lozo]

Hi Guys,

I hope I'm not posting in the wrong thread, but I'd like to ask a question re: crimpers.

We are keen to purchase a new crimper for our connectors (mainly DTM and deutsch Autosport). I have looked through the website for dmctools, and have decided to buy the AFM8. Does anyone know which positioner I should get to go with this crimper?

I've looked through all the datasheets and now I'm even more stumped than before!

Thanks!

Richie Wong
Electron
University of Auckland FSAE

[Damon Pipenberg]

lozo,

I had some trouble with this myself. I would contact Deutsch or your local distributor directly and ask for them to specify the DMC part numbers for the correct positioners. You could also try asking DMC, but when I tried that, I ended up with the wrong positioners. You may have better luck. I believe the AFM8 is good for size 20 and smaller contacts. The AF8 is nice because it is available with a turret head that adjusts to different sized contacts. I don't know if they have an option that would work with all of the contacts that you will be using, but it is worth asking about.

[Courtney Waters]

Dan G,

I stumbled across this page today while looking for some connector info. Lots of good tips for doing sensible aircraft wiring (splicing, connectors, wire sizing, crimping, fuses vs circuit breakers, etc) which could easily be applied to a FSAE car. Sure, it's not quite an instruction manual on building a modern "motorsports" harness, but if it's reliable enough to keep a plane in the sky, it ought to suffice for a FSAE car. The articles actually go into some technical (but easy to understand) detail, unlike most of the home-brew stuff you find on the web.

http://www.aeroelectric.com/articles.html

[Dan G]

Excellent resource, that's exactly the kind of stuff I'm looking for. Thanks Courtney, keep them coming!

[rjwoods77]

These are some nuggets right here off that link.
I think I might pick the book up.

http://www.aeroelectric.com/articles/rules/review.html

http://www.aeroelectric.com/articles/CrimpTools/crimptools.html

http://www.aeroelectric.com/articles/terminal.pdf

http://www.aeroelectric.com/articles/excerpt.pdf

http://www.aeroelectric.com/Catalog/pub/pub.html

[Sebastiaan]

I have build the harness for the delft team for three years now and made a lot of mistakes, but right now we have a harness which didn't fail once although we tested for hunderds of miles.

What I found out is that most of the time it is worth it to spent a few euro's more on a connector that can take the abuse. We design our harness to have as few connectors as possible in the first place, and than go on by looking which connector to use for the different purposses.
Make sure you know how high the currents are in your harness and use that to choose the the appropriate thickness for your wires. Ohms law shouldn't be to difficult for an engineer I hope...

Most important though is fabrication. A well designed harness is worthless if someone is not able to crimp the pin on right. So make sure that no pin is crimped on a wire which is not easy to reach. Also soldering is nothing to be scared of. We solder every single connection on top of the crimping. It's all in the strain relief. Fix your harness every 10 to 15cm, of course away from any sharp edges.

One more thing: If your team runs a single like we do. Make sure that you spent at least twice as much attention to your harness than the four cylinder guys do. Belief me, you'll need it.

[ERS]

Probably not a problem with the DAS type/MIL spec connectors as the contacts are effectively shielded from heat, but soldering crimped connections generally isn't best practice. High current = heat & can tend to melt the solder and then interesting things can happen. Something to be aware of

[murpia]

I have had good results recently with the Deutsch IMC series of connectors. Cheaper than proper Autosport connectors, easy to seal to a loom with adhesive-lined heatshrink.

http://uk.rs-online.com/web/search/searchBrowseAction.h...294905148+4294953928 (http://uk.rs-online.com/web/search/searchBrowseAction.html?method=retrieveTfg&Ne=4294957561&N=4294905148+4294953928)

Best of all you can use these fantastic crimp tools set:

http://uk.rs-online.com/web/search/searchBrowseAction.h...294743606+4294955288 (http://uk.rs-online.com/web/search/searchBrowseAction.html?method=retrieveTfg&Ne=4294957561&N=4294743606+4294955288)

Regards, Ian

[IndyWiringServices]

I have nearly 10 years experience building wire harnesses for motorsport applications (from karting to IRL) and recently established my own wiring company. My goal in my new venture is to provide top quality looms using top quality materials for club pricing. Anyway, I'll tell you what I know.

Materials you should be using:

Raychem 55A or 55M spec wire - I normally use 55A 600V primary wire, unless the application demands lightweight, then I use 55M (motorsport specific) 450V primary wire. 26AWG can handle 4 Amps at 30 deg C, usually the contact will be the amperage bottleneck. This stuff is a bit more expensive, but you probably won't spend more than $20 for a large loom. Worth it.

Raychem Ray90 shielding - This pre-spread electrical shielding is really only necessary in high noise situations, but also provides a healthy bit of mechanical protection to the wires. When canceling noise, be sure to attach to ground and isolate from car chassis. You can carry the shield through a pin in a bulkhead connector. Ray100 provides 100% coverage (as opposed to 90%) and Ray101 is more flexible, but I don't think they are worth the extra cost.

Raychem DR-25 heatshrink - This stuff provides excellent chemical and mechanical abrasion protection. It seems pricey, but it can prevent costly repairs and generally isn't a big contributor to the full price of you loom.

Twisted pairs - Twist your own 55 spec wire using a drill and a heatgun (to set in place) for RS232, CAN or twist signals with ground in noisy areas. Be sure to fully twist from termination to termination. Spring for pre-made twisted/shielded/jacketed pairs (available using 55 spec wire) for highly noisy conditions (near ignition coil/engine).

Connectors - The best I've found are Deutsch Autosport connectors (based on Mil Spec connectors with no backshell). There are several lines of connectors for any application. These are expensive however and can really start jacking up your total price up if you use them for every little sensor. That is the way to go if you can afford it, but I suggest using these for connections to equipment, bulkhead connectors (engine/chassis splits) and going for something cheaper for your sensors. I have had good luck with SureSeal, Binder and Deutsch DTM connectors for sensors. Lemo connectors were once standard, but I tend to avoid these if I can because they are nearly as expensive as Autosports and do not have the same quality. They are easier to rework (opinions vary), easier to terminate shields to body and have a push/pull locking method rather that locking collar.

Strain Relief - If you use an Autosport, give that thing some proper support with Raychem or Hellermann heatshrink boots. Use epoxy to apply it to the connector and cable, but do not apply epoxy directly to boot, it will overheat and lose it's adhesive qualities. Quality glue lined boots are available but are expensive. Use a goo heatgun (Steinel makes good ones) and use a nozzle to direct the heat.

Use proper techniques:

Concentric layer twisting - This is where skill and experience comes in big time. It took me a while to really master this (especially when dealing with CAT5 cable, twisted pairs and a large number of wires). There is a science to it, but at some point it becomes an art as the chaos of the real world defeats theory. This is very important for a quality harness as it increases flexibility and durability, ensures that one wire is not stressed more than another, eliminates the need for harness jigs and allows end user to bend cable any way that is needed.

Removing heatshrink for cable - We've all done it, cut into some heatshrink only to see we've cut into the wire insulation as well. Try just scoring the heatshrink and applying heat, watch it split.

Electrical shielding - Be sure to connect shielding to ground or it isn't doing anything. It is normally a good idea to keep grounds from different devices separate. Often electronics have different ground groups that should remain separate to avoid interference.

Power handling - Be sure to plan for the worst case scenario when deciding how to route your power. Overkill is the name of the game. Use several pins for power and ground when a heavy load is expected. Use a gauge or two higher than you think you need. I always crunch the numbers to make sure and then err on the side of caution. Always get the detailed specs for the materials you are using. Avoid always on connections, switches are almost always a good idea.

Service loops - It is important to allow for slack and play when a heatshrink boot behind the connector. Again, this ensures no one wire has more strain than another. Also, as the name implies, it allows for rework without lengthening the wire. This is accomplished by simple created a loop in the wire before termination. There are specific techniques that I won't go into detail here.

Crimped splices - solder is your enemy, always use crimp splices where possible - be sure to isolate splice

Kapton tape - High temp tape should be used to protect wire from heat when strain relief boot is shrunk. PTFE Plumber's tape can also be used.

Custom fit - It is important the wire harness fits in place correctly to avoid odd angles and mechanical rubbing. A "mock-up" harness should be produced with rope or cable and laid on the car before designing the harness to ensure lengths are correct. Maintaining that spec is as important as any other aspect and care should be taken when constructing the harness.

I could go on and on about technique, but I can't give everything away.

Proper tooling: 55 spec wire is multi conductor so keep that in mind when selecting a stripper. Ideal T-strippers do the trick. A Daniels AFM8 crimper is a must (M22520/2-01). Flush cuts are also important as to not crush the wire you and snipping.

Resources:
www.ismotorsport.com (http://www.ismotorsport.com) - materials distributor
www.deustch.co.uk (http://www.deustch.co.uk) - Autosport tech specs
Wire Twisting Chart (http://books.google.com/books?id=MpJRAAAAMAAJ&pg=PA32&lpg=PA32&dq=number+of+wires+in+concentric+layer&source=bl&ots=wSFZ6fBg1a&sig=Yr-dGtijUTy3h6oBEbSU07HJyRE&hl=en&ei=rWeeS_O8MY34NbzdkIkF&sa=X&oi=book_result&ct=result&resnum=2&ved=0CAoQ6AEwAQ#v=onepage&q=number%20of%20wires%20in%20concentric%20layer&f=false)
indywiring@gmail.com

Please note that I have no commercial deals with any brand I've mentioned. I could go on, but I better get back to work. Feel free to contact me with any specific questions.

[IndyWiringServices]

Originally posted by lozo:
Hi Guys,

I hope I'm not posting in the wrong thread, but I'd like to ask a question re: crimpers.

We are keen to purchase a new crimper for our connectors (mainly DTM and deutsch Autosport). I have looked through the website for dmctools, and have decided to buy the AFM8. Does anyone know which positioner I should get to go with this crimper?

I've looked through all the datasheets and now I'm even more stumped than before!

Thanks!

Richie Wong
Electron
University of Auckland FSAE

I can help you with that, the part numbers listed below are from DMC:

K40 - AS series 22AWG sockets
K42 - AS series 22 AWG pins
K1414 - ASL series 22 AWG sockets
K1413 - ASL series 22 AWG pins
K1S - AS series 20AWG sockets/pins

Those five should cover you for almost anything with the AFM8 (not including ASU, ASC, ASDD).

[Dan B]

I didn't see this posted
http://rgl.faa.gov/Regulatory_...ILE/Chapter%2011.pdf (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2043.13-1B/$FILE/Chapter%2011.pdf)

Here is the whole thing. There is lots of good info in there.
http://www.faa.gov/regulations...ion/documentID/99861 (http://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/99861)

[oz_olly]

Indy Wiring Services (you didn't tell us your name).

Thanks very much for all the information above. I think you have hit the nail on the head as to answering the original posters request for practical wiring loom advice. The idea of mocking the loom up with ropes etc is a great one. Hopefully many FSAE teams will benefit from your experience and willingness to share it.

Cheers

[IndyWiringServices]

Oh right, didn't mean to be impersonal. My name is Jeremy Gibson, and I hope the information posted helps some FSAE teams as well. I've done some work locally with the Purdue guys and I always love to see students have a desire to do things the right way and really get down into the details. Happy to help.

[Erich Ohlde]

concentric layer twisting?

[J. Vinella]

On the note of strain relief:

http://uk.farnell.com/productimages/farnell/standard/42749250.jpg

These types of back shells provide good strain relief also give you a good place to ground your shield if you are caring it through. Wrapping the wires with some rubber tape before you clamp you down them is recommended.

When it comes down to balancing weight with "rugidness", think outside the box. What you are trying to do is not complicated.

[IndyWiringServices]

Yep, concentric wire twisting. It isn't as complicated as it sounds. If you check out the "Wire Twisting" link in my long post, it will give you an idea. Basically it is layers of twisted wires. For example, 6 wires will twist around one wire "perfectly" given they are all the same diameter. I say perfectly because the last wire in the twist will always butt up against the first wire (as long as you make sure no wires cross over each other in the lay). The next perfect layer would consist of 12 wires twisted in the opposite direction (layers are always twisted in the opposite direction of the previous layer so no wires are lost in the interstices - meaning wedge-shaped gap between two twisted wires). Some other perfect combinations are 3+9+15 and 4+10+16, you'll find the difference in wires for each consecutive layer will be 6.

Often, fillers (additional wires) will be introduced when the number of wires in a branch does not equate to a perfect lay. For example if you have 20 wires of the same diameter to twist you would add four fillers of the same diameter twisting in a 2+8+14 pattern. It becomes even more complicated when wires of different diameters are used. One way to do it is to twist a number of smaller wires to approximate the diameter of a larger wire in order to twist them together.

Concentric layers are used to increase flexibility which allow the resulting wire harness to be safely flexed in any direction, eliminating the need for a 3 dimensional rig when building the harness.

Send me an e-mail, and I can send you some pictures and additional details if you are interested.

indywiring@gmail.com

[jordan.k]

Some of the little details that have helped us out the most have been using a color code throughout the entire harness (i.e. engine sensor signal wires are yellow, sensor ground wires are blue) and using labels at every connector. What we have used is a Dymo labeler and just placing clear adhesive lined shrink wrap over the label. Additionally, a reliable harness can be made of components bought in town. Deutsch DT series connectors are easy to work with and while they may be a bit larger, they are readily available (Harley, Caterpillar and Bobcat to name a few) and proven to be very reliable and easy to assemble/disassemble. Also, the Motec, OBR and Cosworth Power Control Module's are awesome but out of the budget for many teams which is not a problem. Automotive relays (Bosch & Hella) are also readily available, an industry standard and work very well when coupled with the proper socket (http://www.alliedelec.com/search/productdetail.aspx?SKU=5871001). Proper planning with a simple schematic with every wire goes a long way towards having a clean wiring harness with minimal rework.

Jordan Krell

SDSM&T FSAE
Electrical & Instrumentation

[Tickers]

The F1 team I worked at on placement didn't have a colour code for wiring. All wiring on the car was white. When I asked why I got a very good response:

When using a colour code people will work on the car without consulting drawings. If you make every wire white the sparkies are forced to use the drawings and not make any assumptions (eg, red could be 3V, 5V, 10V, 12V or more). Assumptions are bad, they lead to mistakes. Your mechanics and sparkies are essentially just tools, not engineers.

The only place there was a colour code for wiring was on flying leads from sensors, so it was possible to fit the sensors with connectors.

[IndyWiringServices]

Interesting, I had never heard that reason for going with all white wire. I had always heard it was to keep the cost of wire down by only have to stock one color. Trying to keep up with stocking many different colors can increase cost more than one might think.

A way to simplify the build without allowing others to make assumptions based on color code is to give each connector on a loom a specific color (when the number of connectors is limited to the number of colors you have available). This allows you to terminate the main connector and then route the wires appropriately. In the case of multiple main connectors you can assign a color to each one of those and terminate them last.

Also, you can use small bits of colored heatshrink to color code the wires for pin number (black=0, white=9, etc).

[Nicky]

After going through the posts in this thread, I've began doubting the techniques i used in making this year's wiring loom. Kindly put my mind to rest. Below are the components i've used.

We've been reusing connectors (injectors, temperature, Ignition coils & modules) and cutting and crimping them into the new harness each time. The reason being that we haven't been able to find these connectors here at India. Importing them would be out of the question as it would be way too expensive. We set out trying to make a wiring harness which could be reused.

We've used a pcb to centralize all power used. Also all sensors are routed on this board. The high load and sensor parts are separated. Its got a 75um thick copper track, which is the highest available in the Indian market. WE tested the board for 40 amps. We've used Goodsky 20Amp solderable relays and 3.5mm screw-in terminals.

Screw terminals were used to reduce crimping and enable a kind of plug-play for extra sensors or connections. Again, I'm not sure as to how reliable screw-in terminals are in terms of being vibration resistant. I did attach a wire to this and tried tugging on it, it was stronger than a crimp connect.

The only type of strain relief i've provided is to harness the entire bundle to the board so that no stress is laid at the point where the wires are connected to the terminals. And this worries me cos most of the restraining i've done is using tie-wraps and velcro. I haven't placed any loops but have ensured that the wires aren't tensioned. Is this enough or is it mandatory to exclusively provide strain relief??

Coming back, this is the type of relay we've used. And as i said before, i don't know how these'll survive although the current rating is apt, but i'm worried for although i've seen certain circuits use them on automobile applications, i'm still worried for i don't know any team thats used this before and therefore is a first for us.
http://www.chansin.com.cn/admin/uploadpic/20053302343670035.jpg

this is the screw terminal we've used
http://static.sparkfun.com/images/products/ScrewTerminal.jpg

this is the local connector we found and 've used on all our connectors, we did melt plastic in the wire side to prevent them from popping out. I did have one wire break from the crimp pin and it was real tough working with it. As you can see I shrink wrapped the whole plastic case and the connector back. This, I believe keeps the wire from bending at the connector due to connect-disconnect usage and also provides a space where i can mark the names. Over the shrink wrap is a layer of plastic-braid.
http://i54.tinypic.com/wvc1s3.jpg

Also, are using multi-conductors a risk? Also are cheap 20awg China made teflon coated wires good enough? I believe these wires have lesser strands and the thickness of the plastic sheath is also considerably less. Also, do you redo wiring harnesses every year or is the same harness more or less re-used? Has anyone tried using Field Effect Transistors(FET) instead of relays????

Operating with a very low budget, we tried making our wiring reusable, but i doubt if it'll sustain 2years. I've heard motec customises wiring looms for each specific lengths. But I haven't come across a team that has done this and moreover again the cost plays a role.


Regards,
Nikhil
Electricals & DAQ
Ashwa Racing
www.ashwaracing.com (http://www.ashwaracing.com)



Insulation tape is your worst enemy!

[timWHS]

hi guys,
stumbled accross this thread searching for something so thought id chime in.
I have 20 years experiance of harsh enviroment wiring harness manufacture. worked those 20 years in Formula one, and funnily enough like our friend Indy ive just gone solo myself...in my case jumping before i was pushed though.
Anyways, on the subject of crimp tools, assuming you are talking Mil circular connectors, the tool you want is definately the MH860 (M22520/7). This tool was designed as a single alternative for the AF8 and AFM8 tools, and is by far the more diverse of the 3. it will have positioners (adaptors) for just about any circular mil series of contacts 30-16AWG. It will also do lemo, which is quite common in motor racing, including the lemo F series.
on colour coding, i think the reason for going all white for most is simply that of cost. As it happens the team i worked for did use colour codes, but the colour denoted the wire gauge..ie 24awg and 14AWG would be yellow (international resistor colour code). this is purely a manufacture aid, and quite sensible id say...i certainly intend to continue this practice as you know with certainly what the gauge of wire is when you are stripping (its not always obvious when you have 100 wires of various gauges all in the same colour)
hope that helps someone.

BTW Tickers, your comment made me chuckle ..."Your mechanics and sparkies are essentially just tools, not engineers."
Well, maybe, but when it comes to wiring, listen to the technicians, not engineers!!

[vgallas]

It is interesting that this post has been started. I always find interesting to go around comp and check out other teams electrical systems to always find out that most teams do their electrical as a last minute deal and don't put too much development into it, which amazes me since it is a critical component of the car. I have been building wiring harnesses for our team since 2005 and during this time I have refined our harness to match the requirements for our team in terms of cost, reliability and serviceability. It is obvious that you wouldn’t want to build your harness from the supplies you can find at your local auto parts store, since most of these components are cheap and crappy. Trust me, they will fail! Do always stick with MIL spec items when possible. Always take your time to PLAN ahead hoes your wires should be routed, bundled and shielded when being installed in the car. How many times I have seen teams melt their wires because they run it too close to heat sources..

So here are some pointers.

Always stick with MIL Spec Materials. This includes MIL Spec circular connectors for bulkhead connectors of the ECU and critical components. These connectors are normally gold plated contacts and will be offered with a built-in strain relief together with a weather proof design is desired. You can use crimp style connectors on these, but the tooling is really expensive as mentioned. Solder type connector work just fine, you need to ensure that you solder it properly following the proper soldering techniques and preparation, just as if you would weld something. Yes I am aware some will say that soldering doesn't work due to vibrations, that is true if you let the wires be pulled and twisted and let them move around the soldered tip. This is where the strain relief prevents these movements so it works just fine. Just keep in mind that solder connectors are used in many road vehicles for the military as well as airplanes and many of what you could call "high end applications". Also if you think these connectors are too expensive, there is really A LOT of options to look into from Allied or Mouser alone. In average we used to spend about 500 in bulkhead connectors for the critical parts, now I have re-designed the systems so that I can use a different connector as well as the quantity of them and I have decreased it to an average cost of 380 per year in the main connectors alone. For the rest of the car you have other viable solutions that still provide a good interconnect design with lower cost.

For wiring, always use MIL Spec. Have I mentioned to use MIL Spec items enough? There is a reason here, MIL spec items not only have to follow strict engineering specifications but also they have to follow the most high quality standards possible. So you will know you won’t be buying crappy stuff. Also, for wiring specifically, MIL spec wiring offers the lightest wires for their size per foot. This is mainly due to the shielding material being made out of Teflon and another chemical that allows for the shielding to be very thin and very resistant. Also the metal strands inside the wires follow a MIL Spec determination on the amount of strand twist per length that is different from the crappy stuff you can buy locally. This different twist is optimized for each wire size, this improves the metals strands ability to deal with vibrations, kinks and any type of mechanical loading you can think. To give you an example, in one of our old FSAE cars, the 2004, I had to re-wire the car after I had found out that the wires used, which were the cheap crap you can buy, where breaking internally from the abusive environment that a racecar imposes. I had the signal wire form the throttle body have many broken sections in its path form the sensor to the ECU. Thus after finding this I simply trashed the old harness and built a new one from the ground up.

Tooling. Here is yet another area most people overlook. I see many people trying to strip wires with their pocket knives, or a very dull and abused set of cutting pliers that is used on the construction of the car. The problem with this is that although you will be successful in removing the insulation, in the process of not using the proper tool you will pull the insulation along with some metal strands away and fracture many metal strands near the area where the insulation is cut, creating a very weak zone right next to where the wire is going to be crimped or soldered. Then when the wire is moved, or suffers from vibrations, it will quickly break at this point. Many times it won’t actually break-off, but rather stay connected by a few strands. When this happens there will not be enough strands left to conduct the current properly, thus increasing the resistance and causing those hard to find intermittent faults. In our case my solution to this problem is a rather simple one. Make a toolbox for wiring only. All the tools in that box should be only used to for wires. And even so, I normally have different sets of wire strippers. One for large, heavy gauge wires, medium sized wires and the small ones such as AWG20 or 22 that we normally use in the car for sensors signal and small current loads.

Planning. There are so many teams that do not plan their wiring harness properly. They simply build the harness as the car is being put together, so not only there are wires running all around the car but then when something needs to be repaired there is a wire in the way or something in the car damages the wires. It doesn’t take too much to so a simple wiring schematic of the electrical items in the car and where each pin connects where. By doing this you can foresee where the wires will have to run along the car and what will be present to create problems. Do plan on making your wiring system composed of many subsystems. Make an engine wiring harness. Then make a chassis wiring harness. These two should interconnect with a good quality connector. When bringing wires into a fuse box or dash, use a connector here as well, essentially you want to build your wiring harness in a well lit bench and mount them into the car as parts that get added to the car. If you do a proper planning on this, you should be able to make it so that anytime a repair needs to be done in the car, you can easily remove a wiring from that section if necessary and avoid having accidents that damage the harness. Also in case you do have a problem, it is a lot easier to repair the harness when it can be removed from the car and serviced on a table than trying to figure it out inside and around the car.

Shielding and insulation. Many teams don’t even bother shielding their wires, bundling them together or understand why this is important. Let’s not even bother spending time talking how crappy a wiring harness looks when wires go all over the place and are not bundled or shielded properly. In terms of shielding, this doesn’t just meant wrapping all the wires together. It also means electromagnetic interference shielding. You will have plenty of issues if you’re sensitive signals are not connected from the sensor to the ECU using at least a twisted pair shielded wire. These wires have two independent wires twisted together with a metal jacked, or ground, shielding around the two twisted wires. This is done so that the metal jacket is grounded at a common point and provides an electromagnetic shield for the wires inside, thus preventing the signal from being lost of distorted due to electromagnetic interference. These shielding is critical to sensors that output a low voltage, sinusoidal signal, such as the crankshaft and camshaft sensors. Sensors that work on voltage levels and digital pulses such as a throttle position sensor can run fine without an electromagnetic shielding since their signals are at higher levels. But do insulate and twist the communication wires, MOTEC has set specifications as to how their CAN signal wires should be twisted, I have found that using a twisted pair shielded wire is the easiest and most reliable solution for communication wires. CAN will work just fine normally, however if the signal wires are suffering from a high level of a electromagnetic interference the CAN protocol will timeout causing connectivity issues.

Bundling. In terms of wiring bundling, many teams rely on the good old electrical tape-I just came out of high school approach. Do not do this. Electrical tape for bundling wires works just fine on the wiring harness of your Ford or Chevy, but electrical tape looks crappy and also the heat combined with the oil and fuel will quickly deteriorate the glue and fall apart and be all ragged just like that nasty dress that your aunt insists on wearing for family gatherings even thou everyone has told her the dress is just too old. You should bundle wires in a planned manner. Don’t just run each wire were it needs to go, think about a main line for running all the wires, then do branches and sections that break apart from the main harness onto other parts as needed, this is where you will make you’re electrical show that it has been planned and built accordingly. In terms of what to use for wrapping the wires you can either heat shrink the entire harness which is very professional and extremely strong in dealing with the environment of a race car. Or you could use a more realistic approach that is cheaper per foot than the heat shrink and allows you to easily service and modify the harness when needed. In this case I have found that using a split-braided nylon sleeve works great. I did consider using heat shrink, but due to the nature of the FSAE program, you are always going to want to add an extra sensor, or do a modification you think will improve the car, so a split-braided sleeve lets you do that really easy. Plus the weight added per foot or the split-braided sleeve is much less than that of the heat shrinks. You may argue that the heat shrink can provide better resistance to heat and chemical damages, which is true, but if you plan your wiring routing properly, heat and chemical damage should not be a problem.

Lastly, installation, AKA Zip-tying. When installation the wiring harness do think of the items near the harness that could come in contact and damage and then determine what needs to be done to prevent this. If the wires are bundled properly and the harness is zip-tied properly then your wires should only be allowed to move, or vibrate, very little near the connection to a sensor or connector. The main idea with using zip ties to hold the wire bundle in place is that you want to place zip ties so the harness cannot move around when the car is being driven. Remember if the wires are not flopping around then they won’t be stressed mechanically and damaged in the process. Of course do use good judgment when using zip ties. Don’t tighten the zip tie so hard as to damage the wires but also don’t leave so loose that the wires can move about. Also consider in doing a zip-tie clean up right after the car is considered done. You will always see places that have a zip tie holding a wire then not 2 inches from it you will see another zip tie holding another wire on the same tube; cut those two zip ties off and place a single zip ties in the middle to hold those two different wires on the same tube, get the idea? A simple method I develop here was to use white re-usable zip ties when first installing the electrical system in the car to mock where each part of the harness should go and how it should be restrained. Then after eliminating those that are not needed go back and use the regular zip ties and remove the re-usable ones.
This is just some pointers I can think at the moment. Of course if anyone’s got a question, feel free to ask.

[Mazur]

No paragraphs, no read, mkay?

[BeunMan]

On the wire:

We use precoded/precut wires with the exact text on them. It is more expensive but saves a lot of time finding errors.
The downside is you have to do the wireing in the cad model of you car. This does minimise the trouble with reserving space however for wires and the "WHY?! did you put a bolt there!" and "I need more space for electronics" problems.

[Tickers]

20/22AWG are not small wires. 28AWG wire can handle an amp, and weighs considerably less than 20/22. 30AWG would be good for sensor wiring, if only there were more options for connectors.

[Nicky]

Have you tried multi-core wires with shields??? We tried them this year and really haven't got a lot of testing so theres no telling how reliable they are. We've used 2,3,4,12 and 16 cored wires in our car with a shield on them, but since we had to make some route changes at the last moment we couldn't ground many of these shields.

We switched from using single wires for each pin of each sensor to these. Since this is a first for us, I'd like to put my mind to rest.

Regards
Nikhil

[Tickers]

An ungrounded shield provides no protection from noise.

There's no problem with using multicore wire, just try to keep it mil spec for the best quality stuff.

[Itcetera]

Just thought I would add A good place to find weather proof connectors and connectors of all types as well as relays, circuit breakers wire protection etc. The Electrical Depot.com (http://theelectricaldepot.com) they will ship out of US if you call them.

[murpia]

Originally posted by IndyWiringServices:
Service loops - It is important to allow for slack and play when a heatshrink boot behind the connector. Again, this ensures no one wire has more strain than another. Also, as the name implies, it allows for rework without lengthening the wire. This is accomplished by simple created a loop in the wire before termination. There are specific techniques that I won't go into detail here.

Hi 'Indy',

Can you elaborate on service loop technique? I've got the rest covered but can't find much info on the right way to do this.

Thanks, Ian

[IndyWiringServices]

I'll do my best to describe it. After you connect all the wires to the connector compress the connector toward the cable so the wires bow out. I basically "hook" the wire with the hook end of a machinist scribe until it is taut between the connector and heat shrunk cable then twist a rotation and a half. The extra half rotation ensures the loop keeps its form. If the length of exposed wire between the connector and heat shrunk cable does not allow for this you may need to trim the cable jacket back. Do this to every wire then wrap with kapton tape or other heat resistant material. Then it is time to test, epoxy and shrink the boot in place with epoxy.

Send me an e-mail at indywiring@gmail.com and I can send you a data sheet from Raychem detailing how they do it.

It is pretty simple, but often overlooked. Learning to get the overall length of the cable just right and account for the service loop when cutting the wire for termination takes practice.

I hope that helps.

[murpia]

Originally posted by IndyWiringServices:
I'll do my best to describe it. After you connect all the wires to the connector compress the connector toward the cable so the wires bow out. I basically "hook" the wire with the hook end of a machinist scribe until it is taut between the connector and heat shrunk cable then twist a rotation and a half. The extra half rotation ensures the loop keeps its form. If the length of exposed wire between the connector and heat shrunk cable does not allow for this you may need to trim the cable jacket back. Do this to every wire then wrap with kapton tape or other heat resistant material. Then it is time to test, epoxy and shrink the boot in place with epoxy.

Send me an e-mail at indywiring@gmail.com and I can send you a data sheet from Raychem detailing how they do it.

It is pretty simple, but often overlooked. Learning to get the overall length of the cable just right and account for the service loop when cutting the wire for termination takes practice.

I hope that helps.

Many thanks for that. I had assumed it was done _before_ the connector was assembled...

Thanks, Ian

[Menisk]

Digging up an old thread because I'm building a wiring harness this year and found a site with some good info others might be interested in.

http://www.rbracing-rsr.com/wiring_ecu.html
http://www.rbracing-rsr.com/sq6wiringloom.html

[Cardriverx]

That is a reference I have used for a year now. The only time I learned more than reading that site is when I actually worked at a motorsports company and built wiring harnesses. I HIGHLY recommend anyone thinking of even touching the harness read the article on that website.




Originally posted by Menisk:
Digging up an old thread because I'm building a wiring harness this year and found a site with some good info others might be interested in.

http://www.rbracing-rsr.com/wiring_ecu.html
http://www.rbracing-rsr.com/sq6wiringloom.html

[Charles Kaneb]

A less-snazzy and heavier alternative to the Deutsch connectors are the GM Weatherpack ones, as seen in every Chevy.

Painless Performance sells them for a fairly decent price. If you're not buying from Painless, make sure to get the GM/Delphi/Packard parts and not some el-cheapo knockoff.

Things to remember when using them:

1) The male-shaped connectors get the female-shaped pins, and vice versa.
2) There are different pins and seals for 14-16ga and 18-20ga wires.
3) Lining up the right portion of the wire and seal when crimping is very important.

[Teranfirbt]

In applications where I don't have access to Deutsch connectors (basically everything that isn't FSAE..) I like to use Molex MX 150 Connectors (http://www.waytekwire.com/products/18/MX150-Connectors/). Every bit as weather tight as Weatherpack, but gives a pin density similar to a DTM connector.

[Warpspeed]

O/k we are not NASA, and we are not Formula One....

But there are a few handy hints to know about assembling a good robust wiring system that will be reliable and easy to diagnose any future problems.

Crimp connectors, any crimp connectors assume that the tooling, the crimp connector and the actual wire itself are ALL 100% compatible.
For an amateur low dollar effort, two out of three will generally lead to trouble.

Crimp connectors are a very good solution for mass production, and a very bad choice for a one off prototype of anything.

A good soldered joint will be far more reliable than a less than absolutely perfect crimp joint.

Heat shrink tubing when properly used is every bit as good as any other method to prevent fatigue from vibration from causing wires to break off right at the termination point.

The actual thermoplastic wire you use can be anything from total rubbish to really excellent stuff, and a lot has to do with the number of strands and the temperature rating of the thermoplastic insulation.
It is very difficult to tell what you are actually looking at, unless you have the original cable spool it came from.

If you buy the good stuff on a roll, you will be forced by necessity to use a very narrow choice of wire sizes and colour codes. Later on, you may have great difficulty trying to diagnose an electrical problem where most of the wiring is all of the exact same gauge and colour.

A much better idea is to grab a few arm fulls of junk wiring harnesses from an auto graveyard.
It will cost almost nothing, but the wire itself will very likely be of much better quality than the rolls of cheap and nasty "Dragon Brand" you will pay far too much for from an auto parts store.

Not only that, you will have an almost infinite variety of wire colours and wire gages to choose from plus some possibly re usable and sometimes difficult to source connectors.

Once an old salvaged loom is completely stripped of it's covering, the original wire underneath will be like new, especially if it came from under the dash or inside the vehicle.

Don't turn your nose up at top quality secondhand wire, it will serve you much better than some of the imported junk wire, some of which can come dangerously close to melting even on just a very hot day !

Many electrical problems can be traced to poor earthing to the chassis. Also wires snapping off where they terminate.

Try flexing each individual wire where it terminates. If it bows in a big smooth loop, that is great.
If it folds sharply over always in one exact spot, it will very soon break off at that point.
Use one or multiple layers of heat shrink, in staggered lengths if necessary to get a nice smooth bending effect.

Protecting wiring from physical damage and heat should all be fairly obvious. As should using grommets and cable ties.

As far as electrical noise goes, your biggest problem will very likely be due to grounding problems. You absolutely must return all grounds to one point which then becomes the reference earth. Very often the engine block/cylinder head is a good choice, because many sensors and the ignition are connected direct to the block anyway.

Then connect a big fat ground strap between block and chassis, maybe more than one. And your noise problems should be minimal if you can keep the high voltage ignition well away from any other wiring, which should not be difficult.

Mostly it is all common sense and good workmanship, once you are aware of some of these ideas, it will all fall quickly into place for you.

[EPMPaul]

Ended up doing the loom on the car this year. Picked up a couple cool references for anybody wanting to make a aeronautics grade wiring loom.
This (http://www.liberatedmanuals.com/TM-1-1500-323-24-1.pdf) and this (http://www.liberatedmanuals.com/TM-1-1500-323-24-1.pdf) should get you started. » Nasa (http://www.hq.nasa.gov/office/codeq/doctree/87394.pdf) also has some pretty good stuff. I believe the second one has something about aranging a wire lay like IndyWiringServices mentions. If you google the other papers in the same series TM 1-1500-323-24-** I think there's a bit more detail.

Anyways, there was someone asking for some full on standards and with those three, there's a lot of info.

Cheers