- When it comes to any professionally built race car,
the wiring harness assembly is one of those critical components.
Generally when it comes to fault finding problems on a car,
it does come down to the wiring as the most common cause of grief.
So when we're building a car from the ground up,
a reliable wiring harness is one of those key aspects.
We wanna know that that wiring harness is something that we can rely on,
and it's not gonna give us any grief over the long term.
However it's really hard to find solid information on how to correctly construct
a professional motorsport harness.
We're here with Zac from Motorsports Electronics to find out exactly what does
go into a professional motorsport harness.
But Zac because it is so difficult to find solid information on professional
motorsport wiring and also it is quite far removed from general auto
electrical practices, can we start by letting us know how you actually got
into this field?
- Sure yeah when I lived in Ohio previously I was doing most of the
fabrication stuff over there.
When I moved to California my business partner Tim was working for a separate
company and when I first had got on there, basically their practices
weren't down to a science but they knew what they wanted to do.
So Tim kind of put me on some material through RB Racing's website
and a few aerospace type of documentation and so I kind of read through that for
a while, practiced every day as I was working and we kind of nailed it down.
And just ran with it.
- So I think that's probably how a lot of people who are currently getting
into motorsport wiring are learning, that particular RB Wiring website
that you mentioned is very popular and there are some official documents
from TE Connectivity on best practice, however it does require a little bit
of testing, practice, to really develop it.
The best practice that they talk about doesn't really give you too much hands
on instruction into exactly how to go about it, would that be fair?
- Of course yeah absolutely.
I mean everything's fine tuned and there's a lot of worksheets that we use,
and it has a lot of formulas and stuff like that that help during the process.
And so fine tuning those, day after day, even to this day,
we're still fine tuning those documents.
And it's just so helpful, and it speeds things up and just makes it easier
for everyone involved.
- Now there's obviously a million things that we could delve into here,
so I wanna try and touch on a few of what I consider to be the key aspects.
Let's start with the wire.
So again there's some significant differences between the motorsport
grade wire that we use and what's now become know as MilSpec.
So the wire that we use for a MilSpec harness versus what would be used
in a typical OE style automotive harness so can you tell us about those differences?
- Yeah sure so the Tefzel wire that we use, it's a little more resistant to heat
than you would find in a normal harness.
So when you're using these high temp materials like the heat shrink and what not
even shrinking those you'll find that some of the TXL wire, or lower quality
automotive wire will actually melt a lot easier and faster.
And using good quality harness material goes a long way in the production.
- The other aspect with the Tefzel wire, the professional motorsport wire
that you use, the insulation is also thinner so this results in a bundle size
that's smaller and also in motorsport, weight's everything so it reduces the
weight, would that be fair?
- Yeah absolutely fair to say.
It's a huge thing, and even with the DR25 we usually use the thin wall material
as well, save every bit we can.
- Now on top of that, once we've dealt with the wiring there or the wire that
you're using, I wanna talk about the technique of concentric twisting.
So this is another thing we're seeing pop up, some great photos all across Instagram
in particular of guys producing these beautiful concentrically twisting
harnesses, it's a technique that's difficult to master.
What I wanna talk about here though is what are the advantages
of a concentrically twisted harness?
- The main thing that I would say that you get is the strain relief from it.
Every single wire in the bundle has no more stress than the other wire.
On a deviation scale.
But for the most part that's the main factor that I have.
You get much more flexibility when you're trying to round a corner that's
sharp in a race car, kinda wanna be able to bend that without worrying
about stressing any of the wires inside.
And it makes everything so much cleaner, easier to install the sheathing,
it's just, there's so many benefits on many different levels.
- Now there is also a bit of an argument there for and against concentric twisting
in terms of weight because it's fair to say with a concentric twist,
because of the angle you're twisting, you actually are using more wire.
And of course often you'll end up putting filler wire in because you need a certain
number of conductors for each layer of the concentric twist,
is that reasonable to say?
- It is reasonable to say.
What we try to do is fill out the IO as best as we can and limit the amount
of filler wires that we obviously can put in there.
But filling out the harness for future modifications is a huge key.
You know your customer's gonna want something different down the road.
So you try to build it as best as you can but you can't always, you know.
- That's actually a really good point that you touched on there,
I'll just elaborate on because with these DR25 sheath harnesses,
where typically autosport connectors and moulded boots are used,
it's all but impossible to modify or add to that harness so instead of adding filler
what you're basically saying is you can add some extra wires in there
to future proof the harness?
- Exactly yeah.
- Alright so let's talk about the connectors now and this is another
area that we see the professional motorsport harness differ from
the hobbyist level.
Typically the autosport connector is the connector of choice.
Brutally expensive unfortunately.
But let us know what you see as the advantages over a lower grade
like maybe the DTM style connectors.
- Sure so I find that it's actually a lot easier when populating that we save
a tonne of time just by the ease of using DMC crimp tools and what not.
Obviously the Deutsch connectors use those as well but they don't have as large
of an IO.
And so the autosports allow you to put a lot bigger bundle size into one connector.
And so when you're going through bulk heads or anything like that it just makes
the process simple.
- Now you talked earlier about strain relieving or the benefits of concentric
twisting with strain relieving.
Another aspect that's really important when you're pinning out or terminating
an autosport connector is service loops again for strain relief.
Can you just tell us what they are and how they work?
- Sure so strain relief is typically about a half inch to maybe three quarter
of an inch extra wire.
Keep it longer before you actually terminate, loop it in,
it gives you a little more slack in there so even though we have a boot
on the back side of the connector that's glued and that's also strain relief
for the harness, that allows for any sort of vibration or movement in there
to not fatigue the actual terminal.
- I think that's a really important part with the motorsport environment,
it is brutally harsh.
There's a huge amount of vibration going on so that strain relief is so important.
We never want the wire to be taught between the conductor and the actual
terminal that it's connected to.
You've also mentioned there, crimping when you're terminating or pinning out
one of these autosport connectors, and this is another area where there's
a huge amount of controversy.
The old crimp versus solder controversy.
So could you give us your take on this?
Is there a place for solder in a professional motorsport harness?
- There's one place for it and that's solder termination for something like
a ground termination when you're shielding a wire.
Other than that, there will be not crimps in our harness that have solder.
Just doesn't work that well.
- So the point here is that even with a correctly performed solder join,
this is gonna end up with a brittle interface at the edge of the solder
and that's a point where potentially we can end up with fatigue failure?
- Absolutely so you could be really doing a great job at soldering but there's
always a little bit that can wick up slightly higher than the crimp itself
and that causes a brittle point in time where the wire can actually be fatigued
at that point.
- Now I'm just gonna go into this a little bit deeper because we know we're gonna
get some comments that are gonna come from all of our viewers saying that
they've soldered every harness they've ever created and they've never had
a problem and well that may all be well and good in the motorsport world,
we just don't wanna take chances and on face value really if we're looking
at a correctly performed crimp versus a correctly performed solder join,
even one that is supported, the crimp is always gonna win.
And in a correctly performed crimp we should have the actual wire strands
fail before the crimp fails.
- Absolutely yep.
- OK so in terms of the sheathing that you're using here on the motorsport
harnesses, you've said they're using DR25, so heat shrink sheath.
Can you tell us the advantages of that DR25 product over lower grades
of sheathing?
- Sure I mean it stands up to heat so much better.
If you have a fire or something in your loom and it's able to handle that much
more heat, there's a chance that your wiring can be saved over
a cheaper solution.
So that's one huge advantage.
It holds up well to a lot of different chemicals.
And there's a few different types that you can get for fuel tanks and stuff like that
when you're going through a bulk head, that needs to be hermetically sealed.
- So essentially pretty much impervious to most of the chemicals that we'll find
in the harsh motorsport environment?
- Absolutely yep.
- And also quite abrasion resistant which is important if there is any relative
movement between the harness and other components?
- Absolutely yeah I wouldn't recommend the thin wall stuff if you're in a high
vibration area where you can't secure the harness but it is a great material
for anything else.
- Alright thanks Zac for giving us some more insight into what makes up
a professional motorsport harness.
If people wanna find out more about you, where can they go?
- So you can go to our company's website www.motorsportselectronics.com
You can also check our some of my other work at zacperkins.com
- Awesome thanks a lot for the chat Zac.
- Cheers.
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