- We're here at Renvale in the United Kingdom, manufacturers
of wiring harnesses for the likes of F1, MotoGP, Formula E, WRC, LMP1, LMP2,
just about any other professional motorsport that you can think of.
And we're going to get some insight into what goes into the design and the
manufacturing and testing of a professional wiring harness.
Let's head inside and take a look.
Given that Renvale produce wiring harnesses for a number of current F1 teams,
it's understandable there's a lot of commercial sensitivity here.
We're not going to be showing you anything from a current F1 harness
but we can look at some development on some of the older harnesses that
Renvale have produced.
There are a number of ways that Renvale can work with customers in order to
develop a harness.
One way would be an engineer from Renvale actually travelling to the team and producing
a mock up of the harness on the chassis.
This ensures that all of the lengths are correct and the position of all of the
connectors are correct.
This mock up harness is made using cheaper connectors and not using
the actual wire bundle itself and this just keeps the cost of the harness down.
Once that mock up harness is complete, it can be brought back to Renvale and then
it can be documented correctly where a proper harness can be created from
that documentation.
These days however it's becoming increasingly common for the teams to do the
design work themselves, producing 3D models of the entire car, including the wiring
harness and then these 3D models can be sent to Renvale and the wiring harness can
be created from this.
In some classes which are tightly regulated, such as Formula 1, initially an overall
design of the wiring harness is constructed and this is a high level, low detail overview
and it's used for homologation of the wiring harness to the FIA.
Once the harness is homologated, it's not legal to then make further changes.
Now this particular design is only used for homologation, it doesn't have the
detail required to actually produce a finished wiring harness.
At the same time as the design is being homologated by the FIA,
Renvale are also developing their own detailed construction plans which is what
the actual harness is constructed from.
The next step of the process is for the technicians to construct the wiring
harness as per the documentation.
Now with Formula 1 in particular, weight and size of the wiring harness is a critical
consideration and generally they'll be working with wire gauges between 22,
all the way down to as small as 30 gauge.
In order to standardise the wiring used in harnesses as much as possible,
there are very few colours used.
Predominantly the wiring will be white and obviously this makes it difficult for
the technicians to decide which wire goes to which connector location.
And this identification is achieved using coloured idents.
And these are essentially coloured pieces of heat shrink tube that are placed on the
end of the white wire.
The colour coding denotes to the technician which connector and which position on the
connector that particular conductor needs to go to.
In motorsport wiring harness construction, in general the technique of concentric
twisting is relatively common, relatively popular, however this isn't a technique
that we'll see in Formula 1 harness construction.
Instead a parallel twist of the wires is used.
Now the advantage here is that no filler wire is required, this means that the harness
weight is minimised as well as the bundle size.
However one of the advantages of concentric twisting of course is the added flexibility.
Now this really isn't an issue in an F1 car because the harness is designed integral
with the chassis.
In some places it is supported within moulded carbon fibre components, making sure
that all of the harness is supported correctly and this doesn't need any
additional flexibility.
Beyond the basic construction, the normal techniques that we'd expect to see at
the professional motorsport wiring level are used, the harness is sheathed and
protected in Raychem DR25 and moulded boots are used at any transitions on
the harness.
Of course Autosport connectors are used at any termination.
With any harness construction, making sure that the length of the harness is absolutely
correct as per the documentation is obviously critical to ensure that the finished harness
is going to fit correctly.
Now this of course starts with the documentation supplied by the
particular team.
Depending on the length of the harness, this may be for example plus three
millimetres to minus zero.
This might be over a length of perhaps 500 millimetres.
Renvale's standards are actually a little bit more exacting than this.
Obviously trying to get the harness exactly as per the documentation to ensure
perfect fitment.
In F1 in particular we see a lot of break out boxes used where one single Autosport
connector will go into a moulded carbon fibre piece and multiple sensors will then be
connected to individual Autosport connectors on that carbon fibre break out box.
This makes it really easy to replace individual sensors without needing to reconstruct
the entire harness.
What we'll see here is on the back of some of these break out boxes, the harness is
exposed, it's not actually sheathed because when the component is finished,
it will be sealed inside another carbon fibre piece.
It's important however here to make sure that any relative movement of the harness
to the carbon fibre enclosure is minimised.
In here a RTV sealant is used and this just makes sure that the harness stays stuck
to that carbon fibre, eliminating any movement and the potential for the
harness to be worn through on the rough carbon finish.
Once the harness construction is complete, it's obviously critical to make sure that it
actually is going to function exactly as intended once it's fitted to the chassis.
Renvale don't take any chances here so they have a thorough testing regime that the
components are put through.
Let's head into their inspection area and have a look at how that works.
Testing any harness is important to make sure that all of the terminations are
actually going to the correct place, giving you the confidence that when it is plugged
in, it's going to function as you'd expect.
Now for us at the enthusiast level we're most likely going to be doing this using the
old fashioned multimeter with a continuity test.
Of course that's painfully slow and it's certainly not going to work for the likes
of Renvale.
Instead, a Cirris hipot tester is used.
Now this performs two functions, first of all, using some special adapter harnesses
that are specifically made up for the harness to be tested, the Cirris hipot
tester can perform a continuity test.
This does exactly what we've just talked about with a multimeter, internally testing
continuity between each termination of all of the connectors on the harness.
This is all done in a split second giving a pass or fail.
And if there is a failure, there's the ability to fault find and see exactly where those
problems may lie.
This is only one part of the testing of the harness though, just proving that there
is continuity between the correct points on the different terminations.
The other aspect of the hipot tester is the actual hipot testing, where a high voltage,
in the region of about 500 volts with very low current is applied to the harness.
What this does is test the integrity of the harness, making sure that the insulation
is intact.
If for example there is a nick in the insulation of any of the conductors, this with a high
voltage applied could provide the opportunity for voltage to flash across to another
conductor or terminal inside of the connector.
As part of the continuity test, the Cirris hipot tester can also check for resistance.
Now this can be used to check the resistance of the wires themselves but particularly in
a lot of CAN communications we will require termination of resistors to be part of
the harness so the Cirris hipot tester can ensure that the correct resistor
has been used and is placed in the correct location inside of the harness.
With the hipot testing complete, Renvale can have complete confidence that the harness
is correctly pinned out.
And once it's supplied to the customer, they can install it and it is going to perform
exactly as expected.
When we're producing any wiring harness, it's not enough just to complete your
harness and then install it on the car and hope that everything works as expected.
Testing is an essential aspect to make sure that the harness has been
constructed properly.
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