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Practical Wiring - Professional Motorsport: Harness Routing

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Harness Routing


00:00 - Harness routing is a process of determining how we will physically run the wiring harness through the vehicle.
00:05 This includes how it is to be mounted where it will be branched out, and how it will be terminated to the connectors at the end of those branches.
00:13 I find this is a part of the harness construction process that I really look forward to as it's the first time you get a good idea of how the finished harness will look when it's completed.
00:22 As mentioned in the course introduction, it is important that the electronic components our harness connects to are physically mounted at this point.
00:30 While it's not impossible to estimate how long a branch needs to be when a component is not mounted, it's much easier to ensure a tidy result if it is in its final position when we undertake this step.
00:42 This is often also the point that any accessibility problems with the way components are mounted come to light and it's best that those issues are tackled now before the harness construction progresses.
00:53 To design the route out harness will take, we need to mock up a substitute harness using a material that mimicks how our finished harness will lay in the vehicle.
01:02 I use nylon rope for this as it's cheap, commonly available, easy to work with, and can approximate the finished bend radii our harness will take quite accurately.
01:11 I start with either the ECU or the power suppply connections and work outwards from here as these locations usually form an end of our wiring harness.
01:20 I then run the nylon rope through the vehicle to the most distant electrical component, this determining the main path that our harness will take.
01:28 Determining this path requires some key considerations.
01:32 We want it to be as short as possible to keep the weight and cost of the harness down, we need it to avoid any heat sources to prevent the harness being damaged, and we want it to be easily accessible to ensure it is as simple as possible to install or remove the harness from the vehicle.
01:48 In practice all three of these points will need to be compromised on and the route the harness takes is very much decided on a case by case basis.
01:56 Once we have determined the main path the harness will take, the next task is to determine where and how the harness needs to branch.
02:05 We need to ensure the harness reaches every electronic component that we need to make a connection to while also minimising the number of branch points as much as possible.
02:14 Branch points are one of the most complex parts of motorsport wiring harness construction and if we can minimise their number, the construction process will be much faster and easier.
02:23 With this in mind, I find I will often branch the wiring harness out into more harness sections than are strictly necessary at a particular point, then run the multiple harness sections tidily cable tied next to one another as they travel to the components that they make a connection to.
02:39 With the location of the harness branch points finalised, the orientation of the harness sections as they leave the branch points needs to be determined.
02:46 This step is key to the final result being tidy and easy to install.
02:51 If not thought is given to the orientation of the harness sections and they all need to cross over one another after the branch points to reach their components, the harness will look tangled and untidy once installed.
03:03 To do this, use electrical tape to attach the additional mock up harness sections to the main harness route and order them in a logical way so that none need to cross over any others to reach their components.
03:15 This is another benefit of using nylon rope for the routing design process as it's easy to work and arrange into the required orientations.
03:23 With the branched out harness sections now attached to the main harnress route, you need to label the end of each harness section, as when we remove the mock up from the vehicle to measure it and create our construction documentation, we will need to know what every branch section was connected to.
03:39 You will also need to give every branch point a unique designation.
03:43 Typically I denote mine branch A, branch B, and so on.
03:48 This will be very important in the next design step which is the concentric twist layer design.
03:53 An important point to make at this stage is that it is the length of the harness sections between branch points that has the most effect on the final fit and finish of the wiring harness.
04:04 A harness section that connects to an electronic device after a branch point, that is it has no further branch points along its length, can end up being a little too long and the final harness will still fit well and look tidy.
04:17 However if a branch point ends up in the wrong place, the overall fit of every harness section after that branch point will be affected, resulting in a poorly fitting harness overall.

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