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Practical Wiring - Professional Motorsport: Step 4 - Generating your Construction Plan

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Step 4 - Generating your Construction Plan


00:00 - With the majority of our documentation now complete, we can move onto developing a construction plan that we'll be working from for the remainder of our worked example.
00:09 It is tempting to jump in here and just start building the harness but it's important to have a proper plan of where we're going to start and how the construction will progress from start to finish first.
00:21 This becomes increasingly important as the harness gets more complex.
00:26 By thoroughly thinking through the construction process and forming a logical and systematic approach, we can help avoid any oversights that could end up compromising our finished harness, or wasting time and money if a section of the harness needs to be remade.
00:42 In this instance, we'll talk through the construction plan for the engine bay side of the harness but the general process will apply to any other parts of our harness such as the interior harness.
00:52 I always like to start from the most complex connection on the harness and work my way out from here.
00:58 In the case of our engine bay harness, this is really defined for us as we need to start the construction at the bulkhead connector and work out from there.
01:07 When dealing with our interior harness however we have the bulkhead connector and the connector at the M170 ECU so we have a decision to make as to where best to get started.
01:19 In this particular instance, I'd start at the bulkhead because this is where we've designed our concentric twist layers to suit the connector and then our engine bay harness.
01:30 As we discussed, this will create a slightly messy termination of the M170 ECU connector as we move from our concentric layers to the relevant pin location that's defined by the ECU manufacturer.
01:42 Building the harness from the M170 out, while not technically impossible, would make our construction process a lot more complex and fiddly.
01:51 Essentially building our harness always follows the same general pattern of pinning out, twisting, sheathing, booting, terminating and labelling.
02:00 It's simply a case of generating a plan that makes sense for each branch of our harness working our way out from the connector until we've reached the end of each branch.
02:10 We do want to be mindful as we begin construction that our lengths match those on our documentation and we always want to keep in mind that the concentric twist process will require longer runs of conductor than our documentation defines.
02:23 Typically, I like to add 15 to 20% additional length to be on the safe side here, ensuring I have a little excess to trim my harness to a final fitted length.
02:33 We'll have a look at the construction plan for the harness to fit our FJ40 in detail now and discuss the reasons why we'll construct it in this way.
02:42 Before we actually look at our construction plan, let's just have a look at our harness design again and particularly here we're looking at our branching diagram.
02:51 Now the key point to note here is the location of some of the elements.
02:55 So for example here we are starting with our bulkhead autosport connector here and we can see that I've labelled each of the branch points as we go through here.
03:05 It is important to keep this in mind because these branch points really form the basis of our construction plan here.
03:12 Also, we've got our lengths here in mm between each of these branch points.
03:18 Now looking at this, we've essentially got a harness that branches out in two separate directions right at this branch point A.
03:26 That's created some complexity with our harness concentric twist layers that we've already discussed in our last module.
03:33 Namely because we need to branch out our cam position for bank 2 right at that branch point A, that cam position you'll remember is a twisted shielded cable and that forms part of our core so we're already trying to disassemble or required to disassemble the harness essentially at that branch point A and we're going to be starting again.
03:55 So now that we've got a bit of a reference there, let's have a quick look at our harness construction plan and what we've done is we've broken this build down into a number of stages and we can see we start here of course with build stage 1.
04:10 Now I find doing this is really a lot like the HPA 10 step process that we base this entire worked example off.
04:18 On face value the process of building one of these harnesses can seem quite overwhelming and perhaps daunting but when we break this down into bite sized increments, each of those specific elements actually becomes pretty easy to deal with.
04:32 So let's have a look at what's involved with our build stage 1.
04:36 And as we can see here, we've added a little bit more detail, this is building our harness section from our bulkhead to our branch point A, head back to our design sheet again and we can see that that involves this element here.
04:50 Important to note here that we do have our fuel composition sensor that's breaking out at that bulkhead but we'll deal with that a little bit further down the track.
04:58 Let's head back to our construction plan and see what we're going to be doing here.
05:00 The first element that we're going to be dealing with here is preparing our core for our concentric twist.
05:07 Now we do use this construction plan in conjunction with our concentric twist design layup so let's have a look at that and we'll head back over to our Google sheet here, look at our concetric lay up and we've got the section of this lay up design here.
05:25 Bulkhead to branch point A so we can see that our core in this case here, involves our ref cable, that's our shielded ref cable.
05:34 Now let's just head back over to our construction plan, we can see that I've got a note in here saying that the shield drain is shared with the sync which is in layer 1, that's important because we're going to need to splice those together.
05:48 Now part of this here, once we've got the shield terminated using a solder sleeve, we're going to be able to then finally pin that core wiring into our bulkhead connector.
06:01 Obviously when we are beginning here by cutting our shielded cable to length, we know, or can calculate the overall length of that particular section.
06:10 We can do that by looking at our engine harness branching and essentially we want to track that ref to its termination which in this case we can see is right here.
06:20 It's simply a case of adding up the lengths of each section of that branch until we've got a total.
06:27 Head back to our construction design plan again here.
06:30 Now once we've got our core, that's what we're going to be doing our first layer of twist around.
06:37 So what we want to obviously do there is prep and pin out our layer 1 wiring and we know that again from our concentric twist layer, that involves the remainder of our shielded twisted pairs as well as our CAN bus wiring.
06:51 Now at this stage we are only going to be laying this up as far as our branch point A.
06:58 As I've mentioned, we're going to essentially be disassembling our harness at this point because we're getting that cam position shielded cable out at that point so there's no point really terminating or constructing this beyond that branch point A.
07:12 We follow this through, it shows us which direction is our lay up for each of the individual layers, we can see as well once we get to our layer 4 here, we've got a little note that mentions that this layer includes our filler wire so we're essentially using this back and forth with our concentric lay up for our engine and we can see here we've got our second layer and our third layer, come through to our fourth layer here and we can see that we've got our filler wires noted.
07:42 So it's a case of looking through our concentric lay up and making sure that we've got each of the relevant conductors included in that particular layer that we've defined in this sheet so that we don't miss anything.
07:54 Let's head back to our construction notes now.
07:57 Once we've got the main section of that harness from our bulkhead connector to branch point A complete here, we do have another couple of jobs to do.
08:04 We do have our fuel composition sensor wiring that we need to terminate and as part of our concentric layer design, we have purposefully made sure that that is on one of the outer layers.
08:16 Let's go across to our design again and we'll have a look at that.
08:21 We can see here our fuel composition wiring, we can also go back across to our bulkhead connector and we'll just see where exactly our wires come from on that particular layer, we'll scroll up here and we have our fuel composition sensor wiring here that is on pin 7 and we can see that that is somewhere around about here on the outside layer so this is going to be nice and easy for us to get access to.
08:51 Now going back to our construction plan again, we also need to add some sheathing to this section and we're going to want to add a label potentially at the bulkhead connector as well.
09:02 This becomes a little bit more relevant when we've got multiple harnesses, in our case we've only got 1 in that area on the bulkhead so it's going to be difficult or impossible to get it in the wrong location but it's always a good practice to get into.
09:15 Just mentioning this DR25 sheathing, we do need to do this as we go through our construction because we're not going to be able to add that at a later point.
09:25 This becomes equally important as well because in a moment we'll talk about our boot that's going to go at that branch point A location.
09:35 Alright with our stage 1 complete, let's move down and we'll have a look at what stage 2 encompasses.
09:42 We can see that we've listed this as building our harness section from branch point A to branch point B.
09:48 Let's head back across to our branching diagram and see why that makes sense.
09:53 We know that our branch point A here is one of the most critical elements of this harness design.
09:59 This is where we've got a lot of conductors and we're branching out in the 2 separate directions.
10:06 We've also got a range of actuators and sensors and grounds that also come off at this point as well so it is a reasonably busy area of our harness.
10:16 Now the key element as well here is that this branch point is going to be booted using a T boot.
10:23 Now we do need to take into account how our harness is constructed because it's not going to be possible to get that boot into location once the harness is completed.
10:33 So we're essentially going to be adding that boot as we go along.
10:38 For this reason it makes sense to look at constructing our harness from branch point A out to B and then we'd also want to look at coming down this location from A to G.
10:49 Once we've essentially got those 2 elements there as well as our additional sensors and actuators and grounds that I've just covered off, at that point we can get our T boot into location and we can also check and make sure that the orientation of that boot matches what we want before it's recovered.
11:09 Now that we understand that, let's head back to our construction plan and see how we've dealt with this.
11:14 So our build stage 2 here, we are building our harness from section A to B.
11:20 Now we actually start here by grouping our wiring into the correct orientations for those 2 branches so again at this point, we've got essentially all of our harness conductors there.
11:32 So we need to spend some time and make sure that we've got these grouped according to what branch of the harness we're going to go down.
11:39 Obviously we also have the sensor and actuators etc at this point as well, we'd want to group those together.
11:45 Making sure that we've got those into the correct orientations and taking our time to work through that, we can then start constructing our harness from branch point A through to branch point B.
11:58 Now again this really follows what we've already looked at here.
12:01 Beginning with our core, we can actually lay this core up a little bit further.
12:06 I don't really like or recommend working all the way out to the end of the harness at this point but we can certainly work a little way beyond our next branch point as desired.
12:17 If we start with that core and then our 2 layers including our filler wire as noted in our construction plan here and then we're going to be adding our DR25 sheathing over the top.
12:26 At this point, we can now get all of our sensor, actuator and grounds from point A, branch point A that we've already discussed and sheath these as well.
12:37 It's also a good idea as we go through this, and you'll see this multiple times in this documentation, to just test fit the harness and make sure that everything is progressing exactly how you'd expect.
12:50 This particularly becomes important with some of these T boots or transitions.
12:55 There's generally quite a bit of bulk to these transitions or boots and sometimes this affects the flexibility of the harness in a way that you didn't anticipate when you were using the roping method to mock it up.
13:07 So sometimes a little bit of testing and adjustment on the fly may be essential.
13:12 Now obviously it's not always going to be possible to test fit your harness.
13:17 Particularly if you are working remotely, however if you do have access to the vehicle and the engine, I always recommend multiple test fits, it can avoid frustration later on.
13:28 Even if you have gone through and thoroughly developed a rope harness before you've developed your construction documentation.
13:36 Moving down, our third step here is really just exactly what we'd expect.
13:42 We're now moving down that other branch A to G as already discussed and I won't cover this off in too much detail here but once we've got all of those branch points in location we can see that we've got a note here to install and recover our T boot.
13:57 In this case it's a Hellermann 1230-1-G.
14:02 Any time we're using one of these moulded boots, it's really important to pay attention to the orientation of that boot and again this is where testing the harness does become really valuable, making sure that essentially once that's recovered down, it is going to be in the correct orientation and make everything work exactly how we'd expect it.
14:22 From here, really the rest of the construction plan just follows this process of working through each of those branch points, mentioning at each of the branch points any of the sensor or actuators that need to be transitioned out there as well and terminating all of these.
14:38 Once we've got to the end of this, we can add notes about adding our labelling as required and terminating to our specific connectors.
14:45 So it is a relatively logical approach here but it just ensures that we haven't missed anything from our branching diagram, makes sure that we've got a nice simple process that we can work through and tick off as we're going.
15:00 Now that we've got an understanding of our harness construction plan and a bit of an idea of how we've developed this, the rest of the harness build really extends out from here, following a branch, twist, sheath and boot process.
15:15 By developing a plan like this before we begin, we can ensure that none of the steps required are overlooked.
15:21 Once you do have a few harness builds under your belt, you're very likely going to be able to look at a harness design and know how it should be built almost immediately but we'd strongly recommend generating a formal construction plan like this for at least your first couple of harness builds.

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