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Practical Wiring - Professional Motorsport: Step 5 - Following the Construction Plan - Part 2

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Step 5 - Following the Construction Plan - Part 2


00:00 - The next stage of our build is going to be prepping our layer two wiring.
00:05 So this is going to be the first of our sensor wiring for the vehicle.
00:10 We're going to have to prep that, there are going to be a couple of splices in there for our sensor supplies and our sensor grounds.
00:17 We're going to pin those into our connector body, service loop them like we have here and twist those into the next layer of our harness.
00:27 Now when we're talking about putting those splices in, it's exactly the same process as what we've just done for our solder shields.
00:34 We're going to prep that wiring beforehand, meaning we will have a single 22 gauge wire spliced to the multiple 22 gauge wires that need to head out into the harness, and we're going to locate that splice in behind our connector here as tidily as possible, making sure it is within the bulbous portion of that connector boot.
00:55 Once we've got all those wires into place, it is going to be a case of stringing this between our vices again, which now will be quite a lot easier as we've got much more of a sub structure to deal with, we'll be able to get that under a good amount of tension and twist that second layer in the opposite direction of lay as what we've done here, so it's going to be a right hand lay.
01:15 I'm going to go ahead and do that process now.
02:46 We've now completed the first of our build stages, finishing that off with our final layer here which was layer three of this harness section.
02:56 Now you can see we've got our actual used conductors in this harness layer, that's these white and green wires in here.
03:04 But we have had to add some filler wires, that's the violet wires to round out and complete the layer, giving us that good circular cross section and that really nice flexibility that we're looking for there.
03:15 Now a note about adding those filler wires in.
03:18 What I did there was to simply cut our lengths of violet wire a reasonable distance longer than I knew that they were going to need to be and then I added them in in stages, six at a time.
03:30 And I started from the middle of the harness section.
03:33 Simply laying them in place and then securing them with a cable tie and lay outwards towards each end.
03:39 Doing it that way splits the job up into two different shorter lay sections.
03:43 Actually makes it quite a bit easier.
03:45 You can typically get the entire wire wound in one direction without needing to support it in the middle half way through that lay operation.
03:53 By putting those wires in in stages of six at a time, I was actually also able to use slightly fewer wires than we'd calculated we were going to need.
04:02 Running through the math, we determined we were going to need 21 filler wires.
04:06 I've actually gotten away with just using 19 and that's because when I laid our actual used conductors in there, I went for a slightly shorter lay length, or a slightly tighter twist angle than you otherwise might which has let me get away with just using the 19 filler wires there.
04:23 Once they were in place, you can secure them at either end and trim them off.
04:26 Now where you want to trim them off is going to be beneath the sheathing that will be covering this section.
04:33 So at this harness end we'll have our sheathing coming up to our connector right angle here and down to our branch point.
04:40 So that's where our filler wires are going to end.
04:43 They're not going to be noticeable and they're going to be keeping everything really nice and tidy.
04:47 The other thing we've done there to finish off this layer is actually to wrap and support our section right behind the connector here, making sure that it's in the correct orientation for how this is going to have to head away in the engine bay.
05:00 Now along with wrapping that, the other thing we're doing there is actually masking it.
05:05 That means when we seal our boot onto this connector and onto our sheathing, none of the sealing compounds or epoxies are going to be able to get to our wires.
05:16 That's going to make it possible to actually dissasemble this in the future if it does ever need to happen.
05:23 We've ended up with a slightly odd looking section here actually.
05:25 This is just the nature of the fact that I have four shield connections in there and two splices which has actually bulked out this portion right behind the connector, a reasonable amount.
05:36 It is still going to fit within the boot though, and it's got around about the same diameter as the rest of the harness section so as that heads away it's still going to end up looking very nice and tidy once it's all sheathed.
05:48 We're going to put this entire harness section to one side now and start work on the next of our build stages, build stage two.
05:57 Which is going to be a very very similar process however we're going to be working with our other connector here which is our actuator connector interface.
06:05 Now this process is going to proceed in exactly the same way, referring to our documentation, we'll be preparing our wires, undertaking any splice joins that we need.
06:15 We're going to start with the core of our harness and then build it up in those layers, keeping everything nice and supported.
06:22 Extending our twist slightly further down the harness than we know we're going to need to as in the third build stage, we're actually going to line these two harness sections up next to one another with them plugged into our connector plate here, and that's going to allow us to get our branch point in exactly the right place, while keeping a really good fitment onto these two connectors as they'll be orientated in the engine bay.
06:45 A couple of things to be aware of with our actuator connector here is that this takes size 20 pins as opposed to size 22 that we've been using for our actuator connector up to now.
06:57 That means I am going to need a different size insertion and extraction tool.
07:01 Also additional to that, we are going to be crimping some 22 gauge wires to these size 20 pins.
07:07 That is absolutely acceptable but we are going to have to be very careful to make sure that we've got the right setting at all times on our DMC crimp tool here.
07:16 Going to go ahead and get started on this process now.
07:19 Our core is going to be constructed out of our four ignition power supply wires which are all 20 gauge so I'm gonna get those cut to length and assemble our core.
08:12 I've got the core of the harness section heading away from our actuator interface connector all pinned into that connector, service looped and twisted and laced now and it's looking really good.
08:24 Good circular cross section and it's nice and flexible as well.
08:28 Twisting a core of four wires together like this by hand can be a wee bit tricky.
08:34 It requires a little bit of dexterity and experience but it is completely possible to do.
08:39 I do tend to shy away from doing this with a drill with our M2275932 wire, as when you twist wires like this with a drill, every time that drill rotates, it's actually rotating each individual wire strand as well and that can lead to stressing the wire.
08:57 It's not so much of an issue at the club spec level where we're using our TXL wire which has a parallel run or a straight run of those copper conductor strands inside the wire.
09:09 But for our M22759 wire here it's actually twisted inside the insulation sheath already.
09:16 So by us then twisting that with a drill, can put it under quite a bit of strain so I do tend to stick away from that.
09:22 There was a slight hiccup which you may have picked up when pinning this connector in that because I was doing it upside down here on the bench, I managed to mispin and put a pin into the S position when it should have gone into the C position.
09:38 Have fixed that now so I've got my ignition wiring here in the a, b, c and the z positions.
09:47 So that's a lower case a, b and c which are the central most positions on this connector.
09:54 It's going to be the exact same procedure now for building up the first layer of our harness and also the second layer of our harness.
10:01 So I'm going to get to work, get those pinned in, service looped and wrapped onto our harness section here.
11:03 We've got our second harness section built now, that's stage two of our build plan completed there.
11:10 That's the harness section that's heading away from our actuator interface connector down to our first branch point here.
11:16 You can see with both of our harness sections plugged into our bulkhead mounting plate here, the harness really is starting to take shape and things are looking pretty good.
11:25 The next part of the process is going to be sheathing these harness sections and finalising the position of our branch point A.
11:32 It's best to do it like that in a situation like this where you've got two larger harness sections making connections very close to one another with the positions of those connectors defined by in this case our bulkhead mounting plate, but another common situation is an ECU.
11:50 The reason for that is, you can see only a very minor adjustment of the angle of this mounting plate or the flex in these cables actually makes a pretty big difference to the lengths relative to one another of those harness sections.
12:08 Which means if you get them in the wrong place in your branch point, you're never going to be able to get a really nice fit up at your bulkhead mounting plate or your ECU.
12:17 By doing it this way, we can get it into the exact situation that we want, make a mark relative to one another on our harness sections, sheath them, and then finalise that branch point and ensure that we're gonna get a really nice fit.
12:29 There are a couple more sanity checks we're going to do at this stage.
12:33 Going to take a measurement of the diameter of our harness section.
12:36 This is of course going to be quite a rough measurement even though I am using digital calipers for it, as simply putting a wee bit more or less pressure on those calipers is going to change the measurement quite a lot.
12:48 All we're looking for is that it roughly matches up to our design documentation just to make sure that nothing's gone catastrophically wrong there.
12:57 On that first harness section, we've got a measurement of essentially 12 millimetres and our design documentation calls out for a measurement of 12.08.
13:08 So we're definitely within any tolerance we were looking for there.
13:11 And the size of heat shrink that we've chosen for that harness section, which is 3/4 inch DR25 is going to be the correct size for that harness section.
13:20 The same measurement on our other harness section there gives us, essentially 7.8 millimetres.
13:28 On our documentation we're looking for 8.04 millimetres.
13:33 So once again definitely within any tolerance we were looking for and our decision to use 1/2 inch DR25 is still going to be the correct call for that harness section.
13:43 You'll notice I've already made a mark on our harness sections here.
13:47 Marking them relative to one another.
13:50 That length there was simply determined by test fitting this into the vehicle with our bulkhead mounting plate, laying the harness sections exactly where they needed to go, getting their bend right as they do actually have to go under some air conditioning pipes and some heater pipes in the engine bay, and making that mark relative to one another, giving us that point we know where we're going to have to sheath up to.
14:10 That sheathing point is essentially the mid point of our branch location.
14:15 When we finalise that branch point and actually install our moulded shape to support that branch point, it's going to span either side of that mark there so our sheathing is going to be well inside that.
14:28 For trimming that sheathing to length, I'm simply going to hold our required sheathing up next to our harness section here to get the length, ensuring that our sheathing does extend into the moulded shape boot that we will be installing on this end of the harness as well.
14:43 I don't have to worry about getting those in place at this stage as those moulded boots have a very large unrecovered diameter and we are going to be able to get them over our connector here.
14:54 So that's not something we have to worry about right now.
14:56 I'm going to pull out my heat shrink supplies and trim some sections off to length.
15:01 And I'm actually gonna go ahead and recover those in place as well.
15:04 Definitely something we want to do now as the next stage after that is actually going to be installing our unrecovered transition sealing boot and we're then going to start merging these harnesses together at our branch location A here.
15:19 At which point we would no longer be able to get our sheathing into place.
15:23 So that's why we're going to go ahead and get that done now.
16:41 We've got our DR25 recovered onto both our actuator interface and sensor interface harness sections there along to our branch point A.
16:51 With that recovered in place, they're really starting to look pretty awesome.
16:54 We've got that really nice circular cross section that we're after and everything is still nice and flexible, it's all looking really really good.
17:03 A couple of details about that process that we've undertaken now while it was a little bit easier to access, was to abrade the ends of our DR25 sheathing where we will be using our sealing epoxy when we're recovering the boots onto those portions of the harness and also using some Kapton tape to just secure our DR25 at the ends there.
17:24 Although it is quite a tight fit on the harness sections, you don't want it to be able to move around at all while you're still working with the harness on the bench so a wee bit of Kapton tape there really helps out.
17:35 The next part of the process now if we refer to our build guide, is going to be installing the labelling for our sensor interface and our actuator interface branch.
17:47 So that's going to be our yellow labels that we'll print out on our heatshrink printer and a clear cover that will go over them as well.
17:54 Really need to get those in place now as once we merge these harness sections together we're not going to be able to get them into place anymore.
18:02 So that's the reason why we go through the process of really thinking through the build process and generating our build guide so we don't miss steps like that.
18:11 I'm going to go ahead and print those labels out and get them into place now.
19:08 We've got our labelling materials in place now and I did actually go ahead and recover those down with our heat gun.
19:14 Once they were in place it was pretty apparent they were gonna get quite dirty as we were handling the harness building the rest of the sections.
19:22 So recovering those down and putting their protective clear coating in place is a really good option at this stage.
19:28 Also while I was getting those labelling materials into place and recovered, I've installed our heat shrink mouldable shape that we're going to be using to boot our transition point A here.
19:39 Once again, once like with our labelling materials, good to get that in place now, even if we're not going to recover it down, just so we know that that job is done and when we merge these harness sections together, we don't get further along the process and actually lose access to being able to install this boot later on.
19:57 Now the boot I've used for this is a Raychem 202K153 which is actually a lipped boot, to go on the back of a circular Rayspec connector.
20:08 They can be a really good option to use for transition points in a harness like this that's a straight transition point.
20:16 That's where you don't have a t junction or any harness sections exiting at odd angles.
20:22 And although the 202K153 that I've got here looks very large relative to our harness at the moment, the lipped end here is going to shrink down to around about 20 millimetres and our other end here will shrink down to around about 8.5 millimetres.
20:39 So that's definitely going to recover enough to tightly grip our transition point here, giving us really good strain relief.
20:45 Now if we have any cavities or voids left over at the point where the majority of our harness sections are going to be exiting this branch point A, we can fill in those cavities with our epoxy potting compound, let that set and it's going to give us our nice totally sealed join.
21:03 The next part of the process is going to be merging these two harness sections at our branch point A here.
21:09 And by merge I mean that because we're going to have harness sections exiting our branch point A that will contain wires from both our sensor interface harness section here and our actuator interface harness section here, these two harness sections are going to end up being essentially woven together underneath our branch point A here.
21:29 That's another reason I've actually chosen the boot that I have here, the 153 boot.
21:34 It's quite long and that's going to give me a nice amount of length here to undertake that transition point, twisting and weaving as tidily as possible.
21:44 You do want to make that job as easy for yourself as you can and using a longer boot like this is just one of the ways that you can do that.
21:52 We mentioned in the transition section of the course that often these transition points do end up looking a little bit untidy.
22:00 it is just the nature of the beast.
22:03 But really the key objectives that you're looking for are that everything is orientated correctly, so none of those harness sections are going to need to cross over one another to get to the components they need to reach.
22:15 And that everything is nicely strain relieved, you don't have any wires under there, under a lot of tension being pulled in an odd direction.
22:23 So I'm going to begin this process by sorting out all the wires that are going ahead down the harness section that spans from branch point A to branch point B here.
22:36 So you can see we've got our core that is made up of our ref, sync and knock sensor signals.
22:43 And actually in the first stage of our build plan there we twisted that core all the way to the very end as we knew it was something we could accomplish at the time and it was gonna save us now.
22:53 So that's actually already completed, we've got those sorted out and twisted together.
22:57 We're gonna jump straight into layer one here.
22:59 I'm going to have to find all these wires at our harness point here.
23:03 Which might sound a little bit tricky but it's actually not as hard as you think it'll be because you've designed your layering pattern, you're going to be able to look for all your red 20 gauge wires that are in the corresponding layer of that actuator interface harness section and you're going to be able to find those very quickly.
23:21 There could be a little bit of multi meter work involved.
23:24 And I do have a good trick to make that a little bit easier.
23:28 If we unplug our actuator interface connector here, you can see if we're going to have to do any multi meter work, we're going to have to make a connection to the pins in this plug here.
23:39 What you can do to make that a little bit easier is to make yourself up a test lead for your multimeter like I've got here, that is simply a size 20 Autosport socket in this case.
23:52 Bit of heat shrink down it, it's nicely crimped onto a 20 gauge wire.
23:55 That heat shrink means that when you install this onto one of the pins on here, it's not going to be in danger of touching any of the other pins.
24:03 You can put this end into your multimeter, install this end into the relevant pin that you want to find at the other end of the harness, and start toning out all the other wires in the harness, and you know this will be making a really nice solid connection.
24:19 I have quite a few of these test leads in my multimeter kit there for most of the common sizes of pins and sockets that you'll be working with, really handy to have.
24:29 So now I'm going to start toning out the plug here, finding my relevant wires and getting the organised into that layer one of our harness section heading from branch point A to branch point B there.
25:26 I've got all of the wires organised now that are going to form the core and the first layer of the harness section spanning between branch point A and branch point B.
25:37 In this instance they were actually really easy to find as layer one is simply made up of every red 20 gauge wire in the harness coming from our actuator interface and our core is simply made up of those three twisted shielded pairs.
25:52 It was still really good to go through with the multimeter and check the pins of all these red 20 gauge wires.
26:01 Just confirmed that all the pin locations are correct there.
26:04 Every little bit of error checking you can do along the way is usually quite helpful, just to give you the confidence that the loom is being constructed correctly.
26:12 And if you do find any issues, the earlier you find those, the easier they are going to be to fix.
26:20 I'm now going to twist the first layer of that harness section between point A and branch point B here, it's going to be in a right hand lay, it's going to be our red 20 gauge wires here and we are going to need some purple 20 gauge filler wires as well.
26:36 Once again, I'm going to twist past where branch point B is actually going to end up and then we're going to determine the final location of branch point B by a test fit on the vehicle.
26:49 If you're building a harness to documentation that you've been supplied by a customer, it's often a very good idea to also twist past where that branch point needs to be then finalise that branch point location from the documentation and untwist your harness section back towards it.
27:05 I'm going to twist our layer one wires into place now, then I'm going to sort out our layer two wires from what has become a little bit of a mess here.
27:15 It is organised chaos however, I've just got some temporary cable ties keeping the rest of the wiring out of the place so it doesn't interfere with this operation.
27:24 Sort out those wires that are in the second layer and then I'm actually going to twist those into place as well.
29:13 We've got our harness section between our branch point A and our branch point B now completely constructed, all twisted together, looking really nice, we've got that good circular cross section and that excellent flexibility that we're looking for there.
29:27 I have twisted the harness section further than that branch point is actually going to be, once again just giving us a good amount of working extra length there.
29:36 We'll finalise the position of that branch point via a test fit on the vehicle.
29:41 We're going to continue working outwards from our branch point A now, constructing the rest of the harness sections that exit that branch point.
29:50 It's very important when we're doing this that we follow our documentation and we get the orientation of all these branch points correct as they're going to exit that transition boot there.
30:02 Ensuring that none of them need to cross over each other as they head off to their various locations as if that does need to happen, it makes the harness look quite messy.
30:12 To help with that process, I've used a freely available piece of CAD software called Fusion 360 to quickly draw up a diagram of how I want those branch points, that branch point to be arranged as it exits that transition point.
30:27 Now we can draw on the information from our concentric twist layer design here as that's going to give us the rough finished diameters of our harness sections and that's going to let us arrange then in the CAD software.
30:38 It isn't going to end up looking exactly like this once the transition point boot has been recovered into place.
30:46 But it gives us the guide to know that we do have enough space around our central A to B harness section here to arrange all of the other harness sections, and it gives us the order that they need to be in radially around that main section that we're working with.
31:01 Now important if you're going to draw a diagram like this, whether it be in a CAD package or in fact just by hand.
31:07 Often that can be quite a lot quicker and simpler to do.
31:11 Is that when you draw that diagram, you need to take special note of which direction it represents facing down the harness.
31:18 So by this I mean this diagram is going to represent the branch orientations as we are moving from branch point A out towards the rest of our harness there.
31:29 Using that information, I can collect together all the wires that are going to form these harness sections and make sure they are exiting that transition point in those correct orientations.
31:39 Now as we've mentioned, transition points like this do sometimes end up just looking a little bit messy.
31:45 That's absolutely fine, what you're aiming for is that everything is as strain relieved as it can possibly be and we are going to wrap that entire transition point in Kapton tape as well.
31:54 So I'm going to go ahead now and organise all of these wires here into their bundles and their correct orientations and then I'm going to continue to progress through our build plan there, twisting those harness sections.
33:28 So we've now completed the harness sections that are exiting our branch point A here.
33:34 So just to recap, that involved organising them into the correct orientation as they exit that branch point to ensure that none of them need to cross over one another as they head off to the various parts of the engine bay that they need to.
33:47 That of course included organising the correct wires into the correct sections which meant we could then go ahead and concentrically twist those wires along those harness sections exiting branch point A, following our concentric twist layer design.
34:02 Once we had that done, once again referring to that concentric twist layer documentation, we were able to cut lengths of the correct size of our DR25 heat shrink, get them into place and get them recovered onto those harness secions.
34:16 Finishing up that branch point A, it's been supported with our Kapton tape, so that is actually now completely ready to recover our moulded boot shape onto.
34:27 We're not going to do that at this point though, we are going to leave that as almost one of the last parts of the harness construction process.
34:34 It's not going to hurt us at all, being in place at the moment.
34:37 We can definitely work around that.
34:39 In the unlikely event that we find that there has been an error made and we need to make a correction, it's going to be much easier to do that before this boot gets recovered into place.
34:51 What we need to do now is continue to follow our build plan there which is going to be going through those exact same processes for our branch point B.
35:01 Now we have shown you all of those processes in detail now so we're going to go ahead and continue on with the harness construction process from branch point B and in fact branch point C off camera.
35:13 You can probably tell from the length of this module that following your build plan is definitely the lengthiest part of the harness construction process.
35:22 So to keep this module to an acceptable length, I'm going to go ahead and do these off camera.