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Practical Wiring - Club Level: Bundling and Branching

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Bundling and Branching

15.07

00:00 - The bundling and branching process is the one of taking all of our prepared wiring and forming it into the basic structure of our wiring harness.
00:08 I'll mention here that you might have seen a particular bundling technique known as concentric twisting and while this is a great technique, it's not necessary in the modified street car or the club day track car level.
00:18 Concentric twisting requires a huge amount of planning as not only do we need to define where every wire begins and ends, we need to define how the wires are built up in specific layers.
00:29 This planning is very in depth and requires a substantial time investment.
00:33 Not to mention the extra time taken for the physical harness construction as well.
00:37 I would estimate that it quadruples the time taken to build a simple harness.
00:41 Additional to this, the technique does not work particularly well with the materials that we use at the club day track car or modified street car level.
00:49 For these reasons, we will not implement it here however we do cover the process In our professional motorsport wiring course.
00:56 The bundling process we are going to use for our example harness is known as a flat lay or a straight lay.
01:01 We're going to build the harness up in steps on the bench, organising our prepared wires into the correct harness sections and branches.
01:08 We'll then use some kapton tape to bind those branch points and fix their location in line with our build documentation.
01:15 To accomplish this, we set out a build template on our bench using some simple cable tie mounts and painter's tape.
01:21 This will then allow us to organise our prepared wiring into the correct branches easily and tidily.
01:27 This step does tend to get a little bit messy as often our wires will want to form a natural curl due to them being stored on reels before we've cut them to length.
01:35 But you should never be afraid to use a cable tie to temporarily organise the wires you're working with to avoid them getting tangled.
01:42 I buy small cable ties like this in bags of 1000 and consider them to be completely disposable when we're building a harness.
01:49 To show the process in detail we'll look at our example harness and we'll build a template for the section on the interior side of the bulkhead sealing grommet.
01:57 We'll then route the power supply wiring from the fuses to the EFI components that require power using this template as this will let us show the key techniques involved.
02:07 I start this process using the power supply wiring as it is usually the most complex part of the harness and contains the most splices.
02:14 To begin building our template we're going to start with the branch point that is immediately on the interior side of our bulkhead grommet.
02:22 So we're going to put a couple of cable tie mounts down as these are going to represent that point.
02:30 Now I'm sticking these down to our bench in the studio here using a bit of blu tack so I'm gonna have to be reasonably careful with them.
02:36 If you were doing this on your own wiring bench, you're likely to want to use some double sided tape as it will be a bit stronger and often if you get a tag along one side of these, you can end up pulling on them and moving them.
02:48 So with that branch point defined, we can see our power supply connector is gonna be a distance of 410 millimetres away.
02:55 So we'll just get our sewing tape measure here and measure that out.
03:02 And I'm going to mark that point using a section of painter's tape as once again that's gonna let us clean everything up and remove this from our bench in the studio without leaving any mark that we were ever here.
03:18 We've got that in place and I'm just going to mark that length on there using a sharpie.
03:25 So that's in place now, I'm gonna get another cable tie mount and I'm just going to put it before that mark that as it's gonna let us out a cable tie through here and give us a loop to organise our wires through and keep them in place while we're laying out the section of the harness.
03:43 Now we're gonna do the entire power supply section for the interior portion of the harness here so I'm gonna have to go ahead and undertake that same procedure for these other branches.
03:52 So I'll go ahead and do that now.
04:18 So with our template constructed, we can begin laying our power supply wiring onto it and getting it installed through our cable tie loops.
04:26 So the first wiring we're going to do here is the power supply wiring from our ECU fuse at our power supply connector taking power to our ECU one connector, our ECU two connector, auxiliary CAN connector and the other two auxiliary connectors in the engine bay.
04:42 So we've got that wiring here sorted and bagged out from when we undertook our wire preparation step.
04:48 So we'll just get this straightened out.
04:51 Now this is going to come form our power supply here out to our devices on this side of our splice.
05:00 So it's gonna have to run through here, all the way up to our power supply connector and we're just gonna leave that as it is there in place for the moment and then get our other three wires on this side of the splice, they're going to make a 180 degree bend here and come back to our ECU one, two, and auxiliary CAN connectors.
05:23 This is a really good time to mention that there are going to be many times when you're building a wiring harness that a wire is going to have to make a 180 degree bend.
05:30 Now it is fine for that wire to make a bend as long as it is done underneath a branch transition point that is going to be supported with some rigid raychem SCL.
05:41 What you don't want is for our wire to be making that bend there and for that section of the harness to be free to move.
05:47 So we know this is gonna be a branch point here that's gonna be supported by some raychem SCL so when our wires make that 180 degree bend, it's gonna be completely fine, they'll be supported and they won't be able to move so we won't see any strain issues there in the future.
06:00 To determine which of our five wires here are the three that we need to bring back into the interior, we can just look and find the shortest three as from our documentation we can see that it is the shortest three that are gonna come to ECU one, two and our auxiliary CAN connector.
06:16 So I'm going to corral these three wires and actually get them back on this side of our branch point here and this is what I mean by this step does tend to get a little bit messy so we're gonna try and get these wires off the edge of the bench here and out of the way.
06:33 And get our other three organised here.
06:35 And then we know that we're going to want a 180 degree turn in the middle of our branch point here.
06:45 So we can make that, bend those wires around and feed them through there.
06:51 Then at this point it'd be a really good opportunity to use one of our cable ties just to give us a little bit of organisation here.
07:03 Right at that point so we can ensure that the five wires coming from our splice there are all the same length so nothing's gonna bundle out or branch out in the middle of our harness section.
07:17 So we've got our three wires here and all three of these connectors are actually the same distance away from our branch point, they're all 250 millimetres from our documentation here so it's not going to matter which of these three wires goes to which of these connectors so we can get those through those cable tie loops.
07:41 And there they are organised in place.
07:45 I'm actually just gonna get another cable tie and put it in the middle of these power supply wires coming away from that power supply connector.
07:54 These really are disposable when you're building a harness and you're going to use them all over the place and don't be afraid to use a cable tie if it's going to help you out, even if it's only temporarily.
08:05 So with our ECU fuse power supply wiring in place, we can get onto the next power supply section which is going to be the power supply wiring coming from our solenoid supply fuse.
08:16 So that's heading off to the engine bay to give power to our boost control solenoid, double throttle control solenoid and our idle speed control solenoid.
08:26 So that means all three of these wires are going to have to be on this side of the engine bay so we're going to run our fuse wire through our branch point here and they're all gonna come up to our power supply connector.
08:49 Now i'm just going to secure these in place with another cable tie and when I do that it is actually going to lock the relationship between these two wiring sections together so we want to make sure that we've got our spliced locations here staggered when we put that cable tie in place.
09:09 As when we have splices like this next to one another, we want to stagger them along the length of the harness as it's gonna help the whole harness keep a smaller cross sectional area and not give us one big bulky point.
09:22 One big bulky point like that can really reduce the flexibility and also make it very very hard to install any of the sheathing when we get to that stage of the harness build.
09:32 So I'll just get a cable tie on that now.
09:43 And trim that tag off.
09:48 So you can see we've got our splices staggered there.
09:52 The rest of this process is very much a rinse and repeat, we're going to take the rest of our power supply wiring that we've got pre prepared here and install it onto our template and then we'll have a look at using our kapton tape to actually bundle that in place and keep everything organised the correct relative distance away from one another and also talk about where we put that kapton tape in relation to where the finished branch point is going to be.
10:16 So I'll go ahead and I'll do that now.
10:34 So for our example section of harness here we've got our power supply wiring laid onto our template so that is the wiring taking the power from our fuses out to the EFI system components.
10:46 For a complete harness build we would now go ahead and install the rest of the wiring in this section of the harness.
10:52 And we would do so in a particular order, starting with the power supply wiring, we would then install the power ground wiring, then the sensor supply wiring, the sensor ground wiring, the communications wiring, the actuator command wiring, and then finally the sensor signal wiring.
11:07 However with our example harness section here we are going to stick with just our power supply wiring as it will keep it simpler on the bench here and still let us show you the important details that you need to be aware of.
11:20 So you can see here all our splices are staggered, they're not all right next to one another so that's gonna prevent us having a big bulky point on the harness there.
11:31 We've got our 180 degree turns here and this is the point that is going to be supported with our raychem SCL, this is our main branch point and that is going to keep those well strain relieved, meaning they're not gonna cause us an issue anywhere down the line.
11:47 What we would do now once we had all of our wiring installed on our template here, is we would go and fix these branch point locations using some kapton tape.
11:56 So I'm gonna go ahead and do that at our branch point here to show the procedure and what you need to be aware of.
12:02 The key thing that you need to be aware of is the location of the kapton tape in relation to the final location you want your branch point at.
12:10 And what we need to do is put the kapton tape around about 25 millimetres before that branch location as this is going to let us slide our sheathing all the way over that kapton tape and still give us enough room on the other side to get our wires tidily organised and branched out.
12:28 So as we know, this point here is where we're gonna want our branch point to end as we've measured from here to here to be our 410 millimetres as defined by our routing mock up.
12:39 Now to tape and support our branch point here, that 25 millimetres back from where our final sheathed branch point is going to be, I'm just gonna have to move this mount point back slightly and trim this temporary cable tie off.
12:53 Now when you're trimming cable ties off a harness section like this, you want to make sure you're using nice flush cutters and they are nice and sharp as it's going to give you less opportunity to split and possibly nick those wires underneath which you really don't wanna do as if you nick the insulation and expose the copper, you are gonna have to replace that piece of wire.
13:12 So now we're going to tape up this branch point here.
13:14 I've got a pre cut section of kapton tape to get us started.
13:18 And we're well within that 25 millimetres of our finished branch point.
13:24 I'll just get that taped up and nicely supported.
13:27 Almost directly in line with the section of those power supply wires that turns 180 degrees as we want to make sure that point is nice and rigid and really well strain relieved.
13:39 So I'm gonna go ahead and just support that there with a bit more of our kapton tape now.
13:53 So we've got our branch point taped up here and well supported.
13:57 It's gonna give us enough room to get our sheathing over there and then still branch out our harness at this point here with our sheathing on it which is exactly what we're after.
14:04 I'm gonna go ahead and put a bit of tape around our splice points here now as well and that's gonna make this section of the harness also quite rigid and avoid any of those splices being subjected to unnecessary strain.
14:14 They are of course also going to be located under a section of raychem SCL which is where our sheathing is going to end and our bare wires are going to head to our power supply connector.
14:24 So I'll go ahead and get some kapton tape on that point now.
14:37 So that should show you the key techniques to the bundling and branching operation, what you need to be aware of, how we build the template on the bench, install our wires into it, get our branch locations in the correct place, and then seal and support them with that kapton tape.