What Is Concentric Twisting?

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What Is Concentric Twisting?

16.54

00:00	Concentric twisting not only requires a different approach to the construction of your harness, it also requires a more thorough and in depth approach to your planning and documentation to help ensure that you've got the right conductors in the right layers.
00:14	Getting this right will speed up and streamline the construction process.
00:18	In this lesson you'll see how we approach this and what we need to consider.
00:23	Next let's jump into our concentric layout design and this is really one of the more significant elements of our design and we really can't do this until we've got all of those other elements already sort of dialled in and figured out, particularly the harness branching.
00:43	The reason that that's, so important with our concentric design is where possible we want to design our concentric layers, so that as we've already discussed, we are not trying to branch our wires from the centre of the harness at our very first branch point.
00:57	Again as discussed, it's not always that simple which is what we will see here.
01:02	So, let's have a look at how this works.
01:05	So, what I've done is I've started from our bulkhead connector, the most obvious place to start there and for example here, right from that bulkhead connector as we've just looked at on our branching design, we actually have a breakout there for our fuel composition sensor.
01:21	Now, for each of these breakouts, so this might be the fuel composition sensor or an injector or an ignition coil for example, the colour coding that I've used is always the same.
01:31	Again as I'm going through this, it sticks out at a glance and I know that this is actually to a termination.
01:38	We've got the conductors here and this will play into this as we go further, all of our conductors essentially are 22 gauge except for our shielded wires.
01:49	And we've got here the function of these, we've got our fuel composition sensor signal.
01:53	This also requires a 12 volt supply and a ground.
01:56	Important to note here, this is an engine ground, this doesn't need to be a sensor zero volt and that supplies a digital signal back to the ECU.
02:05	Relatively simple there, let's just quickly compare that to our engine harness branching and we can see that that is this element that we've just looked at already there for our fuel composition sensor.
02:18	Alright, let's look at a little bit more detail at our concentric layer design here for the section from our bulkhead through to our branch point A and if we just look at our harness branching, we can see that this is this section here, it's 260mm long, we know that this is going to contain every single one of our conductors with the exception of our fuel composition sensor which we've just discussed, that's already been broken out.
02:42	So, let's have a look at some of the considerations that go into this and really the first is how are we going to design our core? We're in a situation here where we have our ref, our sink, our cam position bank one, our cam position bank two and knock bank one and bank two.
03:03	So, we've got six two core shielded cables that we need to run through here.
03:09	Now, if we're going to use those as our core, unfortunately six shielded cables, we're not going to be able to neatly wrap those or lay those together, that's not going to work.
03:22	We've got the alternative here which we've used is that we can run a single two core shielded cable as our core and of course when we are designing our harness we always want to really work from our larger conductors and our shielded cables always work really nicely as a core and then work out to our smaller conductors.
03:42	As we already know, every other conductor in our harness here is a 22 gauge conductor which makes the rest of our job pretty neat and easy.
03:50	Now, this is where we are best to make up a test section of our harness and this gives us the ability to quickly and easily play around with a few different designs and see what is going to work neatest.
04:03	We'll get this under our overhead here and have a bit of a look at it.
04:06	And what I've got here is our single two core shielded cable as a core, it's a bit hard to see but we've got that in the centre there and then we've got our five other two core shielded cables wrapped around it.
04:21	Now, what we'll also remember from the concentric design elements of the body of the course is that if we're dealing with conductors the same size, we have a single wire or conductor, in this case two core shield as our core and then each subsequent layer we jump up by six conductors or a factor of six, so our first layer on the outside there should have six two core shielded, we don't have six, we've only got five.
04:48	So, if we actually have a better look at this, it's a little hard to see, but we do actually have a gap running through this, we can see it for example through here which is where that sixth two core shielded conductor should be running.
05:02	Now, we can still take advantage of this though, so let's jump back into our spreadsheet and have a look at what we've incorporated.
05:09	So, we've got our core, one 22 gauge two core shield, we've got the diameter of that, 2.6 mm and we've got that defined as our reference sensor.
05:22	Reason for this is this one is going the full length of our harness, so nice and easy there.
05:28	Now, what we've also got in our second layer here is our sink, our cam position bank one, bank two, knock bank one and knock bank two.
05:36	So, again that leaves us a little bit short.
05:39	In this case we do also have our can wiring which needs to go to our lambda to can module and the can wiring as we know is a twisted pair.
05:49	This gets a little bit ugly and messy if we are incorporating a twisted pair of wires in an outer layer of our harness, so in this case this actually fits quite nicely in that gap that's left here with our sixth twin core shield that is missing.
06:04	So, that's where we're going to incorporate our can high and low.
06:09	A couple of elements here, first of all our diameters.
06:11	So, this is important to define our subsequent layers when we drop down to our 22 gauge conductors.
06:18	In this case we are simply best just to measure the outside diameter using a pair of vernier calipers and in this case, because it is a little difficult to get a definitive and reliable measurement, we're best to take three measurements and average these.
06:33	So, we can see that we've done exactly that and our layer one diameter there is 7.8 mm.
06:43	Now, one element that is worth mentioning here is we've got our can position bank one and bank two in the core and that's the only place it really makes sense to run that but if we come back to our engine harness branching, what we'll see here is that we've got can position needs to be broken out for bank two right at that branch point A.
07:07	There's no real easy way around this and this is where we can have the best laid plans and intentions, but ultimately a lot of our concentric twist is going to be developed around what makes sense and also what we need to physically do with our engine harness design.
07:24	Likewise our lambda to can branches out at branch point A and that requires our can high and low.
07:32	This is OK, what it simply means is that there's no point constructing our harness much longer than the 260 mm at this point we need to get to branch point A because we know that at that point we're going to essentially have to disassemble our harness to get our can position bank two out of that harness and then we'll reconstruct it.
07:54	It's not the nicest, but unfortunately it is sometimes inevitable.
07:58	Let's head back to our concentric layout and we'll talk about a few more elements.
08:02	So, once we've completed our layer one here in our design, obviously we step up to our layer two and here what we need to use is our diameter that we've already measured, 7.8 and you'll recall that we do have a look up sheet in our concentric design elements of the main body of the course here that will help you define how many conductors are going to be in a subsequent layer.
08:26	So, if we bring up our calculator here quickly and what we do is we take our diameter of the previous layer, in this case 7.8 mm and we want to divide this by the conductor size, in this case our 22 gauge conductor is 1 .12 mm, so we'll divide by 1.12 and it gives us a value of 6.9, let's round that to 7.
08:48	We can use that in our look up table and what that's going to do is show us that for our next layer we're going to need 24 22 gauge conductors.
08:59	We can also work out fairly easily what the diameter of that next layer is going to be and again if we just bring up our calculator, if we go in this case 1.12, that's the diameter you'll recall of the 22 gauge wire and we multiply that by two because we've got that on each side of our core and then we want to add the diameter of the previous layer, in this case 7.8, we can see we get to 10.04.
09:29	So, this is how we can essentially work out what the outside diameter of our finished harness is going to be.
09:36	So, what we've done here is essentially grouped as best we can the conductors that we're going to be running as far in the harness as we can.
09:44	Again we already know that we're going to have this complexity of dragging our cam position out at that branch point A, but for the most part we can still design the rest of our harness as well as we can with the location of the conductors in mind.
10:01	So, for example if we scroll all the way down here to our layer four, what we can see is that we are branching out elements that are going to be coming out at that first branch point A, we're combining those, including those I should say in our outer layer.
10:17	So, for example we've got the wires here for, conductors here for our starter solenoid, we've got our power supply for our lambda to can and our alternator ignition auxiliary 12 volt and again if we come to our branching design, we can see that those elements, our starter and our LTC just for a couple of examples are right there at branch point A.
10:42	Just talking about the number of conductors in our layers, because we are only using 22 gauge, we've already worked out using our look up sheet that our second layer is 24 gauge, we remember that we step up 6 conductors per layer, so of course 24 plus 6, our next subsequent layer will have 30 and our final layer here will have 36.
11:04	What this does result in of course is that we do have a requirement for these filler wires.
11:11	And just like Zac's done, we are defining all of our filler wires in a specific colour.
11:17	We choose violet, you can choose whatever you like, it just means that at a later point if you ever see a violet wire or your filler wire colour of choice, you're going to know that that is in fact filler wire and you're going to know the purpose of that wire.
11:32	Alright, so that really covers the considerations of our concentric design here, particularly with a complex harness where we're sort of forced to drag that cam position out at that first branch point and then reconstruct the harness from there.
11:46	Let's cover a few more elements quickly here.
11:49	We've got some more of our terminations here from branch point A.
11:53	So, for example we've got what we're going to be running to our inlet manifold flap control actuator.
11:59	We've got two wires there, we know that we're going to need our inlet flap signal as well as a 12V supply.
12:07	Quite important here just to focus a little bit on our ground design.
12:12	So, branch point A, we do have a ground that's going to go to a nice simple location on the back of the cylinder head here.
12:20	And we need to consider what's going to go into that.
12:24	So, let's have a look here.
12:26	We are concentrically twisting this, so we have a core, in this case one 22 gauge wire and then we've got a second layer with of course 22 gauge six conductors in this layer.
12:39	Now, looking at this, what we've got here is the grounds for our ignition coils.
12:44	This can be really easy to overlook, let's just jump back to our branching design for a moment.
12:50	Now, for example here we've got our ignition six and this needs three wires, three conductors going to it.
13:00	We're going to have a 12V feed, this is coming from the PDM via our bulkhead connector here.
13:06	We're also going to need to have a signal from the ECU, again coming from the M170 through the bulkhead, through our branch point A, out to our ignition six.
13:15	So, that's pretty straightforward, that's defined at our bulkhead connector pinout but we also need a ground.
13:22	And while this is pretty simple to understand, it can be easy to overlook at our design stage because this ground does not come from the ECU, it doesn't come through the bulkhead connector, this needs to be directly to the engine block or cylinder head.
13:37	So, in this instance, the ignition six will also end up going to this ground point here.
13:44	So, it's a bit of a convoluted design, essentially we're running back through this harness up to branch point A and then we're going to be coming out here to our ground.
13:55	That's going to be the same for all of our ignition coils and we have exactly the same on the other bank of cylinders.
14:02	Why I'm mentioning this is because these ground wires, conductors, need to be incorporated within this section of harness between our branch point A and our branch point G.
14:15	So, pretty straightforward, it's not rocket science here, but it is something that we do need to think carefully about and make sure that we incorporate.
14:23	Another element there which I've already discussed briefly, but our lambda decant, that also has exactly the same requirement for a ground wire, so that's going to be again running up to our branch point A and then out to our ground as well.
14:39	So, we'll come back across to our concentric layout and just see exactly how that all works.
14:45	So, we are incorporating in this case two of our battery negatives as well.
14:52	These come from the M170, so these are the M170 power grounds.
14:56	So, battery neg four and five, those will be incorporated.
14:59	We've also got our LTC ground and then we've got our four ignition grounds.
15:05	So, really important just to make sure that we've got all of those dialled in.
15:09	The rest of this is simply a rinse and repeat of what we've looked at here, so far.
15:14	But important to be really detail orientated, take your time and make sure that you haven't overlooked anything because once you have locked this in and you're ready to start construction, it's very difficult to come back from anything that you have overlooked.
15:31	That was just one of 48 lessons taken from our professional motorsport wiring course.
15:37	This course is perfect to help you learn the skills of designing and constructing professional or mil-spec style wiring harnesses.
15:46	You'll learn the fundamentals of automotive wiring as well as the tools and materials required.
15:51	You'll learn about autosport connectors, how to select the right one for your application and how to correctly terminate them.
15:58	You'll also learn all of the specific practical skills that go hand in hand with constructing these harnesses.
16:05	From here you'll learn a simple 10 step process that you can apply to your own wiring jobs regardless whether you're building a simple sub harness or perhaps wiring your engine and chassis from scratch.
16:17	Each step of this process is quick and easy to complete and in no time you'll have a complete harness that's been properly designed, documented, constructed and tested, so you'll have the confidence that it'll work right the first time.
16:32	We also include a library of worked examples within the course where you can see the 10 step process being applied in real time on a real wiring job.
16:41	This course will be perfect regardless whether you're working on a car, a motorbike or an off road vehicle, the skills are 100% applicable.
16:51	If you want to find out more, click the link.