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Practical Wiring - Professional Motorsport: Booting Connectors

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Booting Connectors

14.44

00:00 - Booting the connectors of our wiring harness is an essential task for a couple of reasons.
00:06 Firstly it seals the connector body to our harness sheathing which further helps to protect the wires and any splice connections beneath from the environment.
00:15 Second, it provides excellent strain relief as any load put on the harness will now be transmitted through the harness sheathing, the boot, and to the connector body.
00:26 This means our wires within the harness don't see that load and all of our crimp and splice connection beneath will remain reliable.
00:34 There are two choices for our booting material, being Raychem SCL, as used in the club level course and specific shrinkable moulded shapes similar to those discussed in the branching sections of this course.
00:47 I find SCL to be a good choice when booting to smaller more OEM style connectors like the Bosch Mini Timer injector connectors, US Car connectors or the Deutsch DTM range.
00:58 The process for booting like this doesn't differ in any great way from as shown in the club level course.
01:05 However if you are booting to a connector that has a well defined lip at the end where the wires exit, using a shrinkable moulded boot shape can be a better option.
01:15 These shrinkable moulded shapes are very similar to those discussed in the branching section of the course and indeed installation process is also quite similar.
01:23 We've linked below to a catalog of those moulded shapes and would recommend browsing through it to become familiar with the different shapes and styles of moulded boots available.
01:33 The type you need will vary with your application so it's best to have an idea of the shapes available.
01:39 We'll have a look at a couple of common scenarios now though and discuss how to correctly size and specify the boot for your application.
01:46 I have a couple of shrink moulded boots here for us to have a look at.
01:51 This is a Raychem product and I've got it here in its unrecovered form so as it would be supplied, and its recovered form, this is after heat has been applied to it.
02:02 Should be very obvious that there is a large difference between these two, and these shrink moulded boots have a very high shrink ratio, particularly at the end here where your wiring harness would be.
02:13 You can see the difference in size there really is quite extreme.
02:17 We'll have a quick talk about how to correctly size a boot like this for your application.
02:23 I've got an 1835 connector plug here and the first thing we're going to need to know is the diameter in behind the lip here.
02:31 This will be available from the documentation for the connector and in this instance is going to be 25.2 millimetres.
02:38 To continue specifying the boot we are going to need the diameter of the harness section that will be heading away from this connector which you will have from your design documentation going from your concentric lay up design and then adding on the thickness of that DR25 sheathing.
02:55 The size range for this end of the boot is actually quite large though, so you're not going to have to be amazingly precise with that measurement.
03:04 The idea is to choose the largest possible boot that will recover to tightly fit all of the items in question.
03:12 So in this instance we'll have a look at specifying a straight lipped boot for this connector with a pretty standard harness section behind it.
03:21 I have the page with the straight lipped boots from the catalog here.
03:26 So we can have a quick look at the information.
03:28 I can see here that a 202K153 boot is going to have a recovered size at its large end of 22.4 millimetres.
03:42 So that's actually quite close to our 25.2 millimetre dimension here.
03:46 The next size up from that in its recovered state, so that's after heat has been applied would be 28.2 millimetres so the next size boot up is going to be too large.
03:57 So the 202K153 is most likely where we're going to want to be.
04:02 Having a look at the smaller end of that connector boot which is where the actual wire harness is going to be exiting from, we can see a recovered size here of 8.4 millimetres.
04:15 So that really is quite small and it would be very rare for you to have a harness section heading away from a connector like this that would actually be smaller than that 8.4 millimetre size.
04:28 Now that's not to say it's not going to happen.
04:31 And if you're in a situation where that is going to happen, you can actually step down a size in boot, as we can see here if we go down the 202K142, our unrecovered size is now 31 millimetres, so that is still going to be large enough to get into place and it is going to recover down which is within the range and it's going to fit nicely onto that lip there.
04:58 Also the smaller end is going to shrink down to a smaller 7.1 millimetres.
05:03 So if you've got a harness section coming away from a connector like this, if you've only used a few pins in that connector and it's quite small, stepping down in size might be an option you want to look at.
05:15 However if you do go down that route, it's very possible you're actually going to lose one of the key benefits of using the moulded boot shapes that we have here and that is that once you've got your harness assembled, you can actually install the boot over the connector from the front end.
05:32 This means you need to be far less conscious of when you're undertaking that booting application, you don't have to get it in place before you actually terminate to your connector body.
05:43 If you step down that size, we've got here for example, it's no longer going to fit over that connector body.
05:50 It is still possible to get this boot nicely recovered into place but you have to be very conscious to get it onto the harness section before you terminate to your connector.
05:59 Now I've mentioned a couple of part numbers in there.
06:02 We'll have a quick talk about those.
06:04 The most common parts that you're going to be using when you are shrinking the moulded shapes like this are going to be straight lipped boots and right angle lipped boots.
06:16 The part numbers for those beginning with 202K and 222K respectively for the Raychem product range.
06:24 After those numbers they will have a suffix and that's going to refer to the size of that boot which you can get from the documentation that we have linked below.
06:33 Going a little bit further into that part numbering system, there is another aspect that you're going to want to look for and that is the part number of the boot you're using having a -25 after those numbers.
06:45 That -25 denotes that material that the boot is made out of.
06:50 And for our application, we want to be using the fluid resistant elastomer material as it's going to bond very well with our epoxys and our DR25 heat shrink sheathing.
07:00 Also available are other part number suffixes that refer to a pre coated glue epoxy inside that booting compound.
07:10 If you can get them pre coated, I would suggest to go that route as it can save a wee bit of time.
07:16 Often they're not available though, so the example we're going to show today, we're actually going to apply our own epoxy compound.
07:22 You can also get the boots with some modifications.
07:26 Primarily being adjusting the overall length of the boot.
07:30 If we have a look at our fully recovered 202K142 here, you can see it has quite a long section.
07:38 It actually has two lipped portions in there that line up with the lip on your connector body.
07:45 What you can do when you get these supplied is actually slice the front off this in its unrecovered state and that can shorten down the boot but still give you a lip to key into that connector body nicely.
07:58 If possible, if you're ordering from a supplier that has a large shelf stock, you may be able to get them with that modification already done.
08:06 However often that extra length of the boot behind the connector body can be really handy as we might want to be locating splices or other joins to say the sheathing of our shielded cable in there and that extra space can be really handy for doing that.
08:22 We'll go through an example now of shrinking one of these moulded shapes onto the back of a connector.
08:27 We're going to use our potted engine position sensor again for this.
08:31 Now in this instance the boot was actually supplied with the connector and it's a Hellermann Tyton 1030-4-G.
08:41 Now that boot being supplied with the connector has actually done a lot of the leg work for us as I haven't had to go through and size this boot myself.
08:49 A quick check of the documentation though does show that the recovered sizes are going to be a good fit for our harness connection point here.
08:57 However there was one key detail to note which was readily apparent when this boot showed up is that in it unrecovered form it's not going to fit over the body of the connector like we talked about earlier so I had to be very cautious about getting that in place before I actually terminated to this connector body.
09:15 With that done though, we can jump into the process.
09:17 The first thing we're going to do is actually use some Kapton tape to cover up our wiring and secure it slightly more at our termination connector end here.
09:29 That's going to keep any of the epoxy compound that we apply to this join from getting onto our wiring and possibly affecting it and it's going to make servicing this joint in the future possible as if we were to cut that connector boot off, we would be able to remove the tape and get to the wires without any of that epoxy compound getting in the way.
09:48 I've got my Kapton tape here so I'm simply going to spool off a little bit of this and wrap up those wires.
09:55 You can actually use PTFE teflon tape for this purpose as well.
10:00 Sometimes it's even easier to use on a smaller connector body like this.
10:05 But in this instance we've got the Kapton tape here so that's what we're going to use.
10:25 With that Kapton tape in place masking away our wires there, it's going to be time to apply the sealing epoxy to the points where that connector boot is going to make contact so I'll go ahead and mix that up as we've shown in a couple of other modules.
10:40 Just like to use the back of a scrap plastic bag, nice rigid one if possible.
10:45 We'll get that out of our gun and get it mixed up.
11:08 I've got my epoxy compound mixed up and in a syringe now.
11:11 What I'm going to do is put a bead of it on the two points where our connector boot is going to recovered to make contact and that's going to give us the sealing we need to make sure our wires are nice and environmentally sealed.
11:24 We're then going to head over to our heat gun and we're going to shrink the large end of that boot down first, working the heat down towards the small end.
11:33 When you're working with a much larger connector body and heat shrinkable boot, chances are you would actually do this in two stages.
11:41 You would put your sealing bead onto the connector body here and shrink this end down, you would then come in and put your sealing bead on your wire harness section and shrink that end down in two different steps.
11:55 However with our small boot here, what is most likely to happen is that I'm going to have a reasonable amount of heat soak or heat spill and while I'm shrinking down that large end, the small end is likely to start recovering as well, so I want to make sure I've got that epoxy compound in place in case that happens.
12:14 So I'll get my bead put in place now.
12:17 So I should be able to squeeze this out of the syringe nicely just rotating this around to give us a reasonably even bead there.
12:27 It will actually flow quite well once the heat gets onto it and we will put a bead down the base here as well.
12:41 I can now slide my boot into place, trying not to disturb that epoxy compound too much, although sometimes it can actually be helpful for keeping the boot in place while we're shrinking it down.
12:53 I've got my heat gun set to 275 degrees celsius here, I've found that to be a pretty good temperature for shrinking these boots down without scorching them and giving you a good amount of control.
13:05 The minimum shrink temperature is listed in the documentation as 135 degrees celsius for our Hellermann Tyton boot here so we know we are quite a wee way above that.
13:16 We will have to be careful with how much heat we're applying to make sure we don't scorch that boot but we will be able to control how it shrinks down quite nicely.
13:24 So I'll turn the heat gun on and get that heating up and we'll head over and shrink that down.
13:43 With that shrunk down into place, we can do a bit of an inspection and see that we've got a good result here.
13:49 So I can see all the way around I've got a nice bead of my sealing compound meaning I've got a good seal up at the connector end and just visible down the fine end here we've got a bead there as well.
13:59 So that is gonna be a good seal and as it's cooled that connector boot's gone nice and rigid, gonna be giving us that really good transmission of force and the strain relief that we're looking for.
14:10 The process is the same as shown here for the larger connector boots and we will show this in more detail in the worked example section of the course.
14:20 Shrinkable moulded shapes like this are really robust and quite visually appealing too.
14:26 They give the cable section a nice finished look, along with the use of our epoxy, providing excellent sealing.