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Practical Wiring - Professional Motorsport: Splicing

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Crimping Tools:


  • Sargent 3137CT
  • Tyco Electronics AD-1377
  • Daniels Manufacturing GMT-232


Stub Splices:


Red Band

  • Tin Plated: D-609-03
  • Nickel Plated: D-609-12


Blue Band:

  • Tin Plated: D-609-04
  • Nickel Plated: D-609-13


Yellow Band:

  • Tin Plated: D-609-05

Nickel Plated: D-609-14

00:00 - At the modified street car or club day track car level, we've used brass open barrel splices to make the wire to wire connections required.
00:08 For a professional motorsport wiring harness, we are going to move to using closed barrel splices and the specialised tooling required to reliably crimp them.
00:17 These splices are more reliable and although failures with a correctly crimped open barrel splice are very rare, every bit of reliability we can get is worth persuing.
00:28 They do come with a draw back however and that is price.
00:31 With an individual closed barrel splice usually costing several dollars as opposed to cents for an open barrel splice, and the required tooling costing hundreds of dollars.
00:40 The closed barrel splices we are primarily going to use are made by Raychem and are known as stub or parallel splices.
00:47 They are available in three sizes easily identified by a coloured band.
00:51 The red band splices are suitable for joining conductors of a combined CMA of 304 to 1510.
00:59 The blue band splices are good for a CMA range of 1058 to 2680.
01:05 And the yellow band splices are topping out the selection with a range of 2350 to 6755.
01:12 The tool to crimp these splices is available under a couple of different names, the one we have here is the Sergeant 3137CT.
01:20 But the Tyco Electronics AD1377 and the Daniels Manufacturing GMT232 are equivalent and all meet the applicable standards for crimping these closed barrel splices and are interchangeable.
01:34 The part numbers for these splices and tools are listed below the module but you will need to find a supplier local to you.
01:41 We're going to have a look at a quick example of using a closed barrel splice to make a wire to wire connection now.
01:47 Going through the details that you need to be aware of when you're undertaking one of these splice joins.
01:53 The first part of the process is determining the size of closed barrel splice that we're going to use and that is going to be dependent on the circular mill area of the copper that we are trying to join together.
02:03 The example that we're looking at here is three 22 gauge wires each of which has an individual circular mill area or CMA of 700.
02:13 So three times that CMA of 700 gives us a combined CMA of 2100.
02:19 That puts us within the range of our blue band splices, so those are going to be the ones we'll use to join these three wires together.
02:27 The next part of the process is going to be determining the amount of insulation that we need to strip from the end of our wires.
02:33 This is going to be based on the length of our closed barrel splice, but also the diameter of our wire.
02:40 So I'm going to take a couple of quick measurements and just note down those.
02:44 The diameter of our 22 gauge M22759 wire here is 1.1 millimetres, and the length of our blue band closed barrel splices measures to be seven millimetres.
03:04 The rule for determining the amount of insulation that we're going to strip from the end of our wire is that when the splice join is complete, and that splice is crimped down, we need to be able to see between one and two times our wire diameter of exposed copper on either side of that splice.
03:22 This means that we do have an upper and lower working range that as long as we stay within, we're going to be fine.
03:28 We'll work out what that range is now.
03:31 So we had our splice length at seven millimetres, if I add two times our wire diameter of 1.1 millimetres to that, so add 2.2, we get our lower range for our insulation strip length of 9.2 millimetres.
03:49 If I take our seven millimetre length and add four times our wire diameter, so that would be two wire diameters on either side of the splice will get our upper working range.
04:00 So I'll add 4.4 to that, which is 11.4 So as long as we stay with our insulation strip range between 9.2 millimetres and 11.4 millimetres, we will be within the working range there.
04:13 The tool we're going to use to strip our insulation is the Ideal Ergo-Elite Stripmaster range and we have an attachment fitted to it that is called a wire stop.
04:23 We're going to adjust the length of this and that's going to set our strip length where we want it, ensuring that all of our wire stripping operations are going to give us the same amount of insulation removed.
04:33 Now unfortunately setting the strip length is not something you can typically do just by measuring on the tool, it is something you do need to do a couple of test strips with, measuring that strip length and adjusting the position to make sure you get within that range that we've spoken about before.
04:48 So I'm going to go ahead and undertake a test strip now.
04:51 Just gonna get my wire installed into the tool there in the 22 gauge spot, butting it up to our strip length gauge at the end there and performing our strip operation.
05:03 I can then measure that strip length, and we have a measurement there of approximately 11 millimetres so that does actually get us into the range that we're looking for but at this point I would probably move this gauge back about one millimetre as I do find you get a tidier splice join if you are towards the lower end of that scale.
05:27 So I'm just gonna move this back ever so slightly.
05:31 And undertake another test strip there and we'll measure the length of that and make sure we're still within that range.
05:49 Measuring that there we've got 9.43 millimetres or approximately 9.5 millimetres so we are now further towards the lower end of that scale which is more where I'd like to be.
05:58 With that tool set now I can go ahead and strip my other two wires here.
06:06 Making sure that we definitely always butt up to that strip length gauge.
06:12 And that is going to keep all those strip lengths nice and uniform.
06:17 Holding all our wires next to one another here we can see we have got that nice uniform strip length that we're looking for.
06:24 We now need to get these bared sections of copper installed into our closed barrel splice.
06:29 This is a point that is typically actually a little bit easier than when you're doing this with an open barrel splice as our closed barrel splice nicely encases our wires entirely, keeping them all together even outside of the tool.
06:42 It is very tempting at this point to twist these wire sections together, however it's not something you want to do as it is going to put unnecessary strain on the point where the insulation ends, possible leading to a failure in the furture.
06:55 Simply by pressing them together and getting our wires nice and organised next to one another, it's pretty easy to make that package small enough to get it installed into our closed barrel splice.
07:06 And of course this will be possible because we have done our wire sizing correctly so we know we've got the right amount of copper to fit in that closed barrel splice.
07:15 So we're going to line all our wires up again and then line up our closed barrel splice so it's in the middle of those bared sections of copper conductor.
07:25 We also have our one wire diameter's worth of copper conductor strands exposed at either end of the splice.
07:31 So with that all assembled we're now going to need to get it into our tool, and we're looking at the different die sizes on the end of the tool here, which are actually colour coded for us to make this really really easy as this tool is specific for this crimping application.
07:47 We've got our red set of dies on the end here, blue's in the middle and our largest which is our yellow right at the mouth of the tool here.
07:55 So I'm gonna get this into the blue section and once again I'm going to line everything up so it's central.
08:01 I want my closed barrel splice to be central in my tool, meaning the crimp is going to happen in the middle of this splice.
08:09 So just sighting down the length of the tool here, I can see when that splice is nice and central in those dies and we're just gonna have one last quick look to make sure our wires are all evenly inserted, and they are, we're gonna apply pressure to the handles and undertake that crimp operation.
08:27 Now this is a controlled cycle tool and what that means is it's got a ratcheting mechanism and it won't actually release until you've applied the correct amount of pressure to undertake that splice join at the end there.
08:39 We can now undertake a vidual inspection of our splice join to ensure that it has been successful.
08:45 There are three critical elements that we're looking for here.
08:48 The first of which is that our crimp has occurred as central as possible in that closed barrel splice.
08:54 That means we're going to have a nice bell mouth on either end which is going to soften the transition back to our stranded copper conductors from the crimped point.
09:03 We're also looking to make sure that we've got between one and two wire diameters of exposed copper conductor strands on either side of our splice which because we have sized our strip length correctly, is the case here.
09:16 And the last thing you're looking for is that there's no cracking around this splice join anywhere that it has retained its closed barrel shape and hasn't opened up and because we've used the correct specified tooling with the correct crimp pressure for this application, that isn't the case and we've got a really nice reliable splice join here.
09:36 Last test that I like to perform is to simply get my fingernails in behind that splice, and give it a bit of a tug test and make sure everything is nice and tight.
09:45 We now need to insulate our splice section here.
09:49 And to do that we're going to use the same material that we've used previously being Raychem SCL.
09:54 The length of section of SCL that we need to cut is determined by the length of uninsulated section that we have here, plus it needs to extend at least one wire group diameter on either side.
10:06 Take a quick measurement of our wire group diameter there and we've got approximately 2.3 millimetres.
10:13 We know that the length of our uninsulated section is going to be the same as our strip length that we determined earlier which was approximately 9.5 millimetres.
10:23 So I'm just gonna get my calculator out here and we'll do a quick calculation to determine that length.
10:29 We've got our wire strip length of approximately 9.5 millimetres, and I'm just going to add twice our wire group diameter there.
10:36 So we'll add that twice.
10:39 Giving us 14.1 millimetres.
10:41 This means we need to cut a section of SCL that is at least 14.1 millimetres long to insulate our wire splice here.
10:49 So I'm gonna go ahead and do that now.
10:58 Got my section of insulation cut to length there.
11:01 We're going to get that installed on our splice join and we're going to centre everything up again, so the centre of this section of insulation here is going to match up with the centre of our splice join.
11:11 There is a little bit of wiggle room here but you want to get it as central as possible.
11:16 So with that in place, we're going to head over to our heat gun and we're going to recover that down.
11:22 I am going to close up the end of the SCL on our insulation here with some flat jaw pliers while it's still hot just to seal that end up.
11:35 Having a look at our Raychem SCL there, we can see it's recovered down nice and tightly onto our wires and we've got good sealing beads meaning everything's going to be protected from the environment there.
11:47 Now if you were undertaking an in line splice, that would be with wires entering from either side of our open barrel splice there, the rule is exactly the same.
11:56 You want your length of insulation to extend at least one wire group diameter past the uninsulated splice section.
12:04 However you obviously won't be sealing down one end with our flat jaw pliers like we've done here.
12:10 If you are undertaking in line splices like that, there are dedicated in line splices available from Raychem that take wires from either end but don't overlap them and they have two crimp locations.
12:21 I find them far less often used than the stub splices however as the stub splices take up less space overall and when you're trying to stagger your splices but keep them all located beneath a connector boot or transition point, they are much better for that application.
12:37 If you do strike a situation where an in line splice would be useful, follow the same rules as we've outlined for the strip length and the SCL sealing lengths.
12:47 You can see from this module that the majority of the same rules that we've applied at the club spec level still apply for our motorsport splices, however we have clarified them further, and the materials and tools have also changed.