Practical Wiring - Professional Motorsport: Materials Selection
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Materials Selection
05.48
| 00:00 | - When we build a dedicated motorsport wiring harness, our choice of materials becomes simpler than when we build a club level or modified street car harness. |
| 00:08 | To withstand the harsh motorsport environment, we will only use the best materials with the highest specifications. |
| 00:16 | Many of the materials we use are borrowed from the aerospace industry as the design objectives of this industry are a good match for our professional motorsport applications. |
| 00:26 | This does drive the price of a motorsport wiring harness up substantially but this higher price is preferable to chasing electrical problems in the pits under the pressure of a race event. |
| 00:37 | We'll look at the key wiring harness elements now and outline the materials that we're going to use. |
| 00:42 | The primary element in our wiring harness as the name suggest, is the wire itself. |
| 00:47 | When building a professional motorsport wiring harness, we will always use Tefzel wire. |
| 00:52 | Tefzel is actually a trade name for the insulation material used on this wire which is ethylene, tetrafluoroethylene, that then undergoes a radiation treatment process called cross linking. |
| 01:04 | The end result of this is a wire that has a thin, tough insulation jacket, that can withstand temperatures as low as negative 65 degrees celcius, while still remaining flexible. |
| 01:13 | And as high as 200 degrees celcius without melting or charring, This wire is often referred to as spec 55 which is another brand name specific to Tyco Electronics. |
| 01:25 | When you're searching for this wire however, the most useful term will be M22759/32. |
| 01:32 | As any wire meeting this specification will be fit for our purpose. |
| 01:36 | The thinness of the insulation jacket does mean we need some specialised tooling to work with this wire, which we will cover later in the practical section of the course. |
| 01:46 | This insulation jacked it also resistant to any chemical we're likely to encounter in the motorsport environment, and has a smooth low friction surface, allowing the wires within the harness to move against one another without chaffing. |
| 01:58 | As mentioned in the power supply design section of the course, often we will select the size of wire we're using based on the connector specification that the wire needs to run to. |
| 02:09 | Running an extra wire in a situation where a larger current handling capacity is required, rather than stepping up to a larger size of wire. |
| 02:17 | As important as the toughness and chemical resistance of the insulation jacket on the wire we use is, the same elements of the sheathing we use to cover our bundled harness are even more critical as it is the sheathing that will bear the brunt of the exposure to the motorsport environment. |
| 02:33 | In fact one of our main aims when we are constructing a motorsport wiring harness is to completely seal the wires within the sheathing to ensure that they are protected. |
| 02:42 | We exclusively use Raychem DR25 tubing to sheath a motorsport wiring harness as its chemical resistance and operating temperature range of minus 75 degrees to 150 degrees celcius make it ideal for this application. |
| 02:56 | This shrinkable tubing has a recovery ratio of 2:1 making it easy to install it on our harness sections and it retains its flexibility when recovered, ensuring our completed harness also remains flexible. |
| 03:09 | As DR25 shrinks to its fully recovered dimensions, its wall thickness increases giving us excellent abrasion protection also. |
| 03:17 | Where our wiring harness needs to branch out to connect to various electronic devices, we seal these transition points using specific moulded heat shrinkable shapes, that recover tightly to our harness sections and then become rigid as they cool. |
| 03:32 | While recovering these moulded shapes, we use an epoxy potting compound to seal the interface between the DR25 outer surface of our wiring harness, and the moulded shape, ensuring the wires within our harness remained completely protected from the environment. |
| 03:48 | As these moulded shapes become rigid after they've recovered, they offer excellent strain relief to the transition points and offer us an ideal place to locate splices and adjust the ordering of the wires in our concentric twist layers. |
| 04:00 | It's a similar situation where our wiring harness is terminated to a connector. |
| 04:04 | Here we also use moulded shrinkable boot shapes to seal the connector back shell, retaining he integrity of the harness and providing strain relief to the connection points, giving us further locations also to perform those splice joins. |
| 04:18 | The connectors we use for our motorsport wiring harness will most commonly be determined by the device we're making a connection to. |
| 04:25 | But the standard is the Deutsch Autosport connector range or the Souriau 8STA range. |
| 04:31 | These are a lightweight compact circular connector derived from a military specification however modified specifically for motorsport use. |
| 04:40 | Many of the Deutsch and Souriau connectors are compatible with one another but both brands also have some connector size or pin arrangements unique to them. |
| 04:49 | So it's common to end up with a mix of the two brands installed on our harness. |
| 04:54 | These connectors require specialised tooling for crimping their pins to the wires in the harness and specific insertion and retraction tools to install and remove the crimped pins from the connectors themselves. |
| 05:06 | We'll look at these tools and techniques in detail later in the practical section of the course. |
| 05:11 | The Autosport and Souriau connectors are all designed with a lip that a moulded shrinkable boot can seal to. |
| 05:18 | However this is sometimes not the case with every connector we'll have on our harness as it's still common to find AMP Superseal 1.0 connectors and Deutsch DTM connectors on a motorsport wiring harness. |
| 05:29 | Along with many other makes and brands. |
| 05:32 | If we have a situation where we need to use one of these connectors, we often need to make modifications to them to accept a sealing boot. |
| 05:38 | Once again we'll cover some examples of this situation later in the practical section of the course. |
