Connecting it all together

Friday, April 05, 2013

Tags :  electronics

Weight is the enemy of the performance car – how many times do we hear that in motorsport circles? But if we are paranoid about the weight of the chassis, engine, gearbox and all the other ancillary bits and pieces – even the paint on a car – then we need to consider the wiring loom as well.

One way of course to rid ourselves of this parasite (for that’s what it is) is to dispense with as much wiring as possible – shorter wiring ‘runs’, thinner wires, even omitting the wires totally if possible. No doubt few of us will be as drastic as this, but when the loom has been pared down to the minimum, I would argue that one ought to consider reducing the size or weight of the connectors themselves. The modern racecar though, much like its road-going contemporary, is festooned with electronics, so however well intentioned our wishes may be, the challenge to minimise electrical wiring is one that few will relish.

But choosing the correct connector is not just about weight. To finish first in any competition, first you have to finish, and so product performance, reliability and suitability for the task intended are surely the primary requirements. Thus the connector not only has to cope with the expected currents – including any unexpected ‘surge’ currents – it also has to do it with the minimum voltage drop across the electrical circuit, and do so without failing in any number of ways. Racecars are well known for their high levels of teeth-chattering vibration, and the temperature environment of a typical race engine will challenge any electrical component, especially if for reasons of necessity it is mounted too close to the exhaust. Vibration can cause connectors to work themselves apart sometimes, so some form of locking feature is also usually essential.

The hydrocarbon fluids of oil and fuel are never too far away either. Not only do they have low surface tension characteristics, ensuring that they will find their way into the smallest of crevices, but more often than not, given time, they might react with the insulating materials to either soften or harden them depending on any one of the complex chemical reactions possible.

Moisture also is a great enemy of the wiring loom. Once present, galvanic cells may be created, which in turn produce chemical corrosion, eventually reducing the effectiveness of the electrical connection. Gold-plating the connector pins is clearly a must for these challenging conditions, but that inevitably adds to the cost in these budget-conscious times. Sealing against the ingress of moisture in the first place is also clearly a good idea, and while shrinkwrap assists and strengthens the wiring into the back of the connector, detail design of the shrouding around the mating male and female parts of the connector itself will preserve the pins inside. And in all this designers still want that extra pin out of the ECU or an extra channel into the data logger, as well as the growing requirement of redundancy in sensor technology.

Reducing the size of the electrical connectors may be desirable to save weight, but as part of the overall criteria in any electrical circuit it comes fairly low on the list.

Fig. 1 - Automotive electrical connectors

Written by John Coxon

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