Cold Shoulder

As engineers we have to test cars in all environments, and whilst a lot of time is spent testing in hot and cold countries the bulk of testing is done back at the engineering centre in special climatic chambers. These are basically glorified garages with a high powered air conditioning systems that can chill the cars down to -40C or heat them up to 50C.

I have to say that -40 is very chilly, but some weird things happen when testing in a chamber. For a start there is no wind, so as soon as you walk in from the nice warm office you don’t feel the cold, not straight away anyway, it sort of creeps up on you and can catch the unwary out leading to sudden loss of blood pressure and blacking out. This results in the strange phenomena of seeing engineers wearing full Arctic clothing in the office in the middle of the summer, often with frost on.

There are a few crucial rules to observe when getting into a chilled car, everything looks normal, the car has no frost on because there is no moisture in the cell, it just looks like a normal shiny new car. Those publicity photos of cars covered in frost are made by spraying water from a plant sprayer over the car first, who ever said the camera never lies!

But even though the car looks normal if you touch a metal part with a bare hand the moisture in your skin will instantly freeze solidly to the metal part, pulling away will rip the outer layer of skin off but staying put will gradually freeze the whole hand, this is to be avoided.

The reason moisture is not present is that at these low temperatures it simply falls out of the air, which is handy as any dampness in the door seals would freeze and lock them up solidly. The test chamber has electrically heated door seal for precisely this reason. I once made the mistake of driving a car into a chamber after it had been raining, many years ago, by the time the car was cold enough to test we couldn’t get the doors open, eventually three crowbars, a dented door and torn door seal later we could start work.

Strange things happen when you take a frozen car out of the chamber, particularly on a typical wet British summers day when there is a lot of humidity in the air. As soon as the chamber doors are opened the warm humid air rushes in and turns to fog, instantly obscuring the frozen windscreen.

As you drive the car out it works as normal, then moisture freezes on the tyres which are still well below zero, they make a crunching sound as the car rolls forward and can skid if the road is wet. Its strange but for a few yards until the tread warms up its like driving on ice, but on a warm day.

The next trick catches many people out, when first moving the car out of the cell the brakes work normally, but as you drive across the yard ice forms a hard layer on the discs and as you park up the brakes don’t work. By which I mean they don’t work at all, the callipers are squeezing on smooth ice and there is no retardation at all, not even the hand brake works. The trick is to drive with the brakes on until the discs have warmed up to zero.

Proper climatic chambers cost a fortune and are always in short supply, so some companies use cheaper options. I once worked for a well known gearbox manufacturer who used a modified artic freezer trailer that used to take frozen fish to the shops. It was just possible to get a car in and open the drivers door enough to get out, but it was tight. The control didn’t have a thermostat, just a lever that ran the chiller to a greater or lesser degree, there was one engineer who had got the feel for how far to push the lever to get the desired temperature. Usually he got it bang on, but not always.

On one occasion I loaded a prototype car in and he set the control to give us -20 for the following mornings cold start test. Or so he thought. But overnight the ambient temperature dropped unexpectedly quickly and instead of -20 we got something nearer -40, a temperature where the engine had yet to be calibrated and stood no chance of starting at. The only solution was for me to attach a large truck battery (the cold oil was to much load for the car battery) and apply a hot air gun to the intake until it stood a chance of starting. Remarkably this bodge worked and the prototype engine spluttered into a very lumpy idle. It was then that I found my thick soled shoes had frozen to the floor! It was a few more minutes with the hot air gun before I could escape.

Such is the glamorous life of an engineer.

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