16 August 2014

James May on: the rotating shaft

Some say that fire changed mankind the most. May thinks they're fools…

James May
Car image

I was wondering: what single thing did the most to advance humankind’s lot? Speech must score pretty highly, I suppose, as must writing, paper, discovering how to light a bonfire and Google image search, especially if you’re 14.

Tools were amongst the earliest things to empower us, and it’s generally accepted that the first tool was the hammer, since a rock is a hammer if you use it as one. You could easily make a one-hour documentary about the evolution of the hammer and all the uses it has – I’d quite like to, in fact. But the problem with the hammer is that, to a man who understands no other tool, everything is a nail. It’s what makes Clarkson seem so prehistoric.

I, however, would like to make the case for the rotating shaft. This is what gives apparent life and vitality to the things we like – cars, aeroplanes, speedboats, posh wristwatches – and is the fundamental means by which such things are produced.

The ancient Egyptians could spin lengths of wood between two centres using something a bit like a violin bow. These were the first lathes, and without lathes we wouldn’t have other machinery. Windmills, waterwheels, steam engines, Victorian sewing-machine foot treadles, capstans on sailing ships and the treadmills of Victorian penal institutions were all used simply to make shafts spin, and once your shaft is in motion, you can make everything from flour to gearwheels, and achieve greatness.

Look at your bicycle. I still think the bicycle is one of the greatest inventions of all time, and the cranked pedals you heave upon are charged simply with making that short shaft in the bottom bracket rotate. Once you’ve got that sorted, the chainwheel, chain and sprockets that set the back wheel spinning and you whooping for sheer joy are something of a formality. Even the passive front wheel works because of the rotating shaft it’s mounted on. I know the shaft is fixed and it’s the wheel that turns, but if you were Einstein sitting on the rim, you’d say it was the other way around.

Round and round; a line of force – a vector – qualified by a radius so that it goes on for ever. Rather brilliant, isn’t it?

Now to the engines in our cars. Layout, number of cylinders, capacity, turbocharging: this stuff is all very exciting and one of the reasons this website is as popular as it is, but it’s all done in pursuit of the same simple goal, which is to make the crankshaft spin. Then we can link it to wheels and be on our way.

Given that the endgame is so simple, the means of achieving it seem quite convoluted. The pistons go up and down (or side to side if you are a Subaruist) to drive the crank in the way your legs do back on the bike. But the crankshaft must make some other shaft spin so that the valves can be operated, and they go up and down. Up and down makes round and round, but that must produce more up and down for the original up and down to happen. If you see what I mean.

Our master rotating shaft, the crankshaft, might also be required to drive the shaft of an alternator, so that sparks can be produced to keep the pistons going. The gearbox – again a collection of shafts with a relationship complex enough to warrant some sort of mechanical pre-nup – simply manages the shortcomings of our original shaft’s output so that it can do useful work, and turn more shafts that eventually turn the wheels. But it all relies in the first instance on a single mother of all rotating shafts, just as the early temples of mass production needed a shaft running across the roof to drive machinery.

Now look at a cutaway drawing of a car engine. Remember all that stuff is there simply to provide us with the bit we need, the shaft. It seems a bit of a palaver, doesn’t it?

The electric motor makes so much more sense. It still gives us what we need, but now the rotating shaft is the only moving part. How much more elegant is that? It’s the right way to power a car, and we’ve known it since before the car was even invented, because the electric motor came first.

All that remains is to bring the dragon of electricity to heel. I still want the curling echo of my Ferrari’s V8 for special moments, but elsewhere, this must be the future. Mustn’t it?

Tags: james may



Before the storm whipped up by the GLA fizzled out, there was another one looming on the horizon. A Category 5, and caused by the arrival of the GLA 45 AMG