James May

James May

James talks gearboxes

You may not want to hear this, but the engine of your car is feeble. I don't care what it is, it's just a limp-wristed bag of bolts. If it had any balls, it wouldn't need a gearbox.

Let's say you drive a middling family hatchback. The engine will produce perhaps 140lb ft of torque. Is that a lot? It shifts over a tonne of car up to over 100mph, so it must be.

But if you've ever reassembled a car engine with a torque wrench, you will know that the human arm can easily produce 140lb ft. I know I can, so that's a measure of just how feckless this so-called engine is. It's weaker than I am.

That's why it needs the gearbox. Without wishing to delve too deeply into the physics of this stuff, the gearbox is actually a torque multiplier. First gear gives you more torque, at the expense of speed, to overcome the inertia of the stationary car. Once it's moving, you can have a higher gear with less torque, and so on. The gearbox is a series of levers of different length, but in circular form.

But how many gears do you need? Well, when TopGear  first appeared on the Baird, that usually meant four, although it was starting to mean five. These days, it's often six, but sometimes there's more. It could be seven or eight.

But let's go back a bit further. Benz's Motorwagen didn't really have any gears. The Model T Ford had two gears, and that was enough to mobilise America. In the Forties and Fifties, lots of cars had just three gears. The proliferation of gears is a measure of the car's progress, it would seem. But I'm beginning to think it's all back to front.

Because the engines of early cars were even more feeble than the ones we know. A really primitive petrol engine will give maximum torque at one engine speed. As refinements were added, the torque spread across the speed range a bit.

First there were things like automatic ignition advance and retard, which previously was the job of a little lever on the steering wheel. Later, there was variable valve-timing. More recently, there has been the widespread adoption of fuel injection and computer-controlled ignition mapping. All these things have helped spread usable torque across the engine's speed range, to make the car more tractable.

Now we are in an era when motoring writers thrill us with descriptions such as ‘a torque plateau like a cross-section of Norfolk'.

“If you’ve ever used a torque wrench, you’ll know that a human arm can produce 140lb ft of torque, so that’s how feckless the engine is – it’s weaker than me”

So surely the number of gears we need should be going down. More usable, more flexible grunt should mean less need to muck about with pesky gear ratios. Yet the number of gears is going up.

Funnily enough, I've just had a shave. Normally, I choose those white and green disposable types. Can't remember what they're called, but you can buy a whole bagful for a few quid.

But here I am in a hotel, and I forgot to bring a razor along, so reception have sent one up. I'm frankly staggered. I remember when the double-blade razor was launched. Again, I can't remember what the first one was called, but I do remember a fatuous advert that said, ‘The first blade shaves you close, the second blade shaves you closer still'.

In which case, why didn't they just fit the second blade? The first one was clearly shirking.

But this razor I've been sent has five blades. What the bloody hell are they all doing?

This razor is rubbish. The head is like the deck of the USS Nimitz, and it won't fit in that complicated bit under my nose. It also has a battery in the handle to make it vibrate. Why? It's a precision cutting tool, and I don't want it wandering around my face like a badly loaded spin dryer. Cabinet makers do not have vibrating chisels, and surgeons do not use vibrating scalpels.

I know what's happened here. Someone launched a three-blade razor, then someone did a four-blader. Then there came the five-blader, so this lot needed a five-blader with vibration for extra shaving satisfaction. It won't end until the head of your shaver is the size of a plasterer's float.

And the same thing has happened with gearboxes. Seven or eight gears just aren't necessary. Six is too many in most cases. It's just a big cog-off between car makers, and it's getting on my nerves.

And that's the problem with working on a programme called TopGear. No one really knows what it should be.

You know where you are with fifth gear.

James May, Column

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