Footprints

It’s years since I’ve read Daniel Defoe’s, Robinson Crusoe, the story of a shipwrecked beard; although I do remember, as a child in the 1960s, watching a TV series based on it.  Or should I say, I remember listening to the theme tune.  When it started it was like nothing you had ever heard before; a sort of wailing that seemed to build in the first second or two, as if someone had forgotten to plug in the record player. Like when you hear a car skidding - a screech that at first you think, ‘What’s that’, and then in a moment it’s full on and you recognize it for what it is.

It was like Crusoe himself: I mean, there was definitely something  lacking at first. When he arrives on the island, Crusoe walks along the beach until he sees footprints, and then thinks someone else is there too.  Surely he must have known he was smack-bang back where he started and the prints were his.  I couldn’t understand how he let himself think he wasn’t alone.  What about the sun? Didn’t he see that because its position appeared to change in respect of his direction of travel he was actually walking around an island? 

And then, by way of explaining his idiotic behaviour as some natural desire not to be alone, Friday arrives. To me, Friday was simply another inexplicable anomaly. Crusoe was so pleased when he finally got a companion.  Why?  All I wanted for him was that he would build machines to pass his day, to ease his life, to give him fulfilment, to make the most of his freedom – not spend his time fussing around with another person.  

There's a rhythm to the story of life and we all have an individual beat to go along with our own lyrics; a rhyme that resonates for us and us alone. Mine has always been the wonder of making things; and my music is engineering. All those years ago I would walk around our family garden thinking of all the things to construct and discover, imagining that I was alone on a desert island - while my mother implored me to put my socks and shoes back on.

I wondered what would have happened if, as a castaway on the island, I had a car, or better still, a truck. I could run lights for my cave off its alternator; attach drive belts and pulleys to its wheels; move great objects with it; haul with it; escape in it; hide in it.  I could even drive round the island to make sure I was alone.  Today, I look back with longing at the simplicity of those childhood dreams and invention. Now I know that things are more complex and if I had a truck, and I drove it round the island, I’d be considering the tyres and what was going on with their footprint.  My mind is too cluttered and my imagination too conditioned for the romance of adventure.  Knowledge has marooned me in a suit and tie.

I would be thinking, not of natives, cannibals and cutlasses but of forces, slip angles and hysteresis. Tyres, I would say, are viscoelastic and exhibit behaviour that`s not quite plastic.  Cornering power, inflation pressure and vertical load, are all connected with tyres, grip and the type of road. And I’d think that if the beach were a road, it would generate not only mechanical grip but adhesive grip as well.  Like when sellotape is stuck onto a smooth surface - a desk, for example.  I’d probably imagine molecules in the tyre and road being attracted to one another and how the tread pattern would be trying to disperse water and make sure nothing got between the two surfaces. I wouldn’t be able to get friction out of my mind.

Mechanical grip would also be there; right there at the front.  I would be seeing in my mind’s eye the tyre slipping on the road as  it rotated onto its footprint.  Every time, its direction of travel being different from the direction it was pointing.  I’d see how the tyre’s carcass and tread deformed and then recovered at the footprint, as the truck cornered.  I’d know that this recovery rate was different to the deformation rate and that’s how the tyre clings on, mechanically.  Materials, they’d be there as well, swirling around my brain: what’s best for tread and what for carcass. High hysteresis; more grip but more heat.  Cross-ply construction, more internal friction but stronger; radial ply, less heat and lasts longer.

When I cornered around the island, I would know that weight was being transferred across the truck and that its cornering power was being compromised.  Grip is increased as vertical load is increased, but the loss on the unloaded side is greater than the increase on the loaded side. All that scenery; those palms and white sands wouldn’t register, as I pondered the question of inflation pressure. Higher pressure, less slip; lower pressure, greater grip.  A tyre possesses a finite amount of friction - use it all for cornering and there’s none left for traction.  Lift-off oversteer, yaw rate gain; nothing will ever be quite the same. 

Sitting at my desk and thinking of those uncomplicated days in our garden, I know there`s no going back and that in the rhythm of my life the music is now softer and almost every word has changed. Footprints in the sand soon disappear.