ROADSIDE TRIBUTE: Three truckies died on the Great Eastern Highway near Coolgardie, Western Australia, during a fierce firestorm in 2007. They were told the area was safe to drive through. By the time they realised they were in trouble and tried to turn back, it was too late.
AT ITS most basic level, a diesel engine - or any internal combustion engine for that matter - is a heat pump. A six-cylinder 16-litre truck engine will need to draw 24 cubic metres of atmosphere in through the air cleaners for every minute it is cruising at 1500rpm. Half of that volume will be used to push the exhaust gasses out in between compression strokes, and the other half will feed the fire in the combustion chamber.
In other words, if you feed pure CO2 or some other oxygen-free gas into the air cleaners, there'll be no ignition and the engine will suffocate. No air, no power.
Just over four years ago, the suffocation of a diesel engine was a contributor to a trucking tragedy that could and should have been avoided.
It was December 30, 2007, and a convoy of trucks had been held up in Coolgardie, Western Australia, as a bushfire raged around the Great Eastern Hwy a hundred kilometres or so further west. Inexplicably, and despite what turned out to be accurate "spot fire" reports, the authorities released the convoy around 7pm.
Within a couple of hours, three truckies were dead and authorities were scrambling to recover as many people from the danger area as possible.
Exactly what happened in the middle of that terrible firestorm we'll never know. But we do know that two of those truckies in a double road train made a fateful decision to turn around when they were only a kilometre from coming out of the fire into clear air.
At the time, it seemed the only possible thing to do. They had accurately decided that they were in grave danger, and although other drivers in rigids and single-trailer rigs had managed to reverse course, their double rig was
going to need a pull-off area to make it.
As soon as one emerged from the boiling black smoke, they made the turn.
That's when the physics took over and sealed their fate.
Firstly, a turning road train draws a lot of power just to handle the scrub-off from four sets of multiple axle groups - 40 tyres in all. The sharper the turn, the more power is needed. So the boys would have been pushing hard to get it turned around and pointing straight as soon as possible. The rig was found on the wrong side of the road heading east, so the guys had straightened out coming out of the turn-off to get speed up faster, and were pushing to cross back to the left.
Unfortunately the intense heat had already started to soften the tyres, which probably doubled or even tripled the power needed to keep the wheels turning.
Think about how much harder it is to push a wheelbarrow when the tyre is soft. They would have found that full throttle just seemed to get them nowhere. Finally, stuck in the middle of a terrifying firestorm, so much oxygen was being sucked from the atmosphere that the engine lost power dramatically, the tyres melted down and the rig ground to a final stop.
Had these drivers known how bad the fire situation was, they'd never have turned a wheel from Coolgardie, no matter what police and emergency services said. No experienced truckie would put himself in such danger.
This tragedy is a powerful lesson in staying away from bushfire danger.
This bushfire season sees extreme heat visiting so many tinder-dry areas across the Australian interior. As the Hill Street Blues TV show sergeant used to say: "Be careful out there."