'Now You see it, now you don't . . .!'

It's 3.30 in the morning in a junction railway yard, in the middle of a very large New Zealand city, the wind is cold and increasing in ferocity, and blowing straight off the sea.

Along the West side of the railway yard is a row of offices and shops - unoccupied at 3.30am, to the East, about half a mile away, houses and hi-rise appartments, while at the Northern end is an open space where the railway line terminates on a bluff.

At the Southern end, a road bridge over two main lines and the end of the yard.

This is New Zealand Railway's Newmarket Railway Yard, teason: Winter, the year: 1983.

Aside from the occasional vagrant - invariably looking for a place out of the wind and trying to keep warm, the yard is uninhabited - although there are 10 fully-loaded tank cars - each filled filled with approximately 5,000 gallons of petrol  (gas, for our US readers) from the refinery at Whangarei, along with an assortment of goods wagons; all bought into the yard by a South-bound Goods train (Freight) and waiting to be picked up by a suburban shunting service (Local switching service?) and taken 'down the hill' into Auckland

The yard does however have one railwayman on duty - a Signalman (Tower Operator) perched up in his Signal-box (Tower) some three-quarters of the way along the yard.

There is no-one else around and the Signal-box is completely isolated - the nearest possible humans being some 400 yards away on a main thoroughfare - behind the office buildings.

 The Signalman can see all the wagons and most of the yard from his airy some 20 feet above the ground, and, because he has according to his  railway masters 'ownership' of the yard, is every so often looking out his 'Box windows to see if everything is OK with the wagons in the yard - not that anything would ever be wrong - it is after all, 3.30am and even the most hardened 'street people' are trying to find shelter and keeping warm - the wind is very cold - and rising!

During one of his frequent checks of the wagons, the Signalman notices a 'flicker' of light under a wagon in the yard. He initially thinks he is seeing things - until it appears again - then disappears.

A trick of the light?

Not sure, so he keeps a closer look, and, once again, sees the 'flicker' which again disappears.

Mmmmm - not good, so, torch in hand he goes down the 'Box steps to investigate, though not being sure what it is hes actually looking for.

Along the first rake of wagons - nothing, but again the 'flicker' appears - and disappears. 

The second rake is next - and again the 'flicker' - and this time the Signalman can see where it is - between the blades of  a ground throw' point (think of the 'Caboose Industries manual point levers).  Nothing to worry about - the  and grease used to lubricate the point blades builds up and mixes with dry vegetation, wind-blown paper etc, to create a combustible mixture, which can be set on fire by a locomotive when it applies its brakes - it only needs a spark and away it goes.

But why does it disappear?

The signalman then notices that the 'flicker' is near one of the tank cars and really starts to wish he was elsewhere, but still doesn't know what is causing the problem.

Slower now, he walks forward to find . . . what?

The 'flicker' - now seen to be a flame is now there - and it IS in the middle the point-set, but so is something else - and the signalman really doesn't wish he knew about it. . . because it is directly under a very full tank car - yet it still goes out!!!!

It is at that point that things become very interesting - and the Signalman really does wish he was somewhere else!

Inspection with his torch reveals that the tank car had a previously-unknown hotbox (an Un-lubricated Wheel bearing caused by a lack of oil in the axle box. Friction builds-up as a result and the bearing becomes hotter and hotter, to the point where it can eventually melt and distort, derailing the wagon ).  The axle-box was glowing cherry red because it was so hot, but this in itself was not the cause of the 'flicker'/flame.

The signalman then became aware of a quiet, quite regular 'hissing' from the vicinity of the 'box and while not sure exactly what it was, DID notice that, as the 'hissing' occurred, the flame grew and then vanished - most odd!!

But not for long!

A further check with the torch revealed that the hissing was caused by a very thin, very fine line of Petrol that was oozing from a seam directly above the 'hot box' and dripping onto the 'box itself.

The hissing was caused by the fuel landing on the axle box, from whence it was 'bouncing off'.

The hot box was generating enough heat to ignite the fuel as it 'richocheted' off it and fell past, yet there was not enough heat to actually ignite the fuel as it fell from the tank-car itself onto the 'hot box' 

It also appeared that because the petrol was liquid, rather than vapour, it was, effectively, putting itself out - as each sucessive 'wave' of drips fell, it put out that which had gone before, before it in turn caught fire 

This seemed to explain 'flickering' - never enough fuel to actually completely ignite before the flames were 'smotherd by the next 'wave', and so on, and so on - a continuing cyle.

And, as noted before, the wind was up, and it  was blowing the vapour away before it could become concentrated and explode.

The signalman of course now found himself in an interesting situation - what could he do to a) put the fire out. and  b) could he be sure  that he would even be able to make it back to his signal box to get 'something' with which he could put the fire out anyway would, after all, only require the leak to increase a very small amount before something in the nature of a loud, explosive, somewhat damaging noise took place.

The dilemma's of responsibility . . .

So, what happened?

Sadly (perhaps predictably) Dear Reader, you will have to wait for another 'Blog, and, in case you are wondering, this certainly did happen to me - Komata - but of course, you knew that anyway didn't you?

Happy modelling - and thanks for reading.

Komata

"TVR - serving the Northern Taranaki . . . "