As the approaching morning sun added a blush of light to the eastern sky, the trainman climbed aboard the silent, resting locomotive. As was part of his morning ritual he set about preparing the massive engine for a day’s work. He knew that today would be an uphill day, as they would be gradually climbing from the eastern plains towards the foothills of the southern Rocky Mountains.
With that agenda in mind, he took extra care and caution as he went about his routine tasks. For he knew that the day’s work for the engine would stress its capabilities and require careful and constant tending from the train’s support crew throughout the journey. So, in the cool of the morning, he busied himself with making sure the all of the routine steps involved in the care and feeding of a steam locomotive were tended to.
First he did a thorough walk-around to make sure none of the wheels were chocked, or otherwise blocked or impeded. Once satisfied of that, he checked one of the most crucial components of the machine’s makeup - the water supply. He did this by means of the sighting glass. This small vertical tube, always directly in the line of sight of the engine’s operators was of utmost importance. It’s simple design, basically a section of glass piping, allowed the trainman to visualize the water level in the engine’s boiler, just forward of the firebox. Too much water and the engine’s output would quickly become inefficient; and could ultimately allow water to digest into the power-delivering cylinders, which, in turn, could quickly cause extreme a mechanical breakdown scenario.
On the other hand, and greatly more concerning, would be having too little water in the boiler. If that happened, there was the very real risk of the firebox becoming overheated from the extreme steam temperatures, to the point of failure. The softened firebox walls could then fail by rupturing, resulting in a jet of high powered steam being blown through the firebox directly into the crew’s cabin. The threat of such a horrible death was not taken lightly by the train’s crew. Our trainman checked, and rechecked the boiler water level in the sight tube; going so far as to purge the sight tube by opening a lower level and letting the water drain then making sure it refilled from the top. The crew would also check the level of the portable water supply carried atop the engine to make sure it had been correctly topped off the evening before when the engine had been shutdown for the night. Running out of water between water supply stations was never a good thing.
With water being one of the key components for the ancient formula for making the steam that would power up this hulking mass of machinery, he set about on making sure the other critical component was available. This he did with a quick glance over his shoulder to the tender car that was coupled to the locomotive, eyeing the small mountain of dark coal chunks. The chemistry and process was simple, yet complex at a deeper level. But at its simplest, the coal would produce fire, and thus heat; the heat would transfer its energy to the water, and the water would magically metamorphose into steam. And through a clever concoction of tubing, cylinders, and connecting rods, that steam would manifest its energy by slowly rotating the massive drive wheels to move the heavy freight cars along steel rails bolted to the ground. Such was the science of trains.
Making sure that the train could roll forward, was only part of the critical startup duties of the trainman. For he next checked the brakes to make sure they were tightly applied, he verified that the regulator was closed, and that the reversing lever was in mid-gear, and the brake cylinder drain cocks were open.
One important step in the checklist of things to do to make sure the train could go and could stop, was to make sure the sand dome was full of the correct grade of sand and that it was prepared and suited for its intended purpose. The sand dome was situated high atop, and in the middle of, the locomotive’s body.
Here it served two purposes; it dried the sand, and it allowed for gravity feed as a delivery mechanism. Both of those characteristics were a critical part of the process of train sanding. The sand was stored and maintained in optimal condition for its intended purpose and, as long as it was in optimal condition, it could make use of the free transport and application method provided by gravity. Optimal condition is the most important element of the train sand formula; if allowed to have too much moisture the sand would clump and thus clog the feeder tubes that allowed the reservoir to empty itself.
So what is train sanding? Consider the nature of train tracks and locomotive wheels; smooth steel wheels rolling on smooth steel rails. Now consider the massive tonnage of mass that a locomotive was expected to leverage into motion from a standstill, overcoming the tremendous inertia of gravity against all that weight; and likewise, consider the opposite situation when a locomotive was expected to bring the careening load of hundreds of thousands of cargo to a safe stop, all while using those same slick wheels rolling on slick rails. Throw in the added impediments of sloping terrain, both uphill and downhill, and the occasional wet, or snowy, or icy, or leaf-covered tracks and you can begin to see the root cause and the seriousness of the situation. After all, the point of actual contact between the large-circumferenced wheels and the relatively narrow rails was a scant few square inches at most.
One might argue that the massive weight of the locomotive pressing the wheels against the track would, by making use of the omnipresent gravity, provide the needed force to keep slippage to a minimum; and for the most part they would be right. But, the exceptions to the rule could make or break a train journey. After all, if you can’t get the train rolling when you are ready to depart, or get it stopped when you need to - it’s not going to be a very effective journey.
And there you have the need and the solution of train sand. At some point, some common-sensical mechanic instinctively knew that applying a few grains of sand to those critical few square inches of steel against steel could work wonders toward overcoming the wheel-to-rail slippage problem.