Rough and Tumble Engineering

by James H. Maggard

How about getting into a hole? Well, you are not interested half as much in knowing how to get into a hole as You are in knowing how to get out. An engineer never shows the stuff he is made of to such good advantage as when he gets into a hole; and he is sure to get there, for one of the traits of a traction engine is its natural ability to find a soft place in the ground.

Head work will get you out of a bad place quicker than all the steam you can get in your boiler. Never allow the drivers to turn without doing some good. If you are in a hole, and you are able to turn your wheels, you are not stuck; but don't allow your wheels to slip, it only lets you in deeper. If your wheels can't get a footing, you want to give them something to hold to. Most smart engineers will tell you that the best thing is a heavy chain. That is true. So are gold dollars the best things to buy bread with, but you have not always got the gold dollars, neither have you always got the chain. Old hay or straw is a good thing; old rails or timber of any kind. The engineer with a head spends more time trying to give his wheels a hold than he does trying to pull out, while the one without a head spends more time trying to pull out than he does trying to secure a footing, and the result is, that the first fellow generally gets out the first attempt, while the other fellow is lucky if he gets out the first half day.

If you have one wheel perfectly secure, don't spoil it by starting your engine till you have the other just as secure.

If you get into a place where your engine is unable to turn its wheels, then your are stuck, and the only thing for you to do is to lighten your load or dig out. But under all circumstances your engine should be given the benefit of your judgment.

All traction engines to be practical must of a necessity, be reversible. To accomplish this, the link with the double eccentric is the one most generally used, although various other devices are used with more or less success. As they all accomplish the same purpose it is not necessary for us to discuss the merits or demerits of either.

The main object is to enable the operator to run his engine either backward or forward at will, but the link is also a great cause of economy, as it enables the engineer to use the steam more or less expansively, as he may use more or less power, and, especially is this true, while the engine is on the road, as the power required may vary in going a short distance, anywhere from nothing in going down hill, to the full power of your engine in going up.

By using steam expansively, we mean the cutting off of the steam from the cylinder, when the piston has traveled a certain part of its stroke. The earlier in the stroke this is accomplished the more benefit you get of the expansive force of the steam.

The reverse on traction engines is usually arranged to cut off at I/4, I/2 or 3/4. To illustrate what is meant by "cutting off" at I/4, I/2 or 3/4, we will suppose the engine has a I2 inch stroke. The piston begins its stroke at the end of cylinder, and is driven by live steam through an open port, 3 inches or one quarter of the stroke, when the port is closed by the valve shutting the steam from the cylinder, and the piston is driven the remaining 9 inches of its stroke by the expansive force of the steam. By cutting off at I/2 we mean that the piston is driven half its stroke or 6 inches by live steam, and by the expansion of the steam the remaining 6 inches; by 3/4 we mean that live steam is used 9 inches before cutting off, and expansively the remaining 3 inches of stroke.

Here is something for you to remember: "The earlier in the stroke you cut off the greater the economy, but less the power; the later you cut off the less the economy and greater the power."

Suppose we go into this a little farther. If you are carrying I00 pounds pressure and cut off at I/4, you can readily see the economy of fuel and water, for the steam is only allowed to enter the cylinder during I/4 of its stroke; but by reason of this, you only get an average pressure on the piston head of 59 pounds throughout the stroke. But if this is sufficient to do the work, why not take advantage of it and thereby save your fuel and water? Now, with the same pressure as before, and cutting off at I/2, you have an average pressure on piston head of 84 pounds, a loss of 50 per cent in economy and a gain of 42 per cent in power. Cutting of at 3/4 gives you an average pressure of 96 pounds throughout the stroke. A loss on cutting off at I/4 of 75 per cent in economy, and a gain of nearly 63 per cent in power. This shows that the most available point at which to work steam expansively is at I/4, as the percentage of increase of power does not equal the percentage of loss in economy. The nearer you bring the reverse lever to center of quadrant, the earlier will the valve cut the steam and the less will be the average pressure, while the farther away from the center the later in the stroke will the valve cut the steam, and the greater the average pressure, and, consequently, the greater the power. We have seen engineers drop the reverse back in the last notch in order to make a hard pull, and were unable to tell why they did so.