Toy Fire Trucks and Diesel Engines I

Toy Fire Trucks and Diesel Engines

I have always been fascinated by mechanical equipment ever since I can remember. When I was a child in Jamaica, I remember that we had very few choices of toys to play with compared to children today, especially in the United States. I learned very quickly that it was always going to be up to me to keep my toys working properly and that I would be the one to have to fix them when they broke. Whether it was my bicycle or a small toy truck that had a mechanical motor, I always learned exactly how they worked and I came to understand what every single part of the device did, how it related to every other part of the device, and what would be the result if that part broke or malfunctioned.

I remember the first time that I experienced the satisfaction of repairing something by figuring out how to find a suitable replacement for a part that had broken by altering an ordinary household item to perform the right function. Looking back on it, there was not all that much involved, but it was the process of figuring out what was needed, taking stock of what materials were available to me, and then approximating the best possible solution from the materials that were available that I found rewarding.

In the first instance that I remember, an axle broke on a toy fire truck that I enjoyed playing with. First, I tried to repair the broken axle by taping it together but the tape always failed after a very short time. Next, I tried to fashion a new axle from a straight section of a wire clothes hanger but it was too thick to fit through all of the holes in the truck chassis and in the holes on the wheels. I thought about trying to enlarge all the holes but I realized that some of them were deep inside the frame where it would be impossible for me to reach in order to file them into larger holes.

Next, I tried to find a material that would allow me to trim it easily to the right thickness to fit all the holes that I could not reach. I selected the straightest twig I could find and then I whittled it down to make it perfectly straight and to make it thin enough for my needs. The new wooden axle seemed to work fine when I inserted it through the holes and fastened it to the wheel and I tested it by spinning the wheels and then by rolling the truck around on the floor. Unfortunately, the axle snapped the first time I played with the truck. I examined the broken axle and I also compared the area where it snapped to the truck chassis and I figured out why it happened: the wood was not strong enough to hold up to the sheering force of the metal edge of the holes where it was inserted. At that point, I realized that a new axle would have to be made from metal and not wood and I returned to my original idea of using the piece of wire hanger.

This time, I borrowed two C-clamps from a neighbor who did a lot of wood carpentry, and he was also kind enough to lend me a strong file. First, I filed down one end just to see how much smaller the entire axle needed to be for my purposes. Then, I secured the entire piece of hanger between the C-clamps and I used the file to reduce the circumference of the whole length of the wire. It took longer than I expected, but eventually, I had reduced it to the right size so that it fit all the holes in the truck chassis. Before fastening it, I place the new axle on top of a glass-topped table and I lowered myself so that my eye was level with the table. I carefully rolled the axle on the table while looking underneath it to see where it was less than perfectly straight so that I could file it down a little more in those areas. My new axle worked so well that I was able to enjoy playing with that fire truck for several years before passing it down to younger relatives to play with.

As an adult, I have always found the same enjoyment from the challenges of fixing more complicated devices. My specialty now is working with diesel engines. In principle, a diesel engine is similar to a conventional gas combustion engine except that it does not use any kind of electrical sparking mechanism to ignite the fuel in the combustion chamber. Instead, it uses highly compressed air and a system that vaporizes the fuel sufficiently so that it can be ignited this way. Generally, this part of the process is the most important because only fuel vapor (and not fuel) is capable of being ignited in this manner by compressed air.

Naturally, diesel engines are much more complicated than toy fire trucks, but there are certain conceptual similarities between the two systems. For example, diesel engines require a governor to regulate and control the amount of compressed air that feeds into the combustion chamber. Otherwise, the idling speed and the maximum speed of the engine cannot be properly controlled and the engine will destroy itself. In the types of diesel engines that I enjoy working on the most, (those with mechanical governors rather than modern electronic governors), there are intricate assemblies of weights and springs that make them work.