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Maritime Machines

Countless machines are used in the design, construction and operation of boats. Simple machines are used individually or in combinations to make a boat work: levers aim a cannon, pulleys lift up cargo, and a windlass can haul heavy loads. Traveling by water is so efficient in part because of the many ways sailors use machines to make their work easier.

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Maritime Machines Introduction
Why Travel By Water?

Before the invention of mechanical engines in the 19th century, there were really only three kinds of power; falling water, wind, and muscle power. For most people this meant that if you wanted to go somewhere you walked. And if you had a load to move, you had to carry it somehow.

This was all done by muscle power. Rollers or wagons could make it easier to pull or push your load. Using the muscle power of animals like horses, oxen and camels could make it much easier for the people. But even if they used strong animals to help them, it was impossible to move things that were too heavy. A long caravan of pack animals or wagons was necessary to move things over the land. In addition, early roads were often very poor or dangerous to travel. However, moving things by water was much easier.

The main reason moving things by water was easier was because they could float. When the water holds up most of the weight it is called "buoyancy". Even though the strongest man can only carry a load of a few hundred pounds a short distance, anyone can push, pull or paddle a boat with a ton of cargo. So putting things on a boat make it easy to move around wherever there is water. It is especially easy if you don't need muscle power at all and are able to flow with the falling water of a river or use sails to be blown by the wind. By using boats and ships, it was easy to move large cargoes long distances anywhere you could get by water. Even today, ships are still the easiest way to transport large cargos long distances. Understanding boats and the maritime machines that make them work is interesting and fun.

Simple Machines

From the earliest times, people have looked for ways to make their work easier and more efficient. This has led to the invention of innumerable machines and tools, from cutting with a sharp rock to blasting off in a spaceship. Despite the complexity of many modern devices, most of the tools we use are combinations of a few "simple machines." Whether used individually or together, having the right machine for the job is usually the first step in getting any work done.

The same simple machines that are used on shore are also used on ships and boats. The tools used to build them, the cranes, wheels and ramps used to load them, the oars, sails, or engines to propel them are all applications of a few simple machines.

Inclined Planes

Inclined planes are perhaps the simplest of simple ma¬chines. They have no moving parts and appear in nature and man-made structures everywhere. They make lifting easier.

The simplest form of inclined plane is a ramp or gradually rising road or trail. Instead of lifting a load straight up, we move it gradually up a sloping surface. By lifting it a little at a time we gain mechanical advantage. The more gradual the slop the easier it is. However, as in all machines, if you gain mechanical advantage you lose something else, in this case distance. To make an inclined plane very gradual it must be very long. At some point it will become too long. So an inclined plane must be long enough to give you mechanical advantage, but not so long that it doesn't fit where you want it.

Ramps, stairs, and ladders are the most common kinds of inclined planes on boats. You use a ramp to launch or pull a boat out of the water. The gangway to board or load a ship is also often a simple ramp. If you cut notches in the ramp so that your feet can stand flat, you create a staircase. A staircase can be much steeper than a ramp. You are able to lift yourself up the staircase easily because your feet are flat on each stair tread. A ladder can be even steeper, or straight up, but allows you to lift yourself one step at a time.

Inclined planes can be combined with wheels or pulleys to make work even easier. This may be as simple as rolling a barrel up a ramp, a conveyor belt, or having moving steps like an escalator. Anything that must be lifted can be done so more easily if we can do it gradually over the distance of an inclined plane.

Levers

Levers are so common that we sometimes don't even realize we are using them. The easiest way to spot a lever is to look for something long and straight, usually referred to as a "bar." It may be very long, like the arm of a crane, or quite short, like the crank on a pencil sharpener. To be a lever the bar must rest on or turn around a "fulcrum." This creates a simple machine when you apply effort to the bar on one side of the fulcrum to produce force on the other side.

A lever can either increase power or speed. It also changes the direction of the force you apply. When you use a hammer to pull a nail, the handle of the hammer is longer than the claw. The extra length produces "mechanical advantage" and you are able to pull the nail out of the wood. When you turn the hammer around to drive the nail into the wood, the extra length of the handle makes the hammer head move faster than your hand. This produces more force to drive the nail into the wood. The longer the lever, the greater the power or speed it can produce. A crowbar has more mechanical advantage than a hammer for pulling nails because it is longer. The tip of a fishing rod moves faster than the head of a tennis racket because it is longer. Of course if a lever is too long it becomes too heavy to move. It is important to have the right size machine for the work it is designed to do.

Wheels and cranks are special types of levers. The fulcrum is the axle around which the crank or spokes turn. Power is increased because the diameter of the wheel is greater than the diameter of the axle. Speed on the outside of a wheel is greater because the turning circumference of the outside of wheel is much greater than the turning circumference of the axle, even though they are turning at the same rate.

Ships and boats depend upon levers to operate them. Many of the tools used to build and repair boats have levers as part of them. The handles of axes, hammers, chisels, and drills are all levers. The rudder, tiller, hand spikes, yards and booms are all levers that are needed to sail a ship. Even nautical instruments like clocks, compasses, and sextants have large and small levers built into their works to make it possible to navigate ships at sea.

Wedges

Wedges are a special type of inclined plane. The advantage of an inclined plane is that a force can be applied over a distance. In a wedge, the force is applied in a very small area, or edge, at first and then spread over a larger area. In a simple splitting wedge, the cutting edge is easily driven into a log. Then as the wedge is driven in further, the log is forced apart wider and wider. All cutting tools work like this.
Wedges can be heavy and powerful or thin and sharp. A heavy splitting maul has a broad head that forms a wide angle at the edge. A knife has a thinner blade that forms a very sharp angle at the edge. Generally, the smaller this angle the sharper the blade.

Choosing the right tool for the job is especially important with wedges. A chef may have a dozen different knives of different sizes for cutting different kinds of food. A carpenter may have several different axes for cutting different sizes of wood. You don't want to try to cut a tomato with an axe. Each tool is designed to have the right amount of sharpness and power to do the job it is intended for.

The usefulness of a wedge is a combination of sharpness and power. The sharper a tool is the easier it will cut. The heavier a tool is the greater its power. A knife is sharper than an axe, but you wouldn't want to cut down a tree with it. The power of the axe will make the job go faster. Some tools have only one wedge, like a knife blade or chisel. However, saws have a whole row of wedges, teeth, working together. Even though each tooth only cuts off a small piece, the motion of the saw can quickly cut through the material.

Wedges, cutting tools, and edged weapons are among the oldest and most important machines we use. They may be made of stone, wood, bone, or metal. We find them everywhere in our daily life and in every part of building and operating boats.

Pulleys

Pulleys are an important part of a ship's rigging. They are called running rigging because the ropes move to lift cargo, hoist yards, and trim sails.

A pulley can change the direction of a force, apply effort far away, or increase power. Pulleys are used to hoist sails so that the work can be done safely far below on the deck. The crew can pull the ropes down to hoist the sail up. A block and tackle system can increase mechanical advantage to make the work easier.

You can determine the mechanical advantage of a block and tackle in three ways. One way is to count the number of ropes that support the load. The more ropes, the less each rope carries, so the less force is needed on the hauling line. Another way is to measure how much rope is needed to lift the load. If there are two ropes supporting the load, each rope holds half the weight. However, twice as much rope must be pulled through the system to lift the load. The third way to determine mechanical advantage is to measure how much effort is needed to lift the weight of the load. If a 100 pound load can be lifted with 20 pounds of effort, the system must have a mechanical advantage of 5.

The more ropes there are in a pulley system the more problems there are with friction. When ropes rub together they produce friction, which reduces the efficiency of the system. Some of the effort must be used to overcome the friction as well as lift the load. So pulley systems are de¬signed to reduce friction whenever possible.

Gears

Gears are often hidden where they are not easily seen, like inside the case of a watch or the transmission box of a car. In their simplest form gears are wheels with interlocking teeth around their edges. As one gear wheel is turned, the other gears it is connected to will turn as well. Like other simple machines, gears can increase power, increase speed, or change the direction of a force.
Gears that are designed to increase power have a small gear wheel that turns a larger gear wheel. The small drive wheel must be turned many times to turn the large wheel just once. Although the large gear is moving more slowly, it will produce more power. The crank on a boat trailer winch must be turned many times for its small gear to turn the large gear that slowly drags a boat out of the water.
To increase speed, a large gear turns a small gear. Every time the large gear turns once, the small gear will turn several times. The wheel gears on a bicycle are smaller than the crank gear, so the wheel turns faster than the peddles. In a hand drill the crank is attached to a large gear that turns a small gear attached to the bit. This causes the bit to spin fast enough to drill into the wood.

A hand drill is also a good example of how the crank gear turns in one direction, but the bit gear turns perpendicular to it. Gears whose teeth interlock will turn in opposite directions. Gears can also be cut to turn at an angle. Changing the direction of a force often makes it easier, or safer, for the person who is applying the effort to operate the machine.

On boats gears are often part of engines, drive trains, steering mechanisms, winches, and instruments. However, the teeth of gears must fit precisely, can be affected by water, and sometimes jam. Because of these problems, traditional vessels relied more on simpler and more reliable mechanisms whenever possible.

Screws

Screws are special kinds of inclined planes. To make a screw you wrap an inclined plane around an axis. The easiest place to see this is in a spiral staircase or circular ramps in a parking garage. Wrapping an inclined plane around doesn't take up as much space. However, most screws are quite small, like nuts and bolts or fasteners for holding wooden or metal pieces together. Screw fasteners are turned into a nut or piece of wood slowly. Each twist draws the screw in deeper. A bolt or screw also holds very tight because there is so much friction along the surface of the threads.

Because they are inclined planes, screws can also be used to move things, often in combination with other gears. The screw in a vise or clamp can be used to squeeze things together. A special screw called a worm gear may be used as part of a winch or ship's steering gear. Very tiny screws are used to adjust a compass or sextant for taking very accurate measurements.

Perhaps the most interesting marine screw is a boat's propeller. A propeller on a ship or airplane is designed to work in a fluid like water or air. The blades of the propeller are turned so that they push the fluid in one direction as they turn. This pushing is called thrust. By thrusting the water behind a boat, it pushes itself forward through the water. If the propeller is turned backward, the boat is thrust in reverse. The development of engines and propellers in the Nineteenth Century completely changed the way ships were powered and propelled through the water.

Experimenting with Machines

Simple machines are all around us and we use them every day, often without realizing it. It is not hard to find them and we can often see their working parts. Understanding where they are and how they work is fun and interesting. The following activities will help you begin to explore the fascinating world of maritime machines.

Lesson Plan Order