CHAPTER 3 : Ping-Pong Ball Minigun

PROJECT SIZE: Small
SKILL LEVEL: ★✩✩✩

Figure 3-1

THERE ARE TIMES WHEN THE COIL GUN will not bepowerful enough for the task that the Evil  Genius has in mind. Sometimes you need to totally overwhelm your enemy with superior firepower. This minigun design will fire ten ping-pong balls per second at considerable speed. An entire magazine of 50 ping-pong balls can be emptied in just five seconds.

It is a very easy project to make and requires little in the way of tools or special equipment, and all the parts can be obtained from the Internet or your local hardware store (see Figure 3-1). This project is seriously good fun and definitely more entertaining than blowing leaves about. However, it is strongly recommended that the Evil Genius have his minions on hand to pick up all the ping-pong balls, as this can become a bit tedious.

This design is described in such a way that you can adapt it for your particular leaf blower. Also, with the exception of a bit of glue, the project does not irreversibly alter the leaf blower, so it can resume its original use should there suddenly be any leaves to blow.

WARNING :

This is not a real gun, and ping-pong balls will not generally damage humans unless shot at very close range, at the eyes, or swallowed. However, a number of aspects of this project are dangerous.
■ It uses electricity, and we do not modify the electrics of the leaf blower. However, you should observe the safety instructions that came with your leaf blower.
■ Do not put your hands or fingers into the leaf blower when it is on or even just plugged in.
■ Do not place your eye or anyone else’s into the gun’s line of fire.

What You Will Need

The components for this gun are all readily available. Leaf blowers are all slightly different, so you will probably have to modify this design to work with your particular leaf blower. Before buying the parts, however, read through the whole project and try out a few tests on your leaf blower to make sure it is suitable, and also to determine roughly what length of pipe you will need. Obviously, the most important part of this project is the leaf blower. Various types of leaf blowers are available: electric ones, gas ones, ones that just blow, and ones that both blow and suck up leaves into an attached bag. The leaf blower used by the author is an electric one, which also has a bag for collecting the leaves. It is the aperture that the leaf collecting bag attaches to that is used to introduce the ping-pong balls.

If you have some other type of leaf blower, then as long as the air outlet is wide enough to accommodate a ping-pong ball and there is a spot in the air path where you can insert the balls, you should be able to make something. So, read through the rest of this chapter to understand the principals of what we are trying to do and then adapt them to work with your particular leaf blower. 

The balls need to be a good fit with the pipe. They should fit into the pipe easily and run slowly through it if you tip it. If the balls are a lot smaller than the pipe, they will not be fired out as fast as they could be. On the other hand, if they cannot move freely enough through the pipe, they will become stuck.

That is why a 40mm internal pipe diameter and 38mm-diameter balls are a perfect combination. This ensures there is just enough space for our round projectiles.

Be wary when buying your ping-pong balls, as the international standard size of balls since the year 2000 Olympic Games is now 40mm. Prior to that, 38mm balls were the most popular, especially in China. Plus, 38mm balls travel faster and can take more spin. This caused controversy at the time, as some saw the introduction of the bigger balls as a way of giving the non-Chinese competitors an advantage. This is clear evidence of the Evil Genius at work in the world of table tennis.

Plenty of people still sell 38mm balls (often from China), but check before you buy. You will also find “plastic” ping-pong balls on eBay. These are made of soft plastic, and tend to be made to far looser tolerances than proper celluloid balls. So even if these types of balls are advertised as 38mm, they may not be exactly 38mm, so try and avoid these, unless you already have some samples to try in a pipe.

It is also a good idea to take a ball along with you when you go to buy the pipe. In addition to the parts just listed, you will also need the following tools:

TOOLBOX :

■ Hacksaw
■ Scissors/craft knife
■ Epoxy resin glue or hot glue gun

Assembly

The Evil Genius still has a yard in which leaves must be blown, so as we mentioned earlier, this project does allow his leaf blower to revert to its original use in the fall. Better yet, it is an easy project to construct, since it is a simple design. The project adds three barrels to the leaf blower that are made of plastic wastewater pipe. These help channel the ping-pong balls, increasing the accuracy of the gun. There is no complex magazine or trigger mechanism; instead, the magazine is hinged onto the side of the leaf blower and the balls are simply tipped into the leaf blower.

When used as a gun, the leaf blower is held upside down to allow balls to be poured into the aperture where leaves are normally collected. The leaf blower used by the author is shown in Figures 3-2, 3-3, and 3-4. Unless you have the same model, you will probably find that your leaf blower is a different shape, but with a very similar basic design.

Familiarize yourself with the design of your leaf blower and compare it with the author’s. Turn it on, and if it has different settings, find the setting for maximum blowing power out of the nozzle. Also, look through it to see the path the air takes. You can also try dropping a ping-pong ball into it at the air-intake while it is running. Do not put your fingers inside the blower. This should be fired out, albeit not very fast or accurately. Work out where the balls will need to be introduced, as this will determine where you attach the magazine. 

Your leaf blower may have a round rather than rectangular nozzle. If this is the case, you can either fit the three waste pipe barrels in a row, as described in these instructions (and perhaps adapt things by fitting them in a triangular arrangement), or use just two barrels.

Figure 3-5 shows the design of the project. This is a simple design; the leaf blower does not need a lot of modification. Essentially, it just needs barrels to direct the balls accurately and a container for the balls. The container is hinged so that to fire the gun, balls are simply tipped into the leaf blower. As we mentioned earlier, the leaf blower is actually held upside down to allow the balls to be tipped into the inlet, where they fall into the path of the air jet, which whisks them into the barrels and fires them out the other end. The barrels are wedged into place with blocks of expanded polystyrene packing material that has been cut to the right size. This also has the effect of blocking most of the air that would otherwise flow around the pipes, thus maximizing the flow through the pipes.

The following sections take you through the construction step by step.

Step 1. Cut the Barrels

The PVC pipe can be easily cut with a hacksaw. You will get a cleaner, more perpendicular edge if you use a large sturdy hacksaw, but if none is available, then a small hobby hacksaw will work fine. They should be cut to a length where one end of the barrel protrudes from the nozzle of the leaf blower by about an inch (25mm) and the other end stops about three inches from the air outlet of the blower (see Figure 3-5).

This should allow the maximum flow of air into the pipes. Having the pipes protrude from the end of the leaf blower serves to make the device look more gun-like. Without it, the enemy of the Evil Genius might get the misleading impression that they are simply about to be blown to death and fail to take the Evil Genius seriously. That is something no Evil Genius will tolerate. The PVC pipe is surprisingly easy to cut. When cutting, first draw a line around the pipe where you want to make the cut. Then, unless you have a large sturdy hacksaw and vice, cut around the line, shifting position as you start to cut into the middle. 

Once cut, use a file or knife to scrape around the newly cut rim and remove any burrs. You should then be able to put a ball in one end and have it freely roll to the other and fall out. Having cut the barrels, tape them together with duct tape a few inches back from each end, as shown in Figure 3-6. This combines them into a
single solid structure. As mentioned earlier, if the pipes will not fit into the leaf blower side by side, you can experiment with either taping them together in a triangular pattern, or just using two barrels.

Before you fix anything in place, hold the pipes where they leave the leaf blower, turn the leaf blower on, and find the position for the pipes where you get the strongest blast of air through them.

Step 2. Fit the Barrels

The pipes are held in place by blocks of expanded polystyrene packing material (Figure 3-7). These are slightly larger than the gap they are filling and wedge the pipes firmly in place. They do not provide a complete seal for the pipes, but they do block most of the air flow around the pipes, so nearly all the air is directed into the pipe. Figure 3-8 shows the block for the nozzle end, and Figure 3-9, the one for the outlet end. Notice in Figure 3-9 how the pipes line up with the air outlet from the outlet vent at the bottom of the figure.

Before we go any further, let’s do a quick test of our gun. First of all, select a disposable minion and stand them about 20 ft (9m) from the gun. Now set the leaf blower to blow mode, turn it on, and pop a ball in front of one of the pipes near the air outlet. This should fire the ball at a considerable speed at the minion. Repeat the experiment, throwing a handful of balls into the “firing chamber” and watch the minion dance for your amusement. Picking a minion that wears glasses will reduce the chances of damaging their eyes.

Step 3. Create the Magazine

A large plastic water bottle was used to hold the balls. The top of this, where it narrows to the cap, is cut in such a way as to leave a flap that can be bent into a hinge (Figure 3-10), producing a shape that is basically cuboid. The hinged flap is then glued to the side of the leaf blower. To fire the gun, simply tip some balls from the magazine into the leaf blower inlet. After much experimentation with various trigger mechanisms, this was found to be the most effective way of controlling the firing of the gun.

Testing

It is now time to try out the gun. The gun should be used indoors, or you are likely to lose the ping-pong balls. Once again, a minion is required as a target. Stand at least five yards (meters) away from the minion. After giving them strict orders not to step on any of the pingpong balls, fire up the leaf blower and tip in a few
balls to get your aim right. Once your aim is accurate, pour in the rest of the balls as quickly as possible.

Finding the Muzzle Velocity

We can measure our muzzle velocity using the same approach we did with the coil gun (see Chapter 1). We will only need a single ping-pong ball and the impact target must be placed much further away. The arrangement we used is shown in Figure 3-11. 

As a target for measuring the speed of the balls,  a wall, window, or other solid object is much better than a minion. Minions are soft, and while they do make a noise when hit by a ball, a considerable delay occurs as the message slowly propagates through their nervous system and eventually reaches their brain. This delay tends to spoil the accuracy of the figures.

Your laptop should be positioned close to the target rather than the leaf blower to reduce the extraneous noise created by the leaf blower. The leaf blower is very noisy, so it is much harder to tell from our sound trace exactly where the ball left the nozzle of the gun. A trace is shown in Figure 3-12. The range between when the ball leaves the gun and when it hits the test target is marked on the diagram. The only way to determine the moment the ball leaves the gun is to repeatedly play part of the sound wave. Your built-in signal processor (brain) will be able to separate the “pop” as it leaves the nozzle from the general roar of the
leaf blower.

From this trace, we can see that our ball took 0.6 – 0.08 or 0.52 seconds to travel 5.5 meters, indicating an average velocity of 10.6m/s, or 24 miles per hour. Being very light and having a large surface area, the ping-pong ball will lose speed quickly, so the muzzle velocity is likely more than this figure.

An alternative to measuring the velocity with sound would be to use video. Use a similar arrangement to the sound, but set up a video camera at right angles to the flight of the balls. If you know the number of frames per second used by the video camera, then by estimating the distance the ball has moved between frames, you can work out the velocity.

The only problem with this approach is that you need a lot of room so you can put the video camera far enough away from, and to the side of, the flight of the balls. The author did not have a lot of success with this approach; the balls just moved too fast. But you may have more room for such experiments and a faster camera.

Theory

A leaf blower is a low-pressure air pump. It is designed to blow out as much air as possible, as fast as possible. By reducing the effective area of the end of the nozzle by fitting the barrels over just half the area, we can increase the velocity of the air traveling through the barrels. Since the leaf blower is open at both ends, if we increase the resistance to flow too much—say, by just having one barrel and blocking up the rest of the tube—then the air may simply bounce off the obstruction and come out the back of the blower, or create a vortex that merely circulates the air and hence the balls.

Trial and error was used to determine the best number of barrels to maximize the speed of the balls and the fire rate. For the author’s leaf blower, this turned out to be three barrels, which conveniently fit across the width of the blower.

Summary

This is one of the most enjoyable and easily completed projects in the book. As you would expect, applying a few kW of power to a bunch of ping-pong balls is always going to produce some exciting results. In the next chapter, we will embark on another weapon-type project, but this time it will be a model weapon, based on a laser and some servo motors.

CHAPTER 2 : Trebuchet

PROJECT SIZE: Small
SKILL LEVEL: ★★✩✩

SOMETIMES THE EVIL GENIUS LIKES to go for that retro-look when creating his projects, and it’s hard to get much more retro than a medieval siege engine.

The trebuchet uses a weight attached to an arm with a sling on the end of it to throw objects. In its time, the projectiles varied, but were often big rocks or dead and rotting horses, thrown into the enemy fortifications during sieges. The Evil Genius’ trebuchet will not throw much more than a tennis ball, but it will throw it a decent distance, and it’s a good project to try if you like woodworking.

Figure 2-1 shows the trebuchet ready for action. It’s a simple design that should only take a few hours to construct and needs little in the way of special tools or equipment. Trebuchets are elegant machines that convert the potential energy stored in a counter-weight into kinetic energy in the projectile. Unlike the coil gun of the previous chapter, trebuchets do this in an efficient manner. The action of a trebuchet is shown in the sequence of diagrams in Figure 2-2.

The trebuchet has a sling attached to the throwing arm. So, initially the projectile is almost underneath the weight (Figure 2-2A). As the weight falls, the throwing end of the arm rises, pulling the sling and projectile along the slide on the base of the trebuchet. At some point, the projectile leaves the slide (B) and is swung round in a wide arc as the weight keeps falling (C).

The sling has one end attached to the top of the throwing arm, and the other end attached to a ring that fits over a hook on the end of the throwing arm. As the arm passes the vertical mark, at some point the sling will slacken and the ring will slip off the hook, releasing the projectile (D).

WARNING

Be careful when cocking the trebuchet, and stand well clear of it when it fires.

What You Will Need

You will need the materials listed in the Parts Bin to build this project. All of these can be easily obtained from hardware stores, and in the case of the plastic container, a supermarket.

Note that lumber is sold in different standard sizes in different countries, so you may not be able to get exactly the same size. This should not matter, and if in doubt, use thicker, more solid wood. In addition, you will also need the following tools:

Assembly

The cutting list for this in Table 2-1 includes all the wood you will need for the project.

NOTE: The author used inches in this project; it seemed appropriate for such an ancient design. So, those measurements are the more exact figures.

Step 1. Make the Frame Sides

The first step in this project is to build the frame sides. These are constructed from pieces of wood, which are arranged in an “A” shape. The apex of the “A” is held together by a metal plate, through which the bolt should be attached, which acts as a pivot. So, before attaching the plate, drill a hole right in the center, big enough for the bolt to pass through.

Figure 2-3 shows the plan for one of the A-frames. One of the A-frames is shown in the photograph of 

Figure 2-4. The sections of wood are just screwed together with a pair of screws at each joint.

Step 2. Build the Throwing Arm

Figure 2-5 shows the construction of the throwing arm. Drill one large hole to fit the bolt used, and two smaller holes for the weight ropes and for attaching the permanent end of the sling. Straighten out the metal hook (Figure 2-6) and screw it into the end of the throwing arm. 

You will need to use pliers to grip the hook while you screw it into the end of the throwing arm.

Step 3. Build the Base

The structure of the base is shown in Figure 2-7. We start by fixing the two A-frames together at the base, using two lengths of wood (J and K in the cutting list) placed under the A-frames. There should be a gap of about 7 inches (180mm) between the A-frames at the base. Also attach the central strut (L) that will hold the side braces, and piece (M) that runs down the center of the base to support the runway board and trigger mechanism.

At the top of the frames, fit the bolt through one plate, a nut, and then the throwing arm and the second plate (Figure 2-7). Fit a nut on the inside of the bracket before the second plate. The nuts are going to hold the two A-frames apart against the side bracing.

Step 4. Attach the Side Braces

The side bracing is formed by a cross piece under the middle of the A-frames (L) and two struts (O and P) from the bottom of the strut up to the apex of the A-frames (Figure 2-8). The struts and braces are both fixed into place using screws. Drill the struts at an angle first and use long screws. More adept woodworkers may elect to cut the ends of the struts at angles so they fit better.

Step 5. Assemble the Weight

The weight is constructed from a plastic box designed to hold breakfast cereal. The box has a 10-pint (5 L) capacity, which when filled with wet sand will have a weight of about 18 pounds (8 kg). Before filling the container, we need to drill four holes near the rim (Figure 2-9). 

Cut two 24-inch (610mm) lengths of the nylon rope and thread them through the holes drilled in the food container and the hole at the weight end of the throwing arm. The rope should be just long enough to allow the weight to stay away from the rotating end of the throwing arm, without being so long that the weight hits the ground at its lowest position.

Check the travel of the whole mechanism, and make sure that there is enough clearance between the A-frames for the weight. Figure 2-10 shows how the container will eventually be attached. Note that it is shown here filled with sand, but it is better to wait until everything is assembled before you fill the container.

Step 6. Assemble the Sling

The sling (Figure 2-11) is made from 64 inches (160mm) of the rope with a square patch of cloth, 8" 10" (200mm 250mm). A reasonably strong material like denim is ideal. The Evil Genius’ minions can often be found wearing jeans with large patches of cloth removed. The Evil Genius tells them that this is the latest fashion and the minions are pleased.

Lay the rope across the cloth as shown in Figure 2-12 and fold the edges over to make a seam enclosing the rope. Sew the seams up, or if you prefer, apply a row of staples down each side. Sewing will be a lot more durable than staples.

Tie a loop into one end of the rope. This will fit over the hook of the throwing arm. 

Step 7. Create the Runway

The runway is a rather grand name for the smooth panel of hardboard (N). It is along this that the projectile will be pulled before it is lifted by the rotating arm.

It fits on top of piece M (Figure 2-13) that sits across the base and doubles as the point to attach the trigger mechanism.

Step 8. Fashion the Trigger Mechanism

The trigger mechanism is quite unsophisticated. It comprises a nail on a string and a hole that goes through the throwing arm and the piece of wood M (Figure 2-14). To fire the trebuchet, simply pull the
nail out.

Fire!

A tennis ball makes a good projectile. It has the advantage of being fairly tough and not being damaged by a collision with a target (minion). To test the trebuchet, a suitable open space should be found and minions dispatched to a reasonable distance in front of the trebuchet. Fit the ball into the sling and pull down the throwing arm until it can be pinned by the trigger nail. Stretch out the sling in the runway, with the ball at the far end, so that the rope is straight and the loop is over the pin on the end of the throwing arm.

Stand clear of the trebuchet and pull on the string to release the nail holding the throwing arm in place. The ball should sail off into the distance. Dispatch a minion to retrieve it and do it again, because it’s fun.

Tuning the Trebuchet

There are various things you can do to the trebuchet to squeeze the best performance out of the engine. You will likely need to make a few adjustments to the pin before this works well. If the ball flies off too low to the ground, then bend the pin back a little so the sling is released earlier. Or, if the ball is released too early and flies straight up into the air, bend the pin forward a little.

This book’s web site (www.dangerouslymad.com) contains links to videos showing the trebuchet in action. These may be useful to refer to.

Theory

The trebuchet takes its energy from the weight that falls as the arm swings. This “potential” energy is transferred to the arm and sling of the trebuchet and is released as kinetic energy in the tennis ball. As we know the energy stored in the weight and know how far the tennis ball can be thrown, we can calculate both the energy going into the system and the energy released into the ball by the system. This will allow us to calculate the efficiency of our trebuchet.

The input energy can be calculated using the formula:
E =  mgh
where m is the mass of the weight, g is the gravitational acceleration on Earth (9.8), and h is the height.

So the energy in joules is approximately:
E = 8 kg * 9.8 * 0.5m
   = 40 joules

On the other hand, we can calculate the approximate amount of energy that was transferred into the ball on the basis of the distance that it traveled and its weight.

E    =  ½ (mv^2)
d     = (v^2/g)

v^2 = dg

E =  ½ (mdg)

The tennis ball weighs about 60 g and a good throw will send it 25m.
E =  ½ * 0.06 * 25 * 9.8
   = 7.35 joules

From this, we can calculate the efficiency of our trebuchet at 7.35/40 18%. This figure of 18% neglects the fact that the tennis ball has to travel through air and is probably not launched at the optimum angle. So, the real figure is probably closer to 25%.

This does not sound great, but actually is quite typical for a homemade trebuchet. These very rarely exceed 30%.

The following are a few things you can do to improve the efficiency of the trebuchet:
■ Vary the length of the sling; start by making it longer.
■ Decrease the weight of the throwing arm by reducing the amount of wood at the sling-end, or cutting it into a wedge shape.
■ Vary the pin angle. Just in terms of increasing the range, without changing the efficiency, increasing the weight is an easy win. You could use a bigger container, or use gym weights. You will, however, quickly need a stronger frame and throwing arm as you increase the weight.

Summary

If you want to see what happens when you scale up a design like this, take a look at YouTube. It shows some truly enormous trebuchets, which can throw people, pianos, barrels of flaming gasoline, even cars. Now that’s evil! 

In the next chapter, we will continue with the theme of weapons and make ourselves a ferocious minigun.

PROJECT 10 : Lighter Struts

Making materials lighter, yet still strong enough for the required need

Suggested Entry Categories

• Engineering
• Math & Computers

Purpose or Problem

Determining the safety stress range of a 2 6 piece of balsa wood, while making it lighter in weight.

Overview

Many times a material needs to be very strong, because it will undergo a lot of stress or pressure. Sometimes, a material must be made from a strong substance, like steel, but it may also have a requirement of being as light as possible. Some bones in birds are strong, yet they are hollow to make them light. The struts used in aircraft often have large holes in them to make them lighter, yet they must still be strong enough for the job they are required to do.

Design engineers must know how much force a material can withstand before breaking, and whether or not that material can be made lighter by cutting holes in it, yet still being able to support the weight needed. While engineers may need a certain material for its strength, the material may be able to withstand much more stress than required. Therefore, they can reduce the mass (weight) of the material by cutting holes in it. A margin of safety must also be included to ensure a safe design. 

For example, if 2 pounds of stress is to be exerted on a material, you may want that material to be able to withstand 6 pounds before it breaks, giving you a two-thirds margin of safety.

Hypothesis 

Hypothesize that you can lighten a piece of balsa wood by cutting holes in it, while still keeping much of its structural strength.

Materials’ List

• Plastic gallon jug
• Two-foot-long piece of strong string
• Wooden sawhorse
• Two pieces of balsa wood, 2 inches wide by 1 foot long
• Piece of 2 4 lumber about 12 inches long
• Two pieces of plywood about 1 foot by 6 inches
• Wood screws
• Screwdriver (or electric screwdriver)
• Hand saw (or a power saw used under adult supervision)
• Gram weight scale
• Bathroom scale or scale to measure pounds
• Utility knife
• Pitcher of water
• Ruler
• Possible adult supervision needed

Procedure
The wooden box device that holds the balsa wood in place is held constant, as is the water jug device for adding weight to stress the balsa wood. The mass of the piece of balsa wood is the variable. Cut two pieces of thin balsa wood, 2 inches wide by 6 inches long, and set these strut-like pieces aside. Cut two pieces of 2 4 lumber in 6-inch lengths. Cut two rectangular pieces of plywood into pieces 1 foot wide by 6 inches deep.
Using screws, attach one piece of plywood to the top of a wooden sawhorse.

Using that as the bottom piece, make a rectangular box by using the 2 4 pieces for sides and the remaining piece of plywood for the top. Leave two sides of the box open.

Using a utility knife, cut a small V-shaped notch on one of the long sides of the balsa wood near the end of the wood. Stand the balsa wood vertically and insert one end into the opening of the box to a depth of 1 inch. Position the balsa wood so the end with the notch in it is outside the box and facing upward.

Tie both ends of a 2-foot-long piece of strong string to the handle of an empty plastic gallon jug, making a loop. Hang the jug from the balsa wood by placing the loop of string in the notch.

Slowly add water to the jug until the balsa wood breaks. Weigh the water in the jug and record this weight. (If the weight of a full jug is not enough to break the wood, tie a second jug to the first one and begin adding
water to it.)

Take the second piece of balsa wood and cut a series of holes in the wood, each spaced at equal distances. Each hole should be 1 inch in diameter. Perform the same weight test. Record the amount of weight needed to break the “swiss cheese” balsa wood strut. 

Engineers need to know weights, percentage relationships, strengths, and other important factors about a material. Use the data you have determined by experimentation to compile stress data on the 2 6 pieces of
balsa wood. 

The fact sheet you compile should include these figures:
• Weight of the solid balsa wood piece (use a gram weight scale):_____
• Weight of the lightened “swiss cheese” balsa wood piece:_____
• Breaking weight of the solid balsa wood piece: _____
• Breaking weight of the lightened “swiss cheese” balsa wood piece: _____
• Percent lighter the lightened strut is to the solid strut (the weight of the lightened piece divided by the weight of the solid piece, times 100 for percent):_____
• The percentage of weight the lightened piece breaks at compared to the solid piece (breaking weight of the lightened piece divided by the breaking weight of the solid piece, times 100 for percent):_____
• The maximum weight the lightened piece can safely support, the safety margin being two-thirds beyond what is required (breaking weight of the lightened piece divided by one-third):_____

Results

Write down the results of your experiment. Document all observations and data collected.

Conclusion

Come to a conclusion as to whether or not your hypothesis was correct.

Something More

If the balsa wood was twice as thick, would it be able to hold twice the weight? Laminate two pieces of balsa wood together with wood glue. Let dry and test.

Project 9 : Flying in the Wind

Wind velocity at ground level may be different at heights above the ground

Suggested Entry Categories

• Environmental Science
• Earth Science

Purpose or Problem

The purpose is to determine if wind speed is different at ground level compared to 30 or 40 feet above ground.

Overview

The rotation of the Earth and differences in atmospheric temperature give birth to an inexpensive and renewable source of energy … the wind.

Down through the centuries, wind has been a powerful source of energy that mankind has harnessed to do work. The wind fills the sails of ships and turns the blades of windmills, which once were used to grind grains and saw wood, and today are used for generating electricity.

Studying the behavior of the wind is one of the most important aspects of meteorology, and it leads to a better understanding of weather and weather forecasting. Is the speed of the wind different at different heights above the ground? Have you ever been sitting on the ground and, while you only felt a slight breeze, you could see the tops of very tall trees swaying in what appeared to be a stronger wind? Are the blades of windmills built up high because it is usually windier up high than it is near the ground?

Hypothesis 

Hypothesize that the wind is often stronger at  a higher distance from the ground.

Materials’ List

• Nine feet of ribbon, 2 inches wide
• One-week period of time
• Several clip-type clothespins
• Use of a high flagpole
• Pencil and sketch pad
• Use of a camera (optional, but useful in making a science fair presentation)
• Possible adult supervision needed

Procedure

The location of the flagpole, the height of each ribbon wind indicator, and the ribbon indicators themselves are constant. The wind speed is the variable. Get permission to use a tall flagpole that is away from buildings and other structures. Sometimes, local businesses will have high flagpoles for promotion. Your school may also have a tall flagpole. Cut three 3-foot lengths of ribbon, the kind used for decorative craft work. The ribbon should be about 2 inches wide. 

Tie the three pieces of ribbon onto the rope that hoists up the flag. Space the ribbons so that when the rope is pulled up, one ribbon will be at the top, one at the middle, and one at the bottom of the pole.

Every day at the same time for seven days, observe the position of the ribbons. Use a sketch pad to record your  observations. The ribbons will give a relative indication of wind speed. The straighter they stand out (parallel to the ground), the stronger the wind speed. If there is a day when no wind is blowing and none of the ribbons are moving, do not record an observation. Instead, wait until another day when there is enough wind to move at least one of the ribbons. 

If stormy conditions exist, do not record your observations. Being outdoors in bad weather is unsafe, especially during a thunderstorm. If the wind is very strong during one of your observation days, and all three ribbons are standing out straight, try adding weight equally to all of them, so they will not all stand out straight. Weight can be added by clipping one or more alligator-type clothespins to each ribbon.

Results

Write down the results of your experiment.

Conclusion

Come to a conclusion as to whether or not your hypothesis was correct.

Something More

1. Compare your ribbon wind indicators at different times of the day: early morning, noon, and dusk.
2. Can you determine any relationship between the strength or direction of the wind and a barometer reading and the type of clouds?

PROJECT 8 : In the Ear of the Beholder

The physics and social classification of “noise”

Suggested Entry Categories

• Behavioral & Social
• Physics
• Adaptable to Math & Computers

Purpose or Problem

Defining “noise” can sometimes be explained by the physics of a sound, but it can also be in the mind of the listener, or it can even be determined by the society the listener lives in.

Overview

Some sounds are musical and some are noise. Music is usually made of vibrations that are organized and come to our ears at regular intervals. A vibrating string on a guitar or a piano is an example. You can feel the
vibrations of your vocal cords by placing your hand on your throat while you sing. Sounds that make irregular vibrations tend be thought of as noise. Such vibrations are made when a door is slammed shut or a
book falls from a desk to the floor. But, it is not always easy to classify a sound as music or noise. The difference between music and noise may be in the mind of the listener. Young people’s music may be considered noise by their grandparents.

Hitting a fence with a stick may be noise, but if you walk along a picket fence and hold a stick against it, the regular repetitive sound may be pleasing, as a drum or other percussion instrument would be. Society also determines when a sound is musical. Do research into the unusual instruments used in other cultures. Have you ever listened to someone squeaking as they learn to play the clarinet, or screeching as they learn to play the violin?

That’s hardly music! Perhaps we can classify sounds as being more musical if we enjoy them. A sound may even be pleasing at one moment, but not at another. A doorbell may make a harmonious sound, but if it dings at 3 o’clock in the morning and disturbs you while you are sleeping, you won’t like it. When music is played softly, it may be enjoyable, but when the volume is turned up to the point where it hurts your ears, the song becomes noise.

The time of day may also affect your feelings about a sound. If you are waiting for a friend to pick you up to go to the movies, the honk of their car horn is welcomed. But someone honking a car horn in front of your house at 4 A.M. can be disturbing. A doorbell ringing during the day does not have the same alarming affect emotionally as it does if it rings in the middle of the night. When a mother knows why a baby is crying (if it needs a diaper changed or is hungry), her emotions are not the same as when she doesn’t know what is wrong.

Some sounds always seem to be pleasant: a babbling brook, the wind rustling leaves through the trees. We are surrounded by sounds all day long, and it is important that we have quiet times and enjoyable sounds in our daily lives. Too much noise can cause stress and fatigue.

Hypothesis

Hypothesize that in the categorizing of common, everyday sounds as to whether they are pleasant or noise, many different responses will be based on the age group.

Materials’ List

• Paper
• Pencil
• Clipboard
• A day of listening
• Ten friends of high-school age
• Ten adults over age 40

Procedure

The list of commonly heard sounds will be constant for all who are surveyed. The age groups of those surveyed will be varied: teenagers and adults over 40. For one whole day, pay attention to all the sounds you hear. Carry paper, a pencil, and a clipboard to make a list of all the daily sounds around your home, school, and neighborhood. Some sounds you may not have paid much attention to before: for example, toast popping up in a toaster, a door chime, a church bell, popcorn popping, a car horn, the crackling of a fire in a fireplace, the telephone ringing, birds chirping, someone tapping a pencil on a desk, an umpire or referee blowing a whistle during a sporting event, insects buzzing in your ear, the screech of car brakes, the blowing of air across the top of a soda bottle, or someone driving by in a car with your favorite song playing.

Compile a survey sheet with a list of 50 sounds, each followed by a multiple choice selection of Pleasant, Noise, and No Response.

At the top of each sheet, make a place for checking the two age groups: Tees and Over 40. (You can also ask for male or female if you want to do the “Something More” suggestion.)

Use a copy machine to make 20 copies, or use a computer word-processing program or desktop publishing program to create your survey sheet, and print out 20 copies. Have ten high-school-age friends and ten adults over age 40 complete the survey. Total the results from each group. Compare the responses by each group.

Results

Write down the results of your experiment. Document all observations and data collected.

Conclusion

Come to a conclusion as to whether or not your hypothesis was correct.

Something More

1. Expand your survey by categorizing your results by male and female, in addition to age. Compare your organized data.
2. Sounds and songs may even bring memories to our minds. Hearing a popular song that was once played heavily on the radio may cause you to remember a special summer or time in your life. When you hear the sound of sleigh bells or a Christmas carol, does a feeling or picture come to your mind about snow falling or the excitement of waiting to open presents with family?

PROJECT 7 : Got Salt?

Comparisons of back bay salt content to tide cycles

Suggested Entry Categories

• Environmental Science
• Earth Science
• Chemistry

Purpose or Problem

Comparing salt content in back bay water during high tides and low tides.

Overview

The gravitational pull of the Moon and the Sun creates a daily flow of water toward and away from sea coasts (high tide and low tide). As water flows toward the coast, the water level along the shore can be seen to rise, and water flows through inlets, filling back bay areas. Hours later, an ebb tide occurs, when the water recedes out of the bays and away from the shoreline. Does this tidal change affect the salt content of the water that accumulates in the back bays? If a significant difference exists between the salt content at high tide and low tide, plants and animals living there would have to be tolerant of these changes.

Hypothesis

Hypothesize that a noticeable difference will occur in the salt content in back bay water depending on the cycle of the tide (high tide, low tide).

Materials’ List

• Access to an inlet and bay areas that experience tidal changes, fed by an ocean or a large body of salt water
• Four wide-mouth jars (peanut butter, pickle, or other food containers) of equal size
• Masking tape
• Pen or marker
• About two weeks of waiting time
• Several small twigs
• A sunny window
• Tide chart helpful, but optional
• Possible adult supervision needed

Procedure

The amount of water gathered for each sample and the location the samples are taken from remain constant. The tide cycle is the variable.

For this project, you must have access to an inlet and a back bay that receives tidal flows from an ocean or a large body of salt water. When you work around water, make safety your number one concern. Know how to swim, wear a life preserver, and always have a friend or an adult accompany you.

Gather four clear glass or plastic jars that have wide mouths. Jars of this type include 16- or 18-ounce peanut butter, pickle, or sauce containers. All four jars must be identical.

Place a strip of masking tape on each jar and label each one as to the location and tidal status that identifies the water sample they will contain. 

You need to determine the time of high and low tides. Tide tables are often found in local marinas, newspapers, or by listening to a National Oceanic and Atmospheric Administration (NOAA) weather station
(weather radios can be purchased at many consumer electronic stores). If you do not have access to a tide table, you can spend a day making note of where the high- and lowtide levels are along bulkheads or other land markings. Throwing a small twig in the water at an inlet and watching the direction it floats tells you whether the tide is flowing in or receding out.

The figure on the top of the next page shows two points where you should collect water samples: one is located in a back bay area, and the other is at the mouth of the inlet, where the bay meets the ocean. When the tide is just beginning to flow in (just past the time of low tide), fill a jar with water from Point A and one from Point B. Secure lids on the jars to keep the water from spilling as you transport them home.

Later, when the tide is just beginning torecede (just past the time of high tide), fill a jar with water from Point A and one from Point B.

[Optional: If you have access to two inlets that feed back bay areas, you can enhance your project by collecting additional samples at points shown in the figure below.]

When you get home, place the jars in a warm, sunny window and remove the lids. It takes about two weeks for all the water to evaporate. You can decrease evaporation time by placing them in an area of increased heat, such as near a heat duct or in an oven at a low temperature. Do not place the jars directly on a stove burner, as the jars are not designed to be exposed to high temperatures. 

When all the water has evaporated, screw the lids on again to prevent any further contamination and to keep the contents intact. Do you see chunks of salt in the jars? Salts are crystals, and one of the characteristics of
crystals is their unique shapes. Do the chunks have shapes characteristic of crystals? You may also want to examine the salt chunks under a magnifying glass or microscope.

Results

Write down the results of your experiment. Document all observations and data collected.

Conclusion

Come to a conclusion as to whether or not your hypothesis was correct.

Something More

1. Is there a difference in salt content in water near the surface compared to water at a deeper level? Construct a device that lets you lower a container to the bottom of the bay, and then open the lid to fill it with water. (Use a brick or a heavy object to weigh down the container.)
2. Does heavy rainfall affect the salt content in a back bay?
3. Is there any difference in salt content between the water in a back bay and the water in the ocean that feeds it?

PROJECT 6 : “Vlip!”

A pet dog responds to sounds rather than understanding the meaning of words

Suggested Entry Categories

• Behavioral & Social
• Zoology

Purpose or Problem

The purpose is to prove that a pet dog who is trained to obey several commands, responds to those commands because of association with the sounds and the action you want from the animal, not because of any understanding of language.

Overview

Pet owners who train their dogs to obey several commands naturally use words in their own language. “Sit,” “bark,” and “roll over” are words those who speak the English language understand. Although a dog may appear as though it understands the meaning of commands, it is merely the sound of these words that produces the appropriate behavior.

Hypothesis

Hypothesize that a dog can be trained to obey several command words that are not words in any language, proving the animal is merely associating a particular sound with a particular expected behavior.

Materials’ List

• Pet dog
• Book on how to train your dog
• Time and patience training the dog to obey several commands

Procedure

Decide on several behavioral responses you want to train your dog to accomplish (sit, stay, run, bark, and so on). Then, make up your own words to substitute for these English words. “Vlip,” for example, could be “sit.” Make up simple one-syllable words.

If you can train your dog to respond tothese made-up words, only the two of you(and no one else in the room!) will understand the commands. Get a good book on how to properly train your dog to obey voice commands. Just as most people like to be rewarded for their achievements, so do your pets. Rewarding (giving a hug or a treat) is the best motivation for your pet to learn. Start by giving three rewards when the dog’s response to a command is correct: give a pat on the head, say “Good dog!” and give a food treat. As time goes on, don’t give food every time. Eventually, just a pat or hearing the tone of your voice saying “Good dog!” will be sufficient to let the pet know you are proud of it.

Time and patience are needed to train your dog, but it will be fun for both of you. The training will seem more like playing together than work.

Results

Write down the results of your experiment. Document all observations and data collected.

Conclusion

Come to a conclusion as to whether or not your hypothesis was correct.

Something More

1. Children can be bilingual and learn two different words for the same thing. This can happen when one parent or grandparent speaks a different language than the other parent or family members. Can a dog learn more than one command for the same behavior?
2. Pet guinea pigs can be taught to squeal and rattle their cages at the sound of chopping carrots on a wood block, in their anticipation of receiving carrot treats. Can they be trained to get equally excited by a voice command indicating a food treat is coming?
3. Dolphins learn to do tricks by watching their trainers’ hand signals. Can dogs learn commands by hand
signals only?