Introduction: (Initial Observation)
All machines make the work easier. Without using machines many tasks are virtually impossible. Although simple machines are used as useful tools, most machines are a combination of two or more simple machines. Such machines are called compound machines.
Compound machines help us to cut and form material, lift heavy objects, transport heavy objects or more complex tasks such as packaging, sewing, mixing and many more.
The main challenge in design and construction of any compound machine is to decide how the pieces must be connected to each other.
In this project you will construct a water wheel.
Adult supervision, assistance and support is required for this project.
Information Gathering:
Find out about simple machines and compound machines. Read books, magazines or ask professionals who might know about compound machines that can be made at home using paper, cardboard, wood and metals. Find out how different simple machines may be connected to each other as parts of a compound machine. Keep track of where you got your information from.
Following are samples of information that you may find:
Simple Machines
Simple machines are types of devices that do work with one movement. These devices were all in common use for centuries before Leonardo’s time. Each one makes work easier to do by providing some trade-off between the force applied and the distance over which the force is applied.
There are 6 simple machines; the inclined plane, the wedge, the screw, the lever, the pulley, and the wheel and axle.
Pulley System
A single pulley simply reverses the direction of a force. When two or more pulleys are connected together, they permit a heavy load to be lifted with less force. The trade-off is that the end of the rope must move a greater distance than the load.
Wedge
A wedge converts motion in one direction into a splitting motion that acts at right angles to the blade. Nearly all cutting machines use the wedge. A lifting machine may use a wedge to get under a load.
Screw
A screw is a central core with a thread or groove wrapped around it to form a helix. While turning, a screw converts a rotary motion into a forward or backward motion.
Lever
A lever is a stiff rod that rotates around a pivot point. Downward motion at one end results in upward motion at the other end. Depending on where the pivot point is located, a lever can multiply either the force applied or the distance over which the force is applied.
Gears
Gears are toothed or pegged wheels meshed together to transmit motion and force. In any pair of gears the larger one will rotate more slowly than the smaller one, but will rotate with greater force. Each gear in a series reverses the direction of rotation of the previous gear.
Compound Machines
Compound machines are two or more simple machines working together. A wheelbarrow is an example of a complex machine that uses a lever and a wheel and axle. Machines of all types make work easier by changing the size or direction of an applied force. The amount of effort saved when using simple or complex machines is called mechanical advantage or MA.
Additional information about simple machines:
Question/ Purpose:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of this project is to construct a model of a water turbine as a compound machine. Simple machines in a water turbine are lever and wheel and axle.
Identify Variables:
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Constructing a compound machine is an engineering project, thus it does not require defining variables.
Hypothesis:
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
Constructing a compound machine is an engineering project, thus it does not require a hypothesis.
Experiment Design:
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Select one of the following experiments to construct a model of a compound machine.
Experiment 1:
In this activity you will construct a model of a water wheel. Water wheels have been used in the past to run other machineries such as mills, textile machines, lathes, presses and forges (automatic hammers). A combination of wheels, axles and belts were used to transfer mechanical forces from the wheel to the machines. Water wheels spin by the force of water. Water wheels can be constructed using different material and in many different sizes (your choice).
If you are using heavy paper or cardboard to construct a water wheel it is best if you limit the diameter of the wheel to about 6 to 12 inches. Larger models will not have a rigid and firm structure. Note that paper models are just for display purpose and may not be tested with water.
The diagram in the right shows the components of a water wheel compound machine you may make.
In this model the rotation of a water wheel is transferred to another wheel with the help of a belt.
A more simplified model may include a water wheel and a wooden bar that spins when the water wheel spins.
Procedure:
1. Cut 2 same size circles of heavy cardboard with the radius of 4.5 inches each.
2. In the center of each circle, make another circle with the radius of 2.5 inches.
3. Divide the center circle to 8 equal sections. Then draw one line perpendicular to the division lines (shown in blue in the diagram), call them bucket lines.
4. Before making the buckets for your water wheel, use small pieces of cardboards to determine what is a good height and length for the buckets. The top of each bucket must touch the bottom of another bucket. The bottom of buckets are aligned to the bucket lines
5. Buckets are plain boxes open in one side. To make buckets that are one inch tall and 3 inches long, start by cutting pieces of cardboard that are 4″ x 3″. Mark the dotted folding lines and solid cut lines as shown in the diagram. After you fold the lines, you can use glue or stapler to connect the sides. Make 8 buckets for your water wheel.
6. Make a small X shape cut in the center of each circle. This will make it easy to insert a wood dowel in the center of the water wheel when it is ready.
7. Apply some glue to one side of the buckets and mount them on the wheel. Allow a few hours for the glues to dry.
8. Insert the wood dowel in the center of the circle.
9. Apply some glue to the other side of the of the buckets, then place the second circle. This requires passing the wood dowel from the center of the second circle as well.
10. Use paper clips or needles to hold the circle over the bucket while the glue is being dried. You may also place a few blocks of wood or similar heavy objects on that so the circle remain in touch with the buckets while the glue is being dried.
11. Apply some wood glue where the wheel is touching the wood dowel. Let the glue dry. Turning the wheel must turn the wood dowel.
12. Cut and fold the side walls for the water wheel. Make holes where the wood dowel will enter. This hole must be slightly larger than the wood dowels so the wheel can spin freely.
13. Your water wheel is ready now. You may optionally attach it to other structures to make a compound machine.
To demonstrate the function of the water wheel, turn it by hand.
14. A water wheel with buckets acts like a set of levers. It constantly tilts toward the bucket that is heavier. Water wheel is also mounted on a wheel and axle setup so the rotational movements can be transferred to other parts.
Materials and Equipment:
Following is a suggested list of material for experiment:
- Heavy construction paper
- 3/8″ wood dowel 6″ long
- White glue
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
This section does not apply to a display project.
Calculations:
No calculation is required for this project.
Summery of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
This section does not apply to a display project.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
This section does not apply to a display project.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
This section does not apply to a display project.
Possible Errors:
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
This section does not apply to a display project.
