Everyone appreciates a well-designed bridge, a sturdy skyscraper, or a flightworthy aircraft. But how many of us who aren’t engineers think, “I could build that”? In fact, you can. You may not have a professional engineer’s credentials, but you can tinker all you want in your own workshop, using readily available materials to build working models that solve all the fundamental problems of the real thing.
01. Why DIY Engineering?
Follow the seven steps in the engineering design process to create a golf ball launcher that can hit a target ten feet away. Apply the principle of conservation of energy to select the right steel spring for the job. After building and testing the launcher, consider the joys of do-it-yourself projects and the insights they provide about fundamental engineering concepts.
02. Exploring the Science of Structure
Get started on DIY project number two: use cardboard to build a tower capable of supporting a 100-pound gravity load and a 10-pound lateral load simultaneously. This exercise closely replicates problems faced by real-world skyscraper designers. In this lesson, use vector math to analyze the forces exerted on each structural element of the building.
03. Design and Build a Cardboard Tower
Now that you understand the forces your cardboard tower must withstand, conduct a series of compressive and tensile strength experiments to determine the size and shape of your structure's beams, columns, and braces. After completing your design, build the tower using ordinary wood glue and simple tools. Then pile on concrete blocks and marvel at the strength of your creation.
04. Bridging with Beams
Design and build an 8-foot beam bridge capable of carrying a swarm of pedestrians across a small stream. First, consider three alternative concepts, with beams made of identical wood, but of different configurations. Then develop these designs, analyzing their stresses and failure modes before selecting the optimum, building it, and inviting your friends onto the span.
05. Make a Suspension Bridge
Elegant and efficient, the suspension bridge is your next DIY effort. Span the same small stream as in the previous project, but support the deck with suspension cables draped between two 5-foot-tall towers. Analyze the flow of forces through the structural system before designing each element. A 3D computer model helps you plan this impressive project.
06. Design a Concrete Sailboat
It may sound suspiciously like a lead balloon, but a concrete boat can be made to float. Your engineering challenge is to create a concrete sailboat that can operate safely in 10-mph winds. Hydrostatics comes into play in designing a hull with sufficient buoyancy, and aerodynamics enters the picture in designing a sail that doesn't cause too much heeling in the wind.
07. Set Sail!
Build your concrete sailboat. Consider the enhanced strength of a concrete shell that has been formed into a curved shape—a feature exploited in many buildings. Then apply basic aerodynamics and vector mechanics to determine how the wind propels a sailboat—sailing with the wind, into the wind, and at right angles to the wind. Try out these points of sail with your model.
08. Make a Radio-Controlled Blimp
Who has not tied a paper cup to a helium party balloon to make a primitive airship? In this lesson, design and build a far more advanced version: a radio-controlled blimp that you can remotely pilot around your house. Calculate the volume of helium required to lift your blimp and its control unit, borrowed from a toy tank. Use two motor-driven propellers for thrust and control.
09. Exploring Aerodynamics
Start your project on fixed-wing flight the way the Wright brothers did: by building a wind tunnel. Use it to test different wing shapes at varying angles of attack, exploring the phenomena of lift, drag, and stalling. Your goal is to design a wing appropriate for a low-speed model plane, powered only by a few strands of rubber and flying without remote control.
10. Build a Model Airplane
Dig deeper into aerodynamic science so you can choose an airfoil shape and appropriate wingspan, aspect ratio, fuselage length, and stabilizer dimensions for your model plane. Pay special attention to aerodynamic stability and such factors as the dihedral angle of the wings, noting these features on full-size aircraft. Then build the airframe, using wood, tissue paper, and metal wire.
11. Take Flight!
Complete your model plane by assembling a rubber motor that will serve as a source of power. Design, carve, and install an efficient propeller. Learn how to balance your aircraft and adjust its flight characteristics. Then find a large, open field, and try a few test glides to fine-tune the plane's performance. Finally, watch it take wing on a full-power flight.
12. Build a Model Helicopter
Now tinker with helicopter aerodynamics by adapting the classic Penni model helicopter design used by many hobbyists. Discover the importance of countering the main rotor’s torque, and investigate the mechanical genius of the rotor hub—fortunately simpler on our model than on full-size aircraft! With its 16-inch main rotor, your super-light helicopter can safely fly indoors.
13. This Is Rocket Science
Tackle the problem of designing a model rocket that carries a miniature video camera to 500 feet and then returns safely to earth by parachute. In this lesson, focus on selecting an off-the-shelf model rocket engine that can do the job. Use the impulse-momentum principle and thrust curves for various engines to predict your rocket's maximum altitude.
14. Build a Rocket
Put together your model rocket, paying special attention to the engine mount and fins, then giving the completed vehicle a drag-reducing finish. Apply the science of aerodynamics to calculate the required diameter of the parachute. Then check the rocket's stability by determining its center of gravity and center of pressure locations. Your creation is now ready to fly.
15. Make an Electric Launch Controller
Get a taste of electrical engineering by designing and building an electric launch controller that will ignite your rocket engine safely. Design a circuit that meets all code requirements. Use Ohm's law to determine the number of batteries and type of resistor required. Also, get a lesson in proper soldering technique for assembling the circuit.
16. Let's Do Launch!
Finish your launch preparations by building a theodolite to measure the altitude of the rocket's trajectory, building a launch pad, packing the parachute, choosing a safe launch site, setting up the site, and coordinating the activities of the mission control team. Once all systems are go, conduct the countdown and press the firing button...
17. A Tale of Three Catapults
Delve into the history of the most potent artillery weapons in the era before gunpowder: catapults. Examine the workings of the ballista, onager, and trebuchet. Then get started on a model ballista capable of hurling a golf ball 200 feet. Analyze the machine's nylon torsion springs to ensure that they can store enough elastic energy to achieve the required 200-foot range.
18. Build a Ballista, Onager, and Trebuchet
Build your model ballista. Then construct two other types of catapult—the onager and trebuchet—designed such that they store the same amount of energy as your ballista. Field test all three to determine which throws a golf ball farthest. Will the winner be the weapon from the Hellenistic (ballista), late Roman (onager), or medieval era (trebuchet)? You may be surprised!
19. Design a Hydraulic Arm
Plunge into hydraulics, learning how force is transmitted from actuators to hydraulic cylinders through fluid-filled lines. Then use this knowledge to design and build a hydraulically powered mechanical arm that can grasp and manipulate a concrete block—controlled by four hand-operated syringes. Along the way, use 3D printing to fabricate several crucial parts.
20. Make a Water Turbine
Harness the power of moving water by building an impulse turbine capable of lifting a 2.2-pound weight through a distance of 2 feet. First, use Bernoulli's equation to determine the required height of the water reservoir. Next, focus on the turbine, plotting power versus load to determine the turbine diameter that will produce the required power output optimally. Then build!
21. Design a Gear Train
Test your water turbine, comparing its performance to the theoretical ideal. Next, modify it by adding a set of spur gears that will allow the machine to lift a 6-pound weight, which is well beyond its ungeared capacity. Calculate the optimum gear ratio, use laser-cutting to fabricate the gears, install them, and watch a modest stream of water lift a disproportionately heavy mass.
22. Make a Mechanical Clock
The pendulum clock was the standard for precise timekeeping for centuries. Plan and build one using your newly acquired knowledge of gears. Start by exploring why a pendulum keeps accurate time. Then calculate an appropriate pendulum length for the clock. Design the escapement mechanism and gear train, then add a suitable power source to keep the pendulum swinging.
23. Design a Motor-Powered Crane
Test the limits of small, inexpensive, off-the-shelf hobby motors by building a motor-driven crane capable of lifting 100 pounds—a tall order for a motor that weighs only a few ounces! First, construct the world’s simplest electric motor to gain insights about how they work. Then calculate the torque requirements for your crane, and add gears and pulleys to achieve mechanical advantage.
24. Creative Design: A Tribute to Rube Goldberg
Your final DIY project is a tribute to cartoonist Rube Goldberg, famous for sketching machines that perform the simplest tasks by the most complicated means. Accordingly, combine twenty design elements from this course—from airfoil to electric circuit—to create a machine that will click a computer mouse. Professor Ressler offers a solution that produces a surprising outcome.