© Creative Learning Systems © Creative Learning Systems Structures and Mechanics with fischertechnik

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Structures and Mechanics with fischertechnik Heavy Loads – Level 2

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What You’ll Learn… What design specifications are and how to establish them for an

engineering problem How screw spindles work How to measure and calculate mechanical advantage of a

compound machine How car jacks are designed How scissor lifts are designed

Stuff You’ll Need… Fischertechnik Profi Mechanic + Static Set

Mechanic + Static Activity Booklet Mechanic + Static Assembly Instruction

Digital camera







ePortfolio Suggestions… Before you begin the activities in this Learning Launcher, write down

anything you may already know about car jacks and how they work. List three interesting things you learned from the What You Should

Know… section. Keep a glossary of new words you learn. Pay particular attention to the

bold, italicized words you find. Record your project design specifications in your project planner. Take pictures of your fischertechnik models and label each of the parts. Give examples of other real machines that use similar gears. Answer each of the questions in the Activity Booklet. Record your

observations in your Project Planner. Create a narrated video demonstrating how your geared

machines work.







What You Should Know…Before beginning the activities in this Learning Launcher You should already be familiar with the fischertechnik

construction system. You should be familiar with the different types of simple

machines and understand the basic principles of each. You should understand how gears provide mechanical advantage

and know how to calculate gear ratios.

If you are not familiar with any of these concepts, you should review the What You Should Know… section of the Level 1 Machines and Gears Learning Launcher.







What You Should Know…Getting to know fischertechnik…fischertechnik is a precision modeling system designed and produced in Germany.

Like many modeling systems, fischertechnik is a great way to model structures and machines on a small scale. Unlike many modeling systems, fischertechnik is the choice of scientists and engineers for sophisticated modeling simulations and experiments.

fischertechnik can be used to model large structures and simulate complex machines. With its sensors and computer programming capabilities, fischertechnik is even a sophisticated robotics system.

If you have not worked with fischertechnik before, take the next 15 minutes and explore your fischertechnik Mechanic + Static collection. If you have worked with fischertechnik before, proceed to the next slide.







What You Should Know…Heavy Loads…

Are you strong enough to lift a car?

Of course you are!

But you need a machine to help you. In fact, there’s a machine in the trunk of almost every car that’s designed to do exactly that! It’s called a car jack and its a good thing to have when you get a flat tire.







What You Should Know…Take a moment and think about the form and function of a car jack. What does it need to do? What does it need to look like?

These requirements are called design specifications and are a critical part of the engineering design process. Engineering design is really just a specialized form of problem solving. When engineers design a machine, they start out with a detailed description of the problem they are trying to solve. In addition to the function they need the machine to perform, they need to think about things like size, weight, reliability, cost, etc.

Write down as many design specifications for a car jack as you can think of in your project planner. List at least four before continuing to the next slide.







What You Should Know…Heavy Loads…What were your design specifications? Here are some you may have considered: First and foremost, a car jack needs to be able to lift very heavy weights

easily. Everyone must be able to use it. It must be self-locking so the car does not come back down when you

release the handle. It only needs to provide a single point of support (since it only has to lift

one side of the car, it can use the two wheels on the other side for stability).

It must be small so it doesn’t take up too much trunk space. It must be strong enough so that it doesn’t collapse under

the weight of the car. It must be light enough so that anyone can carry it. It must be easy to operate.

That’s a lot to ask of a machine!







What You Should Know…Heavy Loads…So how does a car jack work?Car jacks rely on a combination of levers and gears to provide mechanical advantage. There are lots of different kinds of car jacks. The key design element of many is special kind of gear called a screw spindle.

The screw spindle is similar to the worm gear you may have explored the Level 1 Machines and Gears Learning Launcher. But instead of turning a tooth gear, the screw spindle passes through a threaded collar or nut. This gear works on the same principle as a common nut and bolt!







Do It! Building a Model Car Jack…Now that you know some basic principles about how car jacks are engineered, let’s build a model to learn more!

Find the Activity Booklet in your Mechanic + Static kit. Turn to page 30 and build the Car Jack as shown. You can find assembly instructions on page 44 of the Assembly Instruction book.

Activity BookletAssembly Instruction

Be sure to answer the questions in the Activity Guide and record your answers in your Project Planner!

Car Jack







Do It!

Try pressing down (GENTLY!!!) on the lifting arm.

Building a Model Car Jack…

Lifting Arm

Like the worm gear, the screw spindle gear is self-locking; the spindle screw can turn the nut attached to the lifting arm, but the nut cannot turn the spindle screw.







Do It!

The spindle screw is one way the car jack provides enough mechanical advantage to lift a car. The crank also provides mechanical advantage. Do you know what kind of simple machine the crank represents?

Building a Model Car Jack..

Crank

How can we determine the mechanical advantage of our car jack?

Depending on the length our the two lifting arm

members and the location of the pivot

point, the lifting arm can either increase our lifting

power (mechanical advantage) or the

distance of lift. You can try a few different

configurations to see how this works.







Do It! Calculating Mechanical Advantage…

In the Level 1 Mechanics and Gears Learning Launcher we examined a simple class 1 lever (like a see saw). By applying a force on one end over a distance of 5 feet, it allowed us to apply 5 times as much force to lift a heavy object on the other end by 1 foot. We defined this as a 5:1 mechanical advantage.

50 lbs.

Distance 5 ft.

Applied Force of 10 lbs.

Distance 1 ft.







Do It!

The car jack is a compound machine made up of several connected simple machines. The geometry is somewhat complex, but we can calculate mechanical advantage through observation.

Count how many revolutions of the crank it takes to fully extend the lifting arm. You can easily measure the vertical distance traveled by the lifting arm. The distance traveled by the crank takes a little calculation since it travels in a circle.

Building a Model Car Jack..

Vertical distance

travelled by lifting arm

Crank radius

The formula for the circumference of a circle is

π(2r) where r = radius and π (pi) is approximately 3.14.

Multiply the circumference by the number of revolutions to find

the total distance.

Just as with our simple lever, the ratio of the distance traveled by the crank compared to the distance traveled by the lifting arm defines the mechanical advantage. Record your calculation in your project planner.







Do It! The Scissor Lift…If you have time, try building the scissor elevating platform which also uses a screw spindle gear. This kind of machine is often used to safely lift workers above ground level.

Before you start building, write down the design specifications in your project planner. How are the requirements for this machine similar to the car jack? How are they different?

You can find the scissor elevating platform on page 31 of the Activity Booklet. Assembly instructions can be found on page 46 of the Assembly Instruction book.

Scissor Elevating Platform

Activity Booklet

Assembly Instruction







Extend Yourself… Try building the Lathe on page 31 of your Activity Booklet. Is there a way to motorize either the car jack or scissor elevating

platform?

Try building some of the other structures in the Mechanic + Static Assembly Instruction book. Or design one of your own.

Try building one of the structural devices in the Mechanic + Static Assembly Instruction book.

Go online to find innovative car jack designs. How would you design the ultimate car jack?

Go online and search for “fischertechnik projects”. Check out some of the amazing things people have built using this sophisticated modeling system.



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