ENGINEER

TECHNOLOGY GROUP

Baltimore Area Council

The engineer is someone who may be doing just about anything from working on a new chemical process, to planning how to get water to your house. Point out to the Webelos in your Den that an engineer is a planner who is found in many fields: civil engineers - plan towns, electrical engineers - plan power plants and large scale electrical wiring. chemical engineers, mechanical engineers; any field that needs to have its work done for utmost efficiency and reliability.

Circle Ten Council

Scientists who build machines are called engineers.  They do tests and experiments that help them to invent new machines and make old ones work better.  Without engineers we wouldn’t have tools, engines, trucks, trains, clocks or can openers.  Humans are the only animals that invent and make machines.  We use them to build skyscrapers, lift heavy loads, and move faster than the speed of sound.  Humans have even made machines that can travel to the moon.

Den Activities

Baltimore Area Council

Arrange for boys to visit an engineer or surveyor in a municipal or county office. Plan for the boys to look through a surveyor’s transit and “read a rod” or visit a construction site and see the plans, which are being followed.

Make a block and tackle. Be sure to explain its purpose - to lift weights easily. A single block and tackle has an ideal mechanical advantage of two, which means that if there was no friction, a one pound force can pull two pounds. A double block with one pound pulling force could lift four pounds. As additional blocks are added, the mechanical advantage is increased, but each additional pulley also decreases the distance the load is moved. Friction is a factor affecting the lifting power.

Have the boys find pictures of different bridges and bring them to a Den meeting. The differences in many kinds of bridges will become apparent as the boys study them and construct models. The simplest ones are plank, beam, pier, deck, truss, and arch types. The more complex kinds are the bascule (the old castle drawbridge type). vertical lift, cantilever, and pontoon. Many swinging bridges are in use today.

Discuss property lines. Have an expert show the boys how property lines are determined, and how to measure one.

Discuss different types of engineers. If one of the dads is an engineer, ask him to describe briefly to the boys what his duties are.

Surveying Land

Baltimore Area Council

Survey land, it could be yours or a staked out section in a schoolyard or park with fixed points.  To mark the points, you can use a nail pushed through a rag.

To do this, you will need a compass and a 100-foot tape measure. Put the compass on top of a 2 x 4 approximately three feet long. Start at one corner of the area to be surveyed. Take a reading of your compass and measure the distance to the next point. Do this all around the area that you have chosen to be surveyed - marking down your distance and degree.

360 degrees North 40’ Points A to B

90 degrees East 100’ Points B to C

180 degrees South 40’ Points C to D

270 degrees West 100’ Points D to A

A surveyor’s transit works much the same way. It gives the surveyor degrees in elevation as well as the degrees horizontally.

Steam Electric Power Plants

Baltimore Area Council

They create steam by heating water in a nuclear reactor or in a combustion chamber, where coal, oil or gas is burned. The steam turns a turbine that runs a generator. The generator has a rotating electromagnet called a rotor and a stationary part called a stator. A separate generator called an exciter powers the rotor, creating a magnetic field that produces an electric charge in the stator. The charge is transmitted as electricity. A transformer boosts the voltage. Exhaust steam passes cool water pipes in a condenser and turns back to water for re-heating. The water that has absorbed the steam’s heat in the condenser is piped to a cooling tower to be cooled.

Things To Make

Baltimore Area Council

Balance

A balance is not a weight scale, but is a device to measure an amount of one thing equally to another (in weight), not to a scale.

Materials:

1” x 4” - 12” long 

1”x½” – 12” long

½” x 3” x 3” plywood for base

Wire coat hanger

2 cup hooks

2½” long bolt with washers and nut

(2) ½” x 3” diameter plywood circles

6 lengths of 6” chain

Instructions:

·         On the 1” x 1/2”, carefully measure and find the centers for a hole in the middle, equal distance from both ends and from both edges.

·         Drill it.

·         Put cup hooks in the board bottom - 1” from the ends.

·         On the bottom, equal distance from both ends; drill a hole big enough to put a piece of coat hanger through.

·         On the 1” x 4”, drill a hole 2” from the top and equal distance from both sides on the 4” side of the board from top to center.

·         Attach the 1” x 4” to the 3” x 3” in the center of the base.

·         Cut a straight section of coat hanger about 6 to 8 inches long and glue into the hole on the 1”x 1/2”.

·         Bolt the 1” x 1/2” to the 1” x 4” - You want enough play so the 1” x 1/2” moves freely, but not sloppy.

·         On the 3” diameter circles, find 3 points equal distance around the edge and tack a length of chain to each point, then attach the three chains to the cup hooks.

·         If all works well, the coat hanger should lay on the centerline of the 1” x 4”. If this doesn’t happen, weights (bent nails) can be hooked over the lighter arm and moved back and forth until balance is gained.

Bridges

Baltimore Area Council

The earliest bridges were probably a log fallen across a stream. Someone probably learned that several logs side by side made it wider and easier to cross. You could make a longer bridge by putting logs or slabs of stone across stepping-stones over a wider stream. These are the same principles that are used in many modern bridges.

Make a plank bridge out of a piece of poster board or a cereal box 10 inches long and 4 inches wide. Place it between two blocks or thick books. See how many toy cars it will support. Now bend the sides up 1/2 inch from the sides like handrails. See how many toy cars it will now support.

What you have done is changed a plank bridge to a beam bridge. It acts like a much thicker plank without the weight or expense of more material.

Beams are thick at the center where more weight is supported and thinner near the ends where there is less weight. The beams are usually made lighter by making them out of lots of small triangles. The beams are started at the center and built out on both sides equally to maintain balance like a seesaw.

Try this experiment to see why triangles are used. Nail the ends of four scrap boards together to form a frame. Use only one nail per corner. See how easily this four sided structure collapses?  This is how a bridge would act made from a shape other than triangles. Now nail a board on a diagonal between two corners across the frame to form two triangles. See how much stronger it is?

Arch bridges are some of the longest lasting in the world. Some are over 1,500 years old! The arch can be entirely over the roadway, entirely under the roadway, or in the center. You can make a pretty good model of an arch bridge by using a hole saw, like you would use to drill a hole for a door knob, and drilling holes in a board. Cut this out with a cut through the center of the holes and you have the two sides of an arch bridge. Place another board on top for the road the draw and paint the stones on the side.

Bridge Activity

Baltimore Area Council

Have boys build two demonstration bridge side frames - one of rectangles and one of triangles. Use stiff cardboard or thin wood and brass fasteners. Have them experiment to see which type of bridge is stronger.

Ideas for Engineer

Circle Ten Council

Speakers – electrician, heavy equipment operator, plumber, telephone lineman, sanitation worker, railroad engineer, surveyor, city engineer, traffic planner, draftsman, architect.

Places to visit:

·         Visit the municipal offices of the city engineer or surveyor.  Look at a map of your town or city and try to find your house.  Look at some of the surveying equipment and learn some of the simple math calculations.

·         Tour the city water works, sanitary facility or recycling center.  Ask about the current workload, and kinds of daily activities that go on.  How do they handle emergencies?

·         Visit an operational drawbridge, grain elevator, ship or grain loading operation, or other large industrial operation involving large cranes or other lifting equipment.

·         Visit a jeweler and look at various gems under the microscope.  How does the pattern affect the way a jewel is cut?

Den Activities:

·         Ask your local Boy Scout troop to give a demonstration of some of the skills needed for the Pioneering Merit Badge.  One particular item of interest would be to see a rope monkey bridge being lashed together.

·         Ask Webelos to look through books and magazines at home and bring in pictures of bridges.  Note the difference in construction.

Levers

Circle Ten Council

A lever helps you to lift things easily.  A lever can be made by laying a plank over a wooden log or can with both ends intact.  Balance the plank so that there is a short end and a long end.  Place the short end under the object to be raised and push down on the long end. Try raising some bricks.  To experiment you can try to raise things with the short end and you will find that it is more difficult or not possible to raise the object.  The longer end of the plank gives you the ability to create more force and therefore raise weights easier.

Perhaps the simplest machine of all for increasing force is the lever.  A wheelbarrow is a king of the lever.  Many other types of complicated machines are really just collections of levers that are put together to work in different ways.

Simple Levers

Materials:

Length of wood                                                                    Glue

Small wooden dowel                                                          Ruler

Stripes of colored paper                                                   Pencil

Matchbox                                     Weights (washers or coins)

How it works –

A simple lever is a straight rod that rest on pivot or fulcrum.  When you push one end of the rod down with an effort, the other end goes up, lifting the load.

Try making this model seesaw and find out for yourself how levers work.

Mark the length of wood with stripes spaced about 1-inch apart.

Glue the dowel to the matchbox to make a pivot.

Place the center of the length of wood on the pivot so that the two ends balance.

Now try some experiments with the weights.

Put a weight (the load) three marks from the fulcrum.

Where must you place another weight (the effort) to lift the load?

More load for less effort!

If the load is close to the fulcrum, it’s easier to lift and you don’t need so much effort.  You may have noticed this if you’ve ever played on a seesaw – you can lift someone heavier than yourself if they sit nearer to the middle than you do.

Try putting two weights (the load) two marks away from the fulcrum of your seesaw.  Where must you put a single weight to lift the load?

Belt Drive

Merry-go-rounds, sewing machines, record players, fishing reels, washing machines, and bicycles: these are just a few of the many machines that turn, or rotate, as they work.

All the different rotating parts inside a machine can be connected with a drive belt.  As one part turns, it drags the belt around with it, carrying its turning motion to the other parts of the machine.

How it works – a drive belt runs round a series of pulleys to carry the turning force from one place to another.  If the belt is going to work properly, there must be friction between it and the pulleys, so that the belt does not slip.  If the belt is too slack it will not grip.  If it is too tight, it might break or twist the pulleys out of line.

Whirling Acrobats

Circle Ten Council

Sandpaper                                                          Wooden board

Glue                                                                             Cardboard

Velcro – self-adhesive                                                    Ribbon

Wooden dowel                                        Empty thread spools

Directions:

1.       Cut sandpaper into strips, and glue a strip around each of the thread spools.  The rough surface of the sandpaper is needed to make some friction between the reels and the belt.  This way, the belt will not slip.

2.       Draw both the front and the back of each figure on a piece of cardboard as shown, leaving a space between front and back to make a base. 

3.       Cut out the figures. 

4.       Then fold and glue them so that they stand up.

5.       Glue a figure onto each spool.

6.       Cut the wooden dowel into a number of shorter dowel pegs. 

7.       Smooth the ends of the pegs with sandpaper.

8.       Drill holes into the baseboard.  They should be just big enough for the dowel pegs to fit snugly into them.

9.       Put the pegs into the holes,

10.    Put a thread spool onto each peg. 

11.    Check that every reel can turn freely on its peg.

12.    Push a short piece of dowel into the top of one thread spool and glue the spool to the bottom peg.  Put this spool on peg #5.  This is the drive belt handle.  You will use it to turn the drive belt.

13.    Stretch a length of ribbon around the spools so that it touches them all.  Use a piece of Velcro to join the ends of the ribbon.  Then you can adjust it so that it is not too tight and not too slack, and the figures will turn more smoothly.

Changing Direction

Both of the figures will turn in the same direction as the drive belt handle is turned when placed on any combination of spools 1, 2, and 6.  Both of the figures will turn in the opposite direction of the drive belt handle when placed on spools 3 and 4.  Notice what happens when one figure is on spools 1,2, or 6 and the other is on spool 3 or 4.

Changing Speed –

If all the thread spools have the same diameter, they all rotate at the same speed.  But if you use different-sized spools, they turn at different speeds.  To turn a big spool, the belt has to move farther than it does to turn a smaller one, and so the big spool turns around more slowly.

Gears

You’ll find gears inside nearly every machine that turns.  Clocks, watches and bicycles all use them.  Just like belt drive, the gears connect all of the rotating parts, but gears last longer than belts and are more precise.  If you’ve ever ridden a mountain bike, you’ll know that gears are a good way of changing speed.

Cardboard Gears:

Circle Ten Council

This is a great section!!  Having been a Machine Design major for my BS and MS ME, I can get into gears!!  CD

How it works – the best way to find out how gears work is to make some of you own to experiment with.  Each of these homemade gears is made from a jar lid with a strip of corrugated cardboard, stuck around the rim.  The corrugations face put to make the gear teeth.

Materials:

Strips of corrugated cardboard (1/2” wide) with corrugations exposed

Jar lids and bottle tops of different sizes

Pin board and push pins

Short dowel peg

Glue and paper

Directions:

1.       Bend a strip of cardboard around the rim of a jar lid.  Try to stretch it into place so that there is a whole number of teeth evenly spaced around the lid.  Cut the strip carefully to length and then glue it in place.

2.       Make a small hole in the middle of the gear and pin it to the board so that it spins freely.

3.       Make a selection of different-sized gears to add to the board.  Glue a dowel peg to one of the gears to make a crank handle.

4.       To make the gears work you must place them so the teeth mesh.  When you turn one gear its teeth will push on its neighbor’s teeth and make them turn in the opposite direction.

Gear Experiments

Connect a series of gears like the one shown.

If you turn the big gear,

*       What happens to the two smaller ones?

*       Which way do they go around? 

*       Which does a complete turn first?

Now try turning the small gear –

*       Do the bigger gears turn more quickly or more slowly?

Count the number of teeth on each gear. 

*       If you turned a gear with 20 teeth around once, how many times would it turn a gear with 10 teeth?

Drive Chains –

Circle Ten Council

In some machines, gears called sprockets are connected by a drive-chain.  A bicycle chain connects a sprocket on the pedals to another one on the back wheel.  The chain transfers the movement from the pedals to the wheels.

Make a model chain from a long strip of corrugated cardboard with the ends taped together.  Loop it around two different sized gears and work out how far the small gear moves then you turn the larger one.

Hollow Tubes

Circle Ten Council

To demonstrate the strength of hollow tubes, try laying a brick on a Styrofoam cup lying on its side.  Place another cup on its rim and add bricks (2 to 3) until it crushed.  Glue four cups together rim to rim and bottom to bottom with white glue and allow glue to dry.  Place bricks (usually 4) on top until the structure crushes.  Demonstration shows why engineers use columns in structures and bridges.

Springs –

Springs store energy when compressed, which is released when the spring is released.  Catapults are a form of springs.

Catapult

Circle Ten Council

Wood scraps                                                 Ruler or yardstick

It can be any dimension.  Use a ruler or yardstick or any flexible wood for deadman arm.  Leave spring bar loose so you can test catapult with various leverages.

Block and Tackle

Circle Ten Council

Materials:

2 Dowel rods (1” or larger)               Sash cord or clothesline

Tie the cord to one dowel and make three wraps around both dowels.  Have two big Webelos Scouts try to pull the dowels apart while a smaller boy pulls the loose end of the cord.  He will be able to draw the larger boys together, no matter how hard they pull.  The block and tackle does not create more power; it merely trades distance for force.

Baltimore Area Council

To show how a simple block and tackle increases pulling power, try this demonstration. You need two dowels of broomstick diameter and a length of clothesline. Tie the line to one of the sticks. Wrap it around both sticks two or three times. Have two of your larger Webelos Scouts grasp the sticks. Have the smallest boy pull on the line. He will be able to pull the two sticks together no matter how hard the bigger boys try to hold back.