LEGO Adventure 2-2

LEGO ADVENTURE #2-2

NAME ____________________________ AGE __

GEARS (credit to Enrichment Project, Gander Academy,Prepared by Jim Cornish)
http://www.stemnet.nf.ca/CITE

CHECK EACH PART BELOW BEFORE STARTING.

1. Connecting Two Same Sized Gear Wheels

Gear wheels can be connected using axles beams and bushings.

One gear wheel can be turned to cause the second gear wheel to turn.

The directions below will help you construct a simple machine that

uses two gear wheels of the same size.

Look at the diagram, select the Lego pieces required and follow

the directions below.

Lego Parts

two 8-stud beam

two 8-stud long axle

two bushings

two 40-toothed gear wheels

Directions:

Assemble the wheel gears as displayed in the figure above.

Turn one axle to turn the attached gear wheel.

2. Gearing Up and Gearing Down

When two different sized gears are connected, the work the gears can do changes depending on which gear is the driver. This activity explores how a small gear wheel connected to a large gear wheel affects the way they work. Gears are arranged this way on multiple speed bicycles to help the rider climb a hill or to gain speed on a flat surfaces or while going down hill. When the number of teeth in two gears differ, a Gear Ratio is defined. A ratio is another name for a fraction, or just one whole number divided by another (24/8 or 8/24). When multiple gears are joined together, the assembly is called a Gear Train. The power and speed at the end of the train are determined by the Gear Ratio(s). The example has high power (also called torque) but low speed. The power is high because 1/8 of the turning force is transmitted with each gear tooth. The speed is low because the 8-tooth gear has to turn 3 times before the 24-tooth gear turns once. Verify that this is true. Lego Parts List one 8-stud beam two 8-stud length axles two bushings one 8-tooth gear wheel one 24-tooth gear wheel
Directions Assemble the gear wheels as displayed in the figure above. Turn the axle on the large gear wheel for one revolution. How many revolutions does the small gear wheel make? Turn the axle on the small gear wheel until the large gear wheel revolves once. How many revolutions were required? 3. Two Gears and an Idler
Some constructions require one gear to drive or turn another in the same direction. As we have seen in the previous activity, this cannot be done with only two gears. A third one must be placed between them. This middle gear is called the idler.
Lego Parts List one eight tooth wheel gear three 8-stud long axles three bushings one 8-stud beam two 24 tooth wheel gear Directions: Assemble the wheel gears as pictured above. Turn the axle on the small wheel gear (the idler) and observe what happens to the two big gears (the followers). Turn the axle on one of the 24-tooth gears. What happens to the idler and the other 24-tooth gear? 4. Crown Gears

Crown gears can be connected to wheel gears and worm gears to change the direction of motion. Crown gears are gear wheels. Crown gear teeth are raised on one side and rounded-off on the other. This gives them the crown-like appearance. Crown gears are usually attached to the axle at right angles to the one creating the force. Crown gears can be turned by gear wheels and worm gears. They will not, however, operate properly if connected to another crown gear. The construction would be used on a merry-go-round type machine.

Lego Parts:
· two 8-stud beams · four 4-stud beams · two 8-stud length axle rods · one 8-tooth gear wheel · four bushings		·

· one crown gear

· two 1X4-stud plates

· two 1X2-stud plates

· one 2X4-stud plate with holes

Directions:

· Assemble the small gear wheel and crown gear as pictured.

· Turn the axle of the small gear wheel until the crown gear revolves once.

5. Worm Gears

Worm gears are used when a change in the direction in motion is required. Worm gears act like screws and provide a continuous motion. In the sample construction below, a force on the worm gear will be changed when connected to a wheel gear. This construction might be used to turn the wheels on a model car.
Lego Parts List two 4-stud beams one 6-stud beam one 2-stud beam three 1X6 stud plates	one 1X2 plate two 8-stud length axles one 24-tooth gear wheel one worm gear
Directions: Assemble a wheel and worm gear as pictured. Turn the axle of the worm gear and then turn the axle on the wheel gear.

6. Using Pulleys Like Gears

Unlike gears, pulleys have no teeth to cause movement. However, two pulleys can be caused to behave as gears by connecting them with a belt (an elastic band in this case). Belts play an important role in machines. Rather than connect motors and engines to devices directly, they are connected using belts. Should the force exerted be too great, the belt breaks, reducing the chances of causing damage to the machine.
Lego Parts List one 8-stud beam two 4-stud length axles one large pulley wheel one small pulley wheel one belt two bushings
Directions: Assemble the pulleys as pictured. Turn the axle of the small pulley.

7. Bevel Gears

[from wikipedia.org] A good example of bevel gears is seen as the main mechanism for a hand drill. As the handle of the drill is turned in a vertical direction, the bevel gears change the rotation of the chuck to a horizontal rotation. The bevel gears in a hand drill have the added advantage of increasing the speed of rotation of the chuck and this makes it possible to drill a range of materials. The bevel gear finds its application in locomotives, marine applications, automobiles, printing presses, cooling towers and power plants.

Independently from the operating angle, the gear axes must intersect (at the point O).

[from LEGO Tora no Maki by ISOGAWA Yoshihito]

Lego Parts List

· one 2x4 plate

· two 5-stud length axles

· two bevel gears

· one 8-tooth gear

· two 1x2 beams

· two bushings

8. Challenge Problems

Construct a gear train such that when the drive axle is turned once, the gear at the end of the train turns the slowest. How slow? Try fastest. How fast?
Describe your design on a worksheet.