Exploring Gears

This exploration provides an introduction to gears, their purposes, and some key concepts relating to gears.

In a gear system, speed and torque are inversely proportional. If, for example, we double the speed, we have the torque and vice versa. It's also important to remember that, using gears alone, we can't change one of these with affecting the other.

Rotational speed and torque (turning force)

How do gears interact to vary torque and angular speed? Build different gear assemblies to discover these effects.

What do the terms "gear up" and "gear down" mean?

Learning sequence

1. Begin with a class discussion on how gears are used. They are found in cars, elevators and escalators. Gears are used to transfer energy in the form of motion from one place to another. Explain that gears can speed up a process or slow it down.
2. Show students a set up of gears to explain the driver and follower gears. The driver gear “drives” the motion of the rest of the gears, while the follower gear “follows” the motion of the rest of the gears.
3. Ask them if they have an idea of what an idler gear does. Explain that the idler gear is used to change the direction of the next gear and does not change the speed of the follower gear in relation to the driver gear.
4. Show them a locked gear system. Ask the students why it does not work. Explain that all the gears are pushing against each other and restricts the motion of the system.
5. Give each student pair the task of building a gear system that incorporates one of the following: crown gears, worm gears, gearing up, gearing down, idler gears, or tooth rack gears. Allow 10 minutes for building.
6. Gather the students and discuss the different building methods. Ask each group what their gear ratio is. Discuss any problems students encountered and how they modified their design.

Glossary

• Gear ratio - The gear ratio is the ratio of the number of teeth of the driver to the number of teeth of the follower. This ratio is also related to the difference between the diameters of the gears, i.e. the larger the gear the more teeth it has.
• Gearing up - This method is used to speed up the motion of the follower gear. Gearing up will allow for more speed; however it also reduces the amount of torque or driving power. To do this, the driver gear should be larger than the follower gear.
• Gearing down - increases torque (turning power), but decrease speed. This occurs when a smaller gear (i.e. one with less teeth) drives the follower gear.
• Idler gear - this gear is used to change the direction of the following gear. It is not used to change the speed of the follower.

Types of LEGO^® gears

Here is a list of readily available LEGO gears...

• Spur - spur gears are the simplest type of gear. LEGO spurs
• Bevel -
• Crown - once fairly common in early Technic sets, they have now been largely superceded by bevel gears this gear is used to change the direction of motion from one plane to another, or to go around a corner.
• Worm - this gear is used to fix the driver direction of the gear system. Only the spur gear can be used to drive the system.This gear system is used to transfer high torque. The system is also directionally constrained in that it can only be driven from the spur gear.
• Rack and pinion - is a system that changes rotational motion into linear motion. It consists of a circular gear (the pinion) engaging a linear gear (the rack).

For more types of gears, see this page on Wikipedia.

See also

For more informations about gears and challenges that focus on gearing, see these posts:

• Ramp Climber
• Snail Car
• Cranes