Card 5: Belt Drives
Look at the front cover of card 5. What do these devices have in common?
What is an "axle"? LEGO axles are almost always black, and have 4 grooves that run along the length of the axle.
"Belts" can be used to make one axle turn another axle. With LEGOs, belts are almost always rubber bands.
The wheels on the axles are sometimes called wheels, sometimes called "pulleys."
The one on the axle that you (or a motor) turn is called the "driver." The one that the belt causes to turn is called the "driven."
Now build the belt drive shown inside the card.
After step 5, there are 3 different options shown. Make predictions before you build each option. Do you think the driven will turn FASTER or SLOWER or the SAME SPEED compared to the driver? Do you think it will turn the same direction, or the opposite direction?
AFTER you make your predictions, build each option. Were your predictions correct?
What general rule can you make about the driver and the driven? When does the driven turn faster? When does it turn in an opposite direction?
Check in with your teacher before building the pulley sets on the back of the card. Make predictions about each of them before you build. Were your predictions correct? Do you need to revise your general rule?
Card 6: Simple Gear Trains
Look at the front cover of card 6. What do the pictures have in common?
Belt drives work well in many situations, but if you try to put a lot of force on them, the belt sometimes slips.
"Gears" are wheels that have interlocking "teeth" that can take more force. However, gears have to be exact distances apart. When building with LEGO gears, sometimes you have to go up or down an FLU, or use a 1/3 FLU brick to get the spacing right.
When two or more gears are used, the set is called a "gear train." When each axle has only one gear on it, the set of gears is called a "simple" gear train.
Open the card. Look at the gear train you will build in step 5. Using what you learned from card 6, make a prediction. Will the driven gear turn faster, slower, or the same speed as the driver? Will it turn the same direction, or opposite?
When you've made your prediction, check in with your teacher, THEN get the gears needed to build the main gear train AND the second (yellow circle) one.
Build the first gear train. Were your predictions correct?
Now look at the second gear train and make a prediction about the driven gear. FASTER/SLOWER/SAME speed? SAME/OPPOSITE direction?
Build the second gear train and check your predictions.
When you have a simple gear train with more than two gears, the ones in the middle are called "Idlers." Do idlers affect speed? Do they affect direction?
Consider the back of the card. Make predictions about the driven gears, then build and check your predictions. Were your predictions correct? Do you need to revise your general rule?
EXTEND - EXPERIMENT -- try different size gears for the driver vs driven, like in the very last structure on the back of the card. What is the pattern? When does the driven go faster than the driver? When does it go slower?
Card 7: Right Angle Gearing
Look at the front of card 7. What do the pictures have in common?
Sometimes, you need to make the driven axle rotate perpendicular (right angle) to the driver. There are two kinds of gears often used for this. Open the card and look at the kinds of gears you'll be using. The small gear with the angled teeth is called a "bevel" gear. Almost always, you connect two bevel gears to each other to make the right angle. The gear with the teeth that poke up is called a "crown" gear. Almost always, you connect a crown gear to a regular gear.
Look at the two gear trains you'll build in the center part of the card. Make predictions for each - will the driven turn faster/slower/same speed? What direction?
Build the gear trains and check your predictions. Then check in with your teacher.
Now consider the picture on the back of the card. This is the gear part of a LEGO hand mixer or hand drill. What will happen when you turn the red "handle"? What purpose do the three gears on the bottom axle serve?
Time for a Formative.
At this point, you should know how to build structures with triangles to make them strong.
You should know what a "fulcrum" is, and how to build levers.
You should know what a "driver" and "driven" pulley/wheel/gear is. You should be able to correctly predict whether a driven gear/pulley/wheel will turn the same direction or opposite direction compared to the driver, and whether it will turn faster, slower, or the same speed.
You should know what a "bevel" and a "crown" gear are, and how they affect a gear train.
Revisit any of the previous cards and review your notes -- formative coming up!