Replace lost blocks

Did you know that replacement LEGO bricks can be ordered from Lego? 

Pick A Brick is best for common parts. 

Bricks and pieces is better for more unusual Lego pieces. 

 

 

Introduction

Begin by discussing some of the key subject vocabulary that you will be using and their understanding of each word:

• Programming - Giving instructions to a machine to make it work 
• Algorithm - A series of instructions to solve a problem
• Test - See if it works
• Debug - Look for and fix mistakes (in an algorithm)

 

Recap what the children have done before with WeDo (if anything). They may have tried out some of the builds in KS1.

Introduce the kit, expectations for using it and working in a team. Explain that we will be learning about machines and mechanisms over the coming weeks. What is a mechanism? The moving parts (often inside) that make a machine move are known as mechanisms. They will be building and studying a number of these and finding out what kinds of motion they create, and what they let you do with your machine. This will turn them into master builders so they can begin to design, build and program their own machines using the mechanisms. 

Open the WeDo software and Click on the gear icon in the top left of the screen. From this screen you can access example builds for different kinds of mechanisms and WeDo concepts.

 

 

Motor

Open the motor and axle build (no.1) show how you can rotate the example model with the curved arrows and explain that this will be necessary on some of the other builds so they can work out where the parts go (they don’t get step-by-step instructions for these small prototype builds)

Click the arrow at the left of the screen to see the component parts to build the mechanism. Sometimes there is an arrow on the right of the screen which will open a programming tip.

 

 

Without going into any detail, challenge the children to build the model, connect it to their computer (don’t say how or where it plugs in) and make it move. Some will work out they also need the power hub which has the USB cable on it. Some will also find the programming blocks on their own, others may need a nudge towards these two things if they get stuck.

Give them five minutes or so and once most groups and discuss what’s happening and why. A USB cable lets two things pass through it; electricity (5v) and data, just like when you use one with a digital camera or a printer, the data (photo or print job) travels down the cable to/from the computer.

Add the programming blocks from the palette to the building canvas. Try these different programs and note what happens:

 

 

Ask the children to try out the example algorithms and note down what happens. How can they describe the movement? (vocab: fast, slow, turns, rotates, clockwise, anticlockwise?)

 

Motor key concepts

Motors convert energy into motion. The motion it creates is called “Rotary Motion”, which means it turns in a circle, like a wheel! In this case it makes the axle rotate as well as they are joined together. Can they think of any machines that might use this kind of mechanism and motion? 

 

Gears

 

Next direct the children to the gears icon and ask them to build the example prototype model with the pieces in the pop out menu on the left of the screen. 

 

 

Test their model with the same simple algorithm as before, and observe the motion created. Can they explain how gears work? 

 

 

The motion output at the driven gear will be different from the motion input at the driver gear. Ask the children to label the “Driver gear” and “Driven gear” on the worksheet. 

Compare and contrast the Driver and Driven gears:

• how is their motion different? (one moves clockwise, the other anti-clockwise)

• how is their motion similar? (same speed)

 

Gears key concepts 

Gears are toothed wheels that are fixed to axles. The teeth interlock with each other. The first gear (the driver gear) rotates. The Rotary motion is then transmitted to the second driven gear as the teeth push each other to move. 

 

Image courtesy: https://commons.wikimedia.org/wiki/File:Animated_two_spur_gears_1_1.gif

 

Using gears lets you create motion without having to have the motor directly connected to an axle. This can allow the motor to be further away or sometimes drive more than one axle and gears connect together.

 

Gearing Up and Down

 

Begin the builds this week by looking at the gearing down icon and ask them to build the example prototype model with the pieces in the pop out menu on the left of the screen. 

 

 

Test their model with the same simple algorithm as last week, observe the motion created. 

 

What is different about this prototype? (gears are different sizes)

 

Compare and contrast the Driver and Driven gears:

• how is their motion different?

• how is their motion similar?

• What is the relationship between the number of teeth on each gear?

• Why do you think this type of mechanism is called ‘gearing down’

• What do you think ‘gearing up’ means? Can you adjust your model to demonstrate this?

 

Where there are two gears of different sizes, the smaller gear will rotate faster than the larger gear. The difference between these two speeds is called the gear ratio.

Gear ratio = number or teeth on driven gear ÷ number of teeth on the driver gear

• How many teeth does the big gear have? (24)

• How many teeth does the small gear have? (8)

• So what is the gear ratio? (3:1)

 

This means that the small gear has to turn three times to make the big gear turn once.

 

Gearing down key concepts

• Gearing down is when gears change speed from fast to slow
• Driver and driven gears move in opposite directions
• The small gear has 8 teeth, the large gear has 24 teeth. The small gear has to turn 3 times to make the large gear turn once, we call this the gear ratio.
• Gearing down creates more power or strength from the mechanism, while it reduces speed.

 

Gearing up

So what do you think 'gearing up' is? This is when a larger gear turns a smaller gear.

 

 

This produces the opposite effect to gearing down: more speed but less strength. This is a great way to get more speed from a machine even when the power of a motor or engine is at it's maximum output.

Ask the children to experiment with two gears that are different sizes using whatever you have available. There are a good variety of LEGO gears available, such as these:

 

 

They should try larger and smaller gears in the driver and driven gear positions and record what they find.

 

Finish by recapping the three mechanisms that they have built in the lesson; motors, gears and gearing down, checking their understanding of each and how they might be used in other machines.

Dismantle their models and carefully put all the pieces back into their kit box, checking each kit is complete with your WeDo box check sheets.