Making paper gears
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You can make paper gears a few different ways. The way I show you here is fairly simple, and it doesn’t take weeks and weeks to make. Look at Figure to see the principle of the paper gear. Each gear turns on a shaft. The teeth on the smaller gear are made of triangular tubes of paper attached directly to the shaft. The larger gear is double-thickness card with the teeth cut out of it. In this model, the smaller gear has only 4 teeth; the large gear has 12. When you turn the small gear, the large gear turns at 4/12, or 1/3, of the speed. In addition to some card, a pencil, scissors, a ruler, white school glue, and the other standard paper-engineering supplies, you need a drawing compass and protractor so you can correctly draw and measure the the teeth. The following sections explain how to make the gear mechanism.
Creating the small gear
To create the small gear, first make a drive shaft from a 3/8" square tube approximately 3" long.
Each tooth is made from a strip of card, 3/4" x 3/8", as the template in Figure shows.
Attach the four tooth pieces to the drive shaft as Figure shows.
Creating the larger gear
Making a circle of card and then cutting teeth out of it makes the larger gear. First glue two
pieces of card together, creating double-thickness card, for strength.
You need to use a protractor to accurately mark out the teeth. To make a gear with 12 teeth,
each tooth needs to be 30°. Here’s how to mark your double-thickness card:
1. Use a drawing compass to draw two circles, an inner circle and an outer circle.
For the smaller circle, make the radius (the distance between the compass points) 2".
The larger circle has a radius of 21/2".
2. At every 15°, draw a line that goes through the center of the large circle, like the
spokes of a wheel.
First draw a single line that passes through the center of the circle. Line up your protractor,
mark off 15°, and draw another line that passes through the circle’s center.
Continue around until you get back to the first line you drew.
3. Join the places where the lines cross the inner and outer circles to create the teeth. The smaller circle marks the bottom of the teeth, and the larger circle marks the top of
the teeth. Draw a zigzag line between the two circles until you’ve created 12 points. Cut a square hole out of the center of the larger gear to fit a drive shaft and then cut out the gear.
Next, make a square tube and thread it through the hole to act as a drive shaft. If you want to use a cam to move your character, add it to the drive shaft of the larger gear. See how to do it in Figure.
Constructing a box that fits the size of the gears
After making your small and large gears (see the preceding sections), hold the two gears together to see how far apart the shafts need to be. You can then use this information to construct a box. Make the box as Figure shows and assemble it around the gears.
I usually like to have holes in the box so you can see how the mechanism works. You can add these to the end of the box if you like. See Chapters 10 and 11 for more on boxes.
The Snail’s Tale
You can finish off a gear model by adding a Snail character to the top. The head of the snail is the part that moves. It’s hinged to the top of the box, with a cam follower going through a hole in the box top.
You may find that the cam follower needs a little weight to keep it down against the cam. I usually use a coin or two for this purpose. Wrap the coin in a strip of card; you can then glue the card to the cam follower. Finish off the snail model by adding the tail of the snail and the shell. You can make the shell with a couple of ovals of card joined together with a long strip of card.
After the model is complete and the glue is dry, turn the handle, and the head of the snail should rise and fall slowly as if he’s slithering along.
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']]}You can make paper gears a few different ways. The way I show you here is fairly simple, and it doesn’t take weeks and weeks to make. Look at Figure to see the principle of the paper gear. Each gear turns on a shaft. The teeth on the smaller gear are made of triangular tubes of paper attached directly to the shaft. The larger gear is double-thickness card with the teeth cut out of it. In this model, the smaller gear has only 4 teeth; the large gear has 12. When you turn the small gear, the large gear turns at 4/12, or 1/3, of the speed. In addition to some card, a pencil, scissors, a ruler, white school glue, and the other standard paper-engineering supplies, you need a drawing compass and protractor so you can correctly draw and measure the the teeth. The following sections explain how to make the gear mechanism.
Creating the small gear
To create the small gear, first make a drive shaft from a 3/8" square tube approximately 3" long.
Each tooth is made from a strip of card, 3/4" x 3/8", as the template in Figure shows.
Attach the four tooth pieces to the drive shaft as Figure shows.
Creating the larger gear
Making a circle of card and then cutting teeth out of it makes the larger gear. First glue two
pieces of card together, creating double-thickness card, for strength.
You need to use a protractor to accurately mark out the teeth. To make a gear with 12 teeth,
each tooth needs to be 30°. Here’s how to mark your double-thickness card:
1. Use a drawing compass to draw two circles, an inner circle and an outer circle.
For the smaller circle, make the radius (the distance between the compass points) 2".
The larger circle has a radius of 21/2".
2. At every 15°, draw a line that goes through the center of the large circle, like the
spokes of a wheel.
First draw a single line that passes through the center of the circle. Line up your protractor,
mark off 15°, and draw another line that passes through the circle’s center.
Continue around until you get back to the first line you drew.
3. Join the places where the lines cross the inner and outer circles to create the teeth. The smaller circle marks the bottom of the teeth, and the larger circle marks the top of
the teeth. Draw a zigzag line between the two circles until you’ve created 12 points. Cut a square hole out of the center of the larger gear to fit a drive shaft and then cut out the gear.
Next, make a square tube and thread it through the hole to act as a drive shaft. If you want to use a cam to move your character, add it to the drive shaft of the larger gear. See how to do it in Figure.
Constructing a box that fits the size of the gears
After making your small and large gears (see the preceding sections), hold the two gears together to see how far apart the shafts need to be. You can then use this information to construct a box. Make the box as Figure shows and assemble it around the gears.
I usually like to have holes in the box so you can see how the mechanism works. You can add these to the end of the box if you like. See Chapters 10 and 11 for more on boxes.
The Snail’s Tale
You can finish off a gear model by adding a Snail character to the top. The head of the snail is the part that moves. It’s hinged to the top of the box, with a cam follower going through a hole in the box top.
You may find that the cam follower needs a little weight to keep it down against the cam. I usually use a coin or two for this purpose. Wrap the coin in a strip of card; you can then glue the card to the cam follower. Finish off the snail model by adding the tail of the snail and the shell. You can make the shell with a couple of ovals of card joined together with a long strip of card.
After the model is complete and the glue is dry, turn the handle, and the head of the snail should rise and fall slowly as if he’s slithering along.