1. Crumble PowerPoint 4

2. Make a chair-o-plane

3. Learning objectives Understand the forces acting on a chair-o-plane
Use mechanical systems – pulleys, drive belts, shafts and bearings
Make and strengthen complex structures
Interpret cross sectional views
Problem solving and troubleshooting

4. 1. Work safely
Look at the tools and the sample model. Can you spot any potential hazards?
Can you think of ways to reduce the risks?

5. 2. Collect your parts
Make sure you have all the parts listed in your workbook.

6. 3. Understand how a chair-o-plane works
Identify the following:
Motor
Drive belt
Pulley
Rod (shaft)
Bearings
Which of these move?

7. 4. What forces act on a chair-o-plane?
What force pulls the passengers down?
Which forces act to slow the ride down?
Extension questions:
What makes the ride turn?
Explain why the chairs fly out as the ride turns.

8. 5. Make these circles
Mark the circles with the compasses and cut them out.
Use the pencil, ruler and protractor to mark lines at 60° intervals around the top circle (the larger one) as shown.
Top circle Base

9. 6. Make this structure
Turn the base over and glue on three discs and the cardboard craft roll.
Why should there be no cardboard or glue in the central holes of the discs?
Why should you only partially sharpen the rod, not make it pointed?

10. 7. Enlarge the hole in a card disc
Rotate the nose of the scissors in the hole.
Make the hole just big enough for the rod to rotate in it easily.
Make it smooth and round to reduce friction.
What will happen if the hole is tight on the rod?
What will happen if the hole is too big?
Glue the disc to the top of the craft roll.

11. 8. Attach the pulley to the rod
Mark the rod 13 cm from the sharpened end.
Sharpen the other end slightly.
Push the pulley on until it just covers the mark.
Glue two card discs to the top of the pulley.

12. 9. Slide the rod down through the bearings
Hold the rod straight and feel around for when the rod drops down through the holes in the three discs at the bottom (lower bearing) to rest on the base.
Why does there need to be a gap between the bottom of the pulley and the disc below it?
Check the rod (shaft) spins easily, then take it out.

13. 10. Attach the motor and crocodile leads
Glue the motor mount on firmly just below the top disc.
Also hold it on with a rubber band.
Hold the wires onto the craft roll with a rubber band. What could happen if they get in the way of the chairs?

14. 11. Fit the top circle
Glue the top circle to the top of the discs on the shaft.
Lower the shaft back through the bearings.
Make sure the end of the motor shaft isn’t touching the top circle. You could slide the motor down a bit in its mount.

15. 12. Make chairs for the passengers
Cut long strips of corrugated plastic and glue the passengers to the middle.
Bend each strip round the passenger and tape the ends together as shown.
If you haven’t got any passengers you can make your own from corrugated plastic offcuts.

16. 13. Tape the chairs to the top circle
Tape each chair at the end of a pencil line. The tape should act as a hinge so the chairs can swing out as the ride rotates.
Try to put passengers of equal weight opposite one another to balance the ride.

17. 14. Reinforce the joints
Take out the completed chair unit, turn it upside down and lay the chairs out to the sides.
Tape the underside of each chair to the bottom of the top circle to reinforce the joint.
Why is this a good idea?

18. 15. Assemble your chair-o-plane
Stretch the third rubber band over the pulley, keeping hold of the end.
Turn the chair unit the right way up again and slide the shaft down through the bearings.
Stretch the rubber band over the motor shaft as you push the rod back into the holes in the card discs.
Slide the motor in its mount until the rubber band sits at the bottom of the motor shaft as shown.

19. 16. Decorate your chair-o-plane

20. 17. Connect up this circuit

21. 18. Program a ride for your passengers
Come up with your own ride – this is just an example.
Program a delay when changing between forwards and backwards to avoid draining the battery.
If you swap over the crocodile clips on the back of the motor what effect does this have?

22. 19. Troubleshoot your chair-o-plane
If your ride stops working can you work out how to fix it?
Could something have come loose? A crocodile clip perhaps?
Could the rubber band have come off the motor shaft? Do you need to slide the motor up a little in its mount (but not so much it touches the top circle)?
Could you have drained your battery?
Any other ideas?

23. 20. Extension question
If your motor shaft turns twenty-five times per second then your pulley (and hence your chair-o-plane) should turn roughly once per second.
Approximately what distance would the rubber band move in one second?
If you fitted a bigger pulley would your ride go faster or slower? Explain why.

24. What did you learn?

25. Move on to the next module
Copyright © Caroline Alliston 2017