Until the early part of the last century, farmers used horses or oxen to pull carts and help plough the fields. Now tractors are used to do this
and for lots of other purposes as well. Could you make one?
Levels of difficulty:
Level 1 - Make a simple model of a tractor.
Level 2 - As level 1, powered by a battery motor.
Level 3 - As level 2, with a plough on the back, and the plough the sand in a sandpit.
Equipment: KNEX set including small and medium wheels, plus a battery motor and (for level 3) a sandpit.
Approach: What does a tractor look like? What type of wheels does it need? Where does the driver sit? For level 2, how can you make the motor drive the wheels? How will the motor be fastened to the body? For level 3, what is the purpose of a plough? How can you make one out of KNEX? How will it attach to the back of the tractor? Does it work when tested in a sandpit?
Handy Hints (please click to view):
A2 - 3 ways to connect K'NEX rods and connectors
A4 - Making corners with blue & purple connectors
W5 - Wheels and tyres
W6 - Making rods turn with wheels or connectors
M2 - Tethered battery motor
The aim of the project is to build a working model of a familiar mechanical object, and then to experiment with how a pulling force can be used to plough sand.
Possible solution: See photo.
Before starting: Discuss ploughing - how it works and why it is needed, and look at a picture of plough.
Conclusion: Firstly, compare the different designs for tractors and ploughs. Then, see whose tractor can plough the sandpit deepest and in a straight line.
Copyright © Andy Shercliff 1996 and K'NEX User Group 2004