Make a Simple Rover

Robot planetary rovers are will be used a great deal on Mars. So far only one has been used on the Red Planet, the Micro-Rover, Sojourner, which was part of the Pathfinder Mission. This, though was not the first to visit another world. That honour went to the Soviet Union. In the 1970's two Lunokhod Rovers explored parts of the Moon. A fuller story of Robot Rovers is given on here.

Lunokhod at the Paris Airshow, 1971

©Image: NASA/JPL

Here is how you can make a small rover out of scrap materials. All you need are these things:

Materials (Substitute materials may be used)

    Cotton reel - wood or plastic

    Elastic band - a thick one is best, but not too long

    Pencil - any straight stick-like object will do

    Piece of wire or drawing pin - this secures one end of the elastic band to the cotton reel

    Piece of candle - make a ring of wax by cutting a candle and making a hole in the centre


  • Assemble as in the pictures, by putting the elastic band thtrough the centre of the cotton reel and wax.
  • Bend the wire into a U shape , and put it though the band.
  • If the cotton reel is plastic, then fit the prongs of the wire staple into the cavities in the cotton reel.
  • If it is wood, secure the band with a drawing pin. It is vital that this end of the band is fixed to the reel.
  • Pull out the end of the band through the candle ring and secure it with the pencil.

Making it go

  • To make it move, wind the pencil round and round until the band is powered.
  • Put it on the ground and let it go.
  • It will crawl along, trailing the pencil, which acts as a reaction lever.

It works best on rough surfaces - carpet, grass or soil - and should climb small obstacles.

How it works

All machines need energy to work. Here the energy is supplied by the elastic band. You wind it up, and put energy in. How do you know? Do it long enough and you get tired - you use energy. But the elastic band receives it and stores it while it is being wound up.

One end of the band is secured to the cotton reel, the other to the drive stick. If you let go of the wound up drive stick, the stick whizzes round. If however you put the rover on the ground and don't let go until the drive stick is in contact with the floor, the cotton reel will turn, because the drive-stick can't. This is Newton's Third law coming into action!

But what does the piece of candle do? Well, this acts as a lubricant, to allows the cotton reel and stick to turn free of each other. If this is not present, the reel and drive-stick will tend to stop moving when the elastic band is still half wound up. This is due to a force we call friction. The slippery candle reduces friction and lets the elastic band work for longer.

More Things to Do

Hold races for -
climb performance
obstacle courses

Further Development

See if you can develop the rover. Try using different types of cotton reel, different elastic bands.
Can you substitute anything for the candle - soap, perhaps?
Does the length of the trail sick affect performance?
Can you get more traction by cutting notches in the rim of the reel?
Can you design a two-reel machine?

Return to rover


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