© 2019 by Pernille Dahl & Cole Robbins. 

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Mini-Bot

Parts needed:
  • 2 Models

  • 1 Baseboard, small:  2 x 2 and thin

  • Baling wire

  • 1 Motor

  • 1 Battery, C or AA

  • Hookup wires

  • 2 Paper clips

  •  Popsicle sticks

  • 1 ¼” dowel, about 6 inches long

  • Eyes

  • Aluminum foil

  • Small cup or something for head

Extra Tools: 
  • Drill

  • Drill platform

  • 15/64th bit

  • Large nail bit for leg holes

  • Small nail bit for making hole in glue stick

  • Wire strippers

  • Extra hot glue

  • Black tape

  • Pipe cleaners

  • Yarn

Project Description:

You may have never seen anything powered in this manner, and the reason is clear:  it is nearly impossible to control.  Because the motor does not touch the ground or blow on air, the mini-bot is limited to hopping.  The direction of each hop is determined by the swing of the piece of glue stick, the weight and balance of its body, the angle of each leg and its friction with the ground. 

 

If you put a hole right in the center of the glue stick and attach it to the motor shaft – you should try this – the glue stick will spin very smoothly and the mini-bot will not move.  It is only when the glue stick is off center that the jumping occurs. 

 

Think about when an adult swings a child around by the hands.  The adult cannot be exactly vertical; they must lean back in opposition to the direction the child is swinging.  On the mini-bot, the body and legs move in opposition to the glue stick. 

 

If you switch the wires on the motor or the battery, the motor will turn in the opposite direction.  This will have an impact on the direction the mini-bot hops (though it is not always predicable!)  The larger the weight spinning on the motor shaft, the harder the motor will have to work to spin it and so the slower it will spin.  Different numbers of legs may make the mini-bot act differently, but mini-bots made with no legs – just a flat base – also work.  If you make the legs from markers, your mini-bot will scribble you a picture on the table. 

How we Built it:

Drill 4 holes in the baseboard, one in each corner.  Cut a piece of baling wire, bend it and force both ends through holes.  Make the wires stay on the board by bending or adding some hot glue.

  

Strip both ends of both electrical wires. Connect them to the motor. Glue the motor onto the baseboard in any position you think will work

 

Connect a paper clip to the free end of both wires. Fold two pieces of aluminum foil.  Tape them tightly to the ends of the battery. 

 

  

Glue the battery to the baseboard.  

 

If you want a neck, cut a piece of dowel, drill a 15/64th hole in the piece of wood at an angle and insert the dowel.

 

Cut a piece of hot glue stick. Drill a hole with a small nail, off center. Press it on the motor shaft.

  

Make a head and face.  

  

Connect the paperclips to the bits of aluminum foil wires and watch it hop.  Try to control its motion by bending the legs and feet into different positions.

Concepts:

  1. The motor is not touching anything, but it makes the mini-bot move.

  2. The momentum of the glue stick spinning around makes the mini-bot move. 

  3. Newton said:  For every action there is an equal and opposite reaction.  When the glue stick spins to one side, the mini-bot hops to the other side.  When the glue stick swings down, the mini-bot hops up.

Questions:

  1. What happens when the motor is attached to the glue stick in the very center?

  2. What can you do to change the direction that the mini-bot hops?

  3. What would happen if you put on a very large weight instead of the piece of glue?

  4. What would happen if you made only three legs?