So why doesn't it just sit in one place and buzz? Why does it move forward? Most
toothbrush bristles are angled just like the hairs on a gecko's foot, meaning they'll
slide smoothly in one direction, but not so easily in any other. The brushbot is
thrown forward by the swinging weight and the bristles slide along the surface a
short distance. When the weight swings back again, the bristles catch and resist
moving. This way the brushbot creeps along the surface using friction, pushing along
with its bristly feet.
In some ways, your brushbot works a little like how a snake eats. Snakes have teeth
which are angled backwards, just like the bristles on the toothbrush. Any prey they
consume can move in easily.
The surface friction on which a brushbot moves will affect the behavior of the
brushbot. Practice on the surface that the brushbot will be competing on.
Friction is actually a force that appears whenever two things rub against each other.
Friction is a ’catch all’ phrase for any force opposing the relative motion of objects
in contact. Friction releases some of the energy. This release can be in the form of
noise, vibration, and energy transfer. Friction can also transfer energy into heat
energy. If you rub your hands together you will notice that the skin on your hands
warms up. Some of the energy of motion in your hands is transferred to heat energy
through the friction process.
Brushbots fall over easily: consider where your motor and other items added are
attached in order to create a balanced system. Center of gravity is the exact spot on
an object where there is the same amount of weight on one side of the spot as there is
on the opposite side. Once you change the weight anywhere on the object, the center
of gravity changes too. The ease with which an object can be balanced depends
greatly on the location of its center of gravity.
Some ideas for your consideration….
*Mount the motor on the end. This will convert as much vibration as possible into
axial motion.
*Mount the motor on the rear end. This tends to lift the device off the front bristles
and reduce friction.
*Mount the battery on the handle end. (Similar principle as above)
*Remove the middle bristles. This eliminates friction from unneeded center bristles.
*Split the bristles. (Similar principle as above)
*Cut a slot in the plastic. The lightest, longest tends to move faster. (Notice how
ships are designed)
*Cut the sides of the plastic. (Similar principle as above)
*Use a tail. This will tend to convert unwanted sidewards movement into axial
motion along the track.
*Change the vibration pattern by modifying the motor shaft by an unbalanced weight