Floor Vacuum Cleaner Robot - Controlled by Arduino With Motor Shield, With Printed Motor-wheels

Floor vacuum cleaner robot. Version #17. Attempt to make it more simple.
The robot is moved by small DC motors built-in motor-wheels printed on 3D printer:
http://www.thingiverse.com/thing:225576

Components:
Arduino with motor-motor-shield;
Turbine for computer cooler, 5 Volts;
Two DC motor-wheels;
Battery pack for 5 Volts;
Cardboard;
Melting glue;
Plastic box;
Plastic ball;
Wires, resistors (~10 kOhm, ~180 Ohm);
Strong magnets.

Step 1: Create a Robot Chassis

Cut a circle from a cardboard: diameter 16 cm.
Cut holes for turbine and wheels.
Take a one part of a plastic box and glue magnets on it by melting glue.
Put the box with glued magnets on bottom side of the chassis covering the round hole
Set another magnets on the top side of the chassis - so magnets hold the box attached to the cardboard.
Glue these magnets on the top side - now the box can be hold pretty strong on the chassis.
Put the turbine on the top of the chassis on the round hole - so this hole will let air come from the box to the turbine.
Glue the turbine to the top side of the chassis.
Glue four wood sticks on the top side so they keep Arduino board with motor driver - now the board can be set or removed easy.

Step 2: Add Battery and a Caster Wheel

Glue two printed motor-wheels.
Glue a battery to the bottom side of the chassis.
Take a metal wire (or a thick paper clip) and a plastic ball.
Put the wire through the ball and bend the wire.
Glue the wire with the ball to the bottom side of the chassis so that the robot stays on three points - two wheels and the ball.

Step 3: Create a Dustbin

Optionally two cardboard pieces can be glued above the hole so filter does not lay on the chassis.
Cut the piece if fabric (e.g. used on kitchen for cleaning a table) - this is a filter.
But the filter above the hole and try to cover it by the box - magnets should hold the box and the filter under it with strong some force so air cannot come between edge of the box and the chassis.
Make a long hole on the box.
Create a nozzle with the shape of this hole - make it from paper covered by type (initially the paper can be shaped by two pieces of cardboard).
Glue the nozzle inside the hole on the box so the distance from the nozzle to the floor (or a table) where the robot stands is ~1mm - robot should be able to move and the nozzle is carried above the floor on this distance - collecting dust.

Step 4: Create Bumbers, Program Arduino

Cut tree pieces of tin from the aluminium can and attach (and secure) wires with resistors as on schema.
Glue these tin pieces so two of them can touch the third one when they are pushed - they will be pushed by bumpers.
Cut two stripes of cardboard and glue rounded pieces to form them rounded.
Glue these cardboard stripes to the chassis co when they are pushed - they hit tin contacts.
Connect power, motors and bumper wires to the Arduino.
Upload to the Arduino the program from GitHub: https://github.com/satr/Robot-vacuum-cleaner-controlled-by-Arduino-and-motor-shield