Servo - September 2011

LEGO MY PANCAKE

The LEGO Pancake Bot created by Miguel Valenzuela is a work in progress, designed to make pancakes in shapes. Two empty ketchup bottles serve as dispensers on an aluminum protected track, and a three-axis Computer Numerical Control (CNC) handles the movement with Python NXT — a scripting language for LEGO projects. It uses the Z coordinate as the pancake batter dispenser control.

The Pancake Bot is made up of the following parts:

1. A set of linked base plates with three parallel tracks snapped on. One track has a bunch of Technic Gear Racks (1 x 4) riding along the top which makes up the X axis.

2. A moveable bridge that holds one NXT motor on one side and has free rolling wheels on the other. The top of the bridge uses two tracks covered with gear racks that holds the pancake Batter Dispenser Unit (BDU). This track allows for Y axis control.

3. A carrier gantry on top of the moveable bridge that rides on the gear racks and holds the BDU.

4. As mentioned, the BDU consists of two ketchup bottles cut in half and glued together so you have two open ends. This allows you to change the nozzle size on the bottom and allows for input of compressed air on top.

5. A Compressed Air Dispersal Apparatus (CADA) that consists of an NXT motor, two pneumatic cylinders, a tank, and a bi-directional flexible switch which allows for the switch to be flipped based on which direction the NXT motor turns. As the motor turns, the cam changes the flexible switch every time it rotates. In the initial turn, the switch is flipped and stops, and then continues to flex out of the way of the rotating cam. When the motor turns the other way, the cam catches the switch, flips it back, and changes the direction of the airflow. It continues to flex as the cam passes over it. This allows for air to be compressed when the motor turns clockwise, and then the air to be released when the motor turns counter-clockwise.

Valenzuela designed the bot this way because he only had three NXT motors and needed a way to change the direction of the air flow while at the same time, compressing the air. Go to http://makermig.blogspot.com/2011/06/how-pancake-bot-works.html for more details and videos.

DIGGER TEARS THINGS UP

The Digger D- 3 is the most recent addition to my own personal list of robots not to stand in front of. It's a mine-clearing robot, and not the sort of mine-clearing robot that pokes around with a metal detector. Instead, it simply sucks it up and tells the landmines to bring it.

At the front of the D- 3 is a giant spinning metal pulverizer of death which has Tungsten hammers that beat down a quarter meter into the ground, turning everything they touch into mulch. This includes landmines, and although the mines do tend to blow up before getting shredded, the robot hardly seems to notice.

An operator commands Digger from a safe distance using a remote control unit. The hull of the robot is made up of hardened steel plates in a V shape to help limit any damage from antitank mines and unexploded shells of sizes up to 81 mm. The D- 3 has been able to successfully ingest mines containing as much as eight kilograms of explosive — which is nothing to sneeze at. The only potentially vulnerable spots are the air intakes which are themselves protected from flying shrapnel by special grates.

At full throttle, the D- 3 can reliably clear a comforting 100 percent of landmines from the ground at a rate of 1,000 square meters per hour (about 10,000 square feet per hour), while also divesting the land of any unwanted shrubbery and unlucky mole colonies.