Scout is a printable tribot designed for teaching the Boy Scout robotics merit badge. http://www.scouting.org/scoutsource/BoyScouts/AdvancementandAwards/MeritBadges/mb-ROBO.aspxI've marked this as a derivative of MiniSkyBot because I was inspired by it and because Scout still uses the wheels from that project. The frame itself is a complete redesign with similar but different goals.Goals: Provide a kit that meets the merit badge requirements with parts totaling < $50 USD.-Minimum printed parts -Minimum vitamins -Accommodate an arduino diecimila or nano. -use a 9V battery. -Flexible enough to allow boys to improve and extend the design.The frame is a single printed piece. The tabs for holding the servo motors can be tapped with a 4mm tap to avoid the need for nuts.The top holes can be tapped with a 3mm tap to screw on an arduino without nuts.The bracket will hold a 9v battery with just friction. The rear battery bracket has a friction fit cup for a ball bearing caster.Large holes in the bracket minimize the amount of plastic needed and allow wires to be routed up to the arduino.Cost Since affordability was a major consideration, here's a run down of the final project cost. The plastic cost is just the cost of a roll divided by the number of kits we built. There was lots of plastic left over and the boys are using it to design improvements.Frame & Wheels $7.86 (plastic from Makerbot) Tires (2) $2.36 (Hardware store o-rings) 4mm bolts (4) $0.84 wheels screws (4) $0.96 Servos futaba (2) $8.38 (purchased new in bulk on ebay) Arduino Nano $18.99 (purchased new on ebay) Ultrasonic $3.90 (purchased new on ebay) 9v connector $0.81 (Radio Shack) DC power plug $1.86 (Radio Shack) 9V battery $1.25 Total: $47.21Print the frame bracket.Tap the bracket holes.Print two wheels. Mount the servo horns to the wheels. Put on o-rings or rubber bands for traction.Assemble.Route wires up to the arduino. Program add a battery. Go!