Scout - A printable tribot frame

by sliptonic, published

Scout - A printable tribot frame by sliptonic Oct 31, 2011

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Scout is a printable tribot designed for teaching the Boy Scout robotics merit badge. http://www.scouting.org/scoutsource/BoyScouts/AdvancementandAwards/MeritBadges/mb-ROBO.aspx

I'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.

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.

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: $47.21


Print 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.


Route wires up to the arduino.
add a battery.

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Where can i find the wheels?

What size o-rings did you use for the wheels, and what size ball bearing for the caster? Thanks! Love this design.

Both values are parameters of the main .scad file in the section that builds the ball caster. The default is 11.11mm for the diameter of the ball and 56mm diameter of the wheel. IIRC, I used a 2 1/8" o-ring.

I'm looking forward to make this robot!

I, a group of geeks from work, and our kids made two of these this past weekend.

I couldn't find caster bearings or marbles so I turned some PTFE plugs on the lathe. The fit right in the spot for the bearing and seem to work just fine.

Great work!! It would be awsome if you could publish the openscad files. Thanks

Thanks you very much :-)