Well - I finally got around to testing the idea of a tank built on the Lego R/C car. This has one PWM output for speed, with steering rotating an axle hole on the receiver. In a normal car, this drives a steering mechanism, but I wanted to drive a dual track tank. I built a little test rig with wheels and skids rather than tracks just to see if it would work.
The basic idea is to have an adder/subtracter drive, with the R/C "drive" output going to a motor on the base input and the steering output tied to a Lego polarity switch. The polarity switch is supplied from a battery box and the output is connected to a motor on the added/subtracted input of the differential mechanism.
I used the R/C motors for both driving and steering, so it whips around pretty fast. It isn't pretty, but it gives me enough
confidence to make a tracked base with the same drive, now:
A front view showing the polarity switch:
And a shot of the differential adder/subtracter drive, straight from Doug's page here:
I volunteered Saturday to act as a technical judge for the FIRST Lego League (FLL) Niagara Regional Tournament and I must say that even though it was an exhausting time, I thoroughly enjoyed the day.
With 22 teams competing, the pace was incredibly hectic, but everything came off without any significant hitches. This year's FLL Challenge was titled Ocean Odyssey in which the teams' robots have 2 1/2 minutes to get as many point possible by completing 9 missions.
While I was perusing my daily "news sources", I came across a link at BoingBoing that caught my eye. The winner of the British Antarctic Survey's competition to design a new research base is this 800 ton structure that can be moved across the ice on its ski-laden legs.
Oddly, the first think that jumped to mid was a Lego set, #6520 Mobile Outpost from the Arctic Theme.