The only source was the comment in the above link:

To tell the robot which way to go, the driver uses some kind of global positioning system that informs the robot which direction is magnetic north.

The idea of GPS is nonsense (at least indoors), so I took the above to mean a carefully positioned magnetometer - but it occurred to me, too, that the interior of a robot isnt exactly free of distracting magnetic fields. Neat idea if that *is* how they did it.

I missed off the simple idea of just sitting a gyro in the robot and tracking rotation rate with it. I suspect off-the-shelf gyros are limited in the rotation rate they support, though - Ive only seen this reported (in one of the web sites Google gives you with a search for tornado drive) for a thwackbot with a low RPM. This assumption was the basis of my idea for counterrotating the gyro, but if there are standard gyros out there which can accurately represent the difference between 1000rpm and 1001rpm then it wouldnt be necessary.

I like the LED feedback idea, although it could get a bit hypnotising!

As for speed of locomotion handling, certainly a problem. The wobbly-wheel method used by Team Whyachi probably puts less strain on the drivetrain than the alternatives. Looking on the spec page suggested above, the Team Whyachi spinners are capable of appreciably higher rpms than CycloneBot (1000rpm for Why Not and 900 for Y-Pout, vs 400rpm for CycloneBot), but Teslas Tornado (with wheel braking?) has reached 870 rpm according to its web page. I wonder where the limits actually are on the different drive options. I dont know whether the various people suggesting translational spinners - if thats what they meant by them - in this section of the forum (I *so* dont dare build a feather...) have any estimates of RPM yet. Mind you, of course, the faster the spin the less the tweaking required per revolution to get the same final rate of locomotion.

Theyre certainly an interesting technical challenge. Id still like to know whether anyone has a solution for the batteries self-destructing, though!

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Fluppet