Hi Graham,

Tho Im not in an objective position to say so, FeatherWeights.org is great :-)

Geoff has put it very well- you can never underestimate the forces involved with spinners, and you must engineer accordingly. A very ridget, low friction set up is equally as important as the wepon motor you have powering the thing.

As with all things, it a balance- bigger discs can store more energy but take longer to spin up, smaller/lighter discs contain less energy (at a given speed) but consequently take a shorter time to spin up. It is tempting to go for the big disc/lower spin up time option, but I would advise against it- any driver worth his salt whose drawn against a spinner knows the age old tactic is to get up close and stay on the spinner so it doesnt have the oppoertunity to spin up. Hand in hand with this goes the choice for the weapon motor. Its not entirely correct to say that a bigger motor means a more powerful spinner- the actual explanation involves a bit more physics:

A flywheel (a spinner) is a rotating mass storing energy. On impact it releases that energy into its opponent. The motor puts energy into it by spinning it up- its energy comes from the motor. Motor power is measured in Watts- and a watt is a joule per second. So the higher the power, the faster the motor can put energy into the disc. In essence, bigger motors mean faster spin up times. And, as mentioned, the faster you can spin up, the better your postion in the arena. Well aligned, true and ridgid set ups reduce friction and allow smoother operation- all important in getting the most from your disc. In short its not a question of putting the largest disc in that you can- its got to be a more well considered trade off between opposing factors!

If after all that youre still commited, congratulations, you are ready to build a robot! As geoff said, this forum is a great resource, and if you are at all in any doubt about anything, please come and ask us- well all be more than happy to answer your questions.

All the best,

Eddy
http://www.featherweights.org>