Quote Originally Posted by Lord Bob
Ok thanks. i just don't want to build it and find it's too heavy

Sorry, more noob questions.

What is a speed controller?
Why do i need it?
Where can i get one?
A speed controller is an electronic unit which basically switches your motors on/off/reverse and controls how fast they run depending on inputs from your radio receiver and therefore from your controller. You need it because your robot would just sit there without it. You can get one (you'll need two - one for each side of your robot - or a dual channel one) from all kinds of robot suppliers - electronize are okay as a basic cheap kind of thing. else you want to look at a scorpion xxl or sabertooth. Those are the main types used by UK feathers.

Electronize - http://www.electronize.co.uk - or i am selling two. You'll want two 15 amp ones for two drills (FR15HVRs), or two 30 amp (FR30HXs) for two drills a side for four wheel drive.
Sabertooth (you'll want the 2x25 for 2 drills, won't really like anything more than that) - http://www.technobotsonline.com
Scorpion - http://www.robotpower.com/catalog/ - have to order them from the US.