Drive tutorial
These are several tips that you should follow if you want a a well built drive in Stock.
If some don't want to follow these because it's "building like everyone else" or "not original", you're free to build that do you want, but then don't moan if your drive system sucks.
-Naryar
Drive Motors
Obviously those are spin motors.
The best drive motors are HP Z-teks, and you can use right angle drive in the lighter weight classes too.
Power
To have a good drive you need to power your bot correctly.
A minimum of 2 small battery packs should power your drive. But if you can, choose a nifty instead. A Nifty is enough for a maximum of 2 HP Z-teks. A Supervolt is enough for a maximum 4 HP Z-teks.
Don't forget your weapons, too - a VS with 2WD Z-tek drive and a HP Z-tek powered weapon needs one nifty.
Multiple Wheel Drive
For maximum efficiency, you should only use these setups:
1 wheel drive, right angle: This is used only on antweights, to make a powerful HS. You can drive forward/backward using the right angle and turn left/right using the recoil of the spinner motor.
2WD, right angle: Used widely by LW's and make for a decent drive. Personally, most of my LW's use Z-tek drive, but it's just because i don't like slow bots, and i'm not forcing to use it. Most builders say this drive is enough on MW HS's and they could be right because i have little experience on HS's.
2WD, Z-tek : Neat for speedy LW's and decent for MW, although not very fast. Good for Popups or Rammers.
2WD, HP Z-tek: Makes for very fast lightweight rammers (you'll need practice your control while driving). Most MW rammers and popups use this drive. This is the average drive on a HW. Better than 4WD Z-tek drive because lighter for the same power.
3WD: As said by one of my idols, you're on crack. This is extremely difficult to work with, often resulting on asymmetric bots that. It reduces translating speed but increases turning speed. But I must say it is perfect for a MW SnS.
4WD, HP Z-tek: Very fast on a MW (use this on a SnS and a rammer if you want). If you want a good HW popup, use this. Also useful in HS killers.
6WD, HP Z-tek: The best drive train for HW Rammers. Several succesful Pokers use this too (not mine).
8WD, HP Z-tek or more: Too much, even for a HW rammer. You need weapons on your bot, too...
Wheels
Shiny Hubs are considered as the best wheels, mainly because of their low weight (12kg) for a decent diameter. You can make a bot invertible with that if you minimize your chassis's height. Perfect if your bot is on a diet (LWs)
Slipperbottom wheels are a worthy choice too, because they have a larger diameter and a better grip than Shiny Hubs, and are very useful for when you need guaranteed invertibility. However, they weigh 18kg, 6 more kg than Shiny Hubs.
Rubber wheels are also good: these have the best grip of the three and provide Stock's best ground clearance when on Zteks. Rubber wheels weigh 17kg.
Avoid other wheels, there are heavier and are big targets for your opponent. Using miniwheels is not usually worthy even if they are small targets, because they're heavy too.
General Design
You'll notice that often, your bot will drift to the left or right if you go forward, especially in the 2WD category and with fast motors. This is caused by a weight distribution problem or a wheel positioning problem.
Wheel positioning: If your bot drifts, just try rotating wheels (Ctrl key) on their axle. before fixing them on your drive motors. This may seem worthless, but no. I solved several drifting problems with that and Clickbeetle too.
Weight distribution: If this doesn't work, you need to make your bot as symmetric as possible. That is, make a bot where the gravity center is close to the center of the bot. Most cars/trucks/whatever follow this rule. It is all about symmetry.
-When setting up motors, put them aligned horizontally. Like a car, again.
-Try to put the components in a symmetric setup.
-Balance the bot.
-You should also know that batteries doesn't seem to have an effect on weight distribution.
This is extremely important on VS (because of their innate stability problem), Popups (good weight distro makes for good wedges) and Rammers (because they're supposed to drive straight)
Examples
Bad drive setup
(Yes, Redbirds fail at driving)
Good drive setup
Exotic drive systems
(generally not allowed in tournaments)
The most common are discs/tribars with weapons on them used as wheels (called crawlers).
Although this drive system is stronger than actual wheels and make effective damage, they have extremely low grip (get ready to be pushed), phail at turning and are a (very)slow drive system, besides being frowned upon by some of the community. You've been warned.
There are also walkers, reproducing a bot with legs, made with servos or burst motors. Building a succesful walker is a respectable achievement. (Most of them still suck at fighting and there is no more weight allowance for walkers like in Battlebots)
Note: Correction of my average English writing skills would be welcome, but DON'T modify the content before asking me.