[ratdude747]

that thread sounds more like the code side of the drivetrain. i think the OP was looking for the physical design of the drivetrain.

i have never built one but i have seen many others. generally, you want to run them with the wheels parallel to the main direction of travel. wide will turn better but if your manipulation design does not allow for it, don't sweat it (true for all drivetrains other than crab).

as for direct vs chain, there are pros and cons:

chain- less foolproof (thown chain= not good), but has greater flexibility of tranny and motor placement. this year chain was a good choice for mecanum (and any other wheel drives). also allows far addition gear reduction via sprocket sizes

direct- very reliable (spur gears are strong and very few teams if any use multi-speed trannies for mecanum). tranny and motor location limited to next to the wheels. depending on wheel size, stock gearing may need to be reduced to give a proper amount of torque (keep in ming mecanums have less traction so torque is less of weapon).

speaking of traction, that is another issue mecanums always seem to have- they do not have much traction compared to traction wheels. this is why teams will still use crab drive even though mecanum is just as mobile and much simpler. this is a good point to keep in mind when 2011 design time come along.