pic: Concept 8wd Drivetrain

[sdcantrell56]

I don't know where to start with all the questions so I'll try my best.
First of all the reason I chose to do an 8 wheel drive design is due to a couple different factors. I will try to outline my thinking. I wanted to use a small diameter drive wheel to reduce the overall cg of the robot and to minimize material cost. I also thought that there is a decent chance of an obstacle being in this coming years game, hence the use of 8wd which equals the ability to climb a much steeper obstacle without bottoming out given the ground clearance. Also note the cuts in the front and rear of the frame to increase approach and departure angles also to help with climbing. 8wd is also inherently more stable as the rock is less dramatic. The 8 wheels in theory does not increase traction however in the world of FIRST it absolutely does. Not so much in the front-back direction but in the sideways direction. It will be much harder to push this robot sideways and to spin it without us wanting it spun. Finally I am trying to minimize the amount of machining we need for transmissions and such. With this design we can use an almost stock andymark 2 speed. The only thing changed is one gear is turned down and then a custom 7075 output shaft machined that is longer. With 8wd I can have 2 separate chains running one to each center wheel which creates a backup if one chain fails.

I am planning on Roughtop tread for the wheels so traction will be very high.

Additionally the issue of extra weight is very moot with this design. The entire drivetrain will be under 40lbs. that includes motors, transmissions, wheels and all the other little things, as well as all the mounting points for our superstructure. This means we have 80lbs to play with for electronics and the superstructure.

As for there not being much point to 8wd if we raise the outer wheels, look at 1270 from 2007. They raised the outer wheels and were one of if not the strongest pushing robot. They were also quite successful, making it all the way to einstein.