pic: FRC 4532 Drive Base Frame

[John]

Looks like a nice, simple frame. Good job, it should be very durable.

As others have mentioned, you really need to test the turning ASAP so you can fix any problems that come up. More practice time never hurts, either, so even if it comes out great you'll want to get it up and running soon.

Originally Posted by mechanumrules

The wheels are 8" AndyMark Pneumatic ones!

We did all the math! It might be a little slow turning, but at 150lbs it should turn fine!

Would you mind posting this math? Since unless I am missing something key to your drivetrain, this should not be able to turn without jumping.

To turn:
max turning force >= max turning scrub

Assuming center of mass in center of robot:
max turning scrub = 4 * (length/2) * (weight/4) * mu = length*mu*weight/2
max turning force = 4 * (width/2) * (weight/4)* mu = width*mu*weight/2

width*mu*weight/2 >= length*mu*weight/2
width>=length

Since this design is longer than it is wide, you will not be able to turn with all four wheels on the ground*. What will result is one or more wheels skipping off the ground and the drivetrain quickly turning due to the dramatically reduced turning scrub. This motion is extremely difficult for the driver to control because it involves rapid, unpredictable changes in speed.

*Note: I assumed two major things while making this analysis:
1) Your center of mass is close to you center of area. Without knowing your full design I do not know if this is a good assumption, however, if you center of mass is too far to one end you may tip while crossing the bump.
2) You wheels have similar coefficients of friction in the forward and lateral directions. This should be a good assumption for pneumatic wheels, but if you decide to go with omniwheels on one end this no longer holds true and you will have a much easier time turning.

Your best bet to alleviate turning problems is to either:
A) add additional dropped wheels (probably one per side, in dead center)
B) add wheels with lower lateral friction (like omniwheels)