BIG Tires

[Joe Johnson]

The worse you are with the ratio:

Side to side distance between wheels touching the ground
-----------------------------------------------------------------
Fore/aft distance between the wheels touching the ground

the worse you be able to turn.

It's painful to get this wrong.

I give you,

Dr. Joe's Seven Stages of Dealing with a 4WD Robot with Grippy Tires

• First, you'll blame the drivers:

  "Just TURN already will you! How hard can it be?"

• Second, you'll blame your batteries:

  "Why do we keep browning out during a match? Are you SURE that battery was a full charge?"

• Third, you'll try more motors:

  "How about if I have 3 CIMs per side? That's got to work. No? What if I add a mini-CIM? Still can't turn without moving! I've heard good things about those unlimited 775Pro's. 5 motors per side! What can possibly go wrong?"

• Fourth, you'll go for a higher ratio:

  "What do you mean we can't fit a 6 tooth sprocket on that gearbox?!?! I've got to have more POWER*!!!"

• Fifth, you'll wonder why you can't even play defense:

  "We finally got enough motors and ratio to be able to actually turn and NOW the robots we are supposed to be playing defense against keep driving past us by like we're standing still "

• Sixth, you'll try a set of slippery wheels:

  "Now that we've wrapped the front wheels in duct tape we can actually turn with our original ratio... kinda stinks playing defense and crossing defenses with half our wheels slipping and sliding but it's better than what we had."

• Finally, you'll vow to do better next season:

  "There are a lot of people with a lot of experience in FIRST who seem to think that 4WD without some method to address the turning problem is... ...a problem. Maybe I should find out what they know before the next kickoff?"

Dr. Joe J.

*But of course you mean TORQUE. You already tried more POWER back in stage three!