Actuated Drive (Slide / H)

[GeeTwo]

Our 2015 robot was designed to have an H/slide drive, with a fixed altitude center wheel (we did not plan to drive onto or over the scoring platforms). We never did get strafe working well, and removed it from the robot during competition. As one of our fall training exercises, we are going to attempt rebuilding our practice chassis as a pneumatically-actuated H drive. To simulate a competition robot, the whole thing including battery and bumpers will weigh about 140 lb, even if that means adding ballast. The chassis is a 2015 KoP frame, long configuration (31" long, 25" wide), and we'll use AM DuraOmni 4" wheels on the corners. We stripped the tread off of two of the KoP wheels to make a spacer on the drive axle so that we have a 4 wheel drive before adding strafe. We already have some 8.45:1 Toughbox2 gearboxes with the long hex shaft, so that we will have the same gear ratio for the strafe as we're using for the tank drive. This is probably not important for this discussion, but we intend to make bumpers and an active (8-9") ball pickup as part of the prep for the 2016 game as less than a fifth of our current team was with us in 2014.

Now, to the questions:

• This is our first actuated drive; what general lessons learned or pitfalls to avoid with actuated drives can you give us?
• My instincts want to start with about a 2" throw on the wheels (with carpet contact being near the center of the throw), and between 1/4 and 1/2 of the robot weight (nominally 1/3) being supported by the strafe wheel(s) when the cylinder(s) force them down. Are these numbers about right, too high, or too low for motion on level carpet?
• How much advantage is there to doing multiple strafe wheels? Is it a serious problem if a single strafe wheel is a little bit (no more than 2") off of the center of mass?
• Any preference for the hinge/pneumatic axis to be parallel or perpendicular to the wheel axis?
• Any other bits of help, encouragement, or discouragement from this line of attack?

OBTW, I do plan for the strafe wheel contact patch to be directly between the hinge(s) and the cylinder(s) to minimize stray torques.