Image Discuss: Our anchor is more powerful than you bot

[Andy Baker]

This is a good idea and your robot will hold it's position over MANY other robots.

Let's look at this design and evaluate the impact:

It appears that the suction cups are being actuated up and down on a 2" dia cylinder (at 60psi, pulls at 170 lbs, pushes with 180 lbs).

Also, let's assume that they have the same mechanism on the other side of their robot.

From our team's experience, you can pull up on these suction cups with about 100-120 lbs of force before they let go (it depends on the cleanliness of the surface).

So... the cylinders push down, suction cups stick, and the cylinders try to pull up. They probably regulate the cylinder down to 40-50 psi in order to not pull the cups off of the floor. All of the force that they are pulling up on is being transferred to their wheels, and their robot essentially weighs much more than the actual weight of the robot. The downforce on the wheels is shown below in an equation:

Downforce on wheels = robot weight + left side cylinder/cup pulling force + right side cylinder/cup pulling force

Downforce on wheels = 130 + 100 + 100 = 330 lbs.

So... essentially, with both suction cups engaged and the cylinders pulling up, their robot weighs 330 lbs. Although it's not best design practice to simply let the cylinder shaft support the side loads on the vacuum cups, it's the wheels that are exerting the downforce, not the cups. An opposing team not only has to slide the suction cups, but also 330 lbs. of downforce applied to their wheels.

In order to push this robot, an opposing robot has to push with more force than this robot's holding force (at least that's what I call it). Their holding force = 330 lbs. x mu (their wheel's coefficient of friction).

Now, with regard to scratches, these cups still do pretty well. If they had a lower durometer, they may even be more resistent to scratches.

Great 'bot... good luck!

Andy B.