pic: Team 846 Presents: Funk Cannon

[RKIyer]

Originally Posted by Stephen.Yanczura

What has your experience been with those 'W' tread wheels? How long do they last you?

The "W" Tread wheels have worked well on our practice bot so far. We have seen some gradual wear of the outer "spikes" however, through the course of driving for about 4 weeks.

[raphaelchang]

All right, sorry for the late replies; we started traveling this morning and are at last happily situated in our hotel right now. Thanks for all your kind words, we love Funk Cannon and are excited to put her to the test on the field tomorrow. To add on to what Chinmay's said already:

Originally Posted by Stephen.Yanczura

What has your experience been with those 'W' tread wheels? How long do they last you?

The 'W' pattern Versawheels wear quickly, but at a $5 per unit price we are very satisfied with them. With our drivetrain setup, it's a quick swap to get fresh ones on. I anticipate going through a set of center wheels once per event.

Originally Posted by cmrnpizzo14

Another fabulous intake system from you guys. Do you have active control of the ball at all times when its in the robot? That's how it appears to me but I'm not quite sure.

Good luck this season, I hope you can get that regional win this year!

Thank you. The mecanums were something we prototyped early in the season, and it was very satisfying to see them work so effectively on Funk Cannon. The collector does not have active control of the ball once it is in the shooter cradle, but we can easily dump the ball out the other side by reversing the reload motors, satisfying our design requirement that we must always be able to get the ball out of the robot for assists and the 1 pt. goal.

Originally Posted by Tom Bottiglieri

Sky restraining order.

Nice.

We love Skystalker, it's a great bot.

Originally Posted by nuclearnerd

Can you share how you choke the power & angle to get your short shot?

In the detailed design phase, we started by finding a torque profile on our spring/shooter arm geometry that would allow us to have a lower energy, higher angle shot as well as a higher energy, lower angle shot. This necessitated the usage of compression springs rather than constant force springs, torsion springs, etc. Then, we went about figuring out how to stop the arms early so we could get the required lower energy.

At the 17 second mark of our video (http://youtu.be/92IbHU0Z76I?t=17s), you can see the little latches that fall into place next to a slotted tube. A little aluminum piece, with two pegs that stick out of the slots, is attached to a threaded rod that the shooter arms drag back and forth when reloading and shooting as shown at the 24 second mark (http://youtu.be/92IbHU0Z76I?t=24s).

When we fire the short shot, the pegs hit our deployed latches, limiting the travel of the arms and increasing the angle of the shot. This also limits the change in spring compression, resulting in a lower energy imparted on the ball.

When we fire the long shot, the latches are retracted, and the pegs instead hit the end of the slots in the tube. More energy is released and the ball leaves at a lower angle for the longer range shot.

In both cases, when the pegs are stopped, the threaded rod will want to keep pulling through, compressing die springs that absorb the remaining energy, allowing us to safely perform our shots as well as dry fire.

After Buckeye I can post some close up pictures of the mechanism, if anyone is interested. Just let me know.

Originally Posted by xXhunter47Xx

Tell me more about that drivetrain, looks like you have the outer wheels as omnis for less turning scrub but the center wheel for traction to avoid being pushed around.

In order to ensure repeatability of our shot, especially on the fly, we did not desire to have rock in our drivetrain. This led to the decision to put at least a pair of omniwheels on our robot. Additionally, we required that our robot's driving characteristics remain the same going forwards and backwards, as we drive in both directions often. This almost resulted in a 4 omniwheel drive, but we wanted something a bit easier to handle, hence the center wheel.

I won't say we avoid getting pushed around. It doesn't matter as long as we're in range to make the shot. More important to us is that we're slippery; as Chinmay mentioned before, I think it'll be hard to pin us down, as we'll just spin out of it and continue on our way. Of course, that's only what I know from the robots we've practiced against. Maybe Buckeye will prove me wrong; we'll see.