FRC3005 High Shooter

[Steven Smith]

FRC3005 tested our competition robot's high shooter last night, and we were pleased with the initial results (turns out... math works!) We had calculated a release angle for an 18' shot and made a few estimates on the bundle tension to achieve that. We are adjusting our release strap to be closer to the choo-choo full extension point (without shock loading the choo-choo), which should flatten our trajectory and give us our preferred shot.

Check out the video, our Facebook page and Twitter feed (to keep our PR team happy), and feel free to ask any questions on our implementation of the BuildBlitz JVN shooter. We appreciate the great starting point, and we feel we were able to iterate on the design several times to fix some potential failure points (and learn a lot in the process). We're looking forward to competing at the Dallas Regional March 13th-15th.

[notmattlythgoe]

Looks good, what is your full range of makability? It looks like the highest point of your ball's trajectory goes above the top of the goal. If this is true are you worried about having a dead zone in the middle of your range at all?

[Ty Tremblay]

I love the sound the strap makes when it comes under tension.

[Steven Smith]

Originally Posted by notmattlythgoe

Looks good, what is your full range of makability? It looks like the highest point of your ball's trajectory goes above the top of the goal. If this is true are you worried about having a dead zone in the middle of your range at all?

Eventually, it will be from 12' to 20' or so. You are correct, the trajectory is currently a little too steep. We'd like to be hitting our 18' shot on the fall from peak trajectory.

Our strap limits us roughly 4-6 deg from our final flatter shot angle. We didn't want to get too close during initial testing to the flattest angle we can shoot, because if we go too far, we'll shock load the choo choo. Our next stage of testing will hard mount the currently tied off restraint strap, which should flatten our angle. If it doesn't, we might have to lower our power slightly.

Steven

[RaMoore]

Originally Posted by notmattlythgoe

Looks good, what is your full range of makability? It looks like the highest point of your ball's trajectory goes above the top of the goal. If this is true are you worried about having a dead zone in the middle of your range at all?

You're right the highest point in the arc is above the top of the middle goal in this shot. This was our initial test shot based on a calculated angle and guesstimated force but we were surprised how close we got to the shot we wanted. We will be modifying the release angle tonight to lower the peak so we don't' have a dead zone. With the stop-strap it makes launch angle adjustment a pretty simple affair.

We also tested with a fully inflated and under inflated ball and were working out how much that variable was going to affect our shots. Our automatic stop when fully cocked wasn't dialed in yet so we need to repeat that process again now that we have a consistently cockable system done.

[notmattlythgoe]

Originally Posted by Steven Smith

Eventually, it will be from 12' to 20' or so. You are correct, the trajectory is currently a little too steep. We'd like to be hitting our 18' shot on the fall from peak trajectory.

Our strap limits us roughly 4-6 deg from our final flatter shot angle. We didn't want to get too close during initial testing to the flattest angle we can shoot, because if we go too far, we'll shock load the choo choo. Our next stage of testing will hard mount the currently tied off restraint strap, which should flatten our angle. If it doesn't, we might have to lower our power slightly.

Steven

Very cool. Looks good.

[Andrew Schreiber]

Originally Posted by Steven Smith

we'll shock load the choo choo.

And that, kids, is very bad (tm)

[Steven Smith]

Yep. Here was a piece from our first iteration. We had left it slotted for flexibility in determining final geometry. The shock load on the choochoo from about 25% of our final bundle tension was enough to pull a 1/8" or so offset into our 1x2 VersaTube.

Pic

Steven

[juchong]

Just uploaded another version of the video with some more in-depth views of our shooter mechanism! Check it out!!

LINK

[Andrew Schreiber]

Originally Posted by juchong

Just uploaded another version of the video with some more in-depth views of our shooter mechanism! Check it out!!

LINK

Please never have a student reach over the launcher to do that again.. That part of the video made me very very nervous.

[AdamHeard]

Originally Posted by Andrew Schreiber

Please never have a student reach over the launcher to do that again.. That part of the video made me very very nervous.

It looks like there is no tubing attached in that portion of the video.

[Andrew Schreiber]

Originally Posted by AdamHeard

It looks like there is no tubing attached in that portion of the video.

Ok, good... I can relax. It's something We've had to drill into our students' heads repeatedly. I generally treat every stored energy system the same way I treat a gun and assume it's loaded.

[RaMoore]

Originally Posted by Andrew Schreiber

Please never have a student reach over the launcher to do that again.. That part of the video made me very very nervous.

Andrew,

Appreciate your concern for my arm. (I have kid arms?) The shooter was only loaded with about 5lbs of force (the minimum to make the choo-choo turn over properly) in that shot since we were aligning some sensors and I reached over the top so the camera could see what was happening, I assure you that's not a habit...

We were aware from the beginning of the design that we would need to have a safe procedure for releasing/resetting the system to get it on and off the field. Even while we are testing we don't want to rely on dry firing the system to release our shooter.

We tried several unpowered methods to release the shooter safely and ultimately given that our arm can be held cocked with ~40lbs of force and I don't want to be transporting the robot in a cocked state we will use a similar approach to release the shooter at the end of the match (minus the arm through the top obviously). We have a cheater bar that we stick in the end of the shooter to hold it down and then reaching under the shooter where the choochoo can be manually released and the shooter eased up. We are still working out if it's better to put a safety ratchet strap on the arm before we release, or if the process of putting that strap on puts more human bits in danger than it would be protecting. Of course we're also happy to hear suggestions for a better release method.

[Aren_Hill]

Originally Posted by juchong

Just uploaded another version of the video with some more in-depth views of our shooter mechanism! Check it out!!

LINK

I applaud your choo choo gear implementation (Versablock mount), and wish I'd have thought of it during build blitz to save me from making those two custom plates, Bravo.

-Aren

[Madison]

If I may, how are y'all constraining the large gear axially on the shaft?

-Madison