pic: Team 256 presents our offseason robot: Stockade

More pictures available at: http://imgur.com/a/8qnV2

Currently in production. Will compete at WRRF CalGames in October, and Madtown Throwdown in November.
Technical Specs:

-Square 27"x27"x28" frame designed to maneuver under the pyramid
-6 wheel West Coast Drive with a center 1/8" drop utilizing 2" wide, 4" diameter high-traction wheels
-2 Speed WCP Shifters with 4 CIMs geared for 16.1 fps and 6.1 fps allows for speedy cycles and effective defense
-Driven by timing belts and pulleys to maximize efficiency and minimize noise

-24" long linear shooter angled 30º above the ground
-Discs fed into shooter by rapid-fire pneumatic piston from underneath
-Two 4" urethane wheels driven by two RS550s through 4:1 and 3:1 VersaPlanetaries compress the discs by a half an inch to effectively transfer momentum to the discs, launching them into the 3 pt goal

Floor Pickup:
-2 disc wide floor pickup arm uses the “spatula” design originated by Team 1986 to slip underneath discs in the lowered position, and then rotates them near-parallel with our intake in the raised position allowing the discs to seamlessly slide out of the intake and into our hopper
-The polycarbonate used to slip under the frisbees in the lowered position doubles as a pyramid alignment mechanism in the raised position, giving our drivers the ability to quickly line up for accurate and rapid scoring.

-Multiple autonomous modes allow for starting positions on any part of the pyramid, including multi-disc modes that gather the discs on the center line and under the pyramid

-Two pneumatically actuated pistons are designed to retract automatically at the end of the match, ensuring a simple and easy 10 point hang at the last possible second of the match, saving time for more cycles during teleopperated period.
-A removable blocker the width of the robot can be attached to the back of the climbing hooks to instantly shut down any opponent who attempts to shoot full-court with pool noodles that can extend up to 66.5" tall, more than a half a foot above the height of any full-court shooter.

Looks very nice, just a few questions…What is the point of the rectangular rear superstructure? Is there some sort of linear extension on the climber hooks, or are they just connected to the end of the piston rod?

Looks very nice. The only thing I’m concerned about is the hanger. We broke one of our pistons by getting only half of the hanger on the bar before we pulled up, bending one of the piston rods. What I would reccommend doing is a 254 like ball bearing setup so that the piston rods to not take any side load. While the current set up will work, you might find that your pistons get slower/stop working after a lot of matches.

What it looks like to me with all of those holes is that the are able to move the hooks back and forth to get the COG right for hanging.

When this happens to us, we just bend the piston back… with our bare hands. For our offseason robot, though, we are considering some sort of pivot setup.

Andrew, looks sweet. Very judicious use of right angles. I’ll be interested to see how your multi-disc auto works out.

Which, interestingly, makes your pistons illegal since they have now been modified.

the issue with the hanger is actually the hooks being off center. If the hooks had a tweak in them so that when hanging the bar is inline with the cylinder, that’d be much better.

EDIT: Like this

The significance is now the cylinder is loaded purely in tension (aside from the force of you ramming into the pyramid) when you hang. Otherwise you’d have a constant bending moment trying to bend your cylinder shaft.

It also looks like you’re using two 1-1/16" bore cylinders. Unless you’re storing energy in springs when they raise (or you’re very light) this isn’t enough force. Even then it’s marginal.

Looks great, Andrew! Can’t wait to see it at CalGames and Madtown!

Nice robot. Just wondering, is your frisbee storage open behind?

This isn’t the only time the cylinders are loaded, though. If your driver doesn’t approach very carefully (and therefore slowly), you’ll probably ram into the side of the pyramid with the hooks, and bend the pistons. We did just that at the Sacramento Regional. We fixed this issue by Champs by attaching the hooks to long, thin steel rods, which were silver-soldered into a fitting that screwed onto the piston. This allowed our driver to drive at the pyramid as quickly as he wanted, and only the rods would flex. (They were thin enough to still be out of their plastic range at that point.)

After looking at it y’alls shooter is exactly set up like ours. We used the Canadian urethane wheels (1114 and 2056 wheels) in a 3:1 and 4:1 versa as well. The wheels and gearbox combo was VERY reliable and is a great set up. The only thing different with y’alls shooter is we used a vex motor to push the disks into the wheels. we didn’t use pneumatics at all on our bot.


This photo of our robot is from the last few days of build season. The climber hooks are made two pieces of 1/8" sheet aluminum, waterjet cut into a shape like what Adam suggested, then with stand-offs between them and flat-head bolts holding it all together. This mitigates any bending load on the piston when lifting. We then have C-channel that goes around the hooks. The front edge of the C-channel is what would contact the lowest bar of the pyramid when our driver slammed into it. We did end up adding another diagonal brace to the C-channel at our 2nd regional to add stiffness. This design worked well - we have not bent a lifter piston all year.

I prefer to design robots in a way that the driver doesn’t have to think twice about driving hard. If we have to tell our driver “don’t drive to the best of your ability in a way that gives us the best chance of winning a match because this could break,” then we’re doing it wrong.

The draw back of this approach is that our robot cannot go under the pyramid. This ability was already sacrificed by other aspects of our design, so it didn’t really matter for us. We prioritized a simple, linear design, holding 4 discs, scoring upside down discs (before the rule update; only satisfactory prototype was a large rotary shooter), and floor pickup over driving under the pyramid. Maybe if we had used a compact linear shooter or used a bucket hopper and come up with the idea of spring-loaded hooks like we saw on other bots, we could have gone under the pyramid.

Looks solid, Andrew. Does that floor pickup have a pinch bar or roller bar above the lexan plate?

As mentioned earlier in the thread, the back end is so that we can move the pistons back for CoG adjustment.

In the model the back of the feeder currently is open. We use zipties as a “back” since we don’t need too much contact area on a frisbee for it to slide into the bucket. Worked wonders for us during the main season.

There is a 1x1 aluminum pinch bar that holds the frisbees in while the arm rises, and it’s in such a position that in the vertical position the frisbees can freely slide out.

Thanks for the advice on the climber, Adam and Carl. I’ll be sure to look into the centered hook design and reinforcements.

Another thing to consider for the climber:

Unless you have really solid weight estimates everywhere in your CAD model, it’s going to be difficult to know your COG. However, if you want the robot to lift level, you will need to know the forward/aft position of your COG. To achieve this, we left room for the hooks anywhere along the length of the robot within about a 1 foot span. To locate our COG we stood the robot up on its frame with a wheel on each side between the table and the frame and rolled it forward and back until the bot remained level without us supporting it. The location of the COG is directly above the line segment between the contact points of the 2 wheels on the robot frame. This allowed us to locate the hooks such that the robot would lift level.

It looks like you have some play with where you can mount the hooks, so perhaps this will help make your robot lift without much swing.

Yeah, I designed it knowing I’d have to make the climber position adjustable, so I made sure we could change it easily with the multiple holes in the 1x1 it sits on.

How’s this project going? Some students on our team were looking at the bots going to Madtown and it reminded me of Stockade. Will we see this at Madtown?

My thoughts on the 10 pt. hanger: Having cylinders that pivoted (but defaulted to one location with bungee cord) worked out well for us at CalGames. That flexibility allowed us to roll up to the pyramid fast, see the hooks depress a couple of inches in contact with the bar, and know that our hook engagement is good and our robot is going to get off the ground. Don’t have any good pictures accessible right now, but there are plenty of similar systems out there. Team 2590 churned out something nice: http://frc2590.org/team-info/robots/518-athena.html
A rigid system makes it so that if your robot pushes up really hard against the bar, and your robot falls back after that initial push an inch or so (could easily happen if your driver releases the throttle because he is, say, afraid of bending the climber cylinders), you could miss the hang if your hooks can’t tolerate that misalignment. That being said, plenty of teams made it work with large hooks, better support (like 254’s bearings) and/or just really drilling their drivers.

We just found making a flexible pivoting mount and putting in bungee cords to be the best solution for our team; whatever works better for you is best of course.

Thanks for the advice! Stockade is gonna be showcased at Madtown next week, and we’re so psyched to show off our new machine. I’d post pictures but I’ve been asked by some super excited freshman to keep it a secret :rolleyes: (the bot, while designed by me, was built entirely by underclassmen. I’m really proud of them). Can’t wait to play with the Unidentified Funky Object in a week!

Any news on the 7 disc? Will you have it working by MTTD?

Due to lack of adequate testing time, we will not bring our floor pickup to the event. Instead we’ll be a pure cycler, our original plan.

Story of Powerhouse and Calgames for us.