Killer Bees - 2014

[BJC]

Team 33, The Killer Bees, present:

Buzz XIX (http://www.youtube.com/watch?v=btQtnyxyY8E&feature=youtu.be)

Good Luck to All Teams!

[AlecMataloni]

Hard to tell, is that Nonadrive or Butterfly? Looks slick!

[BrendanB]

Love. This. Robot.

[cadandcookies]

Looking awesome! I particularly like the shot with your last four robots.

[Justin2648]

Wow! Amazing bot and a great video! Good luck this season!

[barn34]

The annual incarnation of Buzz is always a very impressive machine. This year's is definitely no exception. Awesome job, guys! And I absolutely love your team's infectious enthusiasm every year and that really shines through in the video, too. Best of luck to you guys this season!

[jrl5595]

Looking really rad, sweet shooting. This robot is real nice. Good luck to you guys!

[JohnSchneider]

Your twitter posted that it looked like a 33 robot, and it sure does. Love the details that your robot has.

[Akash Rastogi]

That driver is looking solid already. Very nice!

[Cory]

That #zondagshuffle.

[Calvin Hartley]

A beautiful machine, as always. I can't wait to get a good look at it in person!

[kenavt]

That driver is looking solid already. Very nice!

It's their driver from last year, so she has some experience already.

Along with the rest of the all-female drive team, dang...

[AllenGregoryIV]

This is stunning, great job 33.

Is the deflection shot off the collector going to be a regular thing? I love it.

[ttldomination]

Super solid.

Mind sharing your shooter releasing mechanism?

- Sunny G.

[cgmv123]

I love your test truss! (And your robot)

[nathannfm]

I spy an Omni wheel (http://screencloud.net/v/oC84)!

Very nice bot, look forward to seeing it at champs!

(I was hoping someone would use this song in a reveal video :D )

[Nathan Streeter]

Excellent robot! Quite frankly, looks like it has it all!

I would by no means be surprised to see 33 one-up their performance from last year... but more than a few things need to go right just to make it back onto Einstein!

[joelg236]

Just blew me away, very impressive robot once again.

[Jonathan Norris]

It's the details that make this robot awesome, the little loop/arm that comes down to hold the ball in place while driving is seriously smart. Looking forward to seeing this robot at Champs.

[Lil' Lavery]

That video needs more #zondagshuffle

[Jim Zondag]

There will be lots more #zondagshuffle at Southfield, Midland, Troy, MSC and CMP. :)

[Boe]

#zondagshuffle
http://i.giflike.com/tD54tAI_sg.gif

[RonnieS]

There will be lots more #zondagshuffle at Southfield, Midland, Troy, MSC and CMP. :)

I will be looking forward to the #zondagshuffle before elims at MSC!!!:D

[Nick Lawrence]

Gorgeous robot, as always from 33.

Definitely looking forward to taking a closer look at the subtle details that make all the magic to this machine. Best of luck this season, I'd be surprised to not see it in the mix of The Final Four.

-Nick

#zondagshuffle

[Carolyn_Grace]

There will be lots more #zondagshuffle at Southfield, Midland, Troy, MSC and CMP. :)

I'm going to miss seeing most of these in person this year. Hopefully the webcasts capture some of them!

Love my Bees! I expected nothing less than stunning from you, and you still out-did my expectations.

Good luck at Southfield on both robot and Chairman's this weekend!

[JVN]

I think this is the best robot we've seen so far. I think you guys made some good tradeoffs and found the simplicity beyond complexity. Kudos! I'd love to see 148 play with you guys (again).

[Jim Zondag]

I think this is the best robot we've seen so far.

This is high praise from JVN, thanks.
We also love Vader, very cool.
Yes, we would love to get together (again).

Jim

[NatashaWhyte]

Looks amazing! Best of luck this season.

[waialua359]

Awesome robot!
In hindsight, why didnt everyone think of the ball catch collector idea like you folks?!
Given the robot dimension rules, this design maximizes the area in which to catch and collect above and beyond what has been revealed so far.

Great song too......I was telling our team 2 weeks ago to use the same also. Good thing we didnt.

-Glenn

[paul_v]

This looks like the best overall machine I have seen yet this year. The shooter/pickup/collector individual systems appear to be very effective; I especially like the roller speed, and the aggressive launching power.

Nicely done! Can't wait to check it out at champs.

-Paul

[M. Mellott]

My favorite so far, both the robot and the video.

What a sweet robot...as mentioned in an earlier post, all of the subtle details to look at...and so smooth! Wow!!

[BJC]

Hard to tell, is that Nonadrive or Butterfly? Looks slick!

I plead the fifth.

This is stunning, great job 33.

Is the deflection shot off the collector going to be a regular thing? I love it.

Every time you see it truss or shoot from in close we are deflecting the ball off the arm - so yes. :]

Super solid.

Mind sharing your shooter releasing mechanism?

- Sunny G.

We are on team choo choo this year. Unfortunately, I don't have any good pictures. Maybe I'll throw something up after Week 1.

[Agentarrow]

I have to wait all the way until Troy to see this thing in person? You guys are killing me.
Looks like some familiar faces are still around though, which is always good to see. Spectacular job guys. I don't think it's Buzz's prettiest incarnation, but its so brutally effective that I don't even care about looks.
Good luck out there, can't wait until we play together.

Edit: I don't think my wording is very well chosen here. This is not intended as a backhanded compliment with an attached insult, I just simply meant to state the truth about my thoughts on the robot. It's not as pretty as your 2012 or 2013 robots, but that's not a statement on this robot beingvugly, it's just that those are a tough act to follow aesthetically. As I said before though, I care more about function than about appearance and this machine does everything it needs to beautifully. That is worth much more than how it looks.

[TravusCubington]

dat #zjshuffle doe

http://i.imgur.com/zXgxH1F.gif

[ThunderousPrime]

Should have know 33 would go for 3 (in auto). :)

Stellar Robot and Design as always. How is your CG? Twice during the video I saw the robot tilt 0:46 (http://youtu.be/btQtnyxyY8E?t=45s) and 0:47. I dont think this is a big deal while shooting, your driver just needs to decelerate a little slower. Additional if you tilt and your height is 60in you're incurring G23, with a regular foul. I'm curious to know what you're exact height is but if you don't want to reveal it I understand.
http://i.imgur.com/nWRZNGw.jpg

I like this design much more than others because it has blocking potential. Some of the catapults this year have very low release points (and to a lesser extent arm with linear puncher designs and Ri3D Boom Done cradle catapults) can be blocked relatively easily by putting a robot in front of them. By taking advantage of the height limit, and I think 33 is at or around 60in, they can probably block most teams regardless of shooting mechanism. One thing that is yet to be seen is how the CG question comes into play while blocking. I don't know for sure if 33 or most teams can take a hit from a ball and not fall let alone tilt massively.

Also this is the best catcher I've seen so far and its not even close. You don't have to move the drive base that much compared other low to the ground catchers like 20, 1772 and 604 which have stuck out to me as some the other good catchers. Again taking advantage of those full 60in seems very beneficial at least from my perspective if CG isn't a problem.

[hobbins]

Wow, as always - Killer Bees continue to impress me.
The first time was 2004 when we partnered with team 60 during our rookie year (1241), and then the total respect for the Bees all these years, especially last year at champs...
I am looking forward to following team 33 throughout the season, and we are sure to see you again in St. Louis...
Go Teams:yikes:

[Kevin Leonard]

I love your enormous catchers.

I also love the off-the-intake lob shot.
Absolutely brilliant.
Just wondering, did you plan for that or was that one of those things you discover at the practice field?

[Chadfrom308]

Maybe we could practice with you? Mike Sulkowski wants to, I sure would like to as well I love the hexagonal intake rollers. Is that the 3rd year using that design!?

[BJC]

I have to wait all the way until Troy to see this thing in person? You guys are killing me.
Looks like some familiar faces are still around though, which is always good to see. Spectacular job guys. I don't think it's Buzz's prettiest incarnation, but its so brutally effective that I don't even care about looks.
Good luck out there, can't wait until we play together.

Edit: I don't think my wording is very well chosen here. This is not intended as a backhanded compliment with an attached insult, I just simply meant to state the truth about my thoughts on the robot. It's not as pretty as your 2012 or 2013 robots, but that's not a statement on this robot beingvugly, it's just that those are a tough act to follow aesthetically. As I said before though, I care more about function than about appearance and this machine does everything it needs to beautifully. That is worth much more than how it looks.

No worries. We didn't take it as an insult. I'd rather have a functional robot than a pretty robot any day of the week. Once you get up close to this robot you'll see we iterated pretty hard on it after everything got powdercoated. Was it worth it? - absolutely.

Hopefully, the pit crew is bored this year: bored pit crew = pretty robot.

Should have know 33 would go for 3 (in auto). :)

Stellar Robot and Design as always. How is your CG? Twice during the video I saw the robot tilt 0:46 (http://youtu.be/btQtnyxyY8E?t=45s) and 0:47. I dont think this is a big deal while shooting, your driver just needs to decelerate a little slower. Additional if you tilt and your height is 60in you're incurring G23, with a regular foul. I'm curious to know what you're exact height is but if you don't want to reveal it I understand.

I like this design much more than others because it has blocking potential. Some of the catapults this year have very low release points (and to a lesser extent arm with linear puncher designs and Ri3D Boom Done cradle catapults) can be blocked relatively easily by putting a robot in front of them. By taking advantage of the height limit, and I think 33 is at or around 60in, they can probably block most teams regardless of shooting mechanism. One thing that is yet to be seen is how the CG question comes into play while blocking. I don't know for sure if 33 or most teams can take a hit from a ball and not fall let alone tilt massively.

Also this is the best catcher I've seen so far and its not even close. You don't have to move the drive base that much compared other low to the ground catchers like 20, 1772 and 604 which have stuck out to me as some the other good catchers. Again taking advantage of those full 60in seems very beneficial at least from my perspective if CG isn't a problem.


The robot's center of gravity is deceptive because the panels visually take up a lot of space. However, There is actually very little of this robot over 13". The center of gravity is about 7-8" and roughly centered (actually lower than last year). The robot has to tip about 80deg in any direction before it will fall over. What you are seeing there is a combination of a full forward reverse slam in conjunction with the thrower firing. We really don't care if the drivers do this so long as the ball still goes in (which it does). I would be amazed if this robot ever tips over in competition.

Someone should correct me if I am wrong, but I believe the 60" rule is in reference to a robot sitting in its normal resting position on flat ground. This has always been the case in the past. If this is not the case, we'll just make the wings ~5" shorter and call it good.

We are intentionally 59" tall in order to maximize catching area and block potential shots. I would be very comfortable with most any robot repeatedly blasting a ball into those wings. They are good at absorbing shock loads, and very durable. If someone does manage to break one? - whatever, we'll fix it in the pits.

I love your enormous catchers.

I also love the off-the-intake lob shot.
Absolutely brilliant.
Just wondering, did you plan for that or was that one of those things you discover at the practice field?

Thanks, We had wanted to do the deflection truss shot/close shot that way because it allowed the thrower to become much simpler. However, it was basically impossible to test until the robot was mostly finished so we had a backup plan in place. Thankfully, we didn't need it - The resultant crazy front spin was unexpected but welcome.

Maybe we could practice with you? Mike Sulkowski wants to, I sure would like to as well I love the hexagonal intake rollers. Is that the 3rd year using that design!?

Sure, this is the first year we've actually had a practice robot that is functionally identical to the competition robot on bag day. Our drivers pretty much practice every day in the space you see in the video and I'm sure would love to get on a regulation field. If you PM Jim Zondag I'm sure we can set something up.

We first saw that roller material used on 2056's robot in 2012 at the world championship. In 2013 we used it in our conveyer and it worked great. This year, we're using it again, because, why not?

[Akash Rastogi]

We first saw that roller material used on 2056's robot in 2012 at the world championship. In 2013 we used it in our conveyer and it worked great. This year, we're using it again, because, why not?

I remember someone told me at IRI, but can we get a part number/source for it?

[Kearse]

I remember someone told me at IRI, but can we get a part number/source for it?

McMaster sells this material. You can find it if you search "Abrasion-Resistant Gum Rubber Tubing". Coincidentally, this is the first year in a while where we won't be using this stuff. If you plan on using this I will warn that it can be a little hard to put on because it grips so well.

[Joe Ross]

Someone should correct me if I am wrong, but I believe the 60" rule is in reference to a robot sitting in its normal resting position on flat ground. This has always been the case in the past. If this is not the case, we'll just make the wings ~5" shorter and call it good.

See Q252.

[AllenGregoryIV]

See Q252.

Q252 (https://frc-qa.usfirst.org/Question/252/per-rule-4-1-r3-c-the-robot-height-may-not-exceed-60-in-does-this-mean-a-robot-that-fits-within-maximum-starting-configuration-may-receive-penalties-if-it-slightly-tips-over-making-it-taller-than)

Q. Per rule 4.1 R3 C, "the robot height may not exceed 60 in." Does this mean a robot that fits within maximum starting configuration may receive penalties if it slightly tips over, making it taller than 60 inches, or does the 60 inch rule only apply relative to the plane of the base of the robot?
2014-01-29 by FRC2900
A. A ROBOT that is not in contact with the carpet in its GOALIE ZONE and is taller than 5 ft will receive a penalty per G22.

[Squeakypig]

We are on team choo choo this year. Unfortunately, I don't have any good pictures. Maybe I'll throw something up after Week 1.

Real Question: Did you choose the Chug Lyfe or did the Chug Lyfe choose you?

Translation: Was the choo choo shooter your first selection of "winch" mechanism or were there other iterations you went through?

[apalrd]

Real Question: Did you choose the Chug Lyfe or did the Chug Lyfe choose you?

Translation: Was the choo choo shooter your first selection of "winch" mechanism or were there other iterations you went through?

We chose the Chug Lyfe based on our experience designing other mechanisms in 2010 and the forces involved in releasing winches. The choo choo has had its share of design iterations, as there is a lot of concentrated force in a small package.

There's quite a lot into the design of that choo choo, the geometry of it, and the gearbox.

[BJC]

See Q252.
Thanks for keeping me honest Joe,

Shouldn't be a big deal to take care of this if it becomes an issue.

[AllenGregoryIV]

Congrats on the win at Southfield.

What are you all using for a "photon cannon" this year and what exactly are you using it for? Normal aligning to wall?

[XaulZan11]

Since you already competed, can you share info about your drivetrain?

[BJC]

Congrats on the win at Southfield.

What are you all using for a "photon cannon" this year and what exactly are you using it for? Normal aligning to wall?

Thanks, we are generally happy with the robot performance this weekend.

The flashlight basically provides a line on the ground in front of the driver which allows us to line up with stuff on the field from far away. When we initially put the light on we immediately saw an improvement in driver performance. I contribute this to the driver being able to look at the light instead of the robot while driving. Effectively, it becomes intuitive to look where the robot is going to be rather than where is currently is.

Since you already competed, can you share info about your drivetrain?

The drivetrain this year is actually has a pretty interesting story behind it. I don't have time to properly do it justice right now, but maybe sometime later this week I'll type it all out.

[Answer42]

I spy an Omni wheel (http://screencloud.net/v/oC84)!


The drivetrain this year is actually has a pretty interesting story behind it. I don't have time to properly do it justice right now, but maybe sometime later this week I'll type it all out.
So.... About that drivetrain.

[s_forbes]

So.... About that drivetrain.

This is one of the first mysteries that I set off to solve when I got to the pits in St. Louis. The answer surprised me: 4 omni wheels, each with a single gear reduction from a CIM motor, nothing more. I chatted with one of the students as they were going through inspection, and the rational for the design choice sounded reasonable. The consistency and range of their catapult seems like a big part of why they are so successful with this approach.

[apalrd]

About the drivetrain:

The drivetrain is very simple. There are 6 pieces of sheet metal (0.050" 6061 T6) which make up a fairly standard square with 2 wheel bays of approximately standard width (I believe 3", don't quote me on that). At each corner, a stiffener plate (0.050" 6061 as well) is used to maintain the center-center distance between a single large CIM with Vex 11t pinion and the Vex omni wheel and 72t gear (held together with versakey parts). The axle is 1/2" 7075 round, dead, taped in the end for a 1/2-20. I can give more details on the exact fabrication if you want.

The omni wheels were replaced every 2 tournaments or sooner, we simply replaced the entire axle-bearing-wheel-gear assembly and had a complete set of identical spares (including axle spacers) in the pit.

We found that the CIM could twist, so we added wood blocks between the CIM and front/rear chassis rail to keep the gear spacing correct. This was done manually by sound, the whole drivetrain is very quiet when running.

We initially used Vex encoders with Vex 2.75" omni wheels as floating odometry wheels, but quickly removed them for weight savings and ran time-based autonomous programs (we did do voltage compensation to try to keep it reasonably consistent). There are no sensors in the drivetrain.

The catapult is a single welded frame, which bolts on top of the chassis to provide significant stiffness. With the 4-omni drive, we don't care about stiffness nearly as much as we did with drop-center traction wheel drives.

The strategy behind the drivetrain was basically to be able to maneuver out of any situation easily enough to prevent direct pushing. We believe this achieved it in the lights, simplest way possible, without any articulating systems. By preventing direct pushing, we also removed the need for a multi-speed gearbox, allowing the 'corner modules' which are extremely light, simple, and efficient.

I can answer more questions if necessary.

[Zebra_Fact_Man]

Are there any better pictures of the drivetrain system posted anywhere?

[apalrd]

Are there any better pictures of the drivetrain system posted anywhere?

I don't have any. I'll see if anyone else does.

[Jim Zondag]

Here are a couple of pics.
As Andrew said, it is very simple. The minimalist design freed up a lot of resources we could then use on other features of the machine such as a giant spring bundle in the catapult and huge catching wings. The lack of chains or belts means we do not need much rigidity in the frame, allowing it to be even lighter. There is a single 6:1 rear reduction to each wheel.

Our priority this year was to make the best catapult possible. The drivetrain needed to take a backseat to this objective.

A lot of people thought we were crazy and/or stupid when we revealed this. Admittedly it is a bold choice. It has its pros and cons, but for this game, I think the pros were an advantage overall. It does require a very good driver, and Ellen is pretty awesome. (7 blue banners, 175/46/1 record over 2 years):)

There is more than one right way to design a robot. The right choice depends on many factors including: experience, driving ability, weight, complexity, and game strategy. I think our 2014 experience proves that you can sometimes step outside the box if you have properly thought through the question.

https://lh4.googleusercontent.com/-latd1vAhNN4/UupzEEWCcyI/AAAAAAAAD0o/8pDQCeEfux4/w913-h685-no/20140129_154526.jpghttps://lh4.googleusercontent.com/-0cMtYjJCSkM/Uwwb8GiBULI/AAAAAAAAECg/MKbfPX8xPBg/w514-h685-no/20140224_134657.jpg

[jagen31]

Nice! Very interesting design philosophy. We have a really good driver, but if I told him we were putting omni wheels on the robot he'd punch me square in the face.

Funny story, during Archimedes, whenever someone would mention 33 in the team 20 stands, a bunch of mechanical people would say, "don't worry, we can just push them around," and finally someone said, "Then do it, if its so easy."

[Mike Marandola]

This is my favorite robot by far. The drivers are so good. Are you guys able to alter the trajectory of the shot with your choo-choo mechanism?

[AlecMataloni]

So, what's the standard bend radius on the .050 sheet you guys use? I've read that 6061-T6 bends poorly/ cracks below a bend radius of double the material thickness. Is this the rule of thumb you follow?

[chiefsfan67]

By the way, thank you Killer Bees, from 1730 Team Driven, for all of the free bee antennae, at the buffet Saturday night, and for wishing our drive coach a happy birthday! That was awesome!

[Ed Sparks]

..... There is more than one right way to design a robot. The right choice depends on many factors including: experience, driving ability, weight, complexity, and game strategy. I think our 2014 experience proves that you can sometimes step outside the box if you have properly thought through the question.

Absolutely ..... and your drivers were awesome. When I first saw the bot on it's back in the pits, I kept looking for the secondary wheel system to provide traction. What are the two green omni wheels doing?

The proof is in the performance and no doubt 33 had it this year (as always). Looking forward to seeing you next time.

[z_beeblebrox]

About the drivetrain:
We initially used Vex encoders with Vex 2.75" omni wheels as floating odometry wheels, but quickly removed them for weight savings and ran time-based autonomous programs (we did do voltage compensation to try to keep it reasonably consistent). There are no sensors in the drivetrain.


Omni wheels are for position measurement.

[yash101]

Omni wheels are for position measurement.

I believe you can use omni wheels to create quite creative drivetrains. They are not solely for position measurements. You can make an omni drive, a kiwi drive, and possibly even a tank drive capable of drifting!

Jim posted (http://www.chiefdelphi.com/forums/showpost.php?p=1380745&postcount=55) a picture, showing how omni wheels were used for the drivetrain, not just odometry!

[tim-tim]

So, what's the standard bend radius on the .050 sheet you guys use? I've read that 6061-T6 bends poorly/ cracks below a bend radius of double the material thickness. Is this the rule of thumb you follow?

I can't speak for 33, but the typical rule of thumb is twice the thickness for 6061-T6. We don't use much .050" or 6061-T6 on our robot, but at work we typically just use a 1/8" bend radius or 3/32" (.094") if we are in a pinch.

[Phyrxes]

Interesting read, thank you for posting. This was our first year using a sheetmetal frame and our sponsor suggested 5052 sheet over 6061 as thats what they use for most of their paying customers and can generally make our parts of of scrap. Any insight on what alloy properties to look for in this application?

[cadandcookies]

I believe you can use omni wheels to create quite creative drivetrains. They are not solely for position measurements. You can make an omni drive, a kiwi drive, and possibly even a tank drive capable of drifting!

Jim posted (http://www.chiefdelphi.com/forums/showpost.php?p=1380745&postcount=55) a picture, showing how omni wheels were used for the drivetrain, not just odometry!

I think he was referring to the question about the purpose of the green omnis in the middle of said picture, which do not appear to be driven.

Another fantastic robot from 33. I remember seeing your 2012 robot at Championships and being immediately inspired to push my team to create more aesthetically pleasing robots. Your robots have been excellent examples of both form and function in a killer package.

[apalrd]

The green wheels were intended for odometry but were later removed. The gray omni wheels are the drive wheels.

We use 6061 T6 as it is a harder than 5052, in FRC this translates into the need for a thinner sheet for the same overall stiffness. In the thicknesses we use (0.050" and 0.063") it does not crack when bent properly, but we have issues bending anything thicker (we have successfully bent a few 0.090" pieces, but also cracked several). 5052 is usually used by sheet metal shops as it is easier to work with, many teams use 5052 successfully in FRC (some on CD will say it's impossible to bend 6061, that is not true). I have only ever seen 6061 and 5052 used for FRC sheet metal applications.


We can in fact be pushed, we intentionally do not resist and instead spin out. That was part of the strategy.

[DampRobot]

Any details on how you implemented your catapult? I'm interested in how you packaged the springs in what looked to be a really tiny space, and how you designed for an optimized shot/designed for adjustability of the shot.

[apalrd]

Any details on how you implemented your catapult? I'm interested in how you packaged the springs in what looked to be a really tiny space, and how you designed for an optimized shot/designed for adjustability of the shot.

I attached some pictures and here is a description.

The moving portion of the catapult itself is a right triangle (or very close, it's a 95 degree corner). One leg spans the length of the robot, and has several applied pieces which hold the ball, a cross bar for the end stop strap (a seatbelt strap), and a cross bar for the pull down strap (a high strength rope). The other leg has mounts for the springs, the hypotenuse is a stiffening member, and the axle is located on the right angle. There are two welded triangles spaced 2" apart with the pull down and end stop strap axles in between, as well as structural pieces.

The fixed portion makes a 'Z' (really an 'N') with a vertical member on the front and rear of the machine connected by a diagonal member, with additional stiffening members triangulating the corners.

There are 6 springs. 2 are 2" diameter and 4 are 1" diameter. The 2" springs have a 1" spring inside of them. All of the springs mount to the ends of the moving portion. 2 of the 1" springs are mounted directly to the fixed portion, the 2 2" and 2 1" springs inside are mounted to a 'banana bar' which is adjusted with a lead screw. The lead screw is driven via a CIM and Versaplanetary 3:1.

The Choo Choo is remote mounted via the orange cable. We learned that we could play with the choo choo geometry to flatten the motor torque as the catapult is pulled in (as the spring force will increase with pull in distance, but we can also decrease the lever arm of the second hump to equalize the torque). The choo choo is driven via a Dewalt gearbox and then 7.2:1 in additional gear and chain reduction (total of 86.4:1). We did this instead of a rachet as we wanted to be able to reverse the choo choo, but this did not end up working. The dewalt gearbox was still handy for packaging, but it's a giant PITA to make and I don't recommend it at all.

As for adjustability, we have 3 primary points of adjustment: end position, start position, and spring length.
End Position: There is a black seatbelt strap which controls the end stop. At the fixed end it is wrapped through a hex shaft which is secured from rotating by a wrench-looking piece (it is visible in the 3rd picture). By removing the wrench-looking piece and using a pair of 1/2" wrenches we can adjust the end position under load.

Start position: The eye bolt which secures the choo choo cable to the catapult arm can be adjusted to set the start position. We do this to calibrate the dwell time, among other things.

Spring length: This is directly adjusted via the spring adjuster lead screw. We can also adjust the 2 fixed springs via their eye bolts, and have several springs which we can swap for major adjustments.


http://imgur.com/a/iQznZ

[BJC]

Any details on how you implemented your catapult? I'm interested in how you packaged the springs in what looked to be a really tiny space, and how you designed for an optimized shot/designed for adjustability of the shot.

I don't have any pictures but I will do my best to explain.

We put the pivot point of the throwing arm all the way at the front of the robot. In order to have a reaction point for extension springs (we looked into others but ultimately were most comfortable with extension) the arm is actually an L shape. There is about 600lbs of springs attached to a 9" lever arm. Their were 6 total springs. Two were 2" OD and the other four were 1" OD. To save space we actually put two of the smaller springs down the center of the two larger. Those four springs were attached to a fork towards the back of the robot. One side of the fork is fixed to the robot while the other side could be driven up and down by a lead screw to finely adjust spring tension. The remaining two springs were attached statically to the robot. In order to pull back the catapult we packaged a choo choo mechanism in the back center of the robot. The second link was a loss link made out of dyneema cord that went forward around a pulley then up attaching to the throwing arm. A seat belt strap could be finely adjusted to change the exit angle of the catapult.

We had three co-dependant variables when tuning the shot:
-spring tension (lead screw)
-angle of thrower when choo choo overcentered (dyneema string length)
-exit angle of thrower (seat belt length)

There were a number of things that I think were key to our catapult's success. The first is the enormous amount of potential energy it had stored combined with an incredibly short change in angle. A very short dwell time in the robot meant that other physics - such as the robot moving, being bumped, or hit - did not meaningfully affect the shot. By the end of the season we were also actually shooting through our ball hoop. This meant that the ball really couldn't move around at all within the robot even while firing. Other small things like using springs instead of surgical tubing meant that the shot never changed once we dialed it in even over multiple competitions.

Glad you like the robot, hopefully Jim or someone will pop in with thrower pictures to better explain.

Cheers, Bryan


Edit: Beaten by Andrew -- not fast enough on the draw

[DampRobot]

I attached some pictures and here is a description.

...

http://imgur.com/a/iQznZ

I don't have any pictures but I will do my best to explain.

...

Cheers, Bryan

Thank you so much guys! I really love reading about your engineering, and I'm really grateful you guys took the time to describe it in such detail. I know I'm not the first one to tell you this, but the omnis and the incredible shot on Buzz really made this one of the best robots in the world. Thanks again for sharing.

[yash101]

I think he was referring to the question about the purpose of the green omnis in the middle of said picture, which do not appear to be driven.

Another fantastic robot from 33. I remember seeing your 2012 robot at Championships and being immediately inspired to push my team to create more aesthetically pleasing robots. Your robots have been excellent examples of both form and function in a killer package.

I figured, but didn't want anyone else to get confused like me :).

That was a great robot, but it's pickup didn't seem as powerful when I saw some match videos!

[Abhishek R]

I figured, but didn't want anyone else to get confused like me :).

That was a great robot, but it's pickup didn't seem as powerful when I saw some match videos!

Pickup seemed fine to me... What about it didn't seem "powerful?"

[yash101]

Well, it looked like it was struggling a little to pick up the ball. However, I shouldn't dock off for this as it was better than ours :). However, I would post that robot in the "Scary Robots" thread because it's quite a beast!

[mman1506]

Did you ever experiment using a brake plate on your robot to prevent the robot from strafing while your in shooting position?

[apalrd]

Did you ever experiment using a brake plate on your robot to prevent the robot from strafing while your in shooting position?

No.

Strafing while in the shooting position is irrelevant, the goal is the whole width of the field.