pic: Shaker Robotics 2014 Robot - Raptor SS

[Chris is me]

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[Akash Rastogi]

Everything about this robot

[Chris is me]

Full Description didn't post, so here it is. Short reveal video included in picture description now.

FRC 2791 Shaker Robotics is proud to present our 2014 robot, Raptor SS.

DRIVETRAIN:
Belt Driven Six Wheel West Coast Drive - Our 4th Iteration
3 CIM Custom Reconfigurable Single Speed Transmissions using Vexpro Gears
Measured Actual Speed 13 FPS using 4" x 1.5" Colson Wheels

ARM:
Second Iteration of 2013 Gear Drive Arm Concept
Custom 6-Stage, 500:1 Transmission Driven by 1 Mini-CIM
Gearbox is Repairable In Place to break the curse of WPI 2013
Pair of 1" Pillow Blocks Ensures Smooth Power Transmission
(Not Shown) Gas Shock Drives Arm Downward to Smooth Motion - Ensures Ball Pickup In Case of Failure

SHOOTER:
Linear Shooter Driven By QTY 2 40lb Constant Force Springs
Custom Ballshifter Winch - 1.5" Spool Geared ~60:1 off 1 Mini-CIM
Magnetic Sensors Detect State of Shooter Reliably
5/8" Anodized Shaft Rides through COTS Linear Bearing and Custom Elevator-Style Block

CLAW:
<7 lb "VersaClaw" Uses VexPro Frame and Gussets Reinforced with 1/16" Sheet and 1/2" Round Standoffs
Blue Banebots wheels powered by BAG motor run through 15:1 VersaPlanetary for Intake
Geometry of Claw, Wheels, Sorbothane Strips Optimized For Ball Pickup at Any Angle. (Really. We were going to do a CD7 Style, but we didn't need it.)
Pair of 2.5" Stroke 3/4" Bore Cylinders Actuate Claw for Shooting / Catching

While far from our simplest endeavor, we think this is our best one yet. A truss shooter specialist, this robot can quickly acquire the ball and shoot over the truss from multiple trajectories, allowing us to adjust our shot for whatever the catcher on our alliance might need. Can shoot into the goal from short range or from about 1/3rd of the field if moving full speed. We look forward to alliance strategy this year, we've got a bunch of tricks up our sleeve.

If you're in the Capital region, please let us know if you would like to practice together.

[BigJ]

Great looking bot. Is almost identical to ours this year (we have a slightly different claw design), even down to what I assume is an "Inspired by" panel

[Akash Rastogi]

P.S. - Nice photoshopping on the sponsors

[Hallry]

Originally Posted by Akash Rastogi

P.S. - Nice photoshopping on the sponsors

And dat background

[Chris is me]

Originally Posted by BigJ

Great looking bot. Is almost identical to ours this year (we have a slightly different claw design), even down to what I assume is an "Inspired by" panel

Yup, quite similar indeed...



Was trying to use the right fonts for teams but time constraints prevented us from working on that detail fully.

1114 is an obvious inspiration for this robot. The "SS" in Raptor SS is to pay tribute to one of the greatest robots of the three alliance era, Simbot SS. We ended up modifying the design and geometry significantly to match the constraints of this game (20" extension, articulating the shooter, more consistent stored energy, bigger release / catch, an early attempt at bidirectional loading / shooting), but we would never have had this concept in mind without 1114's inspiration.

125 was gracious enough to share information about their prototype constant force spring shooter, which they ended up not using. We used the information they gave us as the starting point for our shooter design. Brandon and Andrew have been really forthcoming and helpful whenever we had any questions or got stuck on something.

2826 I'll go into after their first event, but I had enough design discussions with Nik that I feel both our robots were made a little better as a result. Ours probably more than theirs.

973's RAMP videos were invaluable to us. Before the videos came out, there were a few of design elements that I could do well and a few that our other design mentor could do well. These videos essentially allowed both of us to catch up to speed on good CAD techniques, design tips, etc. There's a bunch of 973-inspired stuff on the bot. The drive gearboxes were made using RAMP style layout and pocketing techniques. Our shooter has several components heavily inspired by 973's 2011 elevator. The initial concept for the arm gearbox came from a lot of west coast robots I've seen - using a 1" face to mount and stand off a gearbox.

Thanks for being open and sharing design information, we wouldn't be anywhere near where we are as a team without it.

[Karthik]

Love the robot name. Thanks for the shoutout!

[Brandon Holley]

Very cool move of you guys to include an 'inspiration' panel on your bot. It ties directly into the recently started by JVN thread discussing where ideas come from. There is NOTHING wrong or shameful about tipping your cap to a team or person who helped inspire a solution for your team.

This is something all teams (mine included) should get better at doing, and this is one cool way to do so.

Nice job guys.

-Brando

[asid61]

I love how the arm is made with simple parts. Looks very robust too.
And getting the thing to shoot with just two CF springs is incredible.

[DampRobot]

Very cool. It'SS an amaSSing SShaker RoboticSS robot as uSSual!

Can you talk a little bit more about your arm gearbox? What happened at WPI, and how do you mean it's repairable in place?

[Sh1ine]

Originally Posted by DampRobot

Very cool. It'SS an amaSSing SShaker RoboticSS robot as uSSual!

Can you talk a little bit more about your arm gearbox? What happened at WPI, and how do you mean it's repairable in place?

Yes we have actually done a lot to improve on our arm gearbox design in this itteration. For those who don't know we were number one seed at WPI. We went undefeated for all of qualification matches. In our last qualification match our arm gearbox (which adjusted the shooter and picked up the robot) sheared 1/2 of the teeth on the last stage pinion gear. With the short turn around time of finals and a poor maintenance design we were never able to be 100% again and ended up coming in second overall.

This year we have a reduction of about 500:1 over 6 stages. That is a lot of stages for the amount of reduction. Last year we were able to be close to 1000:1 with only 5 stages. The reasoning behind this, is we wanted to have lager pinions this year, especially at our later stages. Lager pinions create less force on the gear teeth. Our last stage is a 50:84 reduction. The 50 tooth pinion is a AM steel gear (versus a 20 tooth vex gear from last year). This was our first concern when redesigning the system.

Next, we made changing out last reduction much easier. We can now change gears out in less than 20 minutes. We did not think of maintenance last year, and it was so difficult we avoided changing the gears. This year we are adding a maintenance schedule for the last stage. During lunch on Saturday we will replace the last stage of gear. Also we will change gears before our second regional and again before finals. Mind you, our gears sheared at WPI which was our second regional last year, so we are confident that this schedule along with our updates to the system is more than adequate.

Finally, we added a dampening spring to the system (not shown in picture). We use a gas spring to absorb shocks to the gears from momentum and impacts with other robots. We believe that the abrupt movement prematurely wore the gears last year. We are happy to report that the dampening system is working better than expected.

We really liked the gear driven arm last year, when it worked, it worked great. Our current iteration should prove to make a big difference in performance this year.

[AdamHeard]

Originally Posted by Sh1ine

Yes we have actually done a lot to improve on our arm gearbox design in this itteration. For those who don't know we were number one seed at WPI. We went undefeated for all of qualification matches. In our last qualification match our arm gearbox (which adjusted the shooter and picked up the robot) sheared 1/2 of the teeth on the last stage pinion gear. With the short turn around time of finals and a poor maintenance design we were never able to be 100% again and ended up coming in second overall.

This year we have a reduction of about 500:1 over 6 stages. That is a lot of stages for the amount of reduction. Last year we were able to be close to 1000:1 with only 5 stages. The reasoning behind this, is we wanted to have lager pinions this year, especially at our later stages. Lager pinions create less force on the gear teeth. Our last stage is a 50:84 reduction. The 50 tooth pinion is a AM steel gear (versus a 20 tooth vex gear from last year). This was our first concern when redesigning the system.

Next, we made changing out last reduction much easier. We can now change gears out in less than 20 minutes. We did not think of maintenance last year, and it was so difficult we avoided changing the gears. This year we are adding a maintenance schedule for the last stage. During lunch on Saturday we will replace the last stage of gear. Also we will change gears before our second regional and again before finals. Mind you, our gears sheared at WPI which was our second regional last year, so we are confident that this schedule along with our updates to the system is more than adequate.

Finally, we added a dampening spring to the system (not shown in picture). We use a gas spring to absorb shocks to the gears from momentum and impacts with other robots. We believe that the abrupt movement prematurely wore the gears last year. We are happy to report that the dampening system is working better than expected.

We really liked the gear driven arm last year, when it worked, it worked great. Our current iteration should prove to make a big difference in performance this year.

Leaving the ESC in coast mode, as well as turning PID way down in exposed states (like your intake preset) that don't require great precision will help a lot as it removes the motor trying to react to big hits.

[Chris is me]

Originally Posted by DampRobot

Very cool. It'SS an amaSSing SShaker RoboticSS robot as uSSual!

Can you talk a little bit more about your arm gearbox? What happened at WPI, and how do you mean it's repairable in place?

Sh1ne touched on most of it, and I was mostly focused on DT / gripper, but I can expand on this. The blue gearbox side plate comes off with a few bolts at which point you have access to all of the gears and shafts without removing the gearbox from the robot. Ideally the robot is tilted on its side for this.

One of the challenges of a geared arm that relies on Vex gears is the compounding effect of slop on the system. Vex gears are broached bigger than .500, and thus they have a bit of play on the shaft. Vex shafts are undersized to fit bearings. Multiply this by a dozen gears, and factor in the .003 center add, and you have a lot of slop once you get to the arm.

Our dampening system (a gas spring pulling the arm toward the ground) takes up this slop and smooths out the arm motion at key points of travel. The spring also serves a secondary purpose - in the event of gear failure, the arm is pulled toward the ground. This lets us manipulate the game piece for the rest of the match.

I really wish that the hex broaches on Vex gears were tighter, but I understand the desire to fit them to any hex shaft. We'll have to investigate ways to make geared arms with less inherent slop in the future. The geared single joint arm is quickly becoming a "signature" of 2791 mechanical design, so further iterations of this concept will likely find their way to future robots. That, or we'll finally listen to Foss and use cylinders.

[Andrew Schreiber]

Originally Posted by Chris is me

That, or we'll finally listen to Foss and use cylinders.

One of us...