Behind the Design | 2015 PVC Pirates

One of NH’s most identifiable teams explains their unique stack making design.

Team 1058’s 2015 robot, Phat Stacks, was designed to be a premiere human player station specialist. Our strategy and design were determined by our initial reactions to Recycle Rush. We saw that there were two human player stations for a three robot alliance, and there were also 30 usable totes behind the driver station as opposed to 18 in the landfill (we considered the upside down totes and totes on the step as unusable), which prompted us to pick being a human player robot instead of a landfill robot. We also liked that the human player station would give us totes the exact same way every time, while the landfill had totes in multiple orientations. Our number one goal was to be able to make multiple stacks of six totes out of a human player station. Our other main goals were to be able to put co-operitition totes on the step and to not have to drive onto the scoring platforms in order to put down our stack. Our solution for these goals was to have an elevator that could hook totes easily off the ground, in order to perform a co-operitition stack, as well as create our stack by pushing it put of our robot so we would not have to be on the platform while holding a stack. Originally we could only make stacks without a can on top, but by our second event we finished our design and were able to put up one to two full stacks in a match. Every part that was machined for the robot was made on manual machines in house by students. We also powder coated our robot for the first time in 2015, giving us a unique style out on the Recycle Rush fields of New England.

Drivetrain:

  • Dimensions: 33″ long x 27″ wide
  • Type: H-Drive (Strafe Wheel not shown)
  • Wheels: VEXPro 6″ omni wheels and an AndyMark 4″ traction wheel powered by a window motor
  • Motors: 4 CIM Drive
  • Gearboxes: VEXPro 3 CIM Ballshifting Gearboxes
  • Frame made out of 6061 Aluminum C-Channel, welded/bolted together
  • Floating sprockets used to tension #25 chain

This drivetrain was designed to turn quickly, easily line up with the human player station, and be able to cross the scoring platforms easily. We built a prototype in small scale using VEX EDR parts to ensure we would be able to cross the platforms on the field. We originally used two stationary omni wheels in the front and back to strafe, but we eventually switched to a deployable traction wheel to save weight. The frame was welded together except for the outside rails, which were bolted, to make it easy for us to take off and work on the chains and wheels if need be.

Elevator:
The Elevator is used to pick up the stack inside of our robot as we build it and allow totes to be entered into the back of our robot and slide under the stack. The carriage is driven by CIM motor with a 27:1 Banebots planetary gearbox and a set of VEXPro gears. This custom gearbox was welded to a large plate, which was then bolted on to the frame of the robot. This gearbox drives a hex shaft which utilizes #25 chain to drive the carriage up and down. The carraige is a passive tote stacker made with polycarbonate hooks and an aluminum body. The carriage uses custom rollers made from acetyl rod to glide along on a 1″ x 2″ x 1/8″ aluminum box tubing frame.  Hall Effect sensors sense a steel bolt in the carriage to automatically stop the carriage at the bottom and top of the frame. We also added a hook to the front of the carraige to give us the ability to pick up totes off the floor if we had to use the co-operitition totes.

Pusher:
The pusher is used to push the stack we build inside of our robot onto a tote that we keep in front of the robot. We also use the pusher on each tote to push them up against the carriage as they enter the robot to center them on the tote platform before stacking them.The pusher uses a PG-71 Gearmotor from AndyMark and #25 chain to push our stack along the track. Hall Effect sensors stop the pusher at the front and back of its path. The track uses 80/20 extrusion and custom made sliders. The pusher uses a cable to force itself to rotate at the end of its path so it will push the stack over the elevator carraige and all the way out of our robot onto the front tote. The platform is made out of aluminum angle stock with a thin layer of regolith mounted on top of it to allow totes to slide all the way into our robot with ease.

Intake:
The intake wheels control the tote that sits in front of our robot, which the rest of the stack is pushed on top of. The intake wheels are each powered by an RS-550 motor and a P-60 gearbox, as well as a .5″ cylinder to move them in and out. We used 3 7/8″ orange banebots wheels due to their grip and ease of use. These wheels are for slow control of the tote in front, to keep it in place for an incoming stack to be placed on top of it.

Can Arm:
Our can grabbing arm is a long aluminum box tube with a hook on the end of it, and the hook is able to always face the same way by using a cable to create a virtual 4-bar arm. This lifts the can into our robot, and we then build the stack underneath it. The arm is powered by a 1.5″ cylinder.

PVC Usage:
One of team 1058’s design requirements for every robot we build is that we must use PVC in some way. This year we used PVC on the part of the pusher that actually contacts the totes, as well as for chain guards over the electronics panel and as a visual aid (with bright yellow tape) to help the drivers line up to the chute door.

Results:
We competed at the Reading District Event, UNH District Event, New England Championships, and the World Championships on the Carson Division. Along with some non-robot awards, we won the Creativity Award at New England Championships for our unique stacking method.

The end result of our final match of New England Championships: 84 points in a match.

We would like to thank our sponsors: BAE Systems, Parker, Fleet Ready, JMD Industries, Show Ready Events, Dumpster Depot and Londonderry High School.