Pit Carts

Project Background

As our team has grown over the years, so has the quantity of:

• Support gear for offsite activities, including batteries, tools and spare parts for us/others, spirit paraphernalia, etcetera.  What used to fit in two totes and a hand-carry toolbox now needs the equivalent of eight totes and a full-height rolling toolbox.

• Competitions.  We used to attend only one competition each year, but it has since grown to five.

• Community outreach.  We have grown to conduct a variety of robot demonstrations at schools, clubs, technology fairs, and festivals.

We did not have a means to efficiently mobilize the support gear, which often meant several people taking five or more trips between our team trailer and setup location, with gear spread across an ever-changing variety of totes, dollies, carts, boxes, and bags.

At competition venues, we had a walled structure to help get organized in our pit and display our team and sponsor signage.  It served us quite well over the years, but it was a bit cumbersome (large and heavy) to bring to events, and the way it incorporated our overhead signage made getting tall robots in and out of the pit inefficient.

Recognizing the challenges with mobilizing our support gear coupled with our non-optimal pit structure, our team initiated a project to develop a pit cart system that could be used to efficiently transport gear, while also serving as the majority of our pit structure.

Requirements

After forming a project team, we moved forward with creating a feature list of must-haves and nice-to-haves.  That list ranged from having work surfaces and spare parts storage to cup holders and flux capacitors.  Ultimately, the key requirements were summarized as:

• Phase I (Complete)

  • Common system that would enable support gear to be efficiently mobilized, while also serve as the pit structure

  • Modular structure that can be easily enhanced for future needs

  • Fit through a standard 30"-wide door opening

  • Fit in a competition pit space ranging in size from 8' x 8' to 10' x 10'

  • Drawers that allow access to items, with the option to easily remove the drawer of items for use elsewhere

  • A display for showing static and dynamic team and sponsor content

  • Sufficient storage for all support gear required for offsite events

  • Dedicated cart for storing and charging batteries

  • At least 16 sqf. of work surfaces

  • No overhead structure that could interfere with the robot

• Phase II

  • Integrated 120 VAC and 12 VDC power

  • Integrated vacuum

  • Integrated compressed air

  • Integrated trashcans

  • Integrated Gen2 Flux Capacitor (need to first confirm 88 mph rating for caster wheels)

Concept

With the basic requirements agreed on, the team moved forward with concepts.  After many concepts, the chosen one had the following key attributes:

• A design foundation based on the a t-slotted modular aluminum extrusion system to better ensure the system could support future enhancements

• One cart dedicated to storing and charging nine 12 VDC "FRC" batteries.

• Two support gear storage carts that each have compartment boxes in matching drawers for storing hardware and small spare parts, and full-extensions drawers for storing totes that contain large tools and parts.  The boxes/totes can be slid out for quick access, or easily removed entirely for use elsewhere.

• Multiple carts that can be moved separately, but when joined together, form an "L" that is the left and rear "walls" of the team's pit at competitions

• Carts at a height where the top surface can be used as a work surface.

• Three 32" LCD screens mounted above the cart at the rear of the pit to provide an engaging graphical display that is not in the way of the robot

• A multi-purpose credenza to help maximize work space, storage, and LCD screen visibility

Design

With the basic concept chosen, the students moved forward with the following design activities:

1. Complete an initial layout to determine the basic size of each cart

2. Determine specifically what to use for the major COTS (Commercial Off The Shelf) components that would notably impact the design, including the compartment boxes and storage cabinets

3. Divide the major cart elements into the following sub-teams:

   • Battery Cart, with these additional design details

     • Easy to insert/remove battery and plug/unplug its connector

     • Ability to store each battery without its (or any other) cables being exposed beyond the cart frame to make the cart more robust during transportation

     • Integrate a retractable extension cord

   • Storage Carts, with these additional design details

     • Storage area for a trash bag

     • Storage area for future enhancements, such as a vacuum and air compressor

   • Credenza, with these additional design details

     • LCD can be folded down to help fit through a doorway, while simultaneously providing a means to protect the screens during transportation

     • Counterbalanced lift for the storage cabinets and LCD screens so they can be safely lowered for fitting through a doorway, while simultaneously lowering the cart's center of gravity to improve cart stability

The students designed then entire system in SolidWorks to ensure the design materialized as envisioned.

Fabrication

With the design complete, fabrication began.  TSLOTS fabricated all of the extrusion pieces (cut to length), while additionally providing accessories such as t-nuts and linear bearings.

Dynamic Design & Manufacturing and Star Precision laser-cut the flat sheet metal parts (e.g., gussets), while Kenray Manufacturing laser-cut and bent the non-flat sheet metal parts such as the monitor mount.

S & S Anodizing and Specialty Plating anodized all of the aluminum parts black, while Line-X of Northern Colorado coated the wooden work surfaces with a protective coating.

Assembly

Having designed the entire system in SolidWorks prior to fabrication, the process of assembling the 1000+ components went relatively smoothly.  To minimize potential exterior discoloration of the carts if they were to inadvertently get caught in inclement weather, we used stainless steel hardware wherever possible.

The Result

With everything assembled, we quickly put the carts to use and are looking forward to enhancing them in the future.  

Thanks again to Dynamic Design & Manufacturing, Kenray Manufacturing, Star Precision, TSLOTS, S & S Anodizing, Specialty Plating, and Line-X of Northern Colorado for their generous support!