Behind the Design | FRC 558 (2016) – What Withholding Allowance

The 2016 FIRST Robotics season was one of constant iteration for FRC558 and ultimately resulted in the building of not only four robots, but one of the team’s most successful seasons to date. After kickoff the team set its priorities and began building the first pair of competition and practice robots, affectionately named Toaster. The priorities on the whiteboard for the whole season read:

  1. Cross Defenses (Low Bar, Category A, B, & D)
  2. Control/Collect Boulders
  3. Score Boulders Low
  4. Score Boulders High
  5. Scale the Tower

Below we see toaster as driven at both the Suffield Shakedown Scrimmage and the Waterbury District Event. It was designed with a through the bumper CD7 style intake that deployed via two pneumatic cylinders. Though a flywheel shooter with single wheel and single position hood was designed and installed for shooting from the batter it was found to be inconsistent and thus was not ever used on the competition field. During the scrimmage we noticed some of the short comings of our initial design, largely the size of our chassis and the wheels spacing. We began to reevaluate how well we were accomplishing our first three goals. It was decided that we would stick with Toaster as is for the Waterbury District Event due to the scope and time we had available to make changes.

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After careful examination of the 2016 rules, we found that it would be possible to iterate on our entire robot, as long as we did so in increments and made the right steps from the beginning of the competition season. Between scrimmage and our Week 1 event in Waterbury we decided that building a third, but smaller chassis (Inspired by our friends FRC125) and carrying it with us to the event would only open doors for us, not close them. R18 from the Stonghold rulebook is quoted below for your review.

R18

At an Event, Teams may have access to a WITHHOLDING ALLOWANCE of FABRICATED ITEMS, not bagged per R15, to be used to repair and/or upgrade their ROBOT. The WITHHOLDING ALLOWANCE is a static set of items that shall not exceed 30 lbs. With permission from another Team, Teams may also have access to FABRCATED ITEMS that are part of that other Team’s WITHOLDING ALLOWANCE to repair and/or upgrade their ROBOT. The WITHHOLDING ALLOWANCE may only be brought into the Venue when the Team initially loads in at the Event. Items made at an Event do not count towards this weight limit.

For Teams attending 2-Day Events, these FABRICATED ITEMS may be used during the Robot Access Period and/or brought to the Event, but the total weight may not exceed 30 lbs. FABRICATED ITEMS constructed during the Robot Access Period and bagged with the ROBOT are exempt from this limit.

The first Brick chassis was designed to use all of the existing components from Toaster. It was machined and assembled by our students on our mini mill in the two nights prior to Waterbury. For withholding at Waterbury we carried Toaster’s intake assembly, and Brick’s Chassis which together was below the 30 lbs allowable. We competed with Toaster, seeded #1 focusing on breaching and scoring low, and won the event thanks to the help of our alliance. We also snagged the Motorola Quality Award, which because of a bet earned all of the kids an ice cream party.

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At the end of Waterbury, Brick’s chassis went into the bag with Toaster. This was the first public hint that was made that the team considering the option to change up the robot, and the image below was posted on instagram with the hashtag #whatinthebag.

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Over the next week the team discussed the option to switch. After much debate, the team locked into attempting the change and finalized the design. Brick’s intake/shooter was inspired by FRC131’s robot this year. The team loved the simplicity of it, and the over the back batter shot it allowed. For the next few weeks the team built our fourth chassis of the season for practice Brick, and the shooter/intake assembly. The weekend prior to Hartford we were able to visit FRC195’s practice field and do a full systems test and run the practice Brick through its paces. Within the first 30mins we dialed in the batter shot and saw nothing but smiles on our drivers faces. That sealed the deal. Over the week prior to the event we planned out three 2 hour unbag periods to convert Toaster’s chassis to Brick’s. Each night had a set amount of tasks, and we were able to get it all done. You can watch the video of these unbag times below. We wanted to do everything inside the rules, and document it at the same time.

For Hartford our Withholding was the intake/shooter assembly which weighed in at around 18 lbs. Final assembly of the machine was completed at Hartford on the first day, we missed our practice machines and had to inspect the morning before qualification matches started. Below are some images on Brick on the field at Hartford. The first image shows the robot crossing the cheval de frise, something Toaster was not able to do.

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The image below shows Brick in its shooting configuration and location. Brick was designed to shoot only from ramps and slammed up against the base of the tower. This was chosen to eliminate as many variables as possible, and allowed the intake to be controlled with a simple pair of pneumatic cylinders. Brick’s first competition was a success and once the drivers got fully used to its capabilities we began to really see our hard work shine. We seeded 8th, and were the first pick of the number 1 seeded team. We went on to win our second district of the season.

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Having accomplished our first four primary goals the team set out to tackle the challenge of scaling the tower. We settled on a 3 stage telescoping tube arm that could tuck into the chassis and be deployed with a single pneumatic cylinder. The new component was tested in the shop on the practice chassis and they removed and carried to our next event as our withholding allowance. You can see the climbing mechanism in the stowed position below while waiting for a match and the New England District Championship.

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Here you can see the lift after a successful scale during the elimination rounds. Although we did not preform as well as we had hoped at DCMP, it was an excellent test run with a fully functional Brick. No additional changes were made to the robot between DCMP and the World Championships.

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This robot was the direct result of the hard work that our students were willing to put in on a totally insane idea. My job as a mentor is to inspire our students to keep pushing, Brick was the vehicle for that this season. The team learned so much because of overcoming this challenge. Among the biggest lessons learned were time management, and that a team should never fear change.

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