Build Season 2016: Weeks 5 and 6 Recap

The last two weeks of build season were spent making our robot bulletproof.

During one of week 5’s many driver practice and programming sessions, the rotary potentiometer on the intake arm slipped and migrated away from its home position. As a result, the arm moved past the programmed safety stop limit. The robot’s carbon fiber front cross brace acted as a hard stop and the robot’s chassis and the intake arm itself were unscathed. However, the Banebots 775 motor driving the arm through a 256:1 gearbox and 2.57:1.25 chain reduction had way too much torque and bent the 3/8″ hex shaft about which the arm rotates. After replacing the shaft with a spare, the same situation occurred, but this time the 14 tooth sprocket attached to the motor split into two halves before the shaft had a chance to bend.

The Angle of Success used to properly position the goal for driver practice.

The Angle of Success used to properly position the goal for driver practice.

We took several measures to beef up the subsystem and make sure these problems would never occur again. First, we replaced the 3/8″ hex shaft with a 1/2″ steel shaft to prevent it from bending. Second, we replaced the 14 tooth motor sprocket with a 21-tooth sprocket, the largest sized one that would fit in the available space. This change reduced the output torque by 33% and increased the ball arm’s speed by 33%. The lowered torque will prevent the originally over-powered system from destroying itself and the increase in speed will help shave valuable seconds off of our autonomous routines. Finally, we removed the rotational potentiometer and replaced it with a string potentiometer. The string potentiometer will provide much more consistent and reliable readings, regardless of what is happening on the rotation shaft, since it measures only the linear distance the arm has traveled. We also added a beam break sensor to detect when the robot has acquired a boulder.

With these changes in place, we were able to finish programming the low bar autonomous mode we started the previous weekend. We then moved on and were able to finish programming autonomous routines to cross the portcullis and cheval de frise and score a boulder.

Meanwhile, the awards and spirit committees were equally as busy as the builders and programmers. They have been working with students from our school’s film and TV production classes to document the season and create a video for the Chairman’s Award. They also emailed alumni and school administrators to set up times to film interviews. The team standards were delivered and mounts were made to fly them above the playing field and in the stands. Keeping with the medieval/Monty Python theme of FIRST Stronghold and our team’s Hawaiian imagery, we also made coconut clappers to help cheer in the stands and make noise when voting for the audience selected defenses.


Parts cut to size for the climbing mechanism.

Construction of the hanging mechanism continued into week 6. The final design lifts the robot at a rate of 24 in/sec with a final speed of 1 ft/sec after a 2:1 pulley reduction. A custom 2 CIM worm gearbox  powers the winch through a 3-stage mast. Both the ball arm and hanger have rotation points on the front of the robot. This design will allow us to score a boulder at the last second and then hang without needing to rotate the robot 180 degrees between the two actions. The hanging mechanism will be completed during the final days of build season after the 3D printer finishes the tubing plug blocks and mast pulley cable retainer parts.

2016Bumprs.jpg To round out the weekend, we finished making new sets of red and blue bumpers for the robot.

Build season officially ends on Tuesday, February 23rd. Our first competition is in Horsham, PA March 4-5th. We’ll have a six hour robot access period to add the final bells and whistles to the robot before then.

P.S. This year’s robot has been officially named Evil Machine 14: The Executioner!

Build Season 2016: Weeks 3 and 4 Recap

It’s beginning to look a lot like a robot!

Over the last two weeks, our team made tremendous progress on this year’s robot. First, we finished mounting and wiring up all of the control system components on this year’s new chassis. In our last update, we mentioned making extensive use of 3D printed components. Since the robot will be driving across many obstacles in this year’s game, we wanted to keep the electronic components mounted up high to ensure the robot had ample clearance. To accomplish this, we did away with a traditional robot belly-pan and manufactured 3D printed clips to mount speed controllers directly to the drive motors. We also designed and 3D printed gearbox motor plates with integrated servo brake mounts. After the field parts were completed, we spent some time driving the chassis over the defenses. It sailed across the ramparts, moat, rough terrain, and rock wall with ease. The wooden defenses started to fatigue and break from repeated abuse before the drivetrain showed any signs of wear itself.


At the start of week three, we finalized the CAD drawings for the robot’s intake system. Since the intake extends outside of the robot, we decided to cut the parts out of 1/4″ aluminium sheet metal so it could stand up to collisions and rough play. Our sponsor Becton-Dickinson (BD) was up to the job and able to cut the parts for us before the weekend! We spent Saturday and Sunday manufacturing and installing the rest of the components needed for the intake and its arm assembly. At the close of Monday of week four, we installed the motors, belt run, roller, and potentiometer (on its own 3D printed mount) needed to complete the intake. Our driver got a little bit of practice time in, chasing boulders around the shop and picking them up.


Meanwhile, the awards subteam was busy finalizing the team’s Chairman’s essay and two Woodie Flowers Award entries, which were submitted before the February 4th deadline. They then started working on the presentation components, keeping with the medieval theme of this year’s game and our essay. We placed the order for our team standard, which is the flag that will be flown above our team’s player station whenever our robot is playing in a match. The Entrepreneurship Award is due February 11th, so we started working on updating our business plan entry for that award as well. We have also been continuously working on a build season journal to keep as a record of the progress made during each team’s meeting.


On the scouting subteam, the Android scouting application is functionally complete. Arjun, our lead developer, is making user experience enhancements and starting to look into ways for us to better visualize and analyze the collected data.

We spent some time this past weekend strengthening parts of the intake arm assembly. After all, it’s better to break things and make the necessary modifications to improve them now than in the middle of a competition! On Saturday we also had a productive programming session. After adding a gyro to the robot to complement dual drivetrain encoders, a new algorithm to keep the robot driving straight worked even when driving over some of the defenses. With this ability in place, we started programming autonomous routines and almost have our primary one complete. Mike, our engineering mentor, visited the school on Sunday and worked with us on the development of the robot’s hanging mechanism. Featuring constant force springs and gas shocks, we’re excited to see the design spring to life!

Stay tuned as we enter the final two weeks of build season. Stop build day is February 23rd and we’ll be revealing our completed robot shortly thereafter!

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Build Season 2016: Weeks 1 and 2 Recap

The students of Team 25 have been hard at work for the first two weeks of build season. The entire team met the Monday following kickoff for our large group brainstorming session. After discussing some of the rules and analyzing the game, we decided on what we thought was the best strategy to pursue to play FIRST Stronghold.

In the days following this initial meeting, all hands were on deck in every student subteam of Raider Robotix.

Our design team started working diligently to design different robot subsystems using CAD. Meanwhile, the build crew started to construct the classic Team 25 drivebase for this year’s robot, taking into consideration the special requirements of the new game. These two subteams will have a close relationship, as we are making many 3D printed parts for our robot this year.

Thanks to our new sponsor, Abbe Lumber, we were able to get enough wood to construct a field’s worth of obstacles. At the start of week two, roughly half of the field elements had been constructed.

One of the final team standard designs.

One of the final team standard designs.

The communications crew has had their hands full with this year’s set of awards and videos. They have been documenting the 2016 build season better than any other. They have completed the final designs for the team standard that will be hung above our player station during matches and are working on a special 20 year anniversary t-shirt design.

The scouting subteam gathered design requirements and has started programming a new Android scouting application for this year’s competitions. Working alongside them, the programming crew has started developing some robot code for practice purposes. Lastly, the electrical group has constructed a temporary control system to test and practice with the new robot.

Stay tuned for more updates in the following weeks as the robot begins to take shape!