FRC 3506 - YETI Robotics - 2022 Build Thread

Welcome to the first ever 3506 YETI Robotics build blog!

This year we joined Open Alliance to share and support a great effort. We really believe sharing our processes among teams raises the visibility of veteran robot building techniques and helps positively support the competitive nature of FRC to raise the competitive ceiling for everyone.

At our home in Charlotte, North Carolina we have a full size field and workshop and we have always had an open door policy that any team can come into our space and learn. There are no secrets and we share everything with everyone! YETI is an experienced team that has helped start and support teams every single year since inception. We think that we have a lot to share with other teams and we are also really looking forward to the positive community critique of our processes to be a better team!

About our team:

YETI is a student led community based team based out of Charlotte, NC. We exist as a part of the Queen City Robotics Alliance (QCRA) along with several other FRC, FTC, and FLL teams. Since we do share our space and field with teams in the area, you might see other robots in our practice area and shots of other robots during our blog!

Our team composition this year is interesting because we have grown by about 50% as a team year over year. Here are some metrics about our team:

Student count 62
Mentor count 24

Who are we?

  • 68% minority
  • 28% of our team is female
  • 26% of our mentors are female
  • 26% of our mentors are minorities
  • 36% of our team are not public school students
  • The majority of our mentors are FRC Alumni from several teams
  • A whopping 96% of our team is grade 9-11 so our team is mostly comprised of rookie team members!
  • Only 2-3 students have been through a full FRC season without an ongoing pandemic so we are poised for a challenging and fun season!


Our team meets from Wednesday through Friday 6pm to 9pm Eastern and on Saturdays we usually go from 9am to 9pm on average, taking the day in shifts.

Open Alliance:

We plan to update and share our progress 2-3 times a week via this thread (and discord) with major milestones discussed in our Saturday postings. Our team is divided into sub teams for Controls and Mechanical which include the Programming, Electrical, CAD, and Fabrication skillsets.

We use SOLIDWORKS as our CAD solution and we use GrabCAD as our document management solution. CAD will be made available upon request to make it easier to share meaningful data.


We hope teams will use this resource in ANY way they see fit. From learning about a new building technique or replicating one of our designs to get them past a design hurdle let us know how or what we did to inspire! Imitation is the highest form of flattery for our team.

In closing, we are looking forward to a season on the Open Alliance with you all!


YETI had a great kickoff day. We primarily brainstormed climber and shooter concepts. We heard a lot of wonderful concepts yesterday (attached below are some concept sketches). We are exited to continue the journey through build season with all of you.

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Hello all!! I am exited to share our progress with everyone. Today we expanded on intake and hopper design concepts. As we started the day we only had rough sketches and thoughts but I am glad to share that we now have two prototypes that are sound designs. Our intake will be able to pick up cargo off the ground. Our hopper does a great job of getting the ball into the neck. As of now our cargo handling strategy is to funnel the cargo straight through our robot and directly into the shooter. Here are some images of our intake and hopper/neck prototypes. We can’t forget to give a huge shoutout to our wonderful mentors who are building the field. Today they where able to construct the hangar and are currently in the progress of building the rest of the field. The field is also open for use to any team in NC. All you have to do is contact one of our lead mentors (one of them started this thread)

Edit: Added images


As I read other teams’ build logs I am quickly realizing some things we have forgotten to mention. The strategies we have decided on is as follows.

Would be nice to have:

  1. Drive
  2. Climb mid
  3. Shoot high
  4. Ground intake
  5. Open canopy
  6. Shoot low
  7. Climb high
  8. Climb traverse

What we decided on:

1.) Drive
2.) Climb high and traverse
3.) Shoot high and low
4.) Ground intake
5.) 2 ball auto
6.) Have an open canopy
7.) Shoot low goal

Keep in mind this seems very ambitious but we will most likely make changes to our order of priorities (the “what we decided on” list) and possibly not include some of those elements on our robot.

WHAT A THIRD BUILD DAY. Today we expanded our prototypes and started to ut some prototypes in cad.

We have decided on a 6 wheel drive west coast drive train. With the wheel orientation of 2 traction wheels in the back with one Omni in the front with no drop center for maximum stability. At this point, the gearbox has been mounted on the middle wheel instead of the rear. We are very near to having a completed CAD model of the drivetrain. (I will upload a ss of it when it is finished)

Our intake takes heavy inspiration from teams 148, 118, and 254. We also based our 2021 intake off of their three-bar folding intake style. We really like this intake style for its versatility.

The system that moves the ball from the ground intake to the shooter (the neck) made immense amounts of progress. We figured out how much compression is ideal for cargo. We also determined that a straight line neck would be the best choice in order to reduce points for the cargo to get stuck and to prevent losing game pieces mid-game (after intaking).

We are essentially repurposing our 2021 shooter for this game (I will attach a photo). We have yet to decide whether or not a turret is worth the risk but it is definitely something we are heavily considering.

We made sketches in Solidworks with proper dimensions to prove that our concept would work for our high/traverse climb. The basic idea is that we will have 2 climbers and one climber will initially attach to the mid bar and the second will extend to the high bar once we have fully climbed on the mid bar. After the second climber has a grip on the high bar the mid bar climber will unattach itself from the mid bar and attach itself to the high bar and the whole process will repeat itself to get us to the traverse bar. We are still brainstorming the how but we will update this thread with our results as to what we decide on doing.

Neck design vv
Early neck design
2021 shooter vv
2021 shooter
Climber proof of concept sctech vv
Climber geometry sketch
Intake inspiration vvv

148 Intake inspiration vvv
254 Intake inspiration vvv


Our latest update comes with a ton of information so here goes!

Yeti has been working hard to prototype several solutions for the first week and we broke into smaller teams to accomplish this goal. Our thoughts on our design direction - use whatever we have available with a mostly rookie team and try to Recycle Rush our way to completed designs.

How we prototype is kind of weird to anyone passing by, or maybe not? We have several wood drive bases that are cut to scale that represent our robots. Someone recently called it “Wood Coast Drive” we might keep that!

For the last to years, every robot has started out as a little frame, including SubZero here with the wood twin.

The first thing we noticed about this ball during prototyping is that light compression seems to work quite ok. Our roller prototype was designed to see how much compression it takes to sling the ball through our various subsystems to decrease cycle time. Initial measurements say that about half an inch or so works with our little flex wheels but more tuning is required. With that in mind, we started prototyping intakes using some of our old Whiteout (2020 robot) intake copies. Turns out the small flex wheels and nitrile rubber wrapped around a WCP roller work pretty well!

whiteout intake testing

One of our highest priorities is the mid climb. I don’t want to slap a done sticker on this quite yet, but if we wanted to be finished right away with that we might as well be. We created an offseason climber for Whiteout our 2020 robot. This design was actually inspired by Spectrum’s offseason climber but I don’t know if they ever got theirs to work at competition. With our spin on the design, we were extremely successful. The robot climbed every match at THOR without fail and rocketed us to number one with a 2 second lift. The climber is too tall to be legal for this game, but if we lopped off the hook rods slightly, it would be legal and work.

Some details about this device…
whiteout offseason climb

It is a chain driven two stage elevator driven by two Falcon 500s (this we have found is overkill). Maybe Lance can post the ratio, this custom gearbox was his baby. This box worked better than I thought it would. We had our rookies work on it and there were certainly some egg shaped holes.

whiteout climber gearbox

The small air piston and WCP ratchet brake did the trick here. We threaded a small rod, stuck it on a shifter piston, and pushed a screw through it into the pawl. For those designing a brake like this, make sure you put this on the first stage so you don’t need to fight additional torque!

The sliders are the magic bullet for us and I am sure a lot of teams are wondering how they will do some of these custom elevators/telescopes. We 3D printed our blocks. Yep. We are insane. So is the HP 3D printer we have access to through. We are using Nylon 14 and at first we had our suspicions about these but ultimately even if we replaced 5 of them a competition we would still be cheaper in plastic than machining these bad boys. We have yet to replace a single printed part on this device after two offseason competitions and an extremely successful run at both. (it is time to replace a few, but you can see them in the photos working quite well.

As for how we attached the chain? The chain is a continuous loop. We used a WCP chain tensioner with a 1/2" tube running through it, compressed by a 1/4" bolt through the bottom of the main stage (you can see the bolt in the photo below at half extension)

It isn’t the prettiest design out there, but it is simple, effective, and easy for us to use the limit distance function to create soft limits. It will most likely make a modified appearance with some upgrades on our 2022 robot.

Our shooter has also been somewhat copy pasted from what we know. Last season our 2021 robot Subzero was the highest performing robot in NC at the shooting challenges so we decided to take it and improve it. We began by widening it, and giving a couple of options for hole patterns based on the compression test we did earlier in the week. The result was something that was easy enough to slap together, and it taught many of our team members how to tap rods properly.

We used 1/4" lexan and cut these out on our little XCarve in the back.

The pulleys are 1.3:1 if I am not mistaken and we are running two falcons on each side.

shooter concept 1.3

The flywheels we picked are identical to Subzero, but we are using four instead of two to increase the mass of the flywheel. The 4" colsons have been great for us as flywheels!

The resemblance to our 2021 robot is obvious in our design and I saw the robot peeking over as though we were mocking it for being small. We will probably experiment with another “bearing stack turret” since it will only take us a few minutes to design one based off of Subzero. The programming team is working hard on using this robot to master pathfinding for auto runs since the robot is very similar in drive system!

shooter concept 1.4

Are the smiling? I think they are smiling. Our rookies are awesome! We had to put this one together a few times to get it right. A big win as the big shooter looks at it’s older brother undergoing some maintenance as we got ready to strap the finished product onto the earlier prototype.

shooter concept 1.5

We decided to try the middle compression, only about half an inch (maybe 3/4"). Most shooter prototypes yeet the ball so far there is no way those shots will go in on the real field. We dialed our falcons down to a modest 50% to try a bump fire into the high goal and met with success our first shot high at that setting. A 30% shot allowed us to scoot one into the low goal.

From the pad we ran into a very frustrating problem. Our ceiling has a huge HVAC duct right in the middle of our field and there are also roofing nails exposed that we believe WILL catch one of our game pieces one day. We believe a 65-70% shot will land in the high goal from the pad IF we add a mobile hood and scrape below our ceiling. We have a hood design for this on Subzero, but we really don’t want to add a hood if we can control the ball trajectory with just power/speed of the falcons. So far our release angle I believe settled out to be about 15 degrees for a nice gentle arc with mild backspin.

We will post some videos of our shooter and intake tomorrow and hopefully a ton of additional content as we enter Saturday!


Saturday was a busy day for the team!

As promised, the videos from our last test show a high goal, low goal, and pad shot as we tested them. (settings for the low and high goal shots are posted above for anyone curious) We are confident our shooter can hit from the pad without a hood…we are just not confident we can test it inside our current ceiling height, so we started playing with a hood with a sheet of lexan to emulate tipping the ball to get a sharper angle. The jury is still out on whether we need a hood, but we are leaning towards no.

We worked on vision a bit to see what angle we needed to mount the limelight on this years robot. When we finished installing the vision strips we drove Whiteout around the field to try and gauge what angle we could mount the camera at and see the ring on the high goal from anywhere on the field. We need to adjust the angle from last year with some additional testing, but even short robots should hopefully be able to see the ring from any position on the field.

Hopefully that bit of information helps teams without a field debate whether vision is helpful or not this season. From what we can tell so far, filtering that ring out from the ambient lights for short robots is going to be VERY important.

The team continued to refine our climber design, trying a few configurations in SOLIDWORKS to attempt to resolve our current fear, if we intake from one side and shoot from the other then the shooter must clear the climber and the limelight needs to see over whatever climber system we stick on the robot. We created a sled with the climber pivot using an older frame to help us figure out the CG of our robot. We know we will need this as we get closer to a finished prototype.

climber base pivot prototype

The team also kept optimizing the tower. At one point we had a lot of dead zones in the tower that feeds the ball from the intake to the shooter so we decided to pause and do a layout. Going from a prototype to something workable, we found that the most efficient way to rid ourselves of the dead zone was to cut a ramp shape that formed to the shape of the ball. Four jigsaw shapes later and we were much happier with the shape and eliminated the dead zones by sliding some rollers around for a smoother system. The question remains for us still if we need belts or not, and we will probably go that way on the real one although for us it is faster to slap scrap roller chain on these.

tower optimization cad

The next issue to solve will be the side to side alignment that we think we can fix by using different sized compliant wheels. As soon as Fed-Ex coughs up our VERY late package we can test this. (Fun fact our gears for our drive system and some new WCP flywheels were also in this box lost in the void…)

Hopefully I can get someone to post the videos to our channel and update teams on that progress. So far, all of our compression seems to work well at around 1/2".

As we work through the other subsystems, smaller groups have been working on intake devices. We mocked up a common design used by many teams including us last year - a four bar intake. The upgrade we are trying to make here is that we want to go full lexan if possible.

We can cut out many spares and copies of that intake if we go this route, but we need to develop and practice a method of keeping the bearings pressed in during hard impacts. I have seen some teams use the head of a small screw threaded in next to the bearing to keep it from popping out so we will probably test this method soon too.

One of our rookie students was working very hard to get our intake design to a point that we can test. After a long day with a mentor over her shoulder teaching, we had a prototype sans air cylinders ready to go on the robot for testing and optimization. I don’t think she would have imagined a year ago that she could make something like this!

By the end of the meeting, I think almost every team member knows how to install roller chain and I believe I got to blow a few minds up with the age old “sprocket spacer” trick on some loose chains. Yes it works, try it :slight_smile:

Below all that plywood we have a full testbed system ready to merge the wood coast robot into a driving platform. The controls team was working diligently on our practice chassis mule we lovingly call Stumpy.

Stumpy has been a workhorse for us since about 2018. Stumpy is actually what is left of our competition robot Avalanche, but we have a full Avalanche clone sitting in storage. Stumpy has seen many gearboxes, many bumper rail repairs, and many walls from inexperienced drivers. We rue the day we need to retire Stumpy, but until that day he will continue to have our hopes and dreams carried on his tired little frame. Every team should have a Stumpy for programming, wire training, and to act as a prototype platform!

This week we got some winter weather. Anyone else under some ice and snow? Wish you were a Yeti? Hopefully this week after the roads thaw enough we can merge and drive around with our intake, tower, and shooter on one chassis to estimate real cycle times using Stumpy. By the end of week 2, we want to have the climber built for testing and a relatively finished scoring system so we can iterate on it.

Our next meeting is on Wednesday in person, until then we will work on what we can digitally and walk in with some parts ready to go for our Week 2 push! Stay warm and safe out there!

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Looks awesome! Were you able to find a solid fixed output angle that was capable of both a bump shot and launchpad? Or are you planning to trade one of those off for simplicity of not having an adjustable hood

I just want to say I laughed hysterically not expecting to hear slow motion voices in my headphones lol! Looking great you guys!

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We did find the settled angle of about 15-20 degrees! We were adjusting the flywheel power from Stumpy’s Rio (this was a proper test using a robot on blocks) as we ran those tests and not adjusting angle at all. You can see the bot didn’t move positions between our low and high goal shot, although we did slide to the pad to try and emulate that. We think driving the speed of the flywheels using encoders would allow us to not use a hood at all. We are really pushing to lower the complexity here, so that angle you see in the image is our set angle. Currently it is built from just churro standoffs which worked well enough for consistency.

This is a late update, from before Saturday, just to fill in the controls side of the week. YETI’s Controls team has been working on our testing robot: Stumpy!

We got the wiring into safe working order after about a year of sitting still in the shop since last season. In order to test prototype subsystems that we create, we have 2 extra long wires that can power motors outside of Stumpy. These extensions were used to power two falcon 500s that we used for the flywheels on our shooter subsystem. Here’s some links to videos showing demonstrating the shooter.

Just last meeting we got Stumpy to drive, after running into a lot of problems. Originally, we were working with past season’s Stumpy code and trying to fix the drivetrain subsystem. To get past the problems, we ended up creating a new project for 2022’s Stumpy and coding the drivetrain from scratch.

While that was going on, the rest of controls was working on characterizing Subzero, our 2021 robot, in order to get Pathweaver working. We’ve had a lot of trouble with it, but hopefully we can find a solution and have better autonomous this season.