FRC 4481 Team Rembrandts 2020 Build Thread

Welcome to the Team Rembrandts 2020 build thread, presented by #openalliance.

This will be the start of our 8th season after having a successful 2019 season. Last season we learned a lot by playing more matches than usual, talking to a lot of teams, trying to improve designs in between events and getting help from teams locally before the events. Because of this we learned our lessons and decided to shake things up a little for the robot design and build season approach.

We noticed that while your team progresses in multiple elimination phases, you’re pushing your robot to its boundaries causing to break stuff and certain required maintenance tasks you didn’t think of during the design phase. Based on our 2019 season we’ve set some objectives for the 2020 season, to make sure we don’t make the same “mistakes” as we’ve done in the past.

We’re new to being completely open during the build season, we usually have some videos or a couple posts. For 2020 we’re excited to join the #openalliance and will keep up this build thread. Hopefully being informative, extensive and iterative for everyone within the FRC community. We’d love to share our experiences and get your feedback so we’re both learning.

We’ll be meeting on Monday, Wednesday, Friday evenings and on Saturday the entire day from 9:00 – 23:00. Throughout the weeks we’ll do our best to keep this thread live and share our progression through posts, documents, video’s, CAD files.

We’ll be designing in SolidWorks and using the new 3DExperience (3DX) platform from SolidWorks. Within 3DX we’re allowed to design in CATIA xDesign, this is an easy to use web application so you can design without your browser. 3DX allows use to share models through a URL which are viewable externally without an education or paid license.

Our design methodology is based on the theory of knowledge-based product development. Together with the help of our partner CADMES we’ve designed a workflow which we’ll try to follow during the build season. In the first week we’ll elaborate on our working process and structure to give a better understanding on the way of working.


  • Sheetmetal drivetrain which is designed for manufacturability, assembly and maintenance.
  • No more welding, only rivets
  • Adapt a modular design philosophy which will allow for easier upgrades and less robot-downtime in between changes.
  • Being able to add functionality in between our week 1 event and Detroit championship.

We’re excited for 2020 and love to share it with you all!


We have waited many long years for another team to do a build thread. This is great! Thanks for stepping up!


Here is a recap of our kick off weekend:

General design approach
We’ll receive our KOP on Thursday, hence why we’re taking a more detailed approach for week 1. We’re not making any strategic design decisions throughout the build season, only getting rid of absurd ideas like triple climbing. The eventual goal is to end up with a hybrid robot at the end of world championship. We won’t reach the full hybrid, heavy cycle robot in just 4-5 weeks.

To make sure we show up well prepared to our heavily stacked week 1 regional we’re aiming at robust consistent robot which has had plenty of practice time at home. While practicing working on upgrades and fine tuning sub systems and if they’re completely ready before week 1 they could be added.

The design strategy for this season will be to only put the drivetrain electronics, pdp, vrm, pcm, roborio, battery and compressor if needed in the drivetrain/bellypan. All the other motor controllers, wiring, sensors etc have to be mounted on the module/subsystem it self.
To explain this principle and design requirements we’ve made a couple explaining slides in a presentation:

This one sums it up pretty neatly:

To make sure we’re able to work in this way and design sub systems we’re taking on a different working method for the sub systems. We’ll be designing the robot using the principles of lean product and process development/knowledge based product development. We’ve written an article on this application within FRC.
Throughout the week we’ll explain a little more on this method since it will become more clear with proper examples while prototyping.
2019 - Koomen_Visser - Application of LPPD in FRC - Final.pdf (397.2 KB)

We’ve divided the robot into 6 major sub systems, not in order of priority:

  • Drivetrain
  • Intake
  • Storage/sterilizer
  • Outtake
  • Climbing
  • Control panel

Initial breakdown of the game and robot can be found in this spreadsheet:

Tab1 - Robot Skillslist:
We started with breaking down the game in every single function/skill the robot could preform on the field, the list is generated by separating the team in sub teams and eventually pitch and add onto the entire list.

Tab2 - Scoring analysis:
After that we’ve done an scoring analysis on the importance of scoring powercells vs. climbing.


  1. Climbing is key. 25 points for solo climb plus 15 if level, with potentially receiving another RP if our partner climbs and we level the switch.
  2. To equal climbing score (25) with powercells you either need: 4 outer power cycles or 5 bottom cycles.
  3. Reasonable for 4481 for week 1: between 3 to 4 full court cycles. Low = 15/20 points, Outer = 30/40 points.
  4. A outer 3 ball auto = 12 points which almost equals 3 low goal cycles > Outer circle outer is very important!
  5. Reaching stage 2 in week 1 will be less common making the control panel activation les interesting but definitely needed for worlds!
  6. A reliable climb is worth investing a lot of resources in (time etc).

Tab3 - Climbing analysis & Tab4 - Intake analysis:
A quick run down on the first requirements

Control panel, outtake and storage/sterilizer will be worked on at today’s meeting. We’ll be looking at shooting the powercells and a 2 powercell wide intake.
A update from today’s meeting will be posted tomorrow!

We’re going for a 8wd 6" pneumatic tank drive out of sheetmetal, dead axle.
Using the 6" WCP pneumatic tires and designed our own hub.

Dimensions are 650 x 800 mm. Which is ± 25.6’ x 31.5’.
Check out the design below, this will be hopefully manufactured before the next weekend so we can bend and assemble it on Saturday during the day. We’ll also build the AM KOP drivetrain for prototyping.

Currently geared for 14 ft/s with a 12T pinion gear on the NEOs. We can switch to 11T or 10T if we want to gear it down but we’re currently looking at flying over the field dukes of hazard style in 4-5 seconds.

Wheel assembly

It will be a combined out of flat sheetmetal and a 3D printed hub out of polycarbonate/nylon/cpe. We’re receiving our wheel order from WCP on Wednesday and these prints will be done on Wednesday as well.

The dead axle design allows for easy maintenance on the wheels and the eventual hubs will be printed in 2 different colors so we can see which wheel has to go where depending on the amount of sprockets.

This is as far as we’ve gotten at this time!
Goals to accomplish by Wednesday:

  • Designs in progress for all the prototypes we want to build and test on Saturday. We’re trying to design our prototypes with a couple features we can test with the same prototype and test + document the results hence the design takes a little longer.

  • Have everything ordered at the vendors and sponsors to make sure we have 2 drivetrains up and running by Saturday.

  • Have a clear goal for what we’d like to build for week 1 and the level of required performance.


WEEK 1 Update

Update time! Although we were a little quiet on chief delphi, it’s been a busy week. We received our kit of parts on Wednesday which carried 5 powercells in total. As an international team you have the privilege to opt-in for this feature. FIRST wrote about this in a previous blog and have been doing it for a couple years now and we’re highly recommending it to others! You can read the blog for more detailed information.

Having 5 powercells enabled us to start working on the most important subsystem of the robot: storage/serializer. All depending on your requirements but intaking seems rather doable, shooting won’t be a huge problem but the system in between the intake and shooter is what might cause a lot of headaches for teams. (At least something we were worried about from the beginning :wink: )

Strategy & Robot Concept
We haven’t made any permanent decisions yet.
We do have some general take-aways of what we’re currently thinking:

  • Have a wide intake and do ball separation/serializing within the robot. (Preventing the powercells from rubbing together in your intake)
  • Try packaging the designs in a low trench robot but it shouldn’t backfire the build/design progression.
  • Decide on our week 1 strategy and robot concept at the end of week 2.

At the end of week 2 we’ll narrow down our decisions and strategy for week 1. This could mean we’re not comfortably enough with shooting from the trench for week 1 and build a robot that could do a rapid close by/wall shot only. This doesn’t mean we’ll give up on the trench shot but it could be a upgrade for Detroit World championship.
Maybe we’ll have a working trench shooter we’re comfortable enough before week 1 and we can take it with us on the plane and bolt it on at the regionals!

We’ve seen some ball jamming in some video’s of Robot in 3 days, mecanum intake prototypes, CD7 intakes. This leads to our current thought of an over-the-bumper intake which is as wide as our robot width.

Usually we use truck vinyl for our bumpers and since we prefer to intake over the bumper we did a test with our bumper material vs. the standard andymark fabric.

4481 Bumper Material:

Andymark Bumper Material (Used in 2013):

Distance between the bumper and intake wheels were similar in both videos and we didn’t feel any noticeable difference. This meant we could prototype on our own bumper sets we had laying around.

Intake Concept 1

By a linear movement a 4 bar pops out over the bumper with a plate (possible added roller/wheels) on top for the human load.
Complexity might be a tricky one with this concept but it has potential.

Intake Concept 2

Not having to worry about centering the powercells within your intake is nice and “easy”. Rollers, wheels, maybe even some PVC would do the trick.

Intake Concept 3

Here we cannibalized our 2016 intake and held it more vertically.

As you can see it’s two rollers with orange polycord in between, by holding it vertically we wanted to test if the ball transfers up vertically.
Basically to create a similar (scaled) intake as 125 had in 2017:

Eventual design and further prototyping will be depending on the storage/serializer designs. To be continued.

The storage will have to serialize the powercells towards the shooter. As you’ve seen the powercells are sticky and difficult to work with, getting them into the shooter at a fast consistent rate will be difficult.

Storage Concept 1

This idea was based on a video and prototype of #6135. The gap between the bottom rollers is greater then the diameter of the ball and the two belts are spinning opposite directions, the whole hopper is on a angle to the opening.
Looks promising and easy; feed consistency is little unpredictable.

Storage Concept 2

This could be a flat solution of transporting and packaging your powercells in the robot. Could be sensitive for jamming at higher speeds and total packaging in the robot might be difficult since it’s long and wide.

Storage Concept 3

This idea was based on the storage system of #217 in 2006.

This wheel could be spinning slowly while intaking so the powercells divide among the pockets. Hence we’re looking at a 125 - 2017 style intake to transport the balls from the ground to the top of the serializer so they can fall in by gravity.

We’ll be working on building this from sheetmetal next week to do a proper new test run on a drivetrain + intake.

The shooter prototypes we’ve build are shooting similar as other teams have posted videos of. We’ve decided to design a modular test shooter on which we can properly test and gather data.

(No it won’t be a 12 neo shooter :smiley: !)
CAD is still being worked on but with this shooter we’re able to test multiple features:

Shooter variables which we can vary and test with:

  • Speed/power (Can test with 775pro or Neo, 1 or 2)
  • Compression
  • Vary different wheels diameter (4" and 6")
  • Vary different wheel widths
  • Different type of wheels/material
  • Add a flat hood or guide rails (+ different type of materials)
  • Angle vertical of ejecting the powercell
  • Shooter will be able to be mounted at a passable-trench-height and 45" height.
  • Flywheel hood set-up vs. two sided shooter

We’ll be working on a extensive test plan for next week so we know what variables combinations we need to test to make proper design decisions.

We’ve been looking at different locking mechanisms and being able to “drive/move” on the switch.

This was a test with our 2017 robot.

For extending we made a small mock up of a #233 style linear-stage-arm. The mock up was a scaled version of the #558 2016 style climber on their re-build at worlds.

It’s tubes that slide in to each other, powered by a winch and flat torsion springs. By releasing a pin/pneumatic cilinder the torsion springs will pull out the tubes and we can winch the robot up.

This year we’ve chosen to not opt-out for the AMoneforyou drivebase. We’ll be using the drivetrain for prototype testing and eventual driver practice. (Defensive play on our own robot during cycle practice)

Besides the AM14U we’re wrapping up our own drivetrain. The hubs came out neatly, 6" WCP tires with a 3D printed hub and flat sheetmal. Shafts and parts have been manufactured this weekend and the drivetrain should be up and running tomorrow or Wednesday.

Plan for week 2

  • Post more often :smiley:
  • CAD the shooter proto and storage to do further testing
  • Work on a intake that can transport balls to the storage
  • Start designing a climbing mechanism

Could you post some more photos or drawings of the rotational hopper?

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Some of those intakes are looking very familiar… Love the integration of the loading station and floor intake in one mechanism!

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If you go to the thunderchickens’ website and scroll the media gallery to 2006 there’s a cad picture there.

As @Duncan_Macdonald mentioned:
This is the picture we’ve based it on. I’ll snap a picture tomorrow of the cardboard version.

We’ll be working on the CAD of a sheetmetal + 3D printed version. Once that’s finished I’ll definitely get it up on here as well!


Are you guys thinking the rotational indexing system works best? (From current testing results)

I love how well the serializer prototype works. Definitely something we’re going to investigate. Thanks for sharing!

I think high volume serialization is going to be a highly overlooked robot feature this year for a lot of teams. High throughput into any goal you choose is going to be key.


We are going to follow up on it but it’s big in volume and might be complex in the end. We’re working on a CAD version out of sheetmetal and hopefully have that up and running by the end of this week. Based on that we can decide if we’re going to proceed on it or need something smaller and less complex.

But results so far look very promising due to the high feed rate and consistency it can offers. Besides complexity of this serializer there is another very important factor: getting powercells from the intake into the pockets is something we can’t oversee yet.

More work to be done!


Here is a picture of the current setup. We’ve been working on the CAD today and trying to make it smaller but it looks like geometry and decision wise we already had a lot of stuff right the first time.

We didn’t finish it today so it should be done by Wednesday so we can laser cut it in Thursday and Friday evening assembling :ok_hand:


I love this. This was my first thought when it came to a hopper serializer combination. I strayed away from it though since I I thought it would take up space. After seeing how yours shot out of the middle, I am now once again interested. On your competition robot, how do you intend on rotating the serializer as that seems to be the trickiest part for me to understand?

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Thinking about aproaching indexing in a similiar way… out of curiosity what is the purpose of the omnis that hang out over the spinning bit?


I believe that’s how they are going to power it, using the surface of the balls as they pass underneath

What are the dimensions of the hopper and the feeder tower? My team is looking to build something similar but we’re having issues making it compact enough to fit on the robot and would like to know the size of your prototype for reference.

This feeder/hopper is my favorite design I’ve seen. I’m hoping we end up with something similar.

So our team was trying to think about this kind of a “serializer” mechanism but some of the problems that we thought about was that at minimum it was taking up around 23-24 in circular diameter around our robot which was a lot in comparison to some of our other ideas. This also meant that there would need to be a lot of thought going into the packaging of the climb. In addition to this one of our “nice to haves” was loading at the loader station. While this may not be a priority for your team it is still something we considered and with this type of mechanism it may prove to be difficult but definitely not impossible to have each ball go into the correct spot. Finally you touched on the point about loading from the ground intake being difficult but not impossible

Please Note: These are just some things we thought about in our prototypes of this mechanism… Im sure that with some smart design choices it can be done and made to work very efficiently.

You could do something similar to 971 in 2017 where you could spin the serializer the other way to sort the balls into each of their respective racks.


Okay don’t ask those difficult questions yet. :wink:
We can always power/turn it by running a wheel against the outer wall but that’s not the best and neat solution.

Currently we’re thinking of laser cutting a big sprocket for the bottom or mounting the tower to the outer race of the bearing and the pocketed-ball-ring to the innner race. That way we could mount a sprocket in the middle of the hopper underneath and drive that or belt + pulley. Although that will add extra complexity.

For the first proto this week we’re going to power it by spinning by hand and we’ll look into it afterwards if we continue with this prototype

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