FRC 4481 Team Rembrandts 2020 Build Thread

Good questions!

@Justin_Foss with the first proto it was designed such that the colson would hit the powercell before the omni did. Was that on purpose or as first attempt?

I’ll double check on the dimensions :wink:

This is what we’re planning on building today! Sheetmetal just got picked up and almost in the shop. Ready for assembly and hopefully some testing today as well :wink:

The shooter side plates are aluminium but made transparent for the screenshot. The side panels of the hopper will be polycarbonate sheets but not shown in the screenshot.

Side Note: This is just a functional prototype to test the direction we are heading towards. If we’re satisfied with the results this weekend we’ll start detailing.


any detail you can give on the climb mechanism? just a standard 2-stage pulley system or what?

how were you guys able to make the indexer spin?

For the climbing mechanism we made our own telescope system . For the first prototype the students designed a 2 stage climber where both tubes are guided trough eachother with a constant force spring. (dutch suplier)
Atm we’ve started with designing a 3 stage climber with a constant force spring and a control system integrated for the 3th stage so we can do trench.


Cad model is not completed, and proto not intact anymore. But we laser cut our own sprocket driven by a VP gearbox and chain.

What kind of shot range are you comfortable hitting consistently with the neos 1:1 and a 4" diameter roller in the shooter? Do you feel that 23 feet from the goal is plausible?

Do you guys have the CAD published for last year’s robot? I’m interested in your elevator drum.

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4 down… 0 to go!

Well that didn’t really go as planned. The main goal was to have a complete robot up and running by the end of week 4.
Week 3 and 4 were a little rough and chaotic. We’ve never had such an amazing, enthusiastic group of team members who all want to work and participate in the build season. (Usually it was around 20 and this year we’re having 35-50 on a team evening)

Due to this it was a challenge to keep everyone on board and the same page. For example;
people would enter the shop, start working with a couple members on a prototype, send a couple video’s on Slack and then leave. (Making decisions along the way that impact software for example and not telling them about it)

So for the next weeks we’re going to start every team evening with a quick stand up meeting: every subteam lead will have to give a short update. And after every team evening a quick summary has to be given on Slack to inform all the other subteams on the current progression.

Before I officially start on actual updates… firstly:



Metric version of #118 - Everybot 2020

We’ve decided to put our AM14U chassis to good use after our prototyping is done, by building an Everybot. A group of team members has started on re-designing the Everybot in metric units so we can build it here. A good exercise and we’ll end up with a competitive practice robot for driver practice.

Week 4 - Wheel of Doom

We’ve been testing a little more with the no pockets on an angle solution.

This worked relatively good and quite simple. We’ve decided to move onto different storage concepts and see how our week 1 robot will preform. Based on its performance and that of other teams we’ll make adjustments for Detroit.

Limelight + Turret test

We’re going for a static 2 angle shooter as our first concept but maybe we’ll need a turret for worlds. Since the Wheel of Doom was set aside, we’ve had some parts laying around for a nice testrig.

Two students hijacked this together and got it up and running within an hour. (We were all quite amazed)

(Not so amazed by the amazing video recording skills of Joost tho…)

Current Turret plan of approach:

The turret auto-aligns using the error angle given by the limelight. This error is then put into a simple kP controller that calculates the output for the turret motor. We ideally want the turret to be completely self-controlled, so once we get out of range of the target we want the turret to be pointing at roughly the direction of the target, so the limelight can pick it up more easily once we’re in range again. To accomplish this we use an encoder on the turret motor, and a gyro sensor, the encoder and gyro will be zeroed continuously when the limelight detects a target and the turret is inside of a certain error range of that target. Once the limelight loses the target, the gyro will detect rotation of the robot, and using the encoder we can account for this rotation, and roughly align the turret.

They’ll continue working on the turret and then we can decide if we want to swap the current shooter for a turreted shooter.

Software autonomous update

They’ve been working on some auto code. It will be most likely be a combination of motion profiling and limelight for final positioning.

Week 4 - Sheetmetal storage

Some small mistakes were made in the designing so it was a little hacked together but worked quite well.

As other teams might have noticed the powercells stick to everything hence the improvised lexan covering over the wheels. And not to forget duct-tape:

To fully test this concept we’d need the shooter intake wheel to feed out the powercells from the storage into the shooter. This wasn’t designed and build yet but testing this concept gave us enough confidence to keep on working.

Week 4 - Intake

Powercells stick to pretty much everything. Test below was bare PVC on first roller and hockey stick grip tape on the second roller:

Video below used the same Linerless Rubber Splicing Tape as #118 used with the Everybot. (No pipe insulation, just PVC and tape)

The side plates of the intake were aluminium in this version since we don’t have as much lexan and sheetmetal is a lot cheaper for us. Final version will be sheetmetal and lexan for the arms so that it can take a beating on the field.

Tape + PVC + 1 x 775pro + Driving

Dual 775pro #1

Dual 775pro #2

Dual 775pro #3

Folding hopper

We experienced that the powercells bounces back on the top roller. Adding cartboard, sheetmetal, lexan will hopefully resolve those issues. A lot of wobly wobly on this prototype, we’re designing a new version of it for next week.

To make sure the powercells won’t exit the storage hopper while yeeting across the field. It will be tucked in 90 degrees at the start of the match.
After it’s first actuation it will lock off the last 10 degrees so that the next time pulling it back in it only reaches to 80 degrees.
Same as #118 Everybot. (Shown here.)

Our current implementation is as followed:

Week 4 - Shooter Update

To test the powercell path from the 4" storage wheel into the kickerdrum and shooter wheel we designed a new prototype revision. This didn’t have an external flywheel; we could add mass to the shooteraxle.

Shots were a little inconsistent due to being a little to wide internally. I think there was about 5mm, 0.2" clearance on the inside width. Adding cartboard to make it a little more of a snug fit for the powercell helped centering the powercell better.

Our earlier prototype had a flat hood and this one shot with 2 arcs. We felt that shooter with a flat hood was more reliable than the arcs. So for the upgraded design we went back to flat hood and enclosed sides of the exit.

Week 4 - Climber update
We’ve decided that driving on the climbing rung is probably not needed for week 1 but we wanted to proceed on finishing the current proto.

Moving climber horizontal

Moving climber on angle

Climber for now will stick to the 3 stage linear tubes with constant force springs.

The CAD team has made good progression after a long extensive CADathon! The main goal was to have the final drivetrain and storage by Sunday evening and the other sub systems done for 90%.

That way the drivetrain and storage can be manufactured on Monday, Tuesday and start assembly on Wednesday. Then the other subsystems had time until Wednesday evening to make sure all subsystems work properly together in CAD and be ready for manufacturing. We’ll be sending out the parts on Wednesday evening so we can start assembly on Friday and hopefully have a robot up and running by Saturday afternoon.

Specifications for the subsystems haven’t changed much between this update and the last update. So here are just some screenshots of the current status.




Week 4 - Intake
(They’ve had to wait a little until the storage was finished so they’re not as far yet. It will be little less bulky eventually :slight_smile: )


Complete Assembly (Missing Control Panel, Storage walls and Intake currently)

Monday & Tuesday = Production DT and Storage + Finalize CAD from other subsystems
Wednesday = Assembly DT and Storage + Finale check subsystems and start production
Thursday = Production subsystems
Friday & Saturday = Assemble 1 complete robot and DT + Storage for our second robot. Start testing of the complete robot cycle & drive around.

To be continued…


Super excited to hear this. PLEASE share your experience building an Everybot from outside the US. We haven’t done a great job of keeping international teams in mind and want to improve the program on this front.

Also, thank you so much for the amazing resource that this thread is for ALL teams. Not only have you been gracious enough to be open about your design process, but you’ve also found the time and energy to regularly post updates. I’ve loved reading through and there are so many lessons to be learned, both about how to build robots and how to operate a team.

Best of luck this season.


This is so awesome and such a great resource! I wish we (2485) were competing with you again this year at SDR :frowning:
One question: how are you planning on indexing/sensing balls in your magazine both software and sensor wise?


Why did you switch the Omni feeding into the shooter to a colson? Also what is the gear ratio on that?

Hi, it’s always nice to see people sharing about their robot. I have a few questions regarding your new cad system 3DX. Is it great ? What about the collaboration process within your team ? How it performs with a slow connection ? And how did you get the license ?

Thank you for posting all of the work and results your team has produced. I am particularly interested in the WoD versus the single-side motors in your later posts. Your videos and discussion of pros and cons are very helpful.

And we’re back!

After some weeks of radio silence we’re back with some fresh updates! The lasts few weeks of build season were quite hectic! After seeing so many successful WoD robots out there we were kind of feeling sad that we didn’t took ours a step further but it’s definitely cool to see all the other robots out there.

We’d like to give a brief update on how the last 2 weeks of building season went since everyone could’ve seen our performance at LA North. We’ll be updating you all throughout our Buildseason 2.0 where we’ll be working on our improved design to put up the performance needed at Detroit.

Week 5 – Making parts and assembling

After all the parts came in to assemble the robot, it was quickly getting some shape. Firstly we assembled all the separate subsystems in order to test them as separate units. This is all based on our new Unit Philosophy which is a major guideline within the design process of the 2020 robot. The philosophy is based on subsystems that can be tested independently as well as mounted with only a few rivets and bolts. This allowed us to quickly test the separate subsystems and easily mount them on the assembled drivetrain.

Overall the complete robot assembly process took about a single weekend. We are very happy with the final results! Check the assembly photos below:

And of course do not forget one of the most important parts: bumpers.

Concluding the weekend, our 2020 robot was alive and ready for another amazing season. So hereby we, 4481, proudly present our 2020 robot: GURK

Gurk, hanging out with the driveteam at the Los Angeles North Regional 2020

Week 6 – Testing… improving… and more testing….

With a fully assembled robot it was time for the software team to prove their computer magic. The first thing to test; SHOOTING! After an hour of tuning control loops and software improvements the shooter didn’t disappoint. With some accurate rapid fire and wall shots the robot quickly began to feel alive.

After finishing up the full robot code and some practice cycles week 6 came to an end. Which unfortunately meant our robot was going to ship as well. Since our team was competing in a week 1 event (Los Angeles North Regional) and we had to ship the robot overseas. The robot has to ship to the US starting build season week 7. The team flew in a week later, but did some last minute practice and tests on our identical practice bot to make sure no valuable time was wasted.

Practice cycle:

And sometimes we as mentors get a little too enthusiastic (@RonnyV )

LA North Regional

We arrived in the US a few days prior to the event. Luckily, the robot came in on the Thursday before the event, so we still had one full afternoon of assembling revised subsystems on Gurk.

Since we don’t have a workshop in the US we had to improvise our temporary pit a little bit:

Our hotel room:

The practice day started off very rough. When arriving at the event we noticed that there were some CAN issues. Fixing this unfortunately took up most of the practice day. This was quite a bummer, since we expected to have a full afternoon of practice. After all we fixed the robot to be in competition shape, and were able to still play 2 practice matches before leaving the venue. Closing off the practice day we went to dinner together with our friends from The Compass Alliance; #1678!

The qualifiers went quite satisfactory. The focus was to play the front cleanup role and make consistent wall shots every time. The robot operated steady and there were no major fixed that had to be done. In the end we ranked up 4th place, which allowed us to form an alliance with Team #2102 and #6814.

After some intense playoff matches we unfortunately knocked out in the semifinals by Alliance 1 (973, 1678, 4, 5089).

But we were not going home barehanded: we we’re awarded the Team Spirit award. And our student, Rens, also received the Dean’s List Finalist Award!

After all another exiting regional. Make sure you check our regional videos if you want to see more:

Congrats to teams #973 #1678 #4 and #5089 on winning the event. And special thanks team #2102 and #6814 for being awesome alliance partners!

Preparation for worlds

So now we have another 5 weeks before our robot ships of the Detroit again. Which means 5 weeks on developing Gurk 2.0. During week 1 we saw some amazing robots and we took a lot of inspiration on what we wanted to improve for Detroit. Eventually we chose the new robot concept based on a few major tradeoffs:

  1. We do not want to change robot strategy (Front cleanup bot)

  2. We do not want to make major changes for the driver and operator

  3. We want the design to be finished soon, so we can spend more time on testing and improving autonomous

  4. We should be able to quickly shoot from distance (Init line / Trench zone)

  5. We must be able to perform wall shots

Based on these tradeoffs we quickly decided our improved robot concept:


The shooter will be extended to fit multiple (4) balls. Having these balls ready to shoot will significantly contribute to the speed of the shooter, and makes it easy to quickly shoot multiple balls from zones we’re defense is allowed. However, this will mean the robot increases in height. Since we aren’t driving underneath it is important to make sure the CoG is as low as possible so we can quickly jump over the bumps in the centerfield if needed.

In addition to this there will be an extra roller place on top of the hood to decrease the backspin for more ‘laser’-like shots. We’ve taken lots of inspiration from #4414 and #1678 at LA North and were impressed by their shooters.

The initial CAD design can be seen here:

More details on the design will be in next update


Hopper stays the same as we have now. We noticed our hopper still have some struggles when loading up 5 balls. A lower amount of balls will lead to no malfunctioning. (At the end of quals we switched from 5 ball cycles to 4 ball cycles which majorly increased shooting consistency) With the new increased shooter we see no point in changing the hopper since most of the balls will directly be stored into the shooter itself


The intake still had a small dead spot. Because of this, sometimes the balls didn’t come into the hopper, causing extra time making a full cycle. The intake redesign is going to make sure this dead spot is entirely removed.


Some small changes are made on the redesigns of these subsystems. Possibly the Climber will be updated with a hole in the side to perform better maintenance. Also the hook will be improved to be less flexible.

Drivetrain / Control Panel

We are not going to make any changes on these subsystems. Although the current control panel mechanism is going to be fixated on the side of the robot, since we did not use it at the LAN Regional.

The planning for upcoming weeks will roughly look like this:

image (27)

More info coming soon….


Thanks to 4481 for the pick! You guys were performing impressively all weekend, and we thrilled to be on your alliance. Your whole team was a pleasure to work with (and were great neighbors in the pits.)
This is the only picture I got of all our team numbers together:

Looking forward to watching you guys play at Detroit!


We loved being on you alliance, playing with you, and hanging out with you all! Such a welcoming, lively team. I’ll wear my new neon orange hoodie with pride.


I don’t mean to resurrect an old thread but I am curious if any more testing was done on the angled Wheel of Doom concept. I know the season ended abruptly soon after LAN but I am curious if this concept was further explored and if so, what the results were.

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Hi Andrew,

Yeah it’s sad that our season ended while preparing for Detroit last year, but looking back we should be happy we could compete after all. This year we decided not to sign up for the official season due to uncertainties about traveling and even the ability to meet up in person. So we decided to host our own ‘from home’ FRC-challenges for the students. (For example they are now designing a claw/gripper for the 2011 game)

To answer your question, after LAN we were happy with how the other hopper/storage operated and decided not to change the hopper completly to our wheel of doom since that would cause to many design changes. The only adjustment we were planning to make was the high shooter since we couldn’t really fit the climber under the trench anyway and that would give some more space for loading the balls. For that reason i think the video you’re reffering to is one the last video’s we made from our ‘Wheel of Doom’ design. It was a fun one and i’m personally blown away on how good some other teams managed to implement it, at first i was sceptic on how it would work seeing all the difficulties we ran into but once again i’ve been proven wrong.


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