FRC 4481 Team Rembrandts 2020 Build Thread

Just wanted to say it’s the 1/2" ID that is important. You can use different OD and change the geometry to get similar performance. That tube you linked is pretty expensive and there are alternatives.

1 Like

Week 2 Recap Video:
2 weeks down, another 2 to go! We’d like to have our robot up and running within 2 weeks from now so we can start driver practice and software development.

The week 2 recap below shows the prototyping and current concepts we’re working on!

New week 3 update will be posted tonight!


Week 3 - Update 1

WoD - Wheel of Doom or Wheel of Death?

Monday during the team evening we’ve given the WoD concept once last try to succeed and if we weren’t happy enough by it’s performance we would move on to the different concept.

Anti Jam Code - 1 Powercell

Anti Jam Code - 5 Powercells

No Pockets + Omni

No Pockets + Brush

No Pockets + “Spinning” Omni

WoD Decision Time:

  • Does it work? - Yeah-kinda-ish

  • Do we like the performance? - Dumping 5 powercells can be tricky but intake a sequence of powercells is doable

  • Is it fast enough? - Full field cycle, yeah probably. In the clean up roll/close shots, probably not yet

  • Do we already have a shooter that can handle 5 balls in ~0.5 second? - Nope not really…

  • Are we confident enough we could design the final iteration now in order to have a working robot within a week from now? - Probably not

  • What other sub systems are depending on the WoD? - Intake & climbing heavily; powercell intaking over the bumper vs. raising it higher to roll/dump/fall in the WoD and fitting a shooter & climbing in the middle of the WoD will be difficult to package. Shooter and Control Panel are trivial in a way that the Control Panel system can be integrated somewhere in both concepts. And the shooter has a mounting point where a powercell will enter so should be able to fit on both concepts.

The WoD draws lots of attention and interest within the team. We’re in love with the concept but we don’t feel we are far enough in performance to use it for week 1. Since all other subsystems depend on the WoD so much we decided to go for a “safer/easier” concept route which will allow the team to keep working on subsystems.

The WoD will be continued by a couple students and mentors. We’d love to have it working at some point that it’s fast enough and we’re happy with it. It might end up on our robot for Detroit Worldchampionship :wink:

Current WoD ideas are to move the shooter away from the middle, creating space in the center for a smaller column/tower and to possibly mount the climber. The shooter could be on the back or above a powercell maybe and by slightly tilting the WoD the powercells will roll towards the back creating space in the front.

We noticed that dropping in 3-4 powercells is easy but getting the 5th in position is difficult. See current idea below:

To be continued…

We will be proceeding with the concept below:

General Features:

  • Pivoting intake - #254 2017 style:
    2 x 775pro 4:1, 2x 40mm (~1.6") OD dead axle rollers.

  • Storage - #6135 2020 style:
    3 x 3" wheels. Swappable between colson or compliant wheels to test. Wheels will have different ratios to make sure the wheel closest to the shooter hole will spin faster than the outer wheels. Storage slope of 15 degrees and 4" wheel to suck the powercell through the hole into the shooter

  • Shooter:
    Offset to the right of the robot. 2" OD AM Stealth 4" wide kicker drum > individually powered by a 775pro. Shooter drum will be 4" OD, fairlanes or AM Stealth wheels and a external flywheel eventually powered by 2 NEO's 1:1. 2 position hood with ~15 degree angle and ~60 degree angle > Wall shot and longer shots with varying RPM

  • Climber:
    Centered in the middle of the robot. 2 or 3 stage linear tube. Testing this weekend with 2 stage, string and spring/tubing concept. Similar as the #118 Everybot 2020. Eventually package it into a 3 stage arm with constant force springs winched through a custom neo gearbox and a ~ 25mm/1" drum.

  • Control Panel:
    Pivoting wheel which allows to be tucked down to driver through the trench. Rev color sensor from below

Other decisions:

  • If driving below the trench hurts the climbing capabilities and packaging they’re allowed to exceed the trench height for week 1. All other sub systems need to be designed to be able to drive underneath the trench.
  • Switching from 6 NEO Drivetrain to 4 Neo Drivetrain. With the compressor and Limelight plugged in the PDP we were cutting it very close on PDP slots. 4 Neo’s will be plenty of power and giving us the capabilities of adding a extra kicker motor for example.

That’s it basically in a nutshell.
The team has worked hard to CAD the entire robot in a couple days, hopefully have our prototypes up and running by this weekend to have a better and improved integrated version of the one pictured above.

I’ll post screenshots of the CAD once it’s ready. :+1:


Will you guys be powder coating again this year? Loved how clean your robot was at San Diego regional last year.

We’ve been annodizing since 2014, we did the entire robot from 2015 untill last year.
The company who partnered with us throughout the years has grown enormously.

In 2014-2015 we could walk in, drop of a box with sharpie letters: black and another with orange and pick it up the next day. Throughout the years their processes have become more and more digital and advanced plus an increasing amount of work on their end of course.

Last two seasons it delayed is a lot throughout build season, sometimes by 3-4 days/team meetings.

This year we’ve said we won’t be annodizing/powdercoating unless we have a partner who can run parts within 24 or max 48 hours.
It looks like we’ve found a local company that could do powder coating for us… Our biggest priority is performance and then esthetics. (Atleast that’s our new goal for 2020)

So if we’re confident enough with our robot at some point and still have time to powdercoat certain subsystems then we will. Otherwise probably not…


Quick question: is it necessary for the first colson wheel (the one closest to the omni in your setup) to touch the first power cell? Or would it be perfectly fine to just have the omni shoot the first power cell out and then have the colsons agitate the ball?

Also, how big was the prototype, length and width wise?

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.

1 Like

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.