Spectrum 3847 | Build Blog 2023

Faces of inspiration. Well done!



Day 27: Cube Basket

The cube basket actually exists on Alpha now. We were pretty confident it would just be some bent polycarb and hadn’t really tried to solve the problem until yesterday. Today we added a lower basket that goes in front of the bumper during intaking and seems to work well. This setup allows the lower rollers to push the cube far enough back so it doesn’t engage the mid and top rollers and also helps center the cube if we intake along the sides of the intake.

We finally got to change the lower roller to the AndyMark Hex Spacer tube wrapped in ½” ID silicone and it works great for cones and cubes.

Our intake development is likely heading into the final stretch before designing the V1 competition intake. We still want to test REV 2in Compliant wheels on the mid-roller but we are waiting on a shipment for that to happen.

Here are some detailed photos of the current state of Alpha’s intake. We like to use mostly what we have on hand when prototyping so we can move faster. The top roller is a ball launcher roller from our 2017 robot with 3” WCP flex wheels stretched on top. The lower back roller is a spare intake roller from our 2019 robot, the mid roller was one of our very used intake rollers from our 2022 robot. Many of the pulleys used on this were printed in 2017 and just kept around for prototypes like these.

The printed bearing mounts make it much easier to change shafts/rollers since you can remove the whole thing and don’t have to push the shaft out of the bearings.

Sorry for the purple-tinted photos, the LEDs were on for some of the photos.

We are planning to have addressable LED strips up the sides of the robot for signaling our human player, and other robot status indicators.


Where could I find that white silicone tubing?

McMaster links in this post

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Thank you so much, that helps a lot!

Day 32: Design Recap

Week 4 Gallery

Week 5 Gallery


How does the on-the-fly generation work? Is it using custom libraries?

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This uses the fantastic PathPlanner tool and library - PathPlanner 2023 Beta

Here is our current command for On-The-Fly generation, we just got it sort of working for the first time today, so there is still a lot to do and improve.


What angle are you shooting at? Asking for a friend

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45 degrees is the current angle in CAD between the roller centers, I believe.


Day 39: Design Recap

Video Link

Floating Intake Rubber Videos

Setup and Explanation

Video of floating the rubber on to the polycarb tube.


What rubber are you using?

Silicone tubing from McMaster-Carr, this specific stuff is 1-3/8" ID as it’s the largest they carry. Normally going down an 1/8-1/4" of an inch works for most things. So like 0.5" ID for 0.75" OD polycarb/aluminum tube.


Day 45: T-11

There are 11 days until Waco; we haven’t posted much on here but have gotten a lot done. The Controls team has been putting in hard work getting position control of the 4-bar and elevator and the on-the-fly path generation. Today’s blog will be a couple of GIFS and our current control scheme for our drive controls.


Controller Scheme


Modifier Buttons = LB and RB
LEFT Stick = translates robot at all times (no modifiers)
Right stick = stick steer, points robot in the direction of stick
RS+LB = manual elevator
RS+RB = manual four-bar (just in case the operator gamepad messes up, etc.) (up is extend, down is retract); these could be removed or changed if we decide to
Triggers = steering at all time
Dpad up = launch cubes
Dpad down = eject cones
Dpad Left = swerve lock
Dpad right = ?
Dpad+LB = reorient robot
Dpad+RB = ?
A = slow mode
B = zero elevator/four bar
X = fpv mode (robot-oriented drive)
Y = ?

on-the-fly path generation

LB+X= grid 1 left slot
LB+A = grid 1 center slot
LB+B = grid 1 right slot
LB+RB+X = grid 2 left slot
LB+RB+A = grid 2 middle slot
LB+RB+B = grid 2 right slot
RB+X = grid 3 left slot
RB+A = grid 3 center slot
RB+B = grid 3 right slot

Menu = ?
Back = ?


RB = Modifier
LB = Zero System (send elevator and four-bar to down position)
Left Stick = manual Elevator
RB+LS = slow elevator
Right stick = manual FourBar (up is extend, down is retract)
RB+RS = slow four bars
A = spin up cube mid
B = spin up cube top
X = go to cone mid
Y = go to cone top
RB + A = spin up cube hybrid
RB + B = Spin up cube deep launch
RB + X = go to cone hybrid
RB + Y = ?
Left Trigger = cube intake
RB + LT = Cone standing floor intake
Right Trigger = floor sideways cone intake
RB + RT = cone shelf intakeDpad-up: manual intake
Dpad-down: manual eject
Dpad-left: cube LED
Dpad-right: cone LED
RB+Dpad = (Probably cone shelf LED)
Back/select (left side) = re-zero the elevator
Menu/start (right side) = re-zero the four-bar


We have been having a lot of problems with getting tons of dust onto our rollers and having them lose nearly all grip, specifically when we drive with them close to the ground (but not touching).
Our carper is fairly old, and may be producing tons of dust which would not be present at an event, but regardless our rollers lose the majority of their grip after about 30 seconds of driving around with them just above the carpet. It is shockingly fast. Have you experienced similar issues?
We think the majority of it is being picked up because of static electricity buildup in the belts/pulleys/bearings, and any dust along the ground is pulled straight onto it.
For reference, we are using 1" OD rollers (of the McMaster silicon tubing), which run about 1/4" off the ground

Our rollers do eventually get dirty, but we regularly clean them with a microfiber cloth and squirt bottle filled with diluted Simple Green Crystal Amazon.com. This process is done regularly between matches and only takes a few of minutes to clean all of the rollers on the robot.


Our problem is bad enough that we don’t think that just cleaning it in between matches will be sufficient, we expect to see degraded performance within the length of a match. We have some ideas to mitigate the impact, but were wondering if you had any solutions to reduce buildup of dust on the rollers during use? We have tried wiping them off with brushes, better shielding them from the ground, and running them slower, but to no avail.

Bought some similar silicone tube from McMaster and found it cleans really easy. Still decently grippy even when “dirty”.


During events, we regularly wipe down the rollers. We’ve used silicone since 2017 and have found the best solution for us is periodically cleaning with Simple green (non-toxic industrial multi-purpose cleaner). We notice slight performance decreases when extremely dirty, but roller performance returns close to new after wiping the rollers down.

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Day 50: Showcase Video