Spectrum 3847 | Build Blog 2023


You may have already answered these questions but I couldn’t find them in a quick scan of the thread:

  1. Could you explain how you do your 2" roller tubes on your intake?

  2. Do you have a link to the polycarb tube that you use?

  3. Are the hubs 3D Printed? If so, do you have a STL you could share?


I’m not Allen, but here’s the answer to question 1:

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I knew I had seen that somewhere! Thanks!

The geometry for the 3d printed rollers is in the onshape document linked on the first post.

I’m not sure where Spectrum sources their polycarbonate tubes, but McMaster has a pretty wide variety of sizes.


Bumper Numbers & Wrapping Process

“I’d rather have a bad robot and good bumpers [than a good robot and bad bumpers]” - Allen Gregory IV, 2023
Only two weeks late- here’s a bumper post!

Bumper Numbers

We use our laser cutter to cut this adhesive backed material to make our bumper numbers. They’re stickers, so we don’t have to sew anything. They do rub off during matches sometimes so we cut lots of extra sets.


The process takes two to three people. Experienced members usually make and wrap our bumpers to ensure they are of high quality.

You’ll need a staple gun, a hammer, and gaff tape.
Use a hammer to smash down any staples that don’t lie perfectly flat and a flathead screwdriver and pliers to pull up regretful staples.


  1. Cut fabric to size so there’s a few inches of overlap on the inside and about seven inches of overlap in length.

  2. Place the bumpers like this, back side of the bumper on the floor first.

  3. Fold the top side of the bumper down first, so the raw edge faces toward the top side. This is so the raw edge can’t catch on the robot when putting it on the robot. Pull tight and staple down. Staple about ~7 inches or more from the corner so there is enough fabric to wrap it.

  4. Corner time! Rotate the bumper until the corner is in the air. We fold both sides of a corner at the same time, one person on each side. Fold the fabric on the top end like this, so its fold makes a vertical line. The fold should form a pocket away from the corner.

  5. Try really hard to fold the fabric on the other side of the corner to make a 90 degree angle with the first fold. We end up settling for 60 degrees because 90 might actually be impossible.

  6. Once both sides of a corner are folded, hold them in place and flip the corner back to the ground. Snip any inconvenient folds.

  7. Ensure that the fabric overlaps correctly (top side under bottom) before stapling the folded fabric down.

  8. Time for a side. Our bumpers this year have bolts sticking out of them so we cut slits for them. Pull the fabric tight and staple.

  9. Repeat 3-8 around until all the sides except for the first side are finished.

  10. There should be several inches of overlap. Fold the raw edge of the fabric inward about two inches to form a seam. Pull tight and staple.

  11. Tape the inside raw edge down with gaff tape.


Event Recap: Channelview District 2023

Photon #8515 competed at the Channelview District Event.
For those who do not know, Photon is our development subteam geared towards helping rookie Spectrum students. Each year, Photon competes at two district events, but we choose not to compete at DCMP regardless of whether we qualify.

This year, Photon used the Everybot 2023 design and made minor adjustments and improvements to the robot.

A Photon student holds our 8515 mascot, a purple dinosaur named Photon. :purple_heart:



The Photon driveteam holds up their hand signal for “cube” to the human player.

Everybot Changes:

Custom Gussets: Instead of pairing 120° and 135° brackets to make the superstructure angle, we CADed and then routed our own .090” aluminum gussets.

90° MaxPlanetary substitute: “2 Motor Gearbox - Through Bore” from Rev Robotics, we did not use it as its intended purpose, but we have previously purchased it and decided to use it instead of the 90º Max Planetary.

Ballast: Our bellypan consisted of 4 steel plates that each weighed 4 lbs having 1 in the front and 3 in the back which amounted to 16 lbs of steel belly pans. We mounted 40 lbs to the front of the chassis using 2 bolted ¼” polycarbonate plates. This made the robot more stable and lowered our center of gravity which prevented us from tipping over the entire event.

Intake Hard Stops: Our intake arm was not straight, no matter how much we attempted to address this issue. As a solution to this problem, we added two 2” long, ¼” thick polycarbonate plates to each side of the intake to prevent it from getting stuck because the bolts holding the intake together would get stuck behind the superstructure.


Photon went 5-7-0 overall at the event, finished ranked 28th, and was not invited to join an alliance. This is likely contributed to by the fact that Photon allows different students to drive for the first time in qualification matches, which gives us inconsistent results for each match. For elimination matches, however, we ensure that we have the same drive team to respect our alliance partners, knowing that although Photon is our secondary team, other teams do not share that same privilege.

Nevertheless, we are happy to announce that we received the Gracious Professionalism award like we did last year at Channelview 2022. This year, Allen was volunteering as the LRI at this event, and because it lacked volunteers, some Spectrum students helped Allen manage the inspection station to help teams get inspected and worked with teams to make their robots become legal. We also had other Spectrum mentors and alumni volunteer at the event as the FTAA, Field Resetters, Official Scorers, and Judges.

Failures and Fixes:

Failure: Arm was not able to move well during a match.

Fix: The hex shafts for the pivot on the arm were slightly too short which made it able to overtighten and become stiff. We loosened the bolt slightly to allow it to move more easily. We will be making two new hex shafts for the pivot for the Houston district event.

Failure: Throughout the competition, we had trouble balancing on the charge station. This put our robot at a disadvantage since we did not have the opportunity to get points from the charge station. The drivetrain drove far too quickly and was too sensitive; the controls did not aid the cause.

Fix: We added a new button on the controller that, when held down, will significantly slow the drive speed for more accurate balancing on the charge station.

Story Time:

On the first day of competition and for whatever reason, there were hardly any inspectors (there were four in total after a couple hours after the pits were open). So, two of our Photon members decided to spend their valuable hours managing the inspection spreadsheet, weighing robots, and sorting each teams’ inspection folders. At the end of the day, the two students nearly completed all the teams’ inspections.

At the competition, we experienced some issues and we thought that it was due to faulty batteries or electrical problems. After further inspection, we realized that the charge on the batteries were WAY too low (130% is good and the battery was at 90%). We checked all of the batteries and they were significantly low on battery, which prompted a mentor and a student to check the power source and find that the entire charging station had not been plugged in the entire day. We then quickly asked the 118 electrical mentor for a battery and proceeded to win the next match we were in.

Thank You’s

Thank you to our sponsors REV Robotics, Solarcraft, Inc, the Gene Haas Foundation, Analog Device, Texas Workforce Commission, Intuitive Foundation, International Society of Automation, Houston Chapter, QAD Works & St Agnes Academy & Strake Jesuit College Preparatory.

Thank you to all the volunteers that helped make Channelview an awesome event.

Channelview Photo Gallery Link


We Love the “rookie” team! The concept of having a team for new members to build, code, do electrical, basically build up the confidence and grow the team as a feeder team is great! It is an awesome Idea that helps grow the main team while treating them as their own team! And for the record…on their own…they are a force to be reckoned with! Y’all have developed that program very well!


Someone referred me to you guys saying you have a CAD for wheel locks on a swerve? Could you send the STEP for it, or direct me to where it can be found?

Can you explain what “new cable state” is? We had a mysterious CANivore failure last year. Our best guess at the time was a that it failed due to a bad USB cable. Maybe not getting the correct power, so we added external power in addition to USB.

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I think that was a typo, it’s supposed to be “no USB cable” state. I believe it was a double-blink red light, but either red status light pattern means the device didn’t initialize properly over USB.

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I’ve been collecting data on team drivetrains for all events this year on this thread and I’m missing data for Waco and Channelview. It looks like Spectrum was at Waco and Photon was at Channelview so I’m reaching out here to see if you all have any data you’re able to share publicly.

Thank you,
Brendan Manning

Our Photo Library should contain photos of all robots at the event.

Here are more specific links to the libraries:



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Thank you!

Rubber Tread

We have been using rubber tread on our comp robot all season. To make it, we cut sheets of rubber on our bandsaw, match drill holes into it, and bolt it onto our wheels. We have not needed to replace them yet, although they do require cleaning once in a while, like any other tread.
Link to rubber


Curious what led to going to smooth rubber vs the common roughtop profiles?


The rough-top was wearing out rather fast, even with the black SDS, we could go one event with it but it was very worn during playoffs. This rubber has held up much better. We have replaced one tread that was damaged when a center column bolt on a module loosened and it cut through. Otherwise our practice bot and comp bot have been running the same tread for the whole season so far.

It also helps that it’s much cheaper then the cut and drilled SDS tread we were using before.

We have kept a backup set of wheels with SDS tread since this will only be our 2nd event running the the rubber, so if we need to we can swap back, but so far we don’t think we will.


We considered doing something like this with our kits but ended up making custom hubs for colsons wheels. Have been happy with the results so far.


Do you have any details on how you made the custom hub?

I think we have a drawing of the hub, I’ll take a look this evening.

We more or less had to remove all the plastic hub in the wheel up to the rubber on the lathe. This was a process to get right, it’s tricky to hold the wheels in the lathe.

The hub itself was turned on the lathe from round stock. We matched the bearing geometry and through bore on the SDS wheels. And the hole pattern was done on the manual mill, our DRO has a circular hole pattern function.

The trick was getting everything dialed in so that the bevel gears stayed where it was supposed to be.


Thank you very much for sharing!