Spectrum 3847 | Build Blog 2023

We had some earlier ones that we tried with limited success and it’s not a top priority for us. Centering the game piece is useful to an extent but we have seen plenty of teams in past pick and place games do the final adjustments by their driver. If you watch video of 3310-2017, 1619-2017(& 2018) and other teams with a wide dust pan style intake they were able to score very quickly by having their drivers adjust to holding the game piece off center.


Thanks for the response. I know in a previous reply one of your mentors talked about how your sushi rollers cut one of your cubes. How did they cut your cubes and are you looking into switching to 2" wheels for the bottom rollers?

I don’t think we have any pictures, but the cube seemed to wedge between the sushi rollers, and the rollers pinched it. One of the cubes has grill marks on it from the pinching. Our current bottom roller is just a hex shaft with silicone over it.

Adding on the edge of the sushi roller would spin on a cube and be able to splice into it.


Day 17 & 18: Week 3 Design Recap

Drive over the cable bump video

Drive up the charge station video

More can be seen on our Photo Gallery Week 2 and Week 3


Day 19: Elevator Rails and intake testing

Intake Testing

We had some of our best intake tests today. One of the key points in an interactive design cycle is when you begin to understand what can be removed not just what can be added to allow the system to keep working but to make it simpler and more robust.

Yesterday Alpha’s intake had 3” compliant wheels on the top roller and launcher. Today we swapped those for 2” polycarb and silicone rubber (these are the hood rollers from our 2022 practice robot).

This test setup worked very well and allows us to build the intake lighter, simpler, and make it less expensive. This is just today’s version of the intake, we expect it will change many times over the season and probably before next week but it’s at a good progress point.

The current intake can

  • Intake cubes from the floor in the full down position.
  • Intake tipped-over cones from the floor when the nose is slightly pointed at the intake and the flange is inside the width of the intake. We estimate we have around 150 degrees of intake range on the cone. With training, we believe this should be good enough for our pilot to use this as an efficient loading option from the loading zone.
  • Intake standing cones if the intake/four bar are set to the correct height. The current intake is pretty height sensitive to standing cones. We need to be within in about a ¾” height window for it to intake well. This should be good enough for us to intake cones from the Human player shelf.

Things to experiment with

  • Intake from the single substation?
  • Improve storage geometry to make sure the cone tip always goes in the intake so we aren’t holding cones tilted up.
  • Ensure our grip on the cones is firm enough so we never drop a game piece.
  • Improve scoring geometry on high and mid posts.

Intake Standing and Tipped Over Cone

Intake Cube

1/25/2023 Intake Specs

  • Lower roller is just 1/2" hex with silicone tube floated on top.
  • Top roller is a 2" polycarb with silicone tube floated on it around it (actually, it’s just our practice bot hood roller from last season).
  • Gap between the roller surfaces is around 4.75" in these tests and roller C-C is at a 73° angle from the floor.

Elevator Progress

We cut all of our elevator rails for the practice robot and competition robot. We also began laser cutting some of the additional parts.

WCP Inline Clamping bearing blocks are being powder coated, as are The Thrify Bot Elevator Gussets we will be using on the elevators.



The suspense is killing me /s


What does the third (highest) roller do in this design? From the videos you posted it looked like it rarely interacted with the game pieces on intake.

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That’s system #5 our launcher. In its current form, its primary purpose will be to launch cubes from behind the charge station to the nodes. The main idea is to help us get cubes quickly into our community during and immediately following auton. This should let us get some fast cycles, increase the number of game pieces scored in the grids, and make it faster to get to 4/5 links for the RP.

It may also allow us to launch cubes into the high and mid nodes without raising and lowering our elevator, which could save time on our cube cycles. This won’t be our focus until placement time is the highest priority area we need to optimize our cycles but it may be nice to have the option when that time comes. Taking a second out of 4+ cycles may be enough to get one additional cycle per match as we get deeper into the season.


Do you have a McMaster part number for the tubing on the 2in roller? It looks like the white silicone 35A tube only goes up to a 1.375ID, are you stretching that over the 2in roller?


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Something something… 20 lbs of it in a 5lb something something.

Seriously - stretching this tube is hard.

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We have just been using left overs from last year, if we have to do it this year I’ll try to get a video.

@AllenGregoryIV do you have any insight into how much this tube stretches in a general sense? for example, what diameter do you think would work for a 1in OD intake roller?

also, how grippy is it? similar to the low duro green andymark compliant wheels?

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I can’t speak for 3847, but in previous years we’ve used 1.25”ID .0125” thick black tubing on 1.25 OD round aluminum tube, and it stretched slightly when we put it on. For 1” OD tube you would probably be fine with 7/8” or 1”.

This material is pretty grippy which is nice, but it collects alot of dust and debris which reduces the grippiness. we never had any issues though.


what material would you say the grip is comparable to? similar to other soft frc urethane wheels?

We normally try to be an 1/8" down for 1/16" thick silicone (so 7/8" for 1" tube) and on diameter for 1/8" thick. As you get smaller you should probably be on diameter since the percentage of diameter stretch would be more.

We have to do 1-3/8" for 2" rollers because that’s the largest size, it works but it’s not easy.

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It’s been a while since i’ve physically observed this myself, but probably closest to 60A Black Flex wheels from WCP if i remember correctly. the thing is, it doesn’t really flex at all since the tube is rigid. the rubber material itself may feel similar, but it won’t necessarily be squishy.


Day 20-22: Intake and Practice bot


We experimented more with the intake these past two days. We have added a second roller to the bottom to better guide both the cone and cube into the correct position for transporting across the field. This lets us pull the nose cone up more and stops the cone from diving down and being held in an incorrect position for scoring. Other experiments can be seen in the photo gallery including a hard wooden floor that helped guide the nose but reduced the floor cone intake abilities.

Practice Bot

Practice and Competition bot; drive and elevator MAXtube rails were powder coated. We started assembling the practice bot elevator.


Taking some inspiration from James and FRC#95

What questions do you all have that Spectrum can help answer? Anything we have posted videos of that need more explanation?