Spectrum 3847 | Build Blog 2024

FIRST FRC Open Alliance
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Welcome to our 2024 Build Blog. This is the 13th year of the blog. Our 2024 robot will be named “Ultraviolet 2024”

2024 Season Resources

Resources

Spectrum Design Guidelines 2024

We created some guidelines from our past experiences and design discussions over the fall. These aren’t rules so it’s possible and likely that we will break some of these but they are here to remind us that we may be going down a bad path if we have to compromise on many of them. These are specific to our team, it’s entirely possible to build very competitive robots while doing things extremely different from us.

  • Don’t do list

    • Don’t be that far off the Meta design
      • If you’re doing something really weird, stop and think hard about it.
      • Does the advantage you think you are getting actually matter? Will it matter on Einstein?
    • No launching during pick-and-place games
    • No scissor lifts
    • No pinch/claw intake
      • Always spinning intakes with active eject when possible
    • No pink arms (Telescoping arm with center pivot)
    • No picking up flat objects at a steep angle
      • Did it in 17 and 18 and it was a mistake both times
    • No ramp bots
      • platforms/forks are okay, teams are very bad at driving up ramps
    • No Mecanum, h-drive, kiwi/Omni/x-drive, tank treads
    • No 6-32 bolts (4-40 and 8-32 will almost always work)
    • No pneumatics (20 motor slots now)
    • No small motors, no brushed motors
      • only NEOs/Vortex/Falcons/Krakens
      • no NEO55, 775pro, etc
    • No motors in rollers/tubes designs (neat but hard to maintain)
    • No lightening patterns
      • Waste time
      • Easier to bend or break
      • Doesn’t save enough weight, use thinner materials instead
      • If you have to, circles work great and our fast (see 1114 2011-16)
    • No bumper or frame gaps (unless rules don’t allow extensions)
      • This prevents your frame from getting bent
      • allows bumpers to take all impacts properly.
    • Don’t chase magic numbers
      • If there is only a single optimized dimension where your mechanisms function that normally means it’s not going to maintain throughout the season. Especially if one direction makes part of the mechanism easier and the other makes another part easier, trying to find that perfect balance is very difficult.
      • This could be an intake opening, a specific hood angle, etc.

  • Fasteners

    • 10-32 socket head
      • Alloy steel, zinc, or black oxide-coated
      • Nylock nuts or Nylock jam nuts, no regular nuts
      • Button or flat head when needed
    • 3/16 multi-grip rivets
      • Steel mandrel, aluminum head
      • Dome or countersunk
    • Use other bolt sizes sparingly only when required by some COTS part or size requirements

  • Use COTS parts effectively

    • Besides cut plates, prints, standoffs, rollers, etc

  • Materials

    • REV MAXTube or other pre-drilled tube of any sizes
      • 1/16” wall 1x2,2x2 when MAX pattern doesn’t work
      • ⅛” wall drivetrain tube
    • 1/16" or .09”, 0.25” aluminum
      • Can bend flanges for more strength
    • 1/16", ⅛", 6mm polycarb
    • ½" & ⅜" Rounded Hex Shaft
      • REV Rounded Hex ½” and 10-32 Spacer stock
      • WCP ⅜” rounded hex (7075)
    • REV MAXSpline shaft
    • Polycarb, PACF filaments
      • Don’t use PLA on comp robot mechanical parts, covers, etc is fine. (It works but we had issues with cracking last year)

  • ⅛in steel belly pan

    • help with CG
    • unless we think we will need the weight in other places

  • Swerve

    • MK4i, L3 (likely)

  • Bumpers

    • ¾" Baltic Birch plywood (don’t use cheap plywood)
    • Solid core round noodles
    • Nylon fabric
    • Large numbers for larger surface area
    • Bolts hold brackets to the wood, not wood screws

  • Use a mounting rail structure like 3538-2023 when possible

    • allows for clean belly pan electronics
    • Allows for mounting intake plates, etc to the corners which is harder with the MK4i modules.
    • Allows for more cross bars if needed
    • Side plates can be enlarged for 2337-2022 style mounting

  • Handles

    • Handles should be integrated into the robot so that’s easy to carry on and off the field and allows more students to lift the robot easily
    • 2023 offseason handles - McMaster-Carr

  • Power transmission

    • High torque/low speed
      • 25 chain, turnbuckle tensioners
      • MAXPlanetary+motor
      • MAX 90s work well
    • High speed
      • Motor pulley pinion
      • 5mm belt
      • 15mm wide when possible, 9mm if space is needed, much harder to rip 15mm
    • No Pneumatics
    • Support the end of motor output shafts with a bearing when possible

  • Shafts

    • ½” hex and MAXSpline shaft when possible.
    • Snap rings are good
      • Light, easy, reliable
      • Better to have snap rings and tapped 10-32 with a washer in the ends
    • Bearings for all fast motion
      • Launchers, intakes
    • Bushings for slow motion is ok
      • Arms, wrists, pivots, etc.

  • Electrical

    • Battery
      • Flat mount battery on belly pan if at all possible
      • Battery strap with metal buckle
      • Zip tie battery connector every match
      • Leads always point up, NEVER to the side
      • 4 AWG wire
      • Blue Anderson SB120
    • Main breaker
      • NEVER OPTIFUSE!
      • Nord-Lock and Lock Nuts ¼”-28
      • 3D printed breaker shroud
    • 8-12 AWG for all motors
    • 18 AWG for device/aux power
    • 24 AWG for sensor wire
    • Inline Wagos for power
      • Kraken ring terminals direct to PDH
    • Inline dual clear lever nuts for can and signal/low current wires
      • 2 to 6 for swerve
      • 3 lever connector for LEDs, other sensors
    • Slim Ethernet cables
    • Mount radio above bumpers and away (6in +) from motors
    • Hot glue Ethernet and non-locking connectors
    • LED strips should be visible from all sides of the robot.
    • Cameras
      • Limelight for aiming
      • Limelight+coral for game piece tracking
      • Fisheye for driver camera, should be able to see intake
    • Sensors
      • Use internal encoders whenever possible, zero at boot and on a button
      • Digital Hall Effect sensors can be used for homing but are not always needed
      • Sensors for game piece detection in intake/path
      • Swerve absolute encoders

  • Aesthetics

    • Primary purple powder coat, some white powder coat
    • Primary white vinyl wrap, some purple
    • White Polycarb
    • Addressable LEDs
    • Sponsor panels

  • Things to consider

    • Robot starting configuration
    • Handles and how we will carry the robot
    • Electronics layout, gyro, Rio, PDH, etc.
    • Wiring paths
    • Tether location
    • Make sure you have a plan to run the full autonomous while tethered, Ethernet reels, poles to hold the cable up, etc
    • Practice full matches, from cart to cart
    • Avoid shock loads on any systems, even if they work during testing, they will eventually cause damage over a whole season
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Do you have any images or onshape links for the 3538 mounting rail structure?

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We go over it in the Design Review of our off-season robot.

You can see the CAD of the off-season robot here: Onshape

The 1x1 mounting rail is here over the swerve modules and how it’s used to mount the slide.

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Great list for working quick. I always ask myself "what would 973 build? "

Some tweaks to your list that I will follow (keeping in mind the robot success goal isn’t Einstein, just blue banner)

I would personally add a box joint or finger joint in there after seeing bumpers last year. 3357 had some good points in the bumper damage thread I think.

Bellypan:

No blind rivets pointing down, no bolts down, no nuts. Just panhead or countersunk facing up. Goal is the keep bellypan smooth.

Don’t rule out a full width intake that allows gamepieces to go under bumpers and picked up (i.e. 2017 gears)

Shafts:

be careful of Maxspline gear bore tolerance, at least when running 1.125" bearings in those bores. I had .010 oversized on an order (I need to bug rev about this again)

Motors:
Don’t rule out the humble brushed 550 or even Johnson PLG motors. They may open up packaging options.

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Oh yea, it’s all starting to make sense now.

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Assembling all those quotes took a while didn’t it…

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Gotta do something to enjoy my free time for the next 1D 13H 4M 38S

… But in all seriousness. Thank you all again for a wonderful resource. Looking forward to seeing the great things produced!!

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What’s the main benefit of having a smooth bellypan?

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Smooth → less likely to get caught on or broken by something it makes contact with.

Likely not a big issue for 2022 and similar years, but a bigger issue for the charge station in 2023.

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I figured something like that, but we’ve never had any issues with nuts and rivets protruding so I didn’t know if we just haven’t gotten unlucky or if there was a more nuanced reason.

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Or the platform in front of the scale in 2018.

Can also snag foam gamepieces that get under it.

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They catch pretty bad, especially this year. If you watch our match videos you can see when extruding bolt heads hit the charge station and our robot jumps into the air. It happened every time we went over the charge station

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You can just at us next time Allen

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Specifically which dual clear lever nut product do you use? WCP-0486? Other?

Any recommendations on ensuring quality, robust connections with lever nuts on CAN? Strip length, inspection for proper wire insertion/clamping, mounting, retention, etc? We are short one blue banner for a CAN connection that failed after a hard impact while using the WCP-0486 nuts. We were not able to find and repair the CAN break location in time to play a 2nd elimination match. The failure was our fault, not the fault of the nut, but we’ve been skittish about the QC needed to make lever nuts work in CAN ever since.

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We get our levernuts from amazon, but the WCP shouldn’t have any issues.

Here is a 2:6 connector
here is a 3:3 connector

This is the wire stripper we use for most of our wire.

The most important thing we have found is ensuring proper strain relief.

We have always followed the recommended strip length on the back of the housing. We also tug test every connection, and there are times where you might have to cut, and re-strip wires if they fail the tug test.

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This is the 2x2 connector we use but it’s been out of stock for most of this year, annoyingly.

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Lab Upgrades

We spent a good amount of time cleaning, organizing, and upgrading our build space over the past few months. Below are some of the highlights.

3D printers

  • Our Bambu Labs X1Cs are now equipped with LightYear G10 build plates; we no longer need glue sticks with PLA, TPU, or PACF.
  • Prusa Minis now have input shaping firmware so they can print at similar speeds to the Bambus and we added wifi modules and ESP-CAMs to be able to wirelessly print and monitor them with PrusaConnect.

Tapping Station

  • We purchased a Vevor Pneumatic Tapping Station and a 10 tap chuck for it, which should make tapping parts much faster this season. It can always have a #10-32 spiral point tap installed and ready for use.
  • We also built a spoil board drill area and T-track clamping area around it. This lets us quickly hold plates down to tap or drill, etc. There are vises clamped to the table for easy workholding as well.

CNC Router Spoil Board and Vacuum Updates

  • We changed our CNC spoil board to have 3 separate sections and T-track between them. We plan to always have a 1ft x 2ft sheet of 060, 090, and 250 aluminum on the router so we can quickly cut parts from the sheet sizes we use the most.
  • We added a crossbar above the router to support the dust collection hose.
  • We added some sheet storage under the router, using a pots/pans holder from Amazon.

Chop Saw Stop Block and Measuring Tape

  • We added a fence, stop blocks, and adhesive measuring tape to the evolution chop saw, so we can quickly cut shafts and spacers.

Laser Cutter Computer Mount and Camera Install

  • We mounted a computer to the laser cutter so we can operate both our laser and CNC router at the same time. Before they were both running from the same machine so you couldn’t set up jobs on both machines at the same time.
  • In addition we purchased and installed a lightburn camera for the laser that allows us to easily layout cut on oddly shaped scrap or engrave on already cut parts.

M12 Tool Storage

  • We built a storage box for our M12 tools. We wanted a way to keep them stored with their batteries installed so they are quicker to grab and return. This is dense so we can also use it at competitions by placing it on a table. (Before we just stored them all in a Tstack bucket)

HDX Organizer Racks

  • We created some simple racks for the HDX organizers that we use for small parts organization.

Powder Coating Oven

  • We purchased a new powder-coating oven from Light Armor.

New Laptops and Laptop Storage and Charging

  • Our school’s IT department granted us 4 new Framework 13 laptops and we reorganized our laptop storage and charging area.
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Swerve Tread

With the increasing talk of 3d printed tread, we decided to test it ourselves. We will note that the angle noted is where the wheel started slipping, so the real Coefficient of Friction is slightly lower than is noted.

Test Process

Test Chasis (67.35 lbs): CAD

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We screwed a piece of field carpet to a large piece of 3/4" Plywood and used that as a tilt table. We then tilted the platform and found the angle at which the chasis started to slip.

Photos of testing:

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Here are our results:

Black Nitrile 3D Printed Spikes no Suspension Treaded Neoprene 3d Printed Waves (White) Slick Neoprene Colsons
Test 1 56 47.8 56.5 48.5 45 42.5
Test 2 57 58 55 49 45 41.8
Test 3 57.2 60 57.3 47 42 42.8
Test 4 57.9 59 51 52 44.8 41.5
Test 5 57.1 55 55 52 45 41.2
avg Angle 57.04 55.96 54.96 49.7 44.36 41.96
CoF 1.542 1.480 1.426 1.179 0.978 0.899

Black Nitrile (SDS)

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3d Printed Spikes (95a)

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Treaded Neoprene

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3d Printed Waves (95a)

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Slick Neoprene (2024 season)

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Colsons (Buy swerve wheels)

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how it wears

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Other cool wheels

Pneumatic Tire

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spikes with suspension

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:eyes:
this is cool

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Super nice dataset, thanks! Did you perform any repeat CoF measurements after the treads wore down? If so, did you notice any change in the results?