847 PHRED - 2023 Open Alliance Build Thread

Hello, FIRST/CD community! FRC 847 PHRED, is excited to announce that we are joining the #OpenAlliance for the 2023 season, Charged Up!

We were founded for the 2002 season and competed until 2020. We missed last year as we weren’t able to meet for most of 2021, and didn’t have the budget or members to compete in 2022. We are from Philomath Oregon, a town in the Willamette Valley of 6,000ish people. We plan on sharing design, prototyping, strategy, CAD, competition updates, and media. We will make sure to share what does work, but more importantly, what doesn’t. I (Rufus | Team Lead) will generally create our updates, but other individuals might contribute once we get into the season itself.

As a district team, we have two guaranteed district events. We also have the possibility to qualify for PNW District Championships.

  • PNW District Clackamas Academy Event (ORORE) March 2-4
  • PNW District Oregon State Fairgrounds Event (ORSAL) March 23-25
  • Pacific Northwest FIRST District Championship (PNCMP) April 5-8


Website: phred-robotics.com
2023 847 Bot CAD: Onshape
Youtube: Team 847 - PHRED - YouTube
Photos/Videos: PHRED OA - Google Drive
Linktree (Galleries, Onshape Links): https://linktr.ee/PHRED847

Looking forward to seeing everyone else’s blogs!


I’m happy to hear that 847 will be back competing this year in the PNW! Thanks for the update and best wishes at your events this season.


Happy to see your team come back for this season!


** PHRED 847 Kickoff

Every kickoff, PHRED follows a basic formula after watching the reveal. This is not the most structured/official version of the format because I don’t currently have access to it, but I will provide a more thorough end of the week update (including that) later.

  • What are the rules?
    • Bot sizing
    • Bot placement
    • Bot scoring
    • Bot defending
    • Game object interaction
    • Does anything jump out (we ask this throughout the first few sections, and rewatch the animation every hour or so)
  • In what ways can you score in all three stages of the game
    • Autonomous and Tele-op
      • Where can you collect game objects?
      • Where can you score game objects?
      • Are there any other ways of scoring?
      • If there are multiple locations to score, do they have different points? If so, what are they?
    • Endgame
      • Is there a separate task?
      • Will it consume the entire endgame period?
  • What is a maximum score? (and with the most capable robots that could be expected)
    • What is the maximum amount of points possible in a match?
    • How many points are needed to get all ranking points? (win not included)
  • The robot that is a high scorer (what will the absolute top robots accomplish)
    • What strategy(ies) will they use in autonomous?
    • Where will they intake game objects?
    • Where will they score game objects?
    • Will they have a more seamless or quicker way to complete the endgame task?
  • Dream team (Which robot are we?) (this is done in groups, we then go over each groups idea)
    • Strategize the ideal alliance
      • What are the three robots capable of?
      • What do they accomplish during a match?
      • How many points do they each score?
      • Which robot is PHRED?
  • What archetypes did we find from “dream team” (back in one group)
    • Which archetypes fit together?
    • Which archetypes will be reliant on certain strategies from alliance partners?
    • Which archetypes are the most versatile.
    • Which archetype is PHRED
  • Functions we want to perform (priority)
    • Based on our archetype choice, what tasks should our robot perform (priority list) (here are some items that might be on it in no particular order)
      • Manipulate game object
      • Store certain number of game objects at a time
      • Complete endgame task
      • Score at high pointage location
      • Score at low pointage location
      • Complete certain auton task

Charged Up Kickoff

Here is a list of some of our results from the above categories:

Maximum score: 193

Interesting items:

Ability to manipulate multiple game objects in community zone and pickup zone

Ability to somewhat shoot cubes as done in 2018

Cubes move around the ground easily and could possibly be blown with air (defense)

Defensive autos might be possible

Dozer is a viable bot

There were very likely more, but I can’t think of them at the moment

Top tier robots:

  • We felt that the best robots would tend to collect game pieces from the double substation in quals, but have the ability to collect tipped cones for strategic reasons.
  • These bots will score on the top row with the ability to score on the middle as well.
  • They will most likely use “sensors” (I’m a mech person, can you tell?) to quickly balance in the endgame. We will probably see some of them with the ability to help others balance as well.
  • Our alliances consisted of three general bot ideas
    • Defense/low scorer
    • Speedy deliverer/mid scorer
    • High scorer

(with many new new members (about 5 out of 17ish) not everyone was familiar with just how quick swerve is and so a strategy that was more ideal for 2011 emerged. Using one bot that would grab from the ground in the community and place, with another that quickly shuttles objects to the scorer).

After discussion about these archetypes we combined like-features of each and eliminated options.

We decided not to pursue a dedicated high-scorer that might rely on alliance partners strategies to be effective. We also decided we wanted to attempt more than a low scorer. We settled on a mid scorer that might have the potential to score high. We also decided that we would like to specialize in cube manipulation. This decision was made to prevent building a robot that was inconsistent at manipulating both game elements. We intend to pick up both cubes and cones but cones are our priority.

Below are white board photos from our dream team section.

Possible Mechs

For the first two days, we make a point of focusing on things we want to do, and not how we want to do them. However, as a senior and design lead, I couldn’t help myself thinking of different ways to score.

Vertical elevator with horizontally extending arm:

My original thought was to have a vertical elevator. Attached would be a pneumatic-cylinder-powered slider that would hold the intake and would be able to reach at least the mid level.

Diagonal elevator:

This idea was primarily inspired by the folks on the Unofficial FRC discord server, and the elevator of FTC team 17595’s power play bot. This strategy seems quicker, but will make collecting items at the high double substation more difficult.

I also devised a strategy in which we could place both cones and cubes on the mid level, while being able to launch cubes onto the high level. This would be accomplished with an intake flipping mechanism similar to 254’s or 2471’s in 2018.

This elevator was originally planned to be 2 stages. I then did some geometry testing in onshape to see if placing cones and cubes through the elevator onto level 2 would work (with the intake facing away from the alliance wall, my original plan).

This seems exceedingly difficult. Even with many adjustments to angle, the end of the elevator would barely reach horizontally past the 2nd level node.

It seems that (if you’re going the angled elevator route and intend to score both on high and mid levels) either have a separate intake and manipulator, make a 3 staged elevator, or possibly avoid cones for L2 and L3? You could also change the way your elevator manipulator works, I was just trying to make the most simple possible.

Might be missing something here…

Anyway, I’ll probably have another post by weeks end to describe what’s happened. If you have any questions or suggestions, feel free to leave them below, and I’ll try to get back asap.

(the 2nd to last photo is a concept just to be able to visualize the flipping intake, (not to scale).



I tried to give it special formating, but I clearly failed, I’ll try again in the morning.

Updated Elevator/Intake/Scorer CAD Drawings

Again, I’ll do a week’s-end post to show what we’re planning to do priority wise and mech wise. This is a post to share my progress on an idea for a tilted elevator with flipping carriage idea for level 2 scoring of both objects and level 3 cubes. This design now has the ability to grab from the shelf at the double substation (37.375 marked on the left side of the drawing).


The highlighted areas are the intake/scorer. This travels up the carriage and then flips in a similar manner to 254’s 2018 intake (image in my last post). Adjusting the angle of the elevator to be higher might be a good idea (I haven’t done too much testing atm as I have some homework to do).

I’m pretty happy with the general layout. We might not use this design, but I’d like to think that it isn’t a bad option for teams who aren’t super set on getting cones to L3. If anyone has any feedback or questions on it, please ask, mostly because I’m curious if others think it makes any sense.


Week 2 Updates

During week one, we used our priority lists, plagiarism, and prototyping to decide on a bot design. Specifics of bot design will/are changing, but we have an archetype and general drivetrain, intake, and arm/elevator design nailed down. Our prototyping has been mostly limited to intake, but we have been using our intact 2018 elevator to visualize and plan our 2023 iteration. Over the next two days in particular, I’ll be working in our onshape document (available above) to finalize the angle of the elevator and length of the extending slider.


Our current plan is to use a 4 double-wheel 2018-style intake. It will intake cones that are vertical, cubes, and plan to also have it capable of cones with tip towards bot. It will be a fold-down intake with the front wheels being outside the bumper and the rear being in between the bumper. This means we plan to have a front cutout.
On the prototype below, the front wheels have a center spacing of 10”. I somehow lost track of the written spacing for the rear wheels, but I believe it has a center spacing of 5.5”. Though I’m not 100% on this either, I’m fairly certain that the back set is 6.75” behind the front set. The vertical distance between the two layers of wheels is approximately 2.25-2.375”.

(cone not in intended location, freshmen messing around :wink:)


In this configuration, grip of the aforementioned tipped cone is insufficient. This was because the front wheels were not in contact with the lower cone-shaped part of the cone. By shrinking the center spacing of the front wheels to 9” that problem was solved, however, the cube was less ideal. To fix this, we plan to reduce the gap from 10” and try AM “entraption stars” to allow the cube additional space while also being wide enough to provide grip on the horizontal cone.


We’re planning to do something similar to 3847’s original elevator+slide design. Unlike spectrum’s, ours will be a cascade elevator. It will be constructed out of 80/20 because of our significant stock, already owning REV’s 80/20 elevator kit, and no sizable benefit to box tubing in this instance. We haven’t finalized an angle or length of stages yet, but I plan to narrow that down in the next two days.

Our horizontal extender is planned to be a one-stage slide. We will use the Igus “drylin® N guide rail, size 27mm” profile as we have a ton that we’ve never used from previous KOPs. (this could very well change based on lengths and other testing)


For 2023, we are using our Kitbot chassis from 2020 with minor modifications. We’ve cut it down to 25x32, and removed the front plate. We cut 6-inch pieces from each end to use as end caps (unfortunately I don’t have many pics of stuff today, I was pretty busy). To compensate for the removed structure, we’ve added a cross-member in front of the gearbox. We’re also replacing our cims with NEOs.


I’ll try to get some photos of the geometry I’m working on over the next few days and provide updates on the planned dimensions. I’ll probably also start assembling the elevator in onshape once I have dimensions. Once we figure out the best pipeline for our photos, we’ll get a link to that as well. (We used to have all our digital materials on the school network, but they lost them somehow? We now keep them on a 1TB usb drive but we’ll try to start posting our photos to flickr or something. We’ll see. If you have any questions or feedback, please ask away!

Also, we cut our cube on our battery mount, which lead us to realize the edges are a bit sharp. So be careful with cube around kitbot style battery mount.

Rufus, PHRED 847 Team Lead


Careful with this stuff, it can bind pretty dramatically under moderate binding loads.

Do you have any videos of these test to share?>

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When you say “binding loads” what are you referring to? If we’re planning on running to parallel sets out, do you still think this is likely to be an issue?

No, but we’re going to do final (hopefully) intake setup testing tomorrow, and I’ll post some videos and final dimensions then. We’re testing to ensure we’re able to grab tipped cones off the ground from about 1" up. I’m also going to work to finalize the side-view geometry tomorrow evening, so I’ll most likely post that then as well. For now, here is an overhead view of the intake geometry.

With dimensions (sorry it's so messy)

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In 2013 we used two of those rails in parallel for a linear dof. It seemed like anything that twisted the stage in any way caused the slides to bind.

We have used roller bearings for linear motion since and been much happier with the results.

For presentations I will often make a second sketch, convert the first sketch, and add driven dims for only the important features. Makes things easier to digest.

Good work so far! I look forward to assembly and test videos and pictures.


Is there an assembly that you can think of off the top of your head that I could take a look at to gain a better understanding?

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Week 2 Update No. 2

This update is mostly to share some videos testing our intake. These dimensions might not be final, but everything is probably within .75 of its final position. So, here are the dimensions shown in the videos:

  • Horizontal spacing between center points of wheels sets: 6.25”

  • Horizontal spacing between center points of rear wheels: 5.75” (I’m thinking we want these at 5.5)

  • Horizontal spacing between center points of front wheels: 9”

  • Vertical spacing between top and bottom of rear wheels: 1.75”

  • Vertical spacing between top and bottom of front wheels: 2.5”

  • Vertical spacing between bottom of front and rear wheels: 0.625” (rear wheels were lower).

  • Vertical spacing between the ground and bottom of the front wheel set: 1.5-1.75

I’ll have updated intake geometry out tomorrow probably, as well as updated slider geometry (elevator geometry is theoretically complete). Anyways, here are the intake prototype videos:

Cube testing video in the drive (cube is punctured and leaks air):


A handy method to make sure a system won’t bind is applying “Saint-Venant’s principle.” I like Slocum’s discussion of it here: https://pergatory.mit.edu/resources/FUNdaMENTALs%20Book%20pdf/FUNdaMENTALs%20Topic%203.PDF (page 17), your specific case discussed here https://pergatory.mit.edu/resources/FUNdaMENTALs%20Book%20pdf/FUNdaMENTALs%20Topic%2010.PDF (page 52) though the accompanying lectures do it the most justice.

Essentially it’s a rule of thumb for binding relating the ratio of bearing spacing to linear shaft spacing. To not bind I think you want (bearing length)/(shaft spacing) > 1, though preferably closer to 1.5, diminishing returns kicking in around 3.

Also as a side note Slocum’s FUNdaMENTALS, is probably my favorite introduction to mechanical design in general, so many good tips in it and highly worth a read or an audit if you ever get the chance.


Tagged you here in a write-up explaining how to analyze a linear mechanism for binding.


Thank you! I understood the general reason as to why the binding would occur, just wasn’t sure how a setup you were describing would look. Now I know!

Edit: After some research, I think it’s a good idea for us to use our drylin r with 3d printed variations of the outer section of the igus " dryLin® R pillow block RJUM-05" This will mitigate possible binding issues from the dryLin N, while also providing a more secure mount for our intake.

I have a lot of homework tonight, so this isn’t a full update. I’m mostly just posting some CAD pics and what progress we’ve made physically. Update on the horizontal slide: Unless something unforeseen happens, we will use igus n. We did some testing, in a configuration similar to what we’re planning, and we feel it is unlikely to have problems (especially with the bracing we’re adding). Here are the CAD pics:
Robot Assembly (3)
Robot Assembly (1)
Robot Assembly
Robot Assembly (2)
If you want to check dimensions, you can head into our onshape doc (linked in first post).

The 2x1 box tubing (static) is there to mount the igus N profile. I don’t have exact numbers right now, but the first slide will extend around 12.5" and second slide will extend around 9". Again, not exact, but approximate. Also, we have end caps on the front of the kitbot.

Here are a couple of photos of what we have physically


Week 3 Update

It’s been a while, but we’ve also gotten a lot done. I’ve been really impressed by the level of motivation and application by all the 6 freshmen on mechanical (6 out of the 8 are freshmen). In CAD our entire robot is almost complete. We’re missing details like mounts for the elevator motors, sprocket and mount for the top of the elevator frame, chain mount to first stage, connection between the intake and slide, end caps for drivetrain, crossmembers for drivetrain, and churro spacers for intake. (that’s a fairly long list, but they should be simplish and are less important for the CAD right now)


Before fabricating, we’ll need to make sure that the horizontal cones still work when the bottoms of the front and rear sets of wheels are both at the same height. Other than that, everything should work. We haven’t decided on reduction yet (hence only input and output on the versaplanetary. I struggled a bit with figuring out how I was going to mount a motor for this intake as ultraplanatary’s ½” hex adapter isn’t as long from end to end as we wanted, and we don’t have any max at the moment (would solve all of the problems, but we’re on a bit of a budget at the moment). We’re currently settled on versa (though it doesn’t give us as much spacing between the plates as we would ideally like. To be able to fit both sets of chains, we’re going to have to cut down our sprockets by ⅛” (they are like this in the cad model, but they aren’t labeled as such).

Speaking of the CAD model, many of the intake spacers say that they’re a certain length, but aren’t actually. This is because I wanted to be as quick as possible, and so just extruded existing mkcad models for spacers to make custom lengths. I’m confident that the chain won’t pop the cubes, but in case it does, I’m looking into what lengths of belts and diameter pulleys we’ll need.

it’s also possible that we aren’t able to get two more spark maxes. In that case, we’ll have to use bags.


The structural parts of our elevator are currently constructed with 80/20 from our 2018 bot. We’re going to re-machine the inset into new pieces to fit the rev v-groove bearings (because we can’t reuse, but also to show freshmen how you’d go about that). The 1st stage of the elevator is currently cut too long, but since we know the correct length from the CAD model and we’re going to cut new pieces anyway, we’re leaving it as is for testing. It sits at a 56 degree angle.

Starting config:

Intake config (12" extension):


Based on testing in CAD, the first stage of the slide will extend with a 12” stroke cylinder. This will get us to our intaking position and our mid cone node position. The second stage will extend 8”. This will get us to approximately the same distance vertically and horizontally as the mid node (but for the high node). In testing, the igus N slides have performed well, we will unfortunately need to tighten the bolts between carriage and slide more difficult to take apart. Fortunately, we have more than enough to make a whole replacement module for both sides.

Mid Node (12" extension):

High Node (8" extension):


This was already finalized before, but our drivetrain is 32”X25”. We felt we needed to be skinnier to fit better with partners on the charge station because we’re not using swerve (where we could just drive two wheels off the side). We will have additional crossmembers to keep the frame rigid (it’s definitely not at the moment). We’ve currently only have 2 of our NEOs mounted to the drivetrain (the others should be arriving soon).


Our Eboard will be mounted on the seemingly pointless vertical 80/20 on the back of the bot. The 80/20 will have more bracing than currently shown. The electronics will be mounted to the inside, and the outside will serve as a sponsor board. We are planning to use our limelight 2+ (or whatever it is); we haven’t decided on a mounting location yet. A rev power and pneumatic hub just arrived from FIRST choice round 2, so we’ll be using those for the things they’re meant for. (nice eloquence on my part there). We’re also going to use some sort of indicator LEDs to inform the HP what type of game piece we want (this idea is stolen, but I’ve seen it many places so I don’t know who to credit it to).

Physical Robot Work

Also, here’s link to CAD so you don’t have to scroll all the way up: Onshape

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Good progress!

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Thank you so much!
We’ll hopefully have our two intake plates completed tomorrow, and start and we’ll then start to assemble them. We’ll also cut out our polycarb slide mounting gussets. Once we’re done with the intake, we’ll start testing the slides with more realistic scenarios to ensure they’ll be reliable enough. We’re going to machine our new elevator sections Monday. Our next step will be planning mounts for our elevator motor(s) (a little worried about this one).

I should have an update Saturday (tomorrow) night on our progress with physical pieces (the ones above are actually from last week).

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End of Week 3 Update

Okie Dokie dominokie, here’s an end of week 3 update:

Today, we weren’t as productive as we would’ve liked. This was because two mechanical members were derailed by shortening our FTC bot (comp is tomorrow).
We were also had to redraw our intake on polycarb (somehow the original one was off by at least an inch).

Anyway, I got a new one drawn out that I’m 96% sure is how we want it. We’re going to cut it out on Monday, make sure it works, and then cut out another. Because we haven’t been able to get more spark maxes yet, we’re going to start testing with bags for intake and see how it goes.

Elevator-wise, we added cross-members to the top and bottom of our first stage. We also began planning our vertical support for the front of the elevator. We realize that since our chain is going to be running in front of our first piece of 8020:

we can’t attach our support directly to it. This was something we hadn’t considered previously so we had to come up with a couple of solutions. Our current (and hopefully final) is to have the supports come up to a few inches short of the elevator frame, and then send up two long gussets to attach to each side. Our chain gusset will sandwich the frame above where the verticle supports are attached.

Another piece of fitting this puzzle together is our spacer block things that fit between the two pieces of 80/20 and make sure that the frame and the first stage stay at their set distance apart.

We wanted these to be easily removable so that we could quickly slide the first stage and carriage off of the frame if need be. our original solution was to mount ftc hole patterned stuff on either side so that we could unscrew from each side quickly and then slide off.

However, this takes up a lot of length on the frame (leaving less room for travel on stage 1. My solution therefore, is to drill through the front and back of 8020, and just bolt in above and below the slide block. this takes away zero length (doesn’t get in the way of our v groove bearings) and should be simple to remove if we tap the holes.

We also added cross members to our drivetrain to account for the missing endplate. Not a huge surprise as far as electrical, but we’re going to use two energy chains (or whatever the Igus product name is) to carry our tubes and wires up our elevator. Our electrical board will look essentially like this:

Today, we cut out our carriage to slider gussets and started drilling holes:

On a somewhat unrelated note, we tentatively decided to spray paint our bot. We’ve never done significant painting before, but it seems like a good way to stand out. Our scheme will center around our construction theme. We will start by painting all of our verticals like caution tape (black, yellow, black, yellow) and maybe paint something else orange.

I’ll probably edit this tomorrow to make it more coherent and add some photos and CAD pics, but I shouldn’t have stayed up this late anyway.