Spectrum 3847 | Build Blog 2023

Yes just during events, here is the rest of R304

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Are there any thoughts about you all doing a similar pivoting telescope as your 2018 robot?

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After 2018, we added a design rule to our list*.

Never build an “elevator on arm”: we 100% should have built a more standard elevator in 2018. We had many issues with the way we designed and built our “elevator on arm” mechanism. The arm joint, internal bearing setup, wire management, and chain run all caused us multiple problems throughout the season. We rarely needed or used the ability to intake from both sides of the robot. Also of note, we only did a single extension arm, a double (or triple) extending arm is even harder. Most of our discussions about that season are that we should never try that again. The vast majority of games can use an “arm on elevator” or “slider on elevator” structure and be easier to design, build, and control.

Compounding on that in modern FRC there aren’t many COTS options for Pink-style elevator on-arm mechanisms with powered extension and retraction. If you want to pivot around the middle of the arm as we did in 2018 you also have to fully design that clamping mount and joint as well.

* Examples of other items on the list
  • Don’t build ramp bots
  • Never build a scissor lift
  • Don’t use mecanum wheels to drive on the ground

All of these can be done well, Spectrum just isn’t likely to ever try.


Got it, those are all great points. My team was considering it but we were worried that it would take too long to get working right and that there could be lot of issues that could arise with it (you addressed most of them above).

I think there will definitely be some teams that do it this year, and if done right could be extremely effective, although probably pretty annoying to deal with and do maintenance on, especially since you would probably need a multistage telescope.

  • Never go in against a Sicilian when death is on the line

Does this mean the telescoping arm you made or any elevator that pivots? Our team’s current idea is to rotate an elevator and now I’m feeling like:


All of these rules have their exceptions, so it’s really up to you to decide if your design meets your team’s strategic requirements and is an effective use of your team’s resources.

Make a sketch with your robot and all the possible positions you believe the" elevator on arm" will need to be used in and then think about the motion paths it takes to get there. Does it reach all those places? Does it do it efficiently? Will it have other problems? Imagine it driving around doing all the game tasks, are there things you would be worried about? Like being too far away from your bumpers while ground intaking, or when you drive will your center gravity be higher than other options? If you run your mechanism into the Human Player station or another robot at full speed what do you think will break first? Can you ensure that you won’t accidentally extend past the frame perimeter while in an opponent’s loading zone or community?

Also make sure you fully understand the mechanics of the mechanism, the bearing setup, and power transfer for these types of mechanisms can get complicated and be prone to failure if not planned well.


How inflated are the cubes in the shooting video? They look like they might be over filled to me but I am not sure.

We measured them to be close to correct but haven’t made the sizing jig yet so they could be slightly large.

gear sprocket


Why not just do a fixed angle (but steeper) rather than having the elevator + slider? Wouldn’t it be easier? My team is considering it rn and I was wondering why you decided against it.


How about a scissor “arm”? Were thinking about having two horizontal standing scissors and rods holding the scissors together to reduce the overall swaying of the scissors.

That will be a pretty common robot I think, so you may be on a good track.

The slider let’s you extend an intake at the bottom without any type of wrist or other mechanism. The sketch above only has a single stage elevator which is potentially simpler than a cascade or a continuous elevator. With a steeper angle you may have issues with being very extended past bumpers when picking up from the loading station.

That sketch isn’t our final decision or anything so we could still be switching up our plans.

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This may be a dumb question, but what is a slanted elevator? Does it begin vertical and then slant mechanically or does it begin slanted?

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its a normal elevator thats mounted not vertically on the chassis
Think this:


RI3D Team Cranberry has a really good example of a slanted elevator.


I like that design for the most part. Not sure about the gripper. Do you know if they can pick up from the tray? I didn’t see it in the video.

See this response/thread. Lets keep this blog on topic.


I would not consider this a slanted elevator. I would call that a tilting elevator or an “elevator on an arm”


Here is the slanted elevator UMN built.

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