Team 3467 2023 Build Blog

FIRST Open Alliance
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This is a primary factor in why we aren’t doing this. Could be easily solved with a small flat section of the frame.

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Now if you cut a flat on your bumper like 1787, but the width of your arm then you’d be good!

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It looks like they are only extending over the corner of their frame in their LOADING ZONE and COMMUNITY. This would still be legal due to G109b:
image

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2023 CAD Working document here: Onshape

Bit of a mess, and nothing is set in stone, but figured I should share it early.

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Midnight CAD Update

Encoder Mounting

Since we can’t directly mount to the joint’s directly because they’re a dead axle tube we decided to mount it to the lower near the gearbox shaft and have a separate axle geared to the same ratio as the rotating joint. This is geared from a 16t to 32t gear so they are small enough to run inside of the 2x1 and package well.

Gearing

This year we want to put an emphasis on the center of gravity improvement, But for the weight that can not be mounted as low, we want to keep it as light as possible. So this year we also decided to use 3D Printed Onyx herringbone gears because they have significantly reduced backlash and are much lighter than standard COTS gears.

Half A-Frame Support

Obviously, support is almost necessary for an arm of this size. This is a piece of max tube supported at a 55 degree angle (relative to frame). Custom gussets for improved attachment rigidity. Keeping a row of rivets parallel to the 1x1 is more efficient than making them all vertical though it may look pretty weird.

Pros

  • Allows for chain to be tensioned better
  • Decreased sway for more accurate stacking

Cons

  • Consumes valuable space

Ground Intake = Bad :face_vomiting:

We have decided to postpone the addition of a ground intake for several reasons.

  1. Most useful for 2+ game piece auto, not a week 1 situation
  2. Inconsistent cycle times due to orientation time
  3. Potential solutions are complex
  4. Most ground intakes would have the same acquisition zone as the arm claw intake
  5. Handoff will be messy
  6. Not enough tipped cones to be a huge priority

Drivebase Updates

channelizing-device (1)

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Baller

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:fire:

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The herringbone gears are just giving your encoder the same final drive ratio of the actual arm pivot?

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Correct

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It’s an absolute encoder, so were it just attached to the lower shaft, we wouldn’t be getting the exact absolute position of the joint. Any absolute encoder value could be referring to multiple different arm states (in this case 2 possible states, since the ratio between the shafts is 1:2).

By adding the gears, one absolute encoder value should map 1:1 with one arm state

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Had a friend reach out after reading the blog with another robot concept that only uses one degree of freedom! Hadn’t considered the starting position for the arm that he proposed, so I figured we’d make one more of these diagrams.

Virtual 4-Bar Only

image
image1297×735 119 KB

  • Okay at loading game pieces from double substation
  • Scores effectively at all levels
  • Can be very small (image above is mocked up on a 24" chassis
  • Simplest concept listed
  • Floor intake is difficult to make work, likely requires a separate floor intake if that’s a requirement

This robot archetype seems to me to have as high a ceiling as the more complex ideas that have been primarily floating around, and 3467 will discuss it (although we’re already elbow deep into manufacturing v1 of a double jointed arm robot - which will be discussed on the blog…

puppet GIF

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I like the design simplicity but holy moly the CG on this is atrocious.

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I have yet to see a 2023 design that I don’t think is VERY prone to tipping

and it terrifies me

(especially given we lost an event last year to accidental tipping :frowning: )

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after all these years, the wall of hooks still invades my thoughts

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Does this not extend above the frame extension limit when deploying? Does the arm swing below the uprights?

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below/through

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All I hear is an opportunity for a certain thrifty vendor to start stocking bricks.

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“All new Thrifty Bricks®” coming to a vendor near you!

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My team refuses to use anything for ballast besides Supreme™ Bricks due to their superior performance.

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The diagrams that are in the blue box under G109 show a couple of potential solutions:

  1. Add a “side” in the direction you intend to extend. It only needs to be long enough the qualify as a side and then you can extend in that direction. Robots B and E in the blue box are Hexagonal. but there is no reason why you could not clip a corner off a square to create a new “side” of the robot. Anyone know how short a side can be before it is no longer a side? Could you have a 1" long side? Might be a Q&A question?

  2. Make the robot round (See robot C in the blue box). Now you have an infinite number of sides to extend (see the text of G109). Even though they are infinitely small such that any mechanism of finite width would therefore extend over more than one of them, the rule makes it clear that this is legal. The trick is making legal round bumpers for your legal round robot… But I digress…

Edit: Nope on idea #2. My Bad

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