Roller Hatch Measurements/Geometry

Our team didn’t use one but 1684 chimeras, released the cad for theirs. They were the first team I saw using one. If you search for it, you could probably find it. If you can, I’d recommend using solidworks sketches and model the ball and figure out how it would move. I understand you can’t, but if you could, your team could understand the workings of it better and then if needed, apply those skills to next year’s bot.


My team designed a similar mechanism, but took inspiration from 1684. I’ll post a sketch when I get off work tomorrow of our CAD when the intake is closed and in hatch intaking mode.


If you are looking more like a 1323 hatch intake where it is only for hatches, you can look at a model from Ankit Musham


We have one designed as part of an offseason project. As a word of warning, getting the rollers and backstop set up aren’t the hard part. The angular compliance and the linear slide are the hard part.


For that we were planning on having it rotate on a bearing or something at the back a few inches, and have springs to keep it centered. That way if we are off by a few degrees either laterally or angular, the wheels would ideally roll on the hatch until it gets trapped on the inside

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Our hatch intake is simple and lightweight and very reliable

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While I don’t have numbers (The students have them), I can tell you that my team found answers to all of these questions in about an hour and a half of prototyping this past Monday (two returning members, 5 new members working on it - great learning opportunity!). It’s pretty easy to grab a couple of hex shafts, some wood, different wheels, and a couple of drills and put together something that lets you change dimensions to find what you need, change wheels out to identify the best ones for your application.

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I read this in a funny way :grinning:


We switched to this type of hatch intake for our 3rd regional and found it worked very well.

  1. The type of wheel - VexPro Straight Flex Wheel (3" OD x 1" WD, 1-1/8" ID, 30A)
    At first we used the anymark green 3 inch compliant wheels but these broke appart very quickly and the inner hub slipped so we switched to the VexPro wheels with a 3D printed hub.
  2. The center distances between the wheels - exactly 3 inches center to center
  3. If you used one set of wheels in the center, or stacked multiple - we used two sets of wheels, I’m not sure about the exact spacing but it was around 1 inch
  4. The distance to a backstop - we had to experiment with this distance, it really depends on the wheel, just make sure that the hatch goes behind the center point of the wheel (we had some issues with the hatch ejecting when we stopped intaking so we adding some Velcro on a piece of polycarbonate behind the hatch it keep it in place)

Feel free to reach out to me if you have anymore questions or want pictures of our design.


Did you ever need to replace the velcro or did it hold well?

It worked for both our last regional and worlds without being replaced, it’s the hook side which never really wears out.

3" VexPro Compliant Wheel


Double stack, 0.402" gap between

Backstop is 0.1875" behind the center of the wheels. YMMV however what is important is that the hatch is over center when resting against the backstop.

Hope this helps!

Edit: Here’s some CAD screenshots. Here’s a video of an early practice session. Oh and a pic I took yesterday of our ongoing redesign.

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That’s really cool, thanks!

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Did you bolt through the mounting holes, or did you bond your 3D hub to the wheel? If you bonded it, what kind of adhesive did you use?

how does the intake open and close? Is there a pneumatic piston somewhere?

We found the friction between the 3D print and the outside of the hub to be strong enough to use so there was no adhesive needed or bolting needed. (Filament was Markforged Onyx which is a very abrasive material)

Yep! A single pnuematic piston opens and closes the intake arms.

Hmm, interesting. Did you oversize the hubs at all and stretch the rubber over them?

Just for another data point:

-We used the 30 durometer WCP flex wheels with plastic VEX hubs bolted through the holes

-Center distance is 2.803" simply because we had two 56T gears and that’s the pitch spacing plus a 0.003" adder. And the backstop is roughly 1.25" from the center of the wheels

-We used two stacked, with 1.75" between

All of this was determined based on parts we had on hand around week 2, and doing detective work on 973’s Instagram posts.

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