3 NEO ball shifter

Weight is 4.4lbs
Criticism is welcome.

p.s. VEX can you please make longer ball shifter shafts.


This is kinda great

Well done

Can we see a side view?

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Great looking design! I love the simplicity.

Here’s a few questions/ suggestions:

Is this designed for a chain-in-tube WCD chassis? (I’ll be assuming so going forward)

How is the hex part of the output shaft attached to the ball shifter part? (If you got fancy here you could probably remove the gearbox while keeping the chain and wheel in place)

Are the two mounting bolts shown going through one side if the frame rail the only mounting? If so, I would worry that the wall of the tube might deform over time allowing the gearbox to sag. Depending on the wall thickness of course.

On the front plate, I definitely think you should add a strut from the upper bearing hole to the gearbox mounting hole on each side. This will help prevent the face from warping under the side loads from the low gear set.

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Looks good!

You’re pushing it a bit to get the gearbox to work in a single stage. 4.89:1 is really fast, even for 4" wheels. Also be aware that having the shifter shaft be the output shaft means that the air cylinder and coupling is the lowest point on the robot - a pretty dangerous location for vulnerable parts.

We built something similar this year (see below), but we included a 20:80 32DP first stage before the shifter (in the blueish 3D printed part to the right of the aluminum plate). I’m happy to report the 3D printed first stage housing held up perfectly! The pink is a placeholder for a WCD sprocket. We ended up only installing 2 neos per gearbox.

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1.This design is made for chain in tube.
2.The hex is held in by a roll pin but its obscured by the plate currently adding some length to the spacers would make it accessible from the bottom so I might have to look into doing that.
3.The 2 mounting bolts are the only attachment points but with .125in wall tubing and such a light gearbox I wouldn’t be worried about the tube deforming as we have mounted gearboxes weighing more than twice as much in the same manor and not had any problems.
4.I might… im always surprised by how strong aluminum is so I keep making my lightening more and more aggressive so this time I might have gone too far.

For comparison, here are a couple pics from very early in build season of 548’s design. I’ll see if I can get some specs also.


It’s actually not to bad to make your own. Maybe 4 short operations, tops. One of those can be done with a cordless drill but the others have to be on a lathe. That’s what we ended up doing this year. The V1 shaft is even easier iirc, but it has no positive retention.

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that’s what I resorted to and it wouldn’t be hard for our team but it would be nice to just have to take a shaft a cut it to length like the dog shifter shafts.


What design calc did u use?

JVN calc you can find it here https://www.vexrobotics.com/vexpro/examples-guides under additional guides and examples

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