Flipped 2 NEO Gearbox Feedback

So, I took a shot at designing a flipped NEO gearbox, and wanted to get some feedback on it, both with regards to the overall design, as well as the CAD practices.

The first stage has a 14:60 reduction, and the second stage has an 18:28 reduction(with steel gears, because of the higher load on the teeth).

Perspective front view:
Side view:

Back view:
Native Onshape Link:

Any and all feedback is appreciated!


Do you have a picture of the gearbox mounted to a tube with wheels? I’m just curious because from the pictures, I can’t tell if the motors are going to collide with the drivetrain wheels or tube (just making sure they’re not, lol). This is the problem that I was having with my attempt at a one-stage flipped 2 NEO, so I decided to add an idler to push the motors above the tube some more. If you have any questions, don’t hesitate to reach out!

You should also have a place for the sprocket/pulley that you’re going to use for the drivetrain. Even though this might just be a side project, I find that it is still good practice to include everything in the CAD.

Something that I like to do when making gearboxes is to add counterbores for the standoffs to rest in. I’ve found that this provides some extra stability, as well as makes it much easier to assemble!

Something else that I noticed was the removal of material on the plate where the NEO face rests. While I don’t have any statistics or experience with this, I prefer not to pocket that area - the aluminum might act as a sort of heat sink for the motor, improving thermals. Again, this is just an assumption of mine, so if anyone might know of any extra information, let me know!

Overall, nice job - I really like it!


Very nice!

Do the four screws thread into the blue plate or are used to attach the gearbox to the tube? What is the purpose of the two holes on either side of the output shaft? Does it make sense to “clip off” the top corners of the black plate and eliminate a bunch of the pocketing?

This is very similar to a 3d printed version that I’ve been toying with.


You can get rid of the red plate, all it is doing is overconstraining the middle shaft and adding extra parts to machine and more complexity in assembly.


The four screws thread into the blue plate, and the two holes on the side of the output shaft are for mounting the gearbox to the tube. Could you elaborate on what you mean by “clipping off” the corners?

I believe they just mean making the plate arcs around the motors tangent to the motors themselves (instead of having the extra material around them).

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Not super necessary, but I like it when the hole behind the pinion is large enough to slip the pinion out while still keeping it attached to the motor. Just for convenience, in case I want to replace the motor with another.

Also how is the back bearing constrained on the lowest shaft? It looks to me without a proper press fit it would slide out and hit the large 60 tooth gear. You could probably just flip the flange side and it would work perfectly.

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I’m so upset that you didn’t make the back of the neos planar with the outside off the tube.


Do you need the third pink plate? Seems to me that first stage will be just fine cantilevered


There’s a spacer in between

I should do that, but I was too lazy to look up NEO face od, so I just went with 2.5"

That’s true

Agreed on ditching third plate.

973 has ran this gearbox with the cantilevered stage a few times now.

Alright, will do. Did you usually run steel or aluminum gears in the second stage? I’m not too sure whether to be worried about shock loads, given the small gear sizes

We steel on that small stage.


What are the tooth counts?

One piece of feedback I’d like to give is more about the use of the gearbox.

How do you plan to transmit power to different wheels? Looks like 1x2 box tubing, so chain in tube is less of an option.

I whipped up this gearbox a few months ago for funsies:

Biggest difference is that it has sprockets outside the box tubing, so the gearbox is used in the drop center wheel.


Just curious, why does using 1x2 make it less of an option for chain in tube?


Most sprockets don’t have adequate clearance between the inner face of a flanged bearing, assuming that you’re using two bearings in opposite sides of the box tubing.

It also limits the size of sprocket you can use, 2" is barely enough for the smallest vexpro sprocket in #25 chain, so a drop center is nearly impossible.