pic: 3 NEO Low Profile Reverse Mount Gearbox

More photos: https://imgur.com/a/2AdFxj1

Geared for just under 15.5 ft/s with 4" Wheels (12:68, 24:28)

For use with chain in tube using 2x1.5" tube- the tube just barely extends past the NEO. (See top view photo)

I am having difficulty understanding why two of the neos are on a smaller gear and one is on a larger one. Why not just have all three neos placed between idler gears of the same size?
Also I really like the pocketing on the siderails!

Only one of those gears is an idler gear. The larger one is one of the reduction stages.

Amazing looking system.

I wonder if the pinion with load of two motors will stand up to it.

Also interesting that you’ve used omnis on the ends. Would all the wheels be on the same plane, that is, no drop-center?

But the biggest challenge I think will be the size of the wheels. We’ve had essentially flat-floors for two years in a row. I think the odds of having something to drive over (it is in “space”) are very high.

Can you do this in ten-inch wheels?

Not sure about VEX/AM pinions, but years ago we did this with some 32dp steel pinions without any issues. (one year we even had 2 motors running through a pinion, rather than just the 1 that this design has). With proper lubrication I’d imagine you’d be fine.

You would need a far more substantial reduction to use wheels that large (also 10in seems a bit excessive, biggest anyone ever really needed was 8in), possibly even adding an additional reduction stage, but with some modification to the design I see no reason it couldn’t work.

Like Chris said the pinion should probably be fine, but if necessary I could add a bearing and plate to support the end of the shaft similar to how 254 supported the double loaded pinion on their drive gearboxes this year.

The chassis here was just a 6WD I had designed a while ago for a different gearbox, but it did have .1 of center drop on the middle wheel to account for wear in the Colsons wheel.

Like Chris said, to use larger wheels I would require a larger gear ratio, but physically speaking it would work with larger wheels since the motors do not stick out past the drive tube, which was an issue with many reverse gearbox designs that used CIMs or even Mini-CIMs.

Also, if we had to use larger pneumatic wheels I would most likely move the chain out of the tube due to a much higher chance of the chain breaking.

Thanks! We’ve run chain in tube with 2x1.5 for the past 2 years and since we put the bearings directly in the tube we are required to use thickwall tubing, and to save weight instead of full depth pockets which would defeat the purpose of chain in tube, I opted for half depth pockets.

I’ve actually cut a test piece on our CNC and it came out quite nice, see this photo

This looks awesome!

I have a quick question related to bumper mounts for a drivetrain like this since my teams is designing something similar. How you go about doing the front and back bumper mounts?

Edit: Would you have the bumper attach to the front and back frame rails? Thanks in advance!

For this particular drivetrain, I would only leave no bumper support in the front and back if I did a single bumper that went all the way around. As for bumper mounting, we use quick slide latches. For a single bumper that goes all the way around I would put 2 latches on each side. If I had 2 piece bumpers, I would put another 1x1 across the front/back of the robot and put 3-4 latches on the bumper. See this photo from our robot this year for reference. In the off-season we actually took off the latch in the front without any issues as it interfered with our new intake.

Yeah I’m guessing this would be necessary for your application with the new motors. I say that because there is a snap ring groove at the base of the neo output shaft.

Like this?


You’d get more support/strength if you combined the idler and pinion plates into one, but otherwise you’ve got the right idea.

That’s exactly what I was thinking. Combining the plates could also allow OP remove 2 supports since 6 supports (2 for the pinion and 4 for the gear) seems like it’s overkill. Although admittedly I know very little about designing gearboxes.

You are correct, 6 spacers would be overkill if this were consolidated into a single piece.