pic: Inverted Gearbox Concept

One of my older gearboxes I made a few months ago. This is… the 5th inverted I made? Anyways, the main difference between the other ones is the shifting system: this time I’m using two smaller pistons to push against a plate, which moves the rod (unfinished, but should be where the small bearing on that plate is.).

Speeds work out very decently for a 6in wheel drivetrain, and I’m pretty satisfied with its weight (8.34 lbs). I’m not sure if this two-piston method would be the best way to this; I wanted to make this as compact as possible to allow for everything else inside the frame perimeter, so I thought this design would do that best. In addition, I’ve seen 254’s take at this, but with this design I wanted to find out if there’s a different way to approach this.


Maybe this isn’t an issue, but the exposed 1st stage looks like an accident waiting to happen. If it were used one would want to be careful with the chassis design to make sure nothing (wires, etc.) would be in danger of getting nailed.

With every design like this, the first stage will be exposed. Of course, people should be careful about this, but perhaps a case can be made to go over the first stage. I can kind of imagine that happening with a 3d printer.

Why spend the time printing something heavy and fragile (and doesn’t let you see inside) when you could run a thin sheet plastic shield? I know some teams were using lexan for this but that seems overkill… scrap plastic like out of a 2L bottle seems all that would be necessary here.

Exactly. I didn’t say it wasn’t fixable, and pop bottle fixes are 100% valid here. My concern was more of a “if you use this type of design, take care…”, not a “this design is doomed and all teams should avoid it”.

Part of it is my new job as an engineer in an automotive body component plant where I’m always having to take such precautions when designing/modifying machinery. Unguarded pinch points cause me to raise an eyebrow… which maybe isn’t bad?

Out of curiosity, what size gears are you using on your first reduction?

We had a similar setup in 2015. The gears are too far above the belly pan to really grab anything.

I wouldn’t be worried unless your 1678.

The outboard placement of the CIMs looks good, but the high CoG is disconcerting. Rotating the whole assembly about 60 degrees about the output shaft (pick your direction) and moving the then-higher CIM closer to the then-lower CIM would result in a much lower center of gravity and a shorter foundation for the manipulators, without much affecting the shift and other capabilities.

I’ve seen worse. Not that I think the sort of teams that are usually guilty of rat nesting would be making their own gearboxes; but I’ve seen good teams get bit by wire snares (like 1108 at Crossroads Regional Finals in 2013, that was a smoky example). Yeah, common sense, but even good teams make mistakes (Einstein 2012?).