pic: PBL-104: Planetary Ballshifter

[asid61]

Originally Posted by nathannfm

I don't think you understand how it is designed to work, the sprockets ARE the output. You would have 2 chains running out of the gearbox to 2 of the 3-4 wheels per side of the robot, which would also have double sprockets on them and be chained to the other wheel or 2.

Pretty much. For that reason this is a less-than-optimal gearbox for anything that is cantilevered, as you waste weight on the extra sprockets.

An output on the main shaft is tricky, as it always spins at a 5:1 ratio from the cims if you use 12t pinions. The sprockets wiill change speed when shifted, but not the main shaft.
In order to have an output on it, the sprockets would have to be put on another versahub which is attached to another shaft that is coaxial with the main shaft. Kind of a pain, and there's no way to do it while remaining within a couple pounds.

[nathannfm]

Originally Posted by asid61

Pretty much. For that reason this is a less-than-optimal gearbox for anything that is cantilevered, as you waste weight on the extra sprockets.

An output on the main shaft is tricky, as it always spins at a 5:1 ratio from the cims if you use 12t pinions. The sprockets wiill change speed when shifted, but not the main shaft.
In order to have an output on it, the sprockets would have to be put on another versahub which is attached to another shaft that is coaxial with the main shaft. Kind of a pain, and there's no way to do it while remaining within a couple pounds.

Could you replace the 2 sprockets with a gear and put another shaft underneath the whole thing with a 1:1 gear (or not 1:1 if you don't want) and have a cantilevered output that way?

Not super necessary or elegant, but I don't see why it wouldn't work.

[asid61]

Originally Posted by nathannfm

Could you replace the 2 sprockets with a gear and put another shaft underneath the whole thing with a 1:1 gear (or not 1:1 if you don't want) and have a cantilevered output that way?

Not super necessary or elegant, but I don't see why it wouldn't work.

The point of this was to reduce weight and keep the single-shaft design; by adding a large gear and a second shaft it loses both of those advantages unfortunately. If I had to make a 2-shaft gearbox I would just make a regular ballshifter (like ABS-101, although I would probably increase the primary reduction if I were to go that route; that gearbox went a tad too fast for most).