pic: PBL-104: Planetary Ballshifter

[asid61]

Originally Posted by MStump

Looks cool! Where would you plan to get your 5" wheels from? The standard ones from Andymark and VEXPro are normally 3.5, 4, 6, or 8. I would definitely be interested to see a solid 5" COTS wheel because that opens up the world to a lot more possible ratios.

You can get 5" colsons from robotmarketplace, or banebots as stated above.
Because this doesn't direct drive a wheel from the main shaft (although theoretically you could adapt it to do so) you can place the gearbox in a remote area on one side of your chassis and run 3" or 2.5" wheels.

[cad321]

How do you plan on getting the ring gear? Do you plan to make it yourself or do you have a source for one that you can purchase?

[asid61]

Originally Posted by cad321

How do you plan on getting the ring gear? Do you plan to make it yourself or do you have a source for one that you can purchase?

QTC sells part # KSI1-60, which is a 60 tooth 1 Module ring gear. However, it is heavily modified to add mounting holes and remove most of the steel around the enndges.
If you have a CNC it's not too bad of a modification.

[MStump]

Originally Posted by asid61

You can get 5" colsons from robotmarketplace, or banebots as stated above.
Because this doesn't direct drive a wheel from the main shaft (although theoretically you could adapt it to do so) you can place the gearbox in a remote area on one side of your chassis and run 3" or 2.5" wheels.

Cool thanks! Yeah not direct driving any wheels gives you a lot more breathing room for ground clearance for sure.

[RyanShoff]

Are the two sprockets in the STEP file intentional?

How about getting the output to the end of gear box too?

Any kind of bearings/bushings in the planetary gears? That part reminds me of an Andymark GEM gearbox which brings back bad memories of bag-n-tag day 2013.

[nathannfm]

Originally Posted by RyanShoff

Are the two sprockets in the STEP file intentional?

How about getting the output to the end of gear box too?

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.

[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).