pic: ABS-114, supercompact planetary PTO shifter

[asid61]

I forgot to update the Partner Space recently it looks like. I just finished, so you can take a look at the CAD here. As a side note, ABS-110 (the PTO shifter with the 3-position cylinder) is 0.7lbs lighter than this and far easier to machine. It's also about as compact. The only disadvantage it has compared to this one is the lower spread; 2.3 versus 3.4.

Originally Posted by GeeTwo

That's a lot going on in a little space; very impressive, especially if it works.
The CAD or at least a few renders from other angles would be helpful to understand it all, but let's see how much I can get it from the one render:

• Is there a second pancake (or other) cylinder hiding under those CIMs, probably coaxial with the drive shaft that accomplishes the drive train shifing, or is the cylinder on top some sort of 3-state device?
• Where is the PTO output located? I understand it's linked to the ring gear, so the most obvious place would be behind the drive shaft, where I thought the shifting cylinder would be located. Doing this would not only move the shifter out of the obvious place, but it would be difficult to pass all the different coaxial shafts through the large gear, so I'm guessing that the annular gear has teeth on both the inside and outside of the annulus, and the PTO is another spur gear that takes off of that. Doing bevels would require a lot of extra work and thrust bearings for no discernible benefit.
• If I understand this right, the PTO output would have to have the shifter in high speed/low torque (single stage) mode, and the carrier is locked, so the output gear ratio would be (64 / 11) * (72 / 30) = 14.0:1 at the ring gear, possibly higher or lower if the PTO is not directly taken from the ring gear.

Yes, there is another Vex pancake cylinder underneath the CIMs.

The PTO output is a 32 tooth #25 sprocket that sits in between the 60t gear and the ring gear. It is linked to the ring gear via an aluminum hub/plate. Only one shaft; no double-tooth things involved. None of the gear teeth have to be machined fortunately.

That's right, the carrier is locked and the sun gear is engaged to make the PTO work.

Originally Posted by Chak

This is incredible... After half an hour of looking at ABS-111 (the latest one I can find online) and googling planetary gear ratios, I think I sort of understand now. Time for questions:

• which one is the carrier plate?
• how do you lock the ring gear/carrier plate? I'm assuming there's a custom piece of metal the render is hiding... I want to see it.
• checking my understanding: so there is a "suicide mode" (high gear/PTO) where the carrier plate is linked to the input but the carrier plate is locked?
• consider using Andymark's new CIMcoder? I hear that it's thinner than the 3D printed one
• how does one machine their own ballshifter? (looking at ABS-111)
• Is that 60t gear hitting the bolt next to it?
• how close are the CIM gears to hitting the gearbox plate?
• that's a cool way to attach something normal to a gearbox. I might steal one one day.
• what are those 6 holes near the output for? I assume 2 is for mounting a piston on the other side, but 6?

Edit: can we at least get a render of the internals?

The carrier plate is the frontmost aluminum plate, in front of the brown steel ring gear.

The odd tooth-looking dealies on the carrier and ring engage with 1/4" steel pins with rounded ends to lock them. The cylinder simultaneously disengages/engages at the same time.

There is indeed a "suicide mode". Hopefully one would check to make sure the code is working right before activating that endgame mechanism.

Oddly enough, the 3D printed version is better because I actually want less CIM shaft protruding out. It can intersect with the PTO chain if it's too long. I have the second one to act as a spacer.

Usually it's very tricky to machine, but this one is easier than most. Start with a rod, turn down the outside dimensions leaving 13.74mm for thunderhex, bore out the cylinder for the ball part, drill through with a 1/4" drill bit. Then take it over to the mill, stick it on a dividing head, drill the 6 ball holes and mill down the hex. The gears you just stick on a fixture and CNC.
The linkage thingy between the shifting cylinder and the shifting rod is something of my own design, utilizing a 3/8"-16 outer 10-32 inner threaded insert and a couple bearings. Very easy to machine and more compact then the Vex option.

Yes, that bolt is. Good catch, I must have moved something. I just replaced it with a countersunk screw so it no longer touches.

The CIM gears are about 0.6" in diameter, and the hole in the plate to accept the CIM is 0.75", so no danger there.

Thank you, I liked it too.

2 for mounting the cylinder, 4 for mounting. This has a couple options for mounting; you can use the bottom 2 screws that keep the gearbox together or just the 4 holes in the front plate.

There is no real "PTO shaft"; there is a single shaft. The PTO output is attached to the ring gear, which is possible due to epicyclic (planetary)/differential gearing shenanigans.

I would try for an internal render, but the internals are rather convoluted so it's hard to get everything with one picture. Let me give it a try though.