pic: 4x 775pro Ball Shifting Gearbox

Something fun I was working on for 2019…
Geared for 17fps high, 9 fps low (according to JVN’s calc) with 4" wheels.

Looks pretty neat! I would caution against using the aluminum (?) gear for the first stage, as I’ve heard aluminum 32p gears wear down pretty fast in drivetrains.
I love your standoff placement up near the 775s, and the simple 2-plate design. Very good stuff.

Looks great! You should model your wheel geometry and see if your motors would intersect if they’re pushed further out - if they don’t, you can shorten the gearbox and the spacers inside and have the motors hang over the wheel for extra space and weight savings.

And of course, make sure you test a 775drive in the off-season before attempting it in-season!

Yeah we use 20dp gears in our drive and have not had any wear issues in our gear drive after over 50 matches. I think there are better tooth count options in 20dp as well.

20dp gears are great expect they don’t come with matching 20dp pinions that you can press onto 775s (that I know of).

With the great options for 32dp gearing (and 3mm pitch belting), I’d never want to run straight to a 20dp stage off a 775pro!

I was definitely trying to do that when I was modeling this gearbox, although then mounting the spacers on top would have been difficult. Furthermore, since we’re not really that experienced with chain-in-tube, we still put our chain outside of the tube, so there’s just enough space to put in two #25 sprockets from VEXPro, so it all works out kinda nicely, despite the bit of space lost from not letting the motors hang over the tube and wheels.

The great options that don’t let you get the reduction you need, in the form factor you want!
Call me when they get 32p gears in multiples of 2 teeth any pitch diameter from 0.7" to 4.2".

For an initial reduction, they pretty much get you in most ranges you’d want. I use the 12:100 almost every time I use a 775pro gearbox, or sometimes a 12:80. I’ve used the 12:60 in intakes before and know people who have used 12:40 on shooters. The 20dp stuff is great for finer adjustment later on within a gearbox, but when you just need as much reduction in as little space possible, 32dp wins every time!

You can’t fit two 775s on a 40t, and 60t leaves a lot of space unused. 80t is just small enough to make doing a gearbox like the OP posted difficult due to the gear clearances with the cluster shaft, which is part of why 1072 opted to go with the 85t steel gear from AM this year for our elevator.