pic: what do you think?

[Veselin Kolev]

Here's what I think.
If you want to just go for the design, meaning make it even though you probably will never use it, awsome. I think you're just going for a challenge, which is great. As for the mechanical part of it...

Sure, it looks like it'll work and all, if you get the right gear ratios, etc... but I myself have 2 "major"issues with this form of 3 speed. You notice that the spacing on the 3rd gear is a lot larger than for the first 2 gears. That is necesary to clear the first two from engaging, but it eats up space. Second, you are literally using the gear teeth as a shifting medium. Sure, cars do it too, but cars have syncros. Sure, other teams do it a lot, but I look at their gears by the end of the season and they are worn out a lot. For robotics purposes, sure it works. For anything else, I would look for a different method.
If you get a flexible coupler on the output shaft of this transmission so it takes the forces of shifting, your gears will probably be fine. Just look up "lovejoy" couplers online if you want an example of one.

If you're interested in slick transmissions, check out the white paper on the Technokats 2003 tranny. It's a two speed, but, as we've seen from other teams, it can be modified to be much more.

Other than that, this concept can work easily. Cool idea!