[EricH]

Originally Posted by kk052

also the brass on titanium is to make the brass take all the wear, so we dont need to replace the titanium

All the wear, as in "you better replace 'em often". Brass isn't known for wearing well--in fact, it's better known for deforming when harder materials apply force to it (to the point where when a hard material is getting beat up, and brass is suggested as a replacement, engineers start asking "Are you sure about that?" and "Is there another material that will work?"). Try bronze instead--it's a little harder, and to some extent can be made somewhat self lubricating (bronze bushings, NOT brass bushings). Titanium is already really hard, harder than most FRC gears are, which will tend to increase the wear on the brass gears even more than, say, aluminum/aluminum interactions or steel/steel interactions.

Regarding the screws: You're loading the screws in shear. (Quick check: Do you know what shear stress is, in broad terms? If not, we'll be happy to explain.) What that means is that the screws are going to want to "cut" themselves apart, probably at the spacer. The tendency is actually less if there are multiple locations for the shear stress to act at, hence the suggestions to run the bolts through, giving double shear instead of single shear. If you're concerned about clearance, there are ways to deal with that, including sinking the holes for the screw heads and nuts so the heads drop right out of the plane of the side plates.