[Stu Bloom]

Matt,

Depending upon the specific circumstances when shifting, and if you are planning to be able to shift "on the fly" then I believe you will have a couple of significant concerns with this type of design. <disclaimer>I am NOT a gearbox expert - engineers with more gearbox/transmission experience are welcomed/encouraged to coment/correct my statements</disclaimer>

1. Stripping the gear teeth could be a huge problem. When the gears first begin to engage (while moving) there will be a significant load concentrated across a very small shear area as just the edges of the teeth of both gears are in contact. At this instant there is also a much larger than usual (about 2X) moment arm which will cause increased bending stresses at the root of the tooth.

2. It will be very difficult to maximize your efficiency while allowing gear shifting in the plane you suggest. A few thousandths of an inch change in center distance can make the difference between gears binding if too tight, or having too much slop/backlash if too far apart.

OK experts ... fire away and educate me ...