[Kevin Sevcik]

This is more or less the exact tranny that Team 57 used this year. We had an issue with gears disintegrating, but that was poor design and wasn't the shifting gears. We beefed up that pair of gears and things were fine. We also had an issue with the shifter getting stuck, but that was an alignment problem and was fixed with the judicious application of a hammer.

On to some points brought up in this thread...

Yes, there will be times with the gears won't mesh perfectly when you shift. If you think about it, Dog shifters have this problem as well. Anyways, we had no issue shifting on the fly. Occasionally one side would engage before the other, but it was never very bad. The best thing you can do is shift the trannies with pneumatics. They'll naturally act as springs and keep pushing the gears together till they mesh.

I will say that the proposed method of "rounding" the gears isn't really productive. Especially if you that to both of the meshing gears. That won't really make the gears mesh better because you still have the same basic cross-sections trying to mesh. What you really need to do is dremel the sides of the gears down to points. That makes it much easier for the gears to mesh. You can also make it easier by setting the gears a little farther apart than would be strictly advised by pitch diameters. This increases backlash and makes the gears slightly weaker, but it makes meshing even easier.

Also, you can reduce the chance of breaking the gears by moving the shift as far up the gear train as possible. If you can shift gears on the low torque end of the tranny they don't have to be as strong so you can reduce the size.

Finally, I think this kind of transmission is a bit easier and more forgiving. Dog shifting trannies almost mandate a CNC shop to get the dogs right. A reasonable gear meshing tranny will just need a good drill press with an X-Y table without much slop, and possibly a lathe.