Re: A new shift concept for the engineers....
I'm fairly new here but just found this thread and find it interesting and would like to throw out a few ideas. I have built a few two wheelers of various types that I have engineered myself but all of single speed design. I would love to have a two or three speed bike but there are a few problems mostly what have already been discussed here. One is how to change gears, fairly easy on a low powered bicycle where a small chain can be used and moved around easily. Not possible with a chain large enough to handle say a 3 HP or more. At least no one has seemed to make one work yet. There were at least 200 motorcycle companies early last century that tried just about every design and none had anything like a stacked gear setup. All had a sliding gear tranny of some sort.
Another topic is stopping once you get moving at say 50 MPH. A coaster brake stops just fine at about 20, but 50 is something different. Brakes must be upgraded if you value your skin.
Next, I had a buddy try a motor on a three speed bicycle hub, it lasted only a few miles before it self destructed. Not a feasible option.
My humble opinion is if you want to go faster, your going to need gears, more brakes, and possible clutch. Now your talking about motorcycles!
Modern Antique Cycle