Originally Posted by Allen_Wrench
Then there's trikes. Real easy to ride no hands. Say! what if you could build a bike or trike that could be easily steered without hands! For, like, disabled people or people who've lost their hands, like soldiers or accident victims. It could be configured Big-Wheel style, where you pedal the front wheel directly and you could also steer like that. Hmmm...
There are many examples of lean-steer trikes, but almost of them (all but one type I have seen, in fact) are not dynamically stable at higher speeds.
Most people playing with bicycle parts want to build the trike to tilt automatically, but also to stay upright when it is stopped. To do that they mechanically link the lean angle with the steering(turning) angle, and you cannot do that and still have positive stability--though many, many home-builders with a lack of understanding have built fantastic Rube-Goldberg-type steering arrangements to try anyway.
That is also why there were no tiliting trike motorcycles ever, until very recently--(Piaggio MP3
)--and the Piaggio MP3 works by using regular mechanical steering control to turn the front wheels left-and-right, and use a computer and hydraulics to automatically tilt the vehicle the proper amount.
It is possible
to make an all-mechanical arrangement for a bicycle
that is dynamically stable and that will stand up when stopped (with a rider holding the controls) but you must use a free-to-caster steering arrangement that wouldn't work quite like you expect. It would REALLY need a motor to be useful though, because the main advantage is that in high-speed turns, it will never oversteer--but you'd need to be going fast enough for lateral tire slip to occur to see that.
For a motorcycle there are other additional issues, mainly being suspension feedback through the steering controls related to the heavier vehicle weight.
This guy came up with the same idea (long before I did) and built a larger motorized vehicle, and is promoting it as a solution to--well, to the lack of tilting trikes, I guess.
TILTING VEHICLE control systems.... X prize tilting vehicle
I wish him well, but he seems to want somebody to come and dump a pile of money on him for him to allow them to build and sell these things--and somehow I don't think that's real likely to happen. The Piaggio MP3 system is already proven to work well, and is way lighter and more compact than what he is proposing. The website has the same photos/videos it had several years ago.