[hamdani yusuf]

- But I do wonder about the handling in the transition zone, where anything you did with the control surfaces would have no effect...   Maybe it just flew like a paper dart...

Perhaps they have secondary control option, like pressurized air throttle. They are more expensive, so they are only used for some specific cases where cheaper options fail.

[alancalverd]

The US Space Shuttle had a strange quirk that when gliding at hypersonic speeds, the effect of the left/right control surfaces was reversed,

Was that rudder or aileron control? Or both?

Problem at hypersonic speed is that the compression front moves as you change attitude, so in addition to the low-speed lift and drag forces, you have something else shoving the aircraft around in a mode that you don't normally experience. Early "sound barrier" test pilots complained about locking control surfaces and also a supposed reversed control effect but that was all traceable to distortion of the aircraft.

[charles1948]

Yes, but I remember reading, until quite recently, that moving bicycles stay upright because of the gyroscopic effect created by the whirling wheels.

That was the orthodox theory.  Now disproved, or so you claim.

It never appeared in any physics textbooks that I read. Bicycle wheels are designed to have the minimum moment of inertia consistent with their intended load and terrain. If you try to turn a heavy, spinning wheel, say to the left, it will try to flip you over to the right - not what we want on a bike!

Bicycle stability arises from the angle of the front tube. If you lean slightly to the left, the wheel turns to the left, so the bike starts to turn left and centrifugal force stops the bike from falling over.  You can demonstrate this by making a bike with zero or negative tube angle, the latter being pretty impossible to ride.

Thanks Alan.  That makes sense to me.  The front end needs to be leading the direction of motion.

[hamdani yusuf]

Yes, but I remember reading, until quite recently, that moving bicycles stay upright because of the gyroscopic effect created by the whirling wheels.

That was the orthodox theory.  Now disproved, or so you claim.

It never appeared in any physics textbooks that I read. Bicycle wheels are designed to have the minimum moment of inertia consistent with their intended load and terrain. If you try to turn a heavy, spinning wheel, say to the left, it will try to flip you over to the right - not what we want on a bike!

Bicycle stability arises from the angle of the front tube. If you lean slightly to the left, the wheel turns to the left, so the bike starts to turn left and centrifugal force stops the bike from falling over.  You can demonstrate this by making a bike with zero or negative tube angle, the latter being pretty impossible to ride.

Thanks Alan.  That makes sense to me.  The front end needs to be leading the direction of motion.

Something that makes sense isn't always correct.

Which bit of
 

why

did you not understand?
When you answer, be sure to take account of the video hamdani yusuf posted which points out that you can even have a negative trail and still ride the bike.