Topic: the coolest brakes I've ever seen

[Industrial Cafe]

that's how I showed my wife a gyroscopic force example.
except he has a fancy axle.

[Retro Rocket]

That makes no difference whatsoever to a gyroscope

mystic_1

Yes but it changes the forces as it stops it trying to twist in a different way. Also what you can't see in that demo is that if it were you holding one end of the axle that the gyroscopic effect of the wheel would be trying to break your wrist, the is a lot of twist going on. I am not going to turn this into an argument mate but those examples are quite different to a motorcycle setup that we are talking about...

Mick

[Industrial Cafe]

I think it's time for me to make a funny video now.

[Industrial Cafe]

Yes but it changes the forces as it stops it trying to twist in a different way. Also what you can't see in that demo is that if it were you holding one end of the axle that the gyroscopic effect of the wheel would be trying to break your wrist, the is a lot of twist going on. I am not going to turn this into an argument mate but those examples are quite different to a motorcycle setup that we are talking about...

Mick

ok here it is!

I watched it twice and I'm still laughing at myself.

[Retro Rocket]

     Told you there was some twist going on.....


Mick

[Industrial Cafe]

hahaha, yeah it's not much, you can easily hold it straight.
but like you said, it doesn't have much to do with the disc setup.
I have a drill with a miniature of that planetary gear setup in it, maybe I'll do some experiments.

[mystic_1]

The physics of gyroscopes is unaffected by how the axle is mounted.  The mounting of the axle will change how the forces are transmitted to other objects, but the underlying physics don't change.  If you believe that gyroscopic precession doesn't occur in a motorcycle due to the fact that the axle is mounted at both ends, you're mistaken. 

Now, whether all this plays a role in the brake design originally posted, unless the rotating rotors equal the mass of the rest of the wheel, they're not going to be imparting a whole lot of force by comparison.  Can't imagine it's worth the added cost, weight, and complexity.

mystic_1

[Retro Rocket]

If you believe that gyroscopic precession doesn't occur in a motorcycle due to the fact that the axle is mounted at both ends, you're mistaken.

I think you need to read between the lines a little Mystic because that is not what i said at all. Look at my examples or IC's video that is what i said. The forces in your examples are different to what i have said because the forks nullify it to a degree by stopping or reducing the Twist by anchoring both sides of the wheel, thats the difference between what you posted and what i was saying. Getting back to the original theme of the post, the reverse spinning discs won't eliminate the gyroscopic effect but they will lessen it, therefore helping the bike steer easier and also making it easier to flop from left to right in corners. You said..."I don't buy the minimizes gyroscopic effect" and that is what i am saying is wrong, it will minimize the effect, not stop it, but definitely minimize it,  the counter rotational forces of the disc are part of the spinning wheel, therefore acting against the forces of the wheel.....its that simple. Another example, the gyro effect of the wheel traveling forward wants to twist the wheel to the left, the discs want to twist to the right,so the forces are pulling against each other reducing the effect of the dominant force which in this case would be the wheel. This is why Motor cycle manufacturers and race teams have been trying these systems out for over 30 years, it works but it isn't used because of the added unsprung weight.

Ok Just did some reading on the physics of gyro's, This is from a physics site.

Gyro's rotating in opposite directions means that some or most of the effects of precession will oppose and cancel out, giving a platform that is more stable than two gyros rotating in the same direction.

torque = dL/dt

where L is the angular momentum of the gyroscope.

The total angular momentum, L, of a pair of counter-rotating gyroscopes is zero. Thus a system with a pair of counter-rotating gyroscopes rigidly joined together will act just like a system with no gyroscope.

Mick

[mystic_1]

If you believe that gyroscopic precession doesn't occur in a motorcycle due to the fact that the axle is mounted at both ends, you're mistaken.

Another example, the gyro effect of the wheel traveling forward wants to twist the wheel to the left, the discs want to twist to the right

I still think you're misunderstanding precession.  A spinning wheel does not "want to twist", in fact, quite the opposite!  Gyroscopic precession occurs when you try to turn the spinning wheel, the wheel will want to twist at an angle different from the applied input  For example, twisting the wheel around a vertical axis will cause the wheel to want to lean vertically.

Precession is NOT the tendency of a gyroscope to maintain it's alignment, but rather the change in vector when you try to change the gyroscope's orientation.

The second quote you posted is immediately followed by the following sentence:

Note that the joining must be rigid. Large forces can be generated in the process of attempting to change the orientation of a such a pair of gyroscopes quickly, which could break the joining if it were not strong enough.

If all forces were canceled, where would the "large forces" come from that could break the axle?

mystic_1

[mystic_1]

If all forces were canceled, where would the "large forces" come from that could break the axle?

mystic_1

Need to drink more coffee before posting in physics-related threads   Understand that both gyroscopes try to precess in opposite directions, that's what breaks the axle.

Still, don't think the axle mounting has anything to do with the way forces are generated in these systems, just how the forces are transmitted.

Man, now I want to build a big counter-rotating gyroscope out of spare front 750 wheels and run some experiments

mystic_1

[Industrial Cafe]

I'm gonna try to do it on a bicycle wheel scale.

[paulages]

as i understand it, the gyroscopic effects of the rear wheel are desirable, as this is what keeps the bike upright, but such an effect on the front wheel is unnecessary, and a lessened gyroscopic effect could ease steering, as the wheel would not being trying as hard to stay perpendicular to its rotating axis.

real world examples: watch GP riders wheelie out of turns... the bike maintains it's stability, because of the balance of the rider's center of gravity leaning into the turn and the gyroscopic effect of the rear wheel under power that is trying to return itself to upright. the front wheel is unnecessary in terms of gyroscopic stability. if the primary goal of the front wheel as a steering component is independent of the bike's need for gyroscopic stability, then it seems to me that moving that spinning wheel about would be easier without fighting this force.

[mec]

to complicate things furthermore:

maybe unknown to one or the other, activating the FRONT brake during a wheelie can prevent from backflip.
with the counterrotating rotors this positive effect is minimized or not present at all dependent on the relationship of rotor rpms and weight (in comparison to wheel rpms and weigth).

mec

[paulages]

to complicate things furthermore:

maybe unknown to one or the other, activating the FRONT brake during a wheelie can prevent from backflip.
with the counterrotating rotors this positive effect is minimized or not present at all dependent on the relationship of rotor rpms and weight (in comparison to wheel rpms and weigth).

mec

that's not too surprising to me actually, as the energy (inertia) from the spinning wheel has to go somewhere if the brakes lock the wheel up. maybe i'm thinking about it wrong, but it seems like this would try to throw the wheel forward a little.

[Industrial Cafe]

doesn't the stopped front wheel cause a tank slapper when it comes down from a wheelie, or is it the accidental misalignment of the front and rear tire?

[6pkrunner]

Any item rotating around a centrally mounted point will have a gyroscopic effect. Plain physics. The trick is to convince someone that this is a bad thing and then get them to spend ridiculous amounts of cash to try to make it better or lessen the effect.
The guy with the counter rotating brakes spent a huge amount of money for a few percentage points of change. He started off at the point of diminishing returns and went from there. The only sad part may be that the masses think this is a great idea and it becomes standard are on bikes and adds hugely to the cost.

[Industrial Cafe]

The unnecessary product you never knew you needed.











they still look cool.   all twirling around the wrong way.

[MickeyX]

OMFG, another dyna beads thread.





 

[Industrial Cafe]

bwaaah

[paulages]

for the record, i wasn't endorsing this at all, just discussing why a person might want less gyroscopics on the front wheel.

[Zaipai]

An interesting read none the less.. I will be having my step son read this his major is in physics.