Pillar of Wisdom - Gyroscopic forces...not

[HappyMartin]

 

Just do the wheel experiment like I so laboriously spelt out. Try it, then ask specific questions. I really can't explain better than that.

 

Ok so I laboriously did the experiment and my specific question is so what? The bike tracks slightly left and right as you said. The faster the less it tracks left and right. So what if it is not gyro forces keeping me up? Something is keeping me up and it gets easier as I get faster. Momentum is still my friend is it not?

 

It could be magical stickyuppy particles that are in the air and the faster I go the more they stick to me and so I stay up easier. Like I said. If you can't explain the usefulness of it all I don't really care.

[Brian Fantana]

At X-Games, in the Moto-X best trick category you can see gyroscopic forces in action. In certain tricks, riders will gas it at a specific position in the air. The rapid acceleration of the rear wheel generates gyroscopic force, which is needed in order to help them get into proper position for the next, flip/360/landing. However, this only helps while they are in the air, while they are on the ground, I am not sure how big an effect the gyroscopic forces will have to help keep the balance.

Edited June 10, 2013 by Brian Fantana

[BergForce]

Ok so I laboriously did the experiment and my specific question is so what? The bike tracks slightly left and right as you said. The faster the less it tracks left and right. So what if it is not gyro forces keeping me up? Something is keeping me up and it gets easier as I get faster. Momentum is still my friend is it not?

 

It could be magical stickyuppy particles that are in the air and the faster I go the more they stick to me and so I stay up easier. Like I said. If you can't explain the usefulness of it all I don't really care.

 

It is mostly your own balance/steering keeping you up, more so the lower the speed.. Gyro forces helps more with an increase in speed, but I think that if you travel at high speed and your headset is stuck in center position you will topple over even at high speed.

[Johan Bornman]

Ok so I laboriously did the experiment and my specific question is so what? The bike tracks slightly left and right as you said. The faster the less it tracks left and right. So what if it is not gyro forces keeping me up? Something is keeping me up and it gets easier as I get faster. Momentum is still my friend is it not?

 

It could be magical stickyuppy particles that are in the air and the faster I go the more they stick to me and so I stay up easier. Like I said. If you can't explain the usefulness of it all I don't really care.

If you don't care, you don't care. Move on.

[Johan Bornman]

It is mostly your own balance/steering keeping you up, more so the lower the speed.. Gyro forces helps more with an increase in speed, but I think that if you travel at high speed and your headset is stuck in center position you will topple over even at high speed.

 

No.

[BergForce]

No.

 

Null? No.

[nolipoli]

"While remaining upright may be the primary goal of beginning riders, a bike must lean in order to maintain balance in a turn: the higher the speed or smaller the turn radius, the more lean is required. This balances the roll torque about the wheel contact patches generated by centrifugal force due to the turn with that of the gravitational force. This lean is usually produced by a momentary steering in the opposite direction, called countersteering. Countersteering skill is usually acquired by motor learning and executed via procedural memory rather than by conscious thought. Unlike other wheeled vehicles, the primary control input on bikes is steering torque, not position.^[8]"

 

Wikipedia on Motorcycle and bicycle dynamics...

Edited June 10, 2013 by nolipoli

[Robrider]

Without arguing with any of the previous posts, I believe that it is not only your body that keeps your bike upright when you are riding at higher speed, lets say 20km/h +.

 

Your bike geometry, especially the head angle will help you as well. The fact that all bikes I know of have head angles slacker than 90º dictates that a bike will "try" to keep itself straight when travelling at a fair speed. The head angle of a bike is similar to the Kingpin Inclination angle on a car, which is where the self centering action of a car's steering comes from. Imagine trying to ride no hands with a bike with a 90º head angle, it will be very challenging.

 

However, the forces described above are small relative to the weight of the rider (weight not mass). So although the head angle plays a part to keep the bike upright, the intuitiveness(which is a very natural thing) of the rider plays a bigger role in keeping the bike upright.

 

I agree. its about stability, the geometry helps the bike "self correct".

[Capricorn]

I agree. its about stability, the geometry helps the bike "self correct".

 

slacker just makes the steering less sensitive, which is a plus at high speed. But it makes for ultra shite cornering with some major understeer if you rely on turning the bars, which is why DH bikes are crap in tight corners unlike an XC machine with a steeper HA.

 

and the amount of condescension in this thread.. yikes.

[Johan Bornman]

I rode motorbikes for years. Counter steering is the quickest way to get the bike over. Once it dips into the turn you lean with it. I do the same on the road bike in fast corners. No idea on MTB. Too much going on and if I think at all I end up in casualty. Sometimes end up there anyway.

 

If you don't mind Johan please explain to me, I'm not good at this stuff as you will hear, what are the practical implications of all this gyro stuff that does not work as we think it does. It still seems to me that speed is my friend whatever the physics behind it might be.

Speed is your friend.

 

Go and have a look at Mode 1 steering. You'll see that unless you have speed, you cannot travel far enough in the short space of time you have to correct the balance. The analogy I can use here relates to the broomstick experiment. If the stick's top falls to the left and your hand reacts too slowly in moving the base of the stick to the left (directly underneath the top), then the top will outrun the bottom and the stick will fall.

 

When cycling, the same happens. Your head falls over to the left and you have to get your bum underneath that head as quick as possible so that you remain in balance. You do this by steering to the left. However, steering alone doesn't move you, you have to travel forward to move left.

 

Therefore, if you steer to balance and your speed is too low, you will not get your bum in the required position fast enough and you fall or....revert to Mode 2 balancing.

 

Momentum per se is not what you're after, but speed is. Momentum is a function of speed and mass. But what I'm saying, is that you can get the same momentum by moving a higher mass at a slower speed and that will not help you steer quick enough. I'm just being specific when I say that velocity, not momentum is your friend.

Edited June 11, 2013 by Johan Bornman

[Johan Bornman]

If you don't care, you don't care. Move on.

 

@HappyMartin.

 

I didn't mean to sound gruff. I could have tactfully said: "Not everyone will find this interesting and therefore please don't spoil the conversation if it is something you don't care about."

 

Instead, it sounded like "Voertsek!"

 

Sorry.

[RexFuzzle]

Ah, found it: http://www.scientificamerican.com/article.cfm?id=self-stable-bike

[HappyMartin]

 

 

@HappyMartin.

 

I didn't mean to sound gruff. I could have tactfully said: "Not everyone will find this interesting and therefore please don't spoil the conversation if it is something you don't care about."

 

Instead, it sounded like "Voertsek!"

 

Sorry.

 

No problem. You made a fair point.