Counter Rotating Brakes Vid

[PSk]

Originally Posted by Just Riding Along

Now I don't really buy into that leverage of the turning the bars, take a look at the modded Beemer in the Tony Foale link I posted. Also take a look at the hub center bikes, no pivot at the headstock there.

It's still there ... even if just a theoretical point. That fact is thanks to rake, the chassis of the bike has to move, or the front wheel skid.

BTW: I'm no great push bike rider ... never even been in a velodrome .
Pete

[Just Riding Along]

It's easier to slip the wheel than bend the chassis (and recover from the bend). As Scott said earlier the real world angle you need to put in the bars to turn is miniscule. Now compare that with flicking the bars lock to lock when you're stopped.

Now for an extra can of worms, the tires front and rear are slipping when you ride. That's another varible in turning.

[Mashuri]

Originally Posted by PSk

It's still there ... even if just a theoretical point. That fact is thanks to rake, the chassis of the bike has to move, or the front wheel skid.

BTW: I'm no great push bike rider ... never even been in a velodrome .
Pete

After reading all this I'm leaning (pun intended) toward the gyroscope camp. Question, PSk: Why would I, at parking lot speeds, need to steer my bars into the corner to get the bike to lean and turn that direction while, as speeds begin to get above 10-15 mph or so, I now have to countersteer to get the same results? What has caused the forces against the headstock to completely reverse direction?

[AZ Scott]

Originally Posted by Mashuri

After reading all this I'm leaning (pun intended) toward the gyroscope camp. Question, PSk: Why would I, at parking lot speeds, need to steer my bars into the corner to get the bike to lean and turn that direction while, as speeds begin to get above 10-15 mph or so, I now have to countersteer to get the same results? What has caused the forces against the headstock to completely reverse direction?

That's a great question.

At parking lot speeds, you don't feel like you're countersteering, but in a way you actually are. You're just using body english to start the lean. To really notice the countersteering effect, you have to have a little more forward speed.

The problem is, it's really hard to measure what you're doing at parking lot speed. You may feel like you're perfectly straight up and down, and when you turn the bar to the right, you go right. But it doesn't happen that way.

In reality, at slow speeds when you lean your body to the right, you actually start to fall to the right - just as you would if you were parked. You then turn the bar to the right in order to "catch" the bike and keep it from falling all the way over.

So, rather than "turn the bar to the right and the bike goes to the right", it's really the other way around.

Trust me, Mashuri, it's not the gyro effect that makes you turn. I wouldn't *steer* you wrong on this one...

[PSk]

Originally Posted by Mashuri

After reading all this I'm leaning (pun intended) toward the gyroscope camp. Question, PSk: Why would I, at parking lot speeds, need to steer my bars into the corner to get the bike to lean and turn that direction while, as speeds begin to get above 10-15 mph or so, I now have to countersteer to get the same results? What has caused the forces against the headstock to completely reverse direction?

I think AZ Scott has already answered this but I have some points to discuss.

I can feel the inward push of the head stock standing still, thus it is there at all speeds.

I think we choose not to use it at low speeds because we are insecure about our balance. Now we should talk to those m/c freaks that do that jumping logs, etc. on those trail bikes, cause their low speed ability is brilliant. I'm pretty sure that in the few cases where I have actually seen TV footage of this, they move the handle bar all over the place while they do the same to their body to maintain balance.

On my way home tonight I am going to do some tests :

I will lean my bike WITHOUT allowing the handle bars to move. What will happen, will the bike try to turn?

If it does turn then this proves that the lean does produce the turn and the only reason counter steering works is it produces the lean (hence why front wheel direction does not matter).

I've sort of already done this test this morning coming to work, and I proved to myself that counter steering does just (?) produce this inwards force, because I reproduced it with my knee/leg and yep the bike leaned and turned. I though did not rigidly hold the handle bar ... without welding the thing this part of the test will be contentious.

I will also move my weight to oneside and NOT balance the bike by leaning it the other way.

Thus I expect the bike to lean in and turn. Thus proving that the bike and rider CoG does/can produce a turn by causing the bike to lean. An earlier post stated that weight position on a bike has little impact on initiating a turn ...

I think this is a fascinating subject, and if I had a spare bike and some $'s I'd be making a zero rake bike. Man that would be interesting.
Pete

[Dezmo]

everything everybody said about centrifugal force keeping the bike from falling over in the corner is 100% correct.....but thats once in the corner....argue all you want, but the turn is initiated via precession (with help from gravity)


edit: if you think about this, it makes sense....how much can gravity lean a bike over if the momentum is carrying it straight forward?

[Dezmo]

Originally Posted by Mashuri

After reading all this I'm leaning (pun intended) toward the gyroscope camp. Question, PSk: Why would I, at parking lot speeds, need to steer my bars into the corner to get the bike to lean and turn that direction while, as speeds begin to get above 10-15 mph or so, I now have to countersteer to get the same results? What has caused the forces against the headstock to completely reverse direction?

its quite simple really, at low speeds the gyro effect is minimal. Once you get the wheels spinning, gyro effect kicks in, and countersteering starts working.

[banda]

Originally Posted by Dezmo

its quite simple really, at low speeds the gyro effect is minimal. Once you get the wheels spinning, gyro effect kicks in, and countersteering starts working.

I call BS.

If this were true, there would be a wheel speed where steering would be impossible.

Steering is accomplished in two ways, both of which are available at any speed.
One is by the rudder effect of turning the front wheel. At low speeds this produces little or no roll. Try it in your car. It's the same thing. At high speeds, it produces enough roll that the bike starts riding on the opposite side of the tires, coning it around in a circle.

You can rudder turn or cone at any speed. Rudder turning at elevated speeds initiates coning in the opposite direction. That's all.

Stop talking about gyros. You clearly don't understand them.

Read "Proficient Motorcycling" by David Hough for a complete and simple description of motorcycle handling. It is not mysterious. It is quite simple.

[Just Riding Along]

Originally Posted by banda

Read "Proficient Motorcycling" by David Hough for a complete and simple description of motorcycle handling. It is not mysterious. It is quite simple.

Which is better, Proficient Motorcycling, or More Proficient Motorcycling? the library has both (he does ride worms though). I'm refering to Motorcycle Handling and Chassis Design. Side note, if you ever get a chance to sign up for a Tony Foale seminar, and if you've got a group then set up a seminar. I haven't forced myself to think that much in 20 years. You also leave with some nice punch in the #'s bike setup tools. He'll talk your ear off if you sit down with him.

[ChiDuck]

Originally Posted by banda

I call BS.

If this were true, there would be a wheel speed where steering would be impossible.

Dezmo is right

it's the law of conservation of angular momentum. the spinning front wheel has angular momentum. the faster your'e going, the more momentum. when you apply a torque to the bars, the angular momentum equation must be balanced, and the result is a torque that leans the wheel to one side.

and yes, theoretically, if you were going fast enough it would not be possible to apply enough torque to the bars to get the bike to lean..... but at 11ty-billion miles per hour your tires would probably fly apart

[AZ Scott]

Well, golly. I'm going to go right out and buy a set of cast-iron wheels for my bike right now! Not only will it be super stable, it'll steer like lightning with all that gyroscopic help!

Maybe I'll fill my tires with cement, too.

Jeez, you guys don't make any sense at all. If gyroscopic effect is good, why on earth does less make it better?

Lemme guess: Because it just so happens, by sheer coincidence, that while reducing wheel weight, the reduction in steering efficiency caused by the reduction in gyroscopic force is cancelled out because the reduction in unsprung weight makes it handle that much better. In exact proportion.

So...

Reduce the mass of the wheel by 10%, and you get 10% less gyro effect, which makes the steering 10% harder to do.

BUT...

You also get 10% less unsprung weight, so it makes your steering 10% easier!

So it all evens out in the end, right???

Okay, I believe you!

[Mashuri]

Originally Posted by AZ Scott

That's a great question.

At parking lot speeds, you don't feel like you're countersteering, but in a way you actually are. You're just using body english to start the lean. To really notice the countersteering effect, you have to have a little more forward speed.

The problem is, it's really hard to measure what you're doing at parking lot speed. You may feel like you're perfectly straight up and down, and when you turn the bar to the right, you go right. But it doesn't happen that way.

In reality, at slow speeds when you lean your body to the right, you actually start to fall to the right - just as you would if you were parked. You then turn the bar to the right in order to "catch" the bike and keep it from falling all the way over.

So, rather than "turn the bar to the right and the bike goes to the right", it's really the other way around.

Trust me, Mashuri, it's not the gyro effect that makes you turn. I wouldn't *steer* you wrong on this one...

Well, I've ridden my bike in an abandoned parking lot before just to figure some of this out. At low speeds, in neutral with my hands off the bars, I could get it to "fall" into corners but it took a lot of effort. Using one hand on the bars I decided to focus specifically on how I pressured them to turn. I had to steer them into the corner to go that direction (keeping my body upright and letting the bike lean under me) while, once the wheels got going, I had to countersteer. I don't doubt your convictions about this, Scott, but my real-world experience just doesn't seem to jibe with your hypothesis.

[Mashuri]

Originally Posted by PSk

I think AZ Scott has already answered this but I have some points to discuss.

I can feel the inward push of the head stock standing still, thus it is there at all speeds.

I think we choose not to use it at low speeds because we are insecure about our balance. Now we should talk to those m/c freaks that do that jumping logs, etc. on those trail bikes, cause their low speed ability is brilliant. I'm pretty sure that in the few cases where I have actually seen TV footage of this, they move the handle bar all over the place while they do the same to their body to maintain balance.

On my way home tonight I am going to do some tests :

I will lean my bike WITHOUT allowing the handle bars to move. What will happen, will the bike try to turn?

If it does turn then this proves that the lean does produce the turn and the only reason counter steering works is it produces the lean (hence why front wheel direction does not matter).

I've sort of already done this test this morning coming to work, and I proved to myself that counter steering does just (?) produce this inwards force, because I reproduced it with my knee/leg and yep the bike leaned and turned. I though did not rigidly hold the handle bar ... without welding the thing this part of the test will be contentious.

I will also move my weight to oneside and NOT balance the bike by leaning it the other way.

Thus I expect the bike to lean in and turn. Thus proving that the bike and rider CoG does/can produce a turn by causing the bike to lean. An earlier post stated that weight position on a bike has little impact on initiating a turn ...

I think this is a fascinating subject, and if I had a spare bike and some $'s I'd be making a zero rake bike. Man that would be interesting.
Pete

You should try riding Keith Code's "No BS Machine". It has an extra pair of "handlebars" welded to the frame that demonstrates, especially once the wheels get going, trying to steer the bike with your body simply does not work.

[Dezmo]

Originally Posted by AZ Scott

Jeez, you guys don't make any sense at all. If gyroscopic effect is good, why on earth does less make it better?

because you dont need as much as stock wheels have? is it really that hard for you to comprehend? lighter wheels have less gyro force, but its still enough to turn the bike, too light and theres not enough force.

Go ahead and put the heaviest wheels you can find on your bike, it will turn like crazy but require very heavy steering efforts

you seem so adament that I am wrong, but you have yet to come up with 1 valid arguement that disproves the fact that precession makes a bike lean.

I will argue to the death about something if I know I'm right, and in this case, I am 100% positive that I am correct.

[Mashuri]

Originally Posted by AZ Scott

Well, golly. I'm going to go right out and buy a set of cast-iron wheels for my bike right now! Not only will it be super stable, it'll steer like lightning with all that gyroscopic help!

Maybe I'll fill my tires with cement, too.

Jeez, you guys don't make any sense at all. If gyroscopic effect is good, why on earth does less make it better?

Lemme guess: Because it just so happens, by sheer coincidence, that while reducing wheel weight, the reduction in steering efficiency caused by the reduction in gyroscopic force is cancelled out because the reduction in unsprung weight makes it handle that much better. In exact proportion.

So...

Reduce the mass of the wheel by 10%, and you get 10% less gyro effect, which makes the steering 10% harder to do.

BUT...

You also get 10% less unsprung weight, so it makes your steering 10% easier!

So it all evens out in the end, right???

Okay, I believe you!

Wouldn't it be nice if physics were that simple? I think one variable that still has to be taken into consideration is the source of handlebar force: The rider. His/her strength remains constant throughout these changes, therefore the torque applied to the bars remains constant. So long as the gyroscopic force is strong enough to resist that force it will always be counteracted and applied to the headstock. Unless the rider is Superman, the bike will always lean more quickly when it has lighter gyros to resist the bike's desire to lean. Hope this makes sense.

EDIT:

I guess, to sum up what I'm saying, is that the gyroscopic force only has to be strong enough to resist the rider's inputs, which even the lightest unobtanium wheels provide way more than enough of.

[ChiDuck]

reducing angular momentum (or gyro effect if you want to call it that) will make it easier to turn

lighter wheels = easier turning

heavier wheels = more stable in a straight line

say it with me people: conservation of angular momentum

[Mashuri]

Originally Posted by ChiDuck

reducing angular momentum (or gyro effect if you want to call it that) will make it easier to turn

lighter wheels = easier turning

heavier wheels = more stable in a straight line

say it with me people: conservation of angular momentum

Just to clarify,

Heavier wheels would also equal more stable cornering once leaned over as well, right? That's assuming, of course, a glass-smooth surface so unsprung weight won't affect handling.

[Dezmo]

I think I should point out something here:

in a straight line, with no steering inputs, the front wheel acts as a stabilizing gyro, keeping the bike upright.

the instant you put countersteering force into the bars, precession occurs and the bike leans over, the gyro goes from being something that adds stability to something that reduces that stability enough for the bike to turn, so to speak....pardon me if I dont know the snooty college terminology for it.

lighter wheels make it easier to turn because you are having to move less mass to get the effect, and anything lighter can change direction quicker.

and banda: I understand gyros perfectly, whats not to understand about them? Just because I dont have a fancy degree means I cant comprehend a basic law of physics? please.

Please quit ignoring the fact that ANY spinning disc is a gyro, including motorcycle wheels.

[banda]

Originally Posted by ChiDuck

reducing angular momentum (or gyro effect if you want to call it that) will make it easier to turn

lighter wheels = easier turning

heavier wheels = more stable in a straight line

say it with me people: conservation of angular momentum

Rotating wheels do in fact have angular momentum, and a force applied to them is redirected through 90 degrees...

BUT that effect is negligible. Miniscule. Unimportant. It ain't part of how a bike handles. It doesn't mean squat. It's a red herring. To think that it is the root of how a bike turns or stays stable is uninformed folly. It is ignorance of the very real type, where you are ignoring the other physical interactions.

trail = stability and resistance to direction change, proportional to speed.

front wheel yaw (turning the bars) provides a side thrust that does two things: a) changes the direction of travel in the same way turning the wheels of a car does and b) causes body roll of the vehicle in the same way that turning the wheels of a car does. The body roll is proportional to the forward speed and the degree of the turn.

coning = absent other forces, the single track vehicle travels in a circle around the point on the plane of travel where the axis of the axles would intersect. The farther it's leaned over, the closer that point is, and therefore, the tighter the circle.

All of these easily understandable interactions are still in play regardless of the angular momentum of the wheels. Heavy wheels, light wheels, theoretical wheels with no mass, it doesn't matter... the three things above still apply.

There's a bunch of other stuff about motorcycle dynamics I'm sure you gyro heads don't know - Did you know that the front wheel of a motorcycle is constantly "weaving" even when you are traveling in a straight line? It does. It tracks to the right and to the left of the wheel in an oscillation, all the time. Its the caster of the front wheel, the trail, that pushes the wheel just a little bit past being back in line, so it weaves from side to side. Explain that with your gyroscopic forces and angular momentum.

When a motorcycle is traveling around a corner, the front wheel tracks outside of the rear wheel... the rear wheel turns in a tighter arc. In fact, the front wheel is pointed to the inside of the turn ever so slightly, the wheels are NOT in line when traveling around a corner. Explain that with your angular momentum and your gyroscopes.

Just because you saw a kid rotate slowly on a stool while trying to twist a bicycle wheel in 9th grade science doesn't mean that angular momentum is the mysterious unseen force that makes motorcycles work. There's a pile of evidence right in front of you that angular momentum doesn't mean squat when you're talking about motorcycle stability or turning.

Quit making yourself look silly.