C
carlfogel
Guest
On Wed, 16 Jun 2004 08:11:40 -0400, ML
<[email protected]> wrote:
>[email protected] wrote:
>> On Tue, 15 Jun 2004 07:54:28 -0400, ML
>> <[email protected]> wrote:
>>
>>
>>>Benjamin Lewis wrote:
>>>
>>>>[email protected] wrote:
>>>>
>>>>
>>>>
>>>>>Benjamin Lewis wrote:
>>>>>
>>>>>
>>>>>>[email protected] wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>>If you have zero trail you can't steer. You'll fall
>>>>>>>over.
>>>>>>
>>>>>>Huh? I think you need to reexamine your model of how
>>>>>>bicycle steering works. Of course you can steer on a
>>>>>>bicycle with zero trail. It's been done. People have
>>>>>>even successfully ridden bicycles with negative trail.
>>>>>
>>>>>We aren't talking about negtive trail, we're talking
>>>>>about zero trail. If you have zero trail and you lean
>>>>>your bike over while riding it, how do you make the
>>>>>bike steer back under you?
>>>>
>>>>
>>>>By turning the handlebars.
>>>>
>>>>I'm not sure what you're confused about here. If the
>>>>wheel is turned the front of the bike will move in the
>>>>direction of the turn as the bike moves forward.
>>>>
>>>
>>>I believe you are wrong on this but can't really prove
>>>it. Unless you have a bike with true zero trail, you
>>>can't prove your point either so these are just mind
>>>exercises.
>>>
>>>If you consider your contact patch as a point on the
>>>pavement, turning your handlebars on a bike with zero
>>>trail will not do anything for you. It will continue to
>>>try to go forward (I believe) and ultimately you will end
>>>up on the ground. Why do I say this? For a couple
>>>reasons. Consider what happens to your bike when you lean
>>>it to the left while walking it. The front wheel swings
>>>to the right and the bike turns into the direction it was
>>>leaned. This is how a person is able to ride a bike no
>>>handed. The bike naturally does the steering for you -
>>>you affect your direction of travel by strictly leaning
>>>the bike through the saddle. Now consider what would
>>>happen if you leaned a bike with zero trail to the left -
>>>nothing. The bike would just lean, the front wheel would
>>>continue straight down the road. Why? Because with zero
>>>trail there is no torque component in either the CW or
>>>CCW direction. The component of the force vector which is
>>>perpendicular to the fork (the frame of reference at this
>>>point) is applied along the fork centerline. In order to
>>>rotate the fork you must have a component of force offset
>>>by some radius from the center or rotation. With zero
>>>trail, you don't have this. So, if you were on this bike
>>>you would fall down. You can't ride this bike no handed.
>>>Now consider what happens when you are on the bike. You
>>>feel the bike start to fall over as you lean so you turn
>>>the bars to steer into the turn. This is where the
>>>problem comes in. Since you have zero trail all you are
>>>doing is rotating the contact point on the pavement. A
>>>true point source does not have a directional component.
>>>In this case though the reality is that the contact patch
>>>looks more like a square or a rectangle than a point so
>>>it will have a directional component. Will this
>>>directional component be enough to actually direct the
>>>bike into the corner? Yes - the front end will act like a
>>>unicycle. I'm not sure how rideable this bike would be.
>>>My instincts tell me only at very slow speeds.
>>>
>>>BTW, I briefly looked through my copy of Bicycle Science
>>>last night & could find no reference to any experiments
>>>done with zero trail bikes. All references were to
>>>various combinations of positive or negative trail bikes.
>>>If you can direct me to references (or to the pages in
>>>Bicycle Science) documenting zero trail bikes I'd love to
>>>read them. I can't think of anything in normal usage that
>>>would be equivalent. Shopping carts, cars, motorcycles,
>>>scooters - they all have trail components.
>>>
>>>Jobst, any thoughts on this subject?
>>>
>>>MOO, Matt
>>
>>
>> Dear Matt,
>>
>> I think that David Jones concluded that we can ride
>> damned near anything in terms of front-end geometry,
>> although most bizarre versions are good for little except
>> for parking lot demonstrations.
>>
>> Below are some articles mentioned in a post elsewhere by
>> Jonathan Thornburg:
>>
>> < [email protected]>
>>
>> http://www.thp.univie.ac.at/~jthorn/home.html
>>
>> Carl Fogel
>>
>> David E. H. Jones "The Stability of the Bicycle" Physics
>> Today , April 1970, 34-40
>>
>> Framk Rowland Whitt and David Gordon Wilson "Bicycling
>> Science", 2nd edition MIT Press, 1982, ISBN 0-262-73060-
>> X (paperback), -23111-5 (hardcover) ... this book has
>> a chapter devoted to stability,
>>
>> J. Lowell and H. D. McKell "The Stability of Bicycles"
>> American Journal of Physics 50(12), Dec 1987, 1106-
>> 1112
>>
>> G Franke, W Suhr, and F Reisz, "An advanced model of
>> bicycle dynamics", European Journal of Physics 11
>> (1990) 116-121
>>
>> John Maddox's report of the Franke/Suhr/Reisz paper in
>> Nature 346, 2 Aug 1990, p 407.
>
>Carl:
>
>The URL for jthorn is not valid. I did a websearch and
>found no other information.
>
>Thanks, Matt
Dear Matt,
Try him at this page:
http://www.aei.mpg.de/~jthorn/home.html
Carl Fogel
<[email protected]> wrote:
>[email protected] wrote:
>> On Tue, 15 Jun 2004 07:54:28 -0400, ML
>> <[email protected]> wrote:
>>
>>
>>>Benjamin Lewis wrote:
>>>
>>>>[email protected] wrote:
>>>>
>>>>
>>>>
>>>>>Benjamin Lewis wrote:
>>>>>
>>>>>
>>>>>>[email protected] wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>>If you have zero trail you can't steer. You'll fall
>>>>>>>over.
>>>>>>
>>>>>>Huh? I think you need to reexamine your model of how
>>>>>>bicycle steering works. Of course you can steer on a
>>>>>>bicycle with zero trail. It's been done. People have
>>>>>>even successfully ridden bicycles with negative trail.
>>>>>
>>>>>We aren't talking about negtive trail, we're talking
>>>>>about zero trail. If you have zero trail and you lean
>>>>>your bike over while riding it, how do you make the
>>>>>bike steer back under you?
>>>>
>>>>
>>>>By turning the handlebars.
>>>>
>>>>I'm not sure what you're confused about here. If the
>>>>wheel is turned the front of the bike will move in the
>>>>direction of the turn as the bike moves forward.
>>>>
>>>
>>>I believe you are wrong on this but can't really prove
>>>it. Unless you have a bike with true zero trail, you
>>>can't prove your point either so these are just mind
>>>exercises.
>>>
>>>If you consider your contact patch as a point on the
>>>pavement, turning your handlebars on a bike with zero
>>>trail will not do anything for you. It will continue to
>>>try to go forward (I believe) and ultimately you will end
>>>up on the ground. Why do I say this? For a couple
>>>reasons. Consider what happens to your bike when you lean
>>>it to the left while walking it. The front wheel swings
>>>to the right and the bike turns into the direction it was
>>>leaned. This is how a person is able to ride a bike no
>>>handed. The bike naturally does the steering for you -
>>>you affect your direction of travel by strictly leaning
>>>the bike through the saddle. Now consider what would
>>>happen if you leaned a bike with zero trail to the left -
>>>nothing. The bike would just lean, the front wheel would
>>>continue straight down the road. Why? Because with zero
>>>trail there is no torque component in either the CW or
>>>CCW direction. The component of the force vector which is
>>>perpendicular to the fork (the frame of reference at this
>>>point) is applied along the fork centerline. In order to
>>>rotate the fork you must have a component of force offset
>>>by some radius from the center or rotation. With zero
>>>trail, you don't have this. So, if you were on this bike
>>>you would fall down. You can't ride this bike no handed.
>>>Now consider what happens when you are on the bike. You
>>>feel the bike start to fall over as you lean so you turn
>>>the bars to steer into the turn. This is where the
>>>problem comes in. Since you have zero trail all you are
>>>doing is rotating the contact point on the pavement. A
>>>true point source does not have a directional component.
>>>In this case though the reality is that the contact patch
>>>looks more like a square or a rectangle than a point so
>>>it will have a directional component. Will this
>>>directional component be enough to actually direct the
>>>bike into the corner? Yes - the front end will act like a
>>>unicycle. I'm not sure how rideable this bike would be.
>>>My instincts tell me only at very slow speeds.
>>>
>>>BTW, I briefly looked through my copy of Bicycle Science
>>>last night & could find no reference to any experiments
>>>done with zero trail bikes. All references were to
>>>various combinations of positive or negative trail bikes.
>>>If you can direct me to references (or to the pages in
>>>Bicycle Science) documenting zero trail bikes I'd love to
>>>read them. I can't think of anything in normal usage that
>>>would be equivalent. Shopping carts, cars, motorcycles,
>>>scooters - they all have trail components.
>>>
>>>Jobst, any thoughts on this subject?
>>>
>>>MOO, Matt
>>
>>
>> Dear Matt,
>>
>> I think that David Jones concluded that we can ride
>> damned near anything in terms of front-end geometry,
>> although most bizarre versions are good for little except
>> for parking lot demonstrations.
>>
>> Below are some articles mentioned in a post elsewhere by
>> Jonathan Thornburg:
>>
>> < [email protected]>
>>
>> http://www.thp.univie.ac.at/~jthorn/home.html
>>
>> Carl Fogel
>>
>> David E. H. Jones "The Stability of the Bicycle" Physics
>> Today , April 1970, 34-40
>>
>> Framk Rowland Whitt and David Gordon Wilson "Bicycling
>> Science", 2nd edition MIT Press, 1982, ISBN 0-262-73060-
>> X (paperback), -23111-5 (hardcover) ... this book has
>> a chapter devoted to stability,
>>
>> J. Lowell and H. D. McKell "The Stability of Bicycles"
>> American Journal of Physics 50(12), Dec 1987, 1106-
>> 1112
>>
>> G Franke, W Suhr, and F Reisz, "An advanced model of
>> bicycle dynamics", European Journal of Physics 11
>> (1990) 116-121
>>
>> John Maddox's report of the Franke/Suhr/Reisz paper in
>> Nature 346, 2 Aug 1990, p 407.
>
>Carl:
>
>The URL for jthorn is not valid. I did a websearch and
>found no other information.
>
>Thanks, Matt
Dear Matt,
Try him at this page:
http://www.aei.mpg.de/~jthorn/home.html
Carl Fogel
