speed wobble

[bruce]

Well' date=' at least you have increased k then. Should stabilize your bike a bit.[/quote']

 

Ja, but I lost a bit of material in that episode, so my resonance frequency has moved back closer to my natural frequency.

[The_Break]

I think this forum is starting to speed wobble or is it just an earthquake here in China???

[bruce]

oops' date=' that's k * dx and not x.

Still want my discount at the Lab.

[/quote']

 

Don't worry, my calculus is so rusty I'd need a chisel to find it again.

[Guest Big H]

The only wobbles I've got are part of me and not the bike' date=' though sometimes they do occur at speed....

[/quote']

 

Now why cant i get a picture of this harmonic out of my mind?

 

Let me sketch the picture for you...... mr Jan Boreman sitting on a garden swing dressed as a choirboy playing his tyre lyre (plucking the spokes of a wheel to musical overtures) and a whole bunch of sweaty Wielnaaf lede signging in a choir to his music.

[GoLefty!!]

 

Are you making this up or have you been reading bicycling magazines again?

 

Road irregularities play NO role. Try it for yourself. Go no-hands and you'll see that irregularities don't induce a wobble.

 

There is no frictional force "pushing back on your bikes [sic] tyres" In fact' date=' on an inflated bicycle tyre there is no friction between road and tyre at all, unless of course you're wheelspinning your back wheel.

 

Going downhill cannot increase the friction as there was none to begin with and the type of scenario you envisage doesn't exist.

 

Actually, now that I've read your comments on a shortening wheelbase due to flex, I know you're not making this up...you're halucinating.

 

And please don't cry about my tone, when you dish out fairy tales on the tech site you better have a flame suit.

 

[/quote']

 

A very funny response, Sarcasm of the higherst order and a complete lack of understanding of physics still present.

 

Friction is always present. the value of it changes if the tyre is rolling (higher) or sliding (lower - thats why sliding tyres don't stop bicycles riding into taxi's...). Bicycle tyres never work in the realm of adhesion, just very high Friction. Always. Race car tyres, MotoGP tyres, Formula K tyres, those work under the laws of adhesion, not bicycle tyres. Stop all that hallucinating Johan, dagga is bad for you in the quantities you smoke.

 

Riding downhill does not increase friction, it increases the friction forces in the front tyre. You know that F=muN equation thingy. More weight on the front tyre makes for more friction force, less weight well you know the drill.

 

For the Breaks scenario to work the fork would have to be very very flexy, so flexy it's unlikely the bike would be able to turn at speed.. So that is nonsense.

 

AS for speed wobbles, that is simple harmonics. rider weight combination hitting a resonant frequency. Can be cured by shifting weight.

Possible causes are a front tyre with threads in the carcass that has ruptured, visible because the tyre will have a big fat bulge or look like a snake on the rim, loose headset, wheel bearings etc.

 

Fork trail may play a role but I can't prove it.

[Minion]

Simple harmonic motion is typified by the motion of a mass on a spring when

it is subject to the linear elastic restoring force given by Hooke's Law. The

motion is sinusoidal in time and demonstrates a single resonant frequency.

http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/shm.gif

 

The motion equation for simple harmonic motion contains a complete

description of the motion, and other parameters of the motion can be calculated

from it.

 

http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/shm3.gif

 

The velocity and acceleration are given by:

 

http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/shm4.gif

 

The total energy for an undamped oscillator is the sum of its kinetic energy

and potential energy which is constant at:

 

http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/shm5.gif

 

Or simply illustrated graphically:

 

http://www.layoutr.com/graphics/smut/boobs/image/520/bikini-bouncer.gif

 

[GreyOwl]

Thats the best explanation I have ever read!

[bruce]

Perfect example of the lossless conversion between potential and kinetic energy - perpetual motion!!

[GreyOwl]

You gotta love Harmonics!!

[Jason]

Reminds me of my English teacher... Ah the good young days  Just kidding, just kidding...

[Sammajoor]

Simple harmonic motion is typified by the motion of a mass on a spring when it is subject to the linear elastic restoring force given by Hooke's Law. The motion is sinusoidal in time and demonstrates a single resonant frequency.
http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/shm.gif

The motion equation for simple harmonic motion contains a complete description of the motion' date=' and other parameters of the motion can be calculated from it.

http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/shm3.gif

The velocity and acceleration are given by:

http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/shm4.gif

The total energy for an undamped oscillator is the sum of its kinetic energy and potential energy which is constant at:

http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/shm5.gif

Or simply illustrated graphically:

http://www.layoutr.com/graphics/smut/boobs/image/520/bikini-bouncer.gif
[/quote']

 

looking at this my eyes are getting a speed wobble

[The_Break]

Anyone know where I can get a set of those?

[Wonder Woman]

Anyone know where I can get a set of those?

 

I hope you don't want them for yourself

 

Guys, thanks for the good giggle, I needed that

[bruce]

Anyone know where I can get a set of those?

 

I hope you don't want them for yourself

 

Guys' date=' thanks for the good giggle, I needed that

[/quote']

 

Engineering humour   Somehow I was never able to pick up any of the BA Social Anthro chicks with it

[The_Break]

No, I just need to do some testing on them.