How Are Bicycles Like Airplanes and Stilt Walkers Too

[Patrick1000]

This is a fun thing to play around with.

For a long time, lots of people thought bicycles balanced because the frame sat atop 2 gyroscopes, but if you think about it for a minute, that doesn't make a lot of sense as one can balance on a bike while he or she is hardly moving at all.

Bicycles are actually more like stilt walkers than anything else. It is fun to figure out why that is so and how it is that bicycles balance in this way, circus performer like. There is more to it than just that, a bike's balancing, but the stilt walker thing is a big part of it.

Also, a big claim to fame of the bicycle is that it taught the airplane how to turn. Essentially all of the Wright Brothers' contemporaries thought planes should and would turn like a boat, with a "rudder" in the back pressing the turn as a paddle does. The Wright Brothers were not only bicycle builders, but enthusiastic RIDERS as well. As such, they realized planes should turn like their bikes, by way of banking/leaning. This is one of the reasons they succeeded where others failed. They understood bicycles and so understood how it was that a plane should turn. AMAZING!!!!

Anyone else have a fun fact or two or three that has to do with the world's coolest machine?

Here's my favorite article on bicycle balancing/dynamics. It is technical, but one can find others on line as well.


http://bicycle.tudelft.nl/schwab/Publications/06PA0459BicyclePaperv45.pdf

 

[Robrob]

one can balance on a bike while he or she is hardly moving at all.

Operative word being "moving."

 

[Tomtomkent]

Simple experiment: try and balance on a bike or unicycle while not moving at all..

 

[Patrick1000]

Well put Tomtomkent, another thing to do.....

Simple experiment: try and balance on a bike or unicycle while not moving at all..

Well put Tomtomkent. Another thing to do is to think how it is, why it is, that a bicycle is easier to balance on than a unicycle. It is sort of obvious of course, but going through it in detail really puts it all in perspective.

 

[Molinaro]

Bikes don't balance. The rider does the balancing.

I can easily stay upright with zero motion. Heck I can even lounge with 1 leg extended out across the handlebars, and my arms crossed at my chest and stay balanced while at a complete standstill.

And I can assure you that on the many occasions where I rode across this set of train tracks no handed, it was me, and not the bicycle who did the balancing.

I rode 150 miles a day, 5 days a week, 50 weeks a year for 6 years.

Oh and to the idea that bikes turn by banking... hogwash! The bike goes where the front wheel is pointed. If you go slow, banking is completely unnecessary, and yet you still turn. When you are moving faster there is enough of an outward force felt that you need to bank to avoid tipping over. That does not mean the bank is what is causing the bike to turn.

 

[Patrick1000]

An interesting perspective and it brings up one of my favorite points about bicycles.

Bikes don't balance. The rider does the balancing.

I can easily stay upright with zero motion. Heck I can even lounge with 1 leg extended out across the handlebars, and my arms crossed at my chest and stay balanced while at a complete standstill.

And I can assure you that on the many occasions where I rode across this set of train tracks no handed, it was me, and not the bicycle who did the balancing.

[qimg]http://img689.imageshack.us/img689/4217/tracksty.jpg[/qimg]

An interesting perspective Molinaro, and it brings up one of my favorite points about bicycles.

If one compares bicycles with airplanes, there are 2 things that one notices right off the bat, 2 obvious, critical things that have to do with the machines' pilots. Half of all bicycle pilots are much much prettier than the majority of airplane pilots. The other thing one notices right away about bicyclists is that unlike airplane pilots, bicycle pilots are bigger than the machines that they "drive". This is one of the reasons bicycles have eluded rigorous physical description for so long, why they have eluded formal mathematical modeling.

I am 150 lbs, my favorite bicycle is 15 lbs. I weigh 10 times as much as my bicycle. Imagine if a 747 pilot weighed 10 times as much as his/her 747. For this and other reasons as well, it turns out the mathematics of bicycle dynamics/movement/balance/steering is much more complicated than that of airplanes. I am speaking about basics/fundamentals here of course. I am speaking with reference to the development of fundamental mathematical models describing the dynamic behavior of the two different machines. Basic bicycle math is much more complicated than basic airplane math.

Another point.....

Actually, there is no such thing as teaching a child to ride a bicycle. By that I mean that a bicycle will balance itself if the child pedals fast enough. An adult, a parent, running along side a child is functioning as a shaman in a sense, crowding out fear. If you can get the child to look up and pedal fast, the child/bicycle unit/duet will balance without any conscious input from the novice pilot.

There is no such thing as "bicycle balancing skill". FEAR is the only thing that keeps a child from balancing. It is a tad more complicated than that, but not much.

 

[Molinaro]

You seem to be focused on riding in a straight line on perfectly smooth ground. I spent as many miles ridding very rough trails as I did on the roads, and I can assure you, "bicycle balancing skill" is very real.

 

[Patrick1000]

Last thing I want to do is take that away from you Molinaro....

You seem to be focused on riding in a straight line on perfectly smooth ground. I spent as many miles ridding very rough trails as I did on the roads, and I can assure you, "bicycle balancing skill" is very real.

Last thing I want to do is take that away from you Molinaro....Like I said, there is a lot to it and there really is NO mathematical model yet for bikes.

Your "answer" is as good as anyone's...

Sounds like you ride a lot, so do I......

 

[Molinaro]

Last thing I want to do is take that away from you Molinaro....Like I said, there is a lot to it and there really is NO mathematical model yet for bikes.

Your "answer" is as good as anyone's...

Sounds like you ride a lot, so do I......

Rode a lot. Not nearly as much anymore. I was a full time courier who also rode about 20 hours a week on trails. Now, I don't ride anywhere near as much as I would like.

 

[bikerdruid]

why it is, that a unicycle is easier to balance on than a bicycle.

nuh uh.

 

[Molinaro]

nuh uh.

Oh ya, missed commenting on that one. I've tried a unicycle on a couple occasions. I couldn't get 5 feet before falling over. Waaaaaaaaaay harder than a bike.

 

[Patrick1000]

Too bad....

Rode a lot. Not nearly as much anymore. I was a full time courier who also rode about 20 hours a week on trails. Now, I don't ride anywhere near as much as I would like.

Too bad....about not getting to ride as much as you'd like. I live in San Francisco, lots of hills and ride for fun and basic transportation as well. I can get anywhere in the city on a bike pretty much as fast as a car, unless of course it is a pure climb.

I have a one speed, multigeared hybrid and a super high end rode bike. I design as well as ride. Love it......

 

[Patrick1000]

Thanks for the correction!!!!

nuh uh.

Thanks for the correction!!!!

 

[Pulvinar]

...This is one of the reasons bicycles have eluded rigorous physical description for so long, why they have eluded formal mathematical modeling.

So, how do you explain autonomous cycling robots? For example:

Actually, there is no such thing as teaching a child to ride a bicycle. By that I mean that a bicycle will balance itself if the child pedals fast enough.

If true, a bicycle should stay balanced with no rider if rolled down a hill. Have you tried this?

 

[elgarak]

Bikes don't balance. The rider does the balancing.

I can easily stay upright with zero motion. Heck I can even lounge with 1 leg extended out across the handlebars, and my arms crossed at my chest and stay balanced while at a complete standstill.

And I can assure you that on the many occasions where I rode across this set of train tracks no handed, it was me, and not the bicycle who did the balancing.

I rode 150 miles a day, 5 days a week, 50 weeks a year for 6 years.

Oh and to the idea that bikes turn by banking... hogwash! The bike goes where the front wheel is pointed. If you go slow, banking is completely unnecessary, and yet you still turn. When you are moving faster there is enough of an outward force felt that you need to bank to avoid tipping over. That does not mean the bank is what is causing the bike to turn.

How do you explain this, then?

No rider. No robot with active steering/balancing. Just a bike, rolling, and perturbed. A rolling bicycle is self-correcting all by itself.

 

[Furcifer]

I forget the exact quote, but I believe the bicycle is the most efficient machine ever created when used for its intended purpose. They convert almost 100% of the energy input into forward motion. Not to shabby.

 

[SezMe]

No rider. No robot with active steering/balancing. Just a bike, rolling, and perturbed. A rolling bicycle is self-correcting all by itself.

That one brief example in no way refutes P1K's sweeping, erroneous generalizations.

 

[Andy_Ross]

Oh and to the idea that bikes turn by banking... hogwash! The bike goes where the front wheel is pointed. If you go slow, banking is completely unnecessary, and yet you still turn. When you are moving faster there is enough of an outward force felt that you need to bank to avoid tipping over. That does not mean the bank is what is causing the bike to turn.

How about Motorbikes?

When I take a fast corner I have to bank the bike and if it is severe enough i put on a slight opposite lock. I even hang off the seat to put weight further into the bend.
If I turned my bars into the corner I would certainly come off.

I think that a different set of dynamics takes over above a certain speed.

 

[Patrick1000]

The people thing is only part of the difficulty/mystery.......

So, how do you explain autonomous cycling robots? For example:





If true, a bicycle should stay balanced with no rider if rolled down a hill. Have you tried this?

The people thing is only part of the difficulty/mystery.......Of course bicycles balance and balance fairly well without a rider.

AS LONG AS ONE DOES NOT LOCK THE STEERING, a bicycle will balance reasonably well WITHOUT A RIDER rolling downhill.............

"If true" is not the best of terms here........

 

[Patrick1000]

That's RIGHT!!!!!

How do you explain this, then?

No rider. No robot with active steering/balancing. Just a bike, rolling, and perturbed. A rolling bicycle is self-correcting all by itself.

That's RIGHT!!!!!

Why is that?!!!!!!

Bike's balance themselves!!!!!!! So if a parent can get his/her child to simply pedal and "not worry", not be afraid, if the child will only look ahead and pedal, voila!