Question for Thinkers

I wonder if a fellow could ride a bicycle on a conveyor belt moving in the direction of front to back of the bicycle. Would the bicycle stay upright? I think it would be possible,. I have heard of boys walking on the tracks of a crawler tractor while it is moving.

Another question: would it be possible to tide a bicycle backward down an incline?


Too much idle time!

If I was this particular fellow, then the answer is NO.

I see no problem with riding a bike on a conveyor. As to riding one backward down an incline, I feel sure someone can do it. Ever watched some of those BMX type shows on TV? I don't think there is anything they CANNOT do on a bicycle nowadays!

Yes.

Need to be able to steer a bike side to side a tad to keep balance. As the tires are spinning on it, you can move it side to side, so you can keep your balance so you can ride it on a treadmill and appear to be mostly standing still at the same time.

I think a lot of kids have coasted a bike backwards down a hill, doesn't take too long to adjust to the 'rear steering' and keep your balance.

Paul

(quoted from post at 20:10:23 04/03/15) I wonder if a fellow could ride a bicycle on a conveyor belt moving in the direction of front to back of the bicycle. Would the bicycle stay upright? I think it would be possible,. I have heard of boys walking on the tracks of a crawler tractor while it is moving.

Click to expand...

Of course you could, they have been selling a similar thing for decades. Bike people train in the winter on rollers, staying in the same place on a conveyor belt would be the same thing.

http://en.wikipedia.org/wiki/Bicycle_rollers

(quoted from post at 20:10:23 04/03/15) Another question: would it be possible to tide a bicycle backward down an incline?


Too much idle time!

Click to expand...

If your balance is really good you can. BMX guys do it all the time on ramps. I rode alot of mountain bikes as a kid but I rarely was able to do it, usually fell. Sometimes you are going up a really steep spot, maybe you got caught off guard or maybe you missed a shift but you didnt make the hill and had no place to spin around so you might hang in hoping you can ride it back down. Dont do in the thorns heading up the RR tracks, BTDT and didnt care for it too much. There is a certain grace to being able to step off the bike right at the moment you stop forward momentum.

I think it would be challenging. Now the backwards downhill i would think would be worst.

Yes to # 1. A bike doesn't know whether it is moving linear or not. What keeps a bike upright is the gyroscope affect of the wheels turning. Faster they turn the easier it is to stay upright. At a certain speed it will stay up even without a rider. Some of the motorcycle " wheelie kings" that can ride a wheelie all the way around a motocross track , have a small electric motor on their front wheel turning it at a high rate of speed to help keep bike verticle even at ultra slow wheelie speeds. They turn using only weight of their body leaning.

Without looking this up I have to "guess" no. I think keeping the bike up-right is partly an outcome of moving the weight produced by momentum toward, (or away from), a side necessary to offset that side's tendency to fall over. Yeah that sounds idiotic but I think that's the answer in my gibberishese. gm

As kids growing up watching Bugs Bunny, we got lots of ideas watching. One was that if we took turns climbing to the tops of trees while the others cut or chopped them down, if we jumped up just before they hit the ground, we would come to rest easily on our feet and just walk away. It never worked for any of us. All of us lived, but it didn't come close to working. Nice thing about being a kid, you can often smack into the ground, bounce around, not always break bones, and your buddies will help you get back up so you can regain your wind after a few tears and gasps for air.

Mark

What about an airplane on a conveyor?

You mean like a bicycle on a treadmill? Good luck with that.....

Airplane on a conveyor, won't do anything but make the wheels spin. Never develop any air speed, so no lift.

Wheels on a plane are just casters. It's driven by the prop(s). Makes no difference the plane will still move forward like normal.

You guys should watch the TV show.
"The science of stupid"
Lots of people trying to break the laws of nature with disastrous result

:lol:

Contrary to popular belief, it's not "gyroscope effect" that keeps bicycles and motorcycles upright. It's the self-correcting nature of their steering: when you lean, the bike turns in the direction of the lean, which then cancels out the lean. This remains true as long as the bike remains "moving". In the case of a conveyor belt, even though the bike isn't moving in relation to the earth, the surface of the conveyor belt is moving so the self-steering effect still works.

Mythbusters tried that with their dummy named Buster in a falling elevator. Buster got busted, jumping at the last nanosecond didn't help.

Here's another thought, if you have a bunch of birds resting in a large container and weigh it, would it weigh less if they were all flying around?

I beg to differ Mark.

If a motorcycle is driven slowly it will respond to input from the handlebars by turning in the direction the front wheel is pointed.

At some speed the forces change and the bike actually turns in the opposite direction from the input from the bars. Sounds crazy but if you are rolling at 50 mph and you push the right handgrip out (turning the front wheel left) the bike will lean to the right executing a right turn.

Brad

Now you gone and done it! Imma tryin' to conjure me up one of them-there thoughts and it's givin' me a powerful headache! Hurt so bad I durn near fell offin' the stump I wuz a-settin' on.............

Before stationary exercise bikes became so sophisticated, bicycle rollers were common: two cylinders about eight inch dia. with enough space between to catch the rear wheel, and one roller to set the front wheel on. The rollers were 18 to 22 inches wide. Rails along each side held the rollers in position. The front and rear rollers were connected with a belt. You put your bike on and with a little difficulty got going. You could ride in place on your regular bike. Even the best of them would rumble. People in adjacent apartments would complain. It was possible to steer off of the rollers so constant vigilance was necessary or off you would go in the furniture.

Ever see Doug Domokos wheelie the entire Unadilla circuit? I have. If memory serves me it was at the 1987 Motocross De nations. As mentioned, the BMX guys can do the downhill backwards stuff. Anyone ever watch the movie, "On Any Sunday"? There is a segment on trails riding competition. There was some incredible footage of Malcom Smith riding a trails bike up a near vertical rock face, stops for an instant, and comes back down backwards, stops at the bottom for an instant and then rides off in a different direction.

Brad, the effect you're talking about is called "countersteering", and it happens at ALL speeds. It's more noticeable at high speed because the forces trying to keep the bike upright are greater. You learned to countersteer the first time you rode a bicycle, you just weren't aware of it.

The next time you're on your bike, try doing the "push" at low speed. I guarantee you, no matter how slow you go, the bike will turn the opposite direction of the push.

"It's more noticeable at high speed because the forces trying to keep the bike upright are greater."

Might this be the gyroscopic effect of the wheels and tires rotating at high speeds?

Brad

>Might this be the gyroscopic effect of the wheels and tires rotating at high speeds?

Perhaps. But accepting the role of gyroscopic forces defeats your original argument, which was that countersteering doesn't work at low speeds.

An interesting thing about gyroscopic precession is that it acts on an axis 90 degrees from where axis where the rotational force is applied. So when you turn the handlebars (yaw), the front wheel reacts by precessing on its roll axis. And when you lean (roll) the bike, you feel the precession effect through the handlebars (yaw).

I call BS!!!
Contrary to your statement, "popular belief" is CORRECT. There is no other explanation for the stability of a bicycle at any significant speed. Gyroscopic forces are the ONLY plausible explanation.

Interesting discussion.

Introducing yaw into the conversation is a bit interesting. As I understand it yaw is primarily an aeronautical term for the effect produced by actuating the rudder on the rear of the craft which causes the plane to rotate relative to the direction of travel.

This also eventually induces a roll force which can be counteracted by cross-controlling, inducing a sideslip. As the bike is pretty much locked into its direction of travel by the wheels I fail to see how yaw is a factor.

Also there is the factor of camber, also known as fork rake on a cycle which insets another variable into the equasion.

Brad

You are overlooking inertia, the tendency of an object to keep moving at the speed and direction it is traveling. A person with very good balance can ride a bicycle on a conveyor or treadmill, but it will take better balance than on a moving one, in addition to many other things the conveyor is a lot narrower than the road. LOL. I agree that the gyroscopic action of the wheels help, but their contribution is only part of the overall factors.

(quoted from post at 22:14:13 04/03/15) What about an airplane on a conveyor?

Click to expand...

Those Nebraska girls must have some pretty big treadmills to be able to put an airplane on em.... *shivers*

(quoted from post at 08:22:33 04/04/15) At some speed the forces change and the bike actually turns in the opposite direction from the input from the bars. Sounds crazy but if you are rolling at 50 mph and you push the right handgrip out (turning the front wheel left) the bike will lean to the right executing a right turn.

Click to expand...

While the wheels [b:70723cea53][i:70723cea53]are[/b:70723cea53][/i:70723cea53] acting like a gyroscope, they are not what makes the turn. In a turn as you describe above, what makes the bike go to the right is when you push the handlebar to the left, the bike drives out from under the rider causing a lean which is what makes the bike go right. After the lean is established, the rider is not pushing quite as hard on the bars so the bike actually is turning right but with still pushing on the bars. Throughout the turn, you need to keep pushing the handlebar left because the bike needs that correction since the rider is pushing against the seat (high side of the bike) making it want to tip over toward the outside of the turn. Once the turn is complete, you are easing off the counter steer push and the bike rides back under the rider and the riders force pushing the bike to the outside of the turn quits. Soon everything reaches equilibrium and the rider goes straight.

It should be noted, that during the turn, the handlebars [b:70723cea53]do[/b:70723cea53] turn to the right. If they didn’t, the bike couldn't go around the turn with lean alone; it still has to turn around the corner weather its going 1 mph or 100mph. Don’t take my work for it though; wrap a coat hanger around the handle bars with the end pointing right at the gas cap. Now, have a friend drive and you look over his shoulder. What did you see? Neat, huh? Never knew your bike did turn right when you were giving it counter steer to the left, did you?

The wheels are like a gyroscope but that causes it to be harder to make the turn, not easier, nor is it the reason for the turn. Don’t believe me, test it for yourself. Take one of your kid’s bike wheels off the bike. Hold the axel in your hands and have someone spin the tire really fast. Now, try to turn the wheel. Now, wrap your brain around the fact that its a wheel that weighs 2 or 3 pounds, spinning maybe 10mph. Multiply that to 10 pounds spinning 50 mph.

FWIW, anybody that says counter steering works at low speeds has never rode a bicycle, much less a motorcycle. If you try to counter steer on a bike at slow speed (any bike, motorized or peddle) the bike will just ride out from under you and you will be on the ground. But don’t believe me, try it. Better yet, watch any 5 year old that just got his training wheels off. They don’t understand the lean part yet so they try just steering like they did with training wheels which is in effect the same as counter steering. Watch as they steer the bike right out from under themselves. You can try the same thing with your hog or dirt bike but you will fall all the same. Want to go right, pushing the right handlebar away will steer the bike left and it will go right out from under you. Why? The human body it not pushing to go straight through the turn and it isn’t pushing on the bike.

That Newton and his 3 laws, he was a smart fellow, wasn’t he? I don’t even think they had Harleys back then but he accurately predicted what would happen.

There is even a wiki page about this stuff and it likely does a much better job of explaining it than I did. http://en.wikipedia.org/wiki/Countersteering They cover this a lot if you take a motorcycle safety class.

Brad, I only used the terms "yaw" and "roll" to indicate the axes of the front wheel, not to indicate any sort of motion by the bike itself.

As for rake (and the resultant "trail"), rake and trail are what make a bicycle or motorcycle work. A bike with zero trail, meaning the axis of the front fork passes through the contact patch between the tire and road, is almost uncontrollable.

You can say "BS", but you might want to think it through first. Do really think a motorcycle wheel that's barely turning has enough angular momentum to keep an 800 pound Harley from falling over? If gyroscopic forces keep the bike upright, you wouldn't be able to budge the handlebars while the bike was in motion.

If you want to take a few minutes, there's plenty of info that describes how bicycles and motorcycles work. You can start with the link below.
Bicycle and motorcycle dynamics

People that ride a lot more than I do sometimes use rollers in the house in the winter.
That's a contraption that has two rollers for the back wheel and one for the front. A
belt runs from one rear roller to the front roller. A good rider can stay balanced and
ride.

So yes, your conveyor belt ride is possible.

I was getting dizzy just reading this . now if I go for a motorcycle ride I am going to think its going to fall over.
so if you roll a wheel across the yard it says upright as long as its rolling so if you put the same wheel on a treadmill and its spinning in place? I want to say if wont fall over?

Most of the opinions stated in this thread on how a bicycle remains upright, or whether a plane can take off from a treadmill, are based on things from Bugs Bunny cartoons.

My son and I saw Doug Demokos wheelie the entire motocross track at RedBud in Buchanan, MI in about 1982. He was wheeling a 3 wheeler in the pits later. I have some distant pics.

My brain cell is on overload now

no cussing on this site please!!

MarkB has it correct:

I used to teach motorcycle safety and would demostrate using the broom from the corner of the classroom. I would place the wooden handle end in the open palm of my hand with the broom end up. To balance the broom I would move my hand opposite to the direction the broom was falling. I would walk around the classroom with the broom balanced on my open palm. To go forward I would move my palm back as the broom fell forward I would begin walking forward and move my palm as required to rebalance the broom. To turn left I would move my palm right then walk left as the broom fell to the left and move my palm to rebalance the broom. Gyroscopic effects are not needed and are not significant at low speeds.

BTW - A baseball bat (heavy end up) is easier to balance however, they would not allow me to have a baseball bat in the classroom.

I watched him in the late '70,s at the Silverdome (Supercross) do same thing and that front wheel was spinning so fast you couldn't see any spokes and that was without ever touching ground for the total time it took to crawl around that long track. It was being "spun" and for good reason. Not taking anything against Doug but facts are facts.

Well, if we had video cameras when we were kids and video taped our failures, they wouldn't have wasted a perfectly good elevator or dummy.

Mark