My reading of the No BS bike (from the OP’s links) is that there is a standard set of handle bars that can steer the bike, and a fixed set of handle bars that can’t. It seems to me that when riding with the fixed handle bars the front wheel is free to turn in just the same way as a bicycle wheel will when riding hands-free. So why is the No BS bike so hard to ride compared to a bicycle? Does it really prove that you can’t body-steer a bike due to physics or is it more that motorbikes don’t have enough freedom of movement in the steering to allow the front wheel to naturally counter-steer and steer on its own?
I can’t get to your video. Even after I downloaded the latest Quicktime software, I couldn’t see it on Quicktime. I tried it on Real, too. No dice. Rather than a simple 404, I got a Windows error message every time, that shut down the browser.
So, I can’t tell whether it argues with me or not. Perhaps I wasn’t clear, but I contend that a bicycle with the steering locked (not articulated) can still be steered by leaning. When you lean the frame, the slightly banana-shaped tire footprint forces a turn.
I think you’re wrong and here’s why. When you lean a bike you need a very specific amount of turn on the front wheel to keep the bike turning at a rate that prevents you from falling over sideways. In other words, a given lean angle and speed requires a particular steering angle on the front wheel, any other steering angle results in either the bike not turning enough and you falling off, or the bike turning too much and you straightening up. Given that when you turn a bike you also turn the front wheel into the turn (after the initial countersteer), it would appear that not turning the wheel would result in a fall.
Also I think that having two wheels connected and not articulated results in the banana effect being either severely reduced, or removed altogether.
Experiment. Get a toy bike without articulated steering and a coin. Roll the bike along the floor. Any lean on the bike will result in it falling over. Roll the coin and it will turn in to counter any lean. So people riding on a unicycle or doing a wheel-stand on a motorbike can steer, but when they have two wheels on the ground they need to able to move the front wheel or they fall. They may not be aware of what they’re doing with the front wheel, but remove their ability to do it and they won’t be able to ride.
Don’t know all the physics but there is quite a difference between a 20 lb bicycle with a 200 lb rider and an 800 lb chopper with a 200 lb rider.
As I understand it, countersteer is when riding in a straight line on a flat surface and the front wheel is turned in the opposite direction from the desired direction change.
When that happens the mass of the riders tends to want to stay in the plane and direction it is going and the machines wheels move to to the right if that was the direction the rider turned them. Now gravity pulling down on the whole mess with the wheels now located to the right of the center of mass helps the lean increase and the machine rolls up on the side of the tires so to speak. The lean is such, that like a coin, the wheels roll in a circle (Mass wanting to keep on and wheel wanting to fall over) but not in the same track. ( look behind you on a surface that leaves a track. )
Now, get your self crowded to the curb by a redneck asshat in a pickup where yo can’t turn the wheel to the right because it is rubbing on the curb. Most times you will crash to towards the curb because you can’t or won’t LEAN towards the pickup. So down you go.
But… If you will lean away from the curb, the machine will track away for the curb. The tire is running more and more on it’s side which allows more and more turning. That contact patch that is referenced up thread is helping you. (But, try riding hands free one of those fat credit card monstrosities that they make on TV for putting in a show case with the really wide, fat, stupid rear wheels and a real skinny front wheel way out in front.)
Now, more about not wanting to change the direction of mass.
A dead skunks appears in the riding track from under the cage ahead of you. Instant bad karma that. With a flick of the bars, the heavy motorcycle’s wheels can be moved as much as 8-12 inches to the side without hardly any turning happening for a short distance. So, with this flick movement, the wheels pass to the side of the skunk and your chest and head pass right over the top of it. The flick of the bars the other way, brings the wheels back under the center of mass and very little actual turning was done. A lot less than the distance the wheels were moved to the side.
The reason the locked steering will not work on a bicycle and will on a unicycle is that when the lean is done, the wheels are trying to turn in two different over lapping circles and not just one. It has to fall over.
Just as balancing as you ride along, there are constant minor movements of weight shifting and steering head movement.
Ride real slow and counter steering will dump you but actual turning or the front wheel in the desired direction works just fine. The human can not take out subtle weight adjustments. The things going on when the speed is so slow that “object in motion wants to keep on keeping on” is over powered by gravity reaction speeds and distance from the contact patch by the mass that a flat statement that all steering is initiated by count steering is not quite the whole story. When riding a bicycle or a big heavy motorcycle hands free I have not seen the machine or the resultant track show that the front wheel first turned the wrong way in a counter steer. On a long chopper with bad geometry and a wheel that is easy to see that has excessive trail, well, it don’t do that when riding hands free.
So tot he OP, no the wheel does not need to turn. To remain upright in a controlled condition for any distance requires some wheel turning. If a machine is welded up with the wheels perfectly in line, and you got a shove along in a perfect straight line and then leaned, the machine would start to turn as it crashed. So a turn was done. There was no condition stated that it had to be successful.
YMMV
You are assuming that the rider’s body weight must remain in line with the frame’s center line. The rider can easily lean the frame right and his body left. Riding with locked steering would certainly be difficult, and I wouldn’t want to ride that way often. I’m only asserting that the tires will steer when leaned.
One style of bicycle road racing involves keeping the frame upright in corners while leaning the body to the inside of the curve. The advantage is that pedaling can continue without dragging the pedals. I’m only mentioning that to show that the body weight can be far off the center line.
Others have covered this well but note that a motorcycle has much greater mass. Thus, while it can be coerced into leaning it ain’t gonna’ lean much.
I say it won’t be ridable. Only way to find out for sure is to try it, which I don’t have the inclination to do.
I read this description, and this describes a bike with a set of handlebars that are fixed to the frame, in addition to the usual set. Note that the front wheel is not fixed in place. What they were trying to show was that some riders believe they are steering the bike when they lean, but when they put their hands on the fixed handlebars they could not get the bike to turn by any amount of leaning. This showed that when they were leaning they were unconsciously countersteering.
Here we seem to come full circle, because the OP cites two descriptions of this bike in the question. In fact, one of those links gives the answer to the question being asked:
I believe the “unrideable” situation would be a front wheel locked into place so it could not turn.
This trick isn’t limited to motorcycles. I was taking pictures at a criterion bicycle race once, standing on a corner inside a turn. I thought I had plenty of room, then I noticed one of the top riders (I think it was Davis Phinney) would sometimes take his track through the curb and flick the bike out from under himself for an instant, basically taking the corner in free fall. I stood back a bit more after I saw that that.
Perhaps I’m picturing this much different than some of you. I’m riding a fixed steering bike in a straight line on a level surface. If I stand up on the pedals and try to lean to the left (in an effort to turn left), I end up pushing the bike to the right. My contact patch undergoes what I’m about to call acute inverse radial bananafication…my contact patch curves slightly right, not toward my intended turn. My body is extended to the left of my bike - which is leaning right - but NOT my center of mass (whose location remains the same). Since my center of mass doesn’t change, I can’t turn.
This is more or less how I see things working.
I agree with this summary. I don’t think the very slightly banana-ish contact patch would actually cause the bike to turn.
The only doubt I have would be at very high speed, where the very slight banana-shaped contact patch would be enough to compensate for the lean required.
On the other hand, that still wouldn’t be a ridable bike, because there would be no stability - no negative feedback to correct imbalances.
Bicycles and motorcycles are similar, but not the same. The weight and gyroscopic forces are much higher on a motorcycle.
Motorcycles turn by leaning. The (oval shaped) contact patch moves up the left side of the tire in a left hand turn. Because the left side of the contact patch is on a portion of the tire with a smaller radius than the right, it travels less distance with each revolution, causing the turn. Think of a solid axle with a bigger wheel on the right side. It would turn left when rolled.
So motorcycles turn by leaning. The lean is controlled with the steering. To turn left, you steer right. This moves the wheels out from under the center of gravity and (along with the gryoscopic affect), cause the bike to lean left. Steering is relatively neutral during the turn, and you then turn the wheel left to straighten the bike.
A bike with locked steering would be unrideable.
If the rider leans in one direction and the bike leans in another (with locked handlebars), the center of mass of the system is going to stay in the exact same spot. Like the diving off the boat example. Not sure if you saw the video, but check out how far this dude leans off the side of his bike with no result turning http://www.youtube.com/watch?v=3nRUeEkS644
At slow speeds, the motorcycle technique is the exact opposite of your second paragraph (but then again, at slow speeds, countersteering is not employed). The rider, when making a left turn, hangs his right cheek off the seat. It’s actually pretty fun.
I don’t think that would be unrideable, because at slow speed you could use your feet to balance, and at high speed, you’ve got three huge gyroscopes keeping you upright (the engine is the third).
I don’t know how true it is, and I’m sure we could find video evidence, but I’ve heard that if th rider falls off the bike it will maintain itself upright until it hits something or slows… like the earlier coin example, but without turning.
Consider this. There is a banana shaped contact patch on a single wheel that causes a single wheel to turn into the direction it is leaning, however, a two wheeled, non-articulating vehicle does not have a “banana” patch when viewed as an entire system. Each wheel may have an inward turning tendancy but the two wheels together each present an identical contact patch front and rear so the whole system has no turning tendancy unless one of the wheels is articulated.
One of us needs to read for detail. From your link
So if I am reading that correctly, they do not lock the handlebars in place, rather they have a second set of handlebars that do not rotate the forks as they are fixed to the frame.
I never said that my bike did not countersteer by itself, I was responding to Flander’s comment
to which I have to reply, bullshit, because I can turn my bicycle by just leaning.
Now of interest is the next paragraph in the linked article which says
I suspect that there is a difference in the steering geometry of a trail bike and a road bike that is causing this, not the knobby tires. Furthermore I would venture to guess that my bicycle has geometry that is closer to that of a trail bike than the super bike that they set up as the no BS bike.
I think the reason he can turn an off-road bike by pushing on the inside peg is that when you do that, you can physically displace the tire through the soft earth. You can’t do that on a hard flat surface.
I think someone needs to look for a video (or make one) that shows if counter-steer occurs during a no-handed turn, as Rick claims to be doing (I believe correct if I’m wrong).
But the very article you’re quoting from was the experiment where they added fixed-in-place handlebars which have the only effect that they prevent countersteering, and people who did this experiment were not able to turn by leaning. They said countersteering was necessary.
How do you know you can turn your bicycle by just leaning?
:rolleyes: How do I know that I can steer my bicycle just by leaning? Just the fact that I have been doing exactly that for the last 45 years or so.
As I mentioned in my last post, I suspect a slight difference in the geometry of a bicycle and a road motorcycle.
There have been a couple of interpretations so far…
Are you saying that you can initiate the turn without countersteering, or are you saying that you can ride your bike along a curved path while the front wheel is pointed straight ahead?