bobm@convexs.UUCP (04/06/86)
mojo@kepler.UUCP says > I'm a teaching assistant in a motorcycle rider course accredited by > the Motorcycle Safety Foundation. During the teaching of the course > it would be extremely useful to have a large gyroscope to demonstrate > the physical principle behind "countersteering" -- the process of > applying pressure to the handlebars in the direction that will force > the motorcycle to lean into a turn. Um, what do gyroscopes have to do with countersteering? Countersteering is not related to precession. Consider a bicycle going slowly. At a speed of 5 MPH or less, the precessional forces generated by a pound or so of bicycle wheel are just a few ounces, but a 200 lb. bike+rider combination can be effectively countersteered. (Probably heavier ones too, but that's all I weigh. :-) Then how does countersteering work? When the bars are turned to one side, the front wheel moves IN THE DIRECTION IT IS POINTED. The bike above it doesn't. So shortly, when the wheel is no longer under the bike's center of mass, the bike starts to tilt, IN THE OPPOSITE DIRECTION. Then the rider who doesn't want to fall over points the wheel into the turn to stop tilting. You also have to countersteer (no comments from the dirt-bike crowd; I ride a 550 lb. motorcycle and leaning isn't effective on it ;-) to straighten up coming out of a turn. The same argument as above applies. You point the wheel further into the center of the turn so that the bike starts to fall outward (because of centripetal force), then straighten the wheel when the bike is upright. The fact that the wheels spin has nothing to do with this phenomenon. If you could build a bike with tracks or skates where the front and rear tires are you would still be able to turn it using countersteering. Did I miss something? Is there some way to demonstrate countersteering using a gyroscope? K<bob>
beaver@tolerant.UUCP (Robert Beaver) (04/11/86)
> Um, what do gyroscopes have to do with countersteering? > Countersteering is not related to precession. > > You also have to countersteer ... to straighten up coming out of a turn. > You point the wheel further into the center of the turn so that the bike > starts to fall outward (because of centripetal force), then straighten > the wheel when the bike is upright. > > The fact [is] that the wheels spin has nothing to do with this phenomenon. > > Did I miss something? Is there some way to demonstrate countersteering > using a gyroscope? > > K<bob> You obviously don't understand. You certainly need a MSF refresher course or or an introductory course to physics. Countersteering is a basic principle of turning. As you lean, you are actually pulling on the handgrip opposite the lean (turning the wheel out). Therefore, you are turning the gyroscope (wheel) away from its direction of travel. The gyroscope will attempt to correct, causing the bike to turn (the bike is attached to the wheels you remember). Try this little experiment on your bike - drive straight, pull on you left grip very slightly and watch yourself start to bank and turn right. Countersteering is related to physics, not "precession[?]". When you come out of a turn you are letting up on the countersteer, not increasing it. Please take an MSF course. The origional poster of this article knows what he needs and you need him. --beaver -- {allegra!oliveb, seismo!mordor, ihnp4!nsc, ucbvax}!tolerant!beaver
mojo@kepler.UUCP (Morris Jones) (04/13/86)
In article <800011@convexs> bobm@convexs.UUCP writes: >Um, what do gyroscopes have to do with countersteering? >Countersteering is not related to precession. Well, you're correct that countersteering is not related to precession, but it has everything to do with gyroscopes. There's a different principle of gyroscopics involved. If you apply a force to a spinning gyroscope, it will respond by moving in a direction 90 degrees to the force being applied. The direction of movement follows a right-handed cross vector (if I remember my physics correctly). Thus if you apply a rotational force to your front wheel as a left yaw, it responds by rotating with a right roll. Demonstrating it with a bicycle wheel on handles will be very fun. Ask someone to hold the spinning bicycle wheel, and try to turn it to the left. The wheel will immediately tilt to the right. If you really wanted to yaw the wheel to the left, you'd have to apply force in the direction of a left roll (er, right roll? lessee ... thumb, first finger, aw shoot ... ). In any event THIS IS WHY COUNTERSTEERING WORKS. -- Mojo ... Morris Jones, MicroPro Product Development {lll-crg,ptsfa,dual,well,pyramid}!micropro!kepler!mojo
toddv@copper.UUCP (Todd Vierheller) (04/14/86)
I really don't care why countersteering works. (I know why and so does K<bob>.) My complaint concerns the spirit of a reply. K<bob> showed no antagonism, yet he came under attack by R. Beaver. K<bob>'s comments are preceeded by a ">". R. Beaver's comments are preceeded by a ">>". > Um, what do gyroscopes have to do with countersteering? > Countersteering is not related to precession. > Consider a bicycle going slowly. At a speed of 5 MPH or less, the > precessional forces generated by a pound or so of bicycle wheel are > just a few ounces, but a 200 lb. bike+rider combination can be > effectively countersteered. (Probably heavier ones too, but that's > all I weigh. :-) Note above, the argument based on *physics*. > Then how does countersteering work? When the bars are turned to one side, > the front wheel moves IN THE DIRECTION IT IS POINTED. The bike above it > doesn't. So shortly, when the wheel is no longer under the bike's center > of mass, the bike starts to tilt, IN THE OPPOSITE DIRECTION. Then the > rider who doesn't want to fall over points the wheel into the turn to > stop tilting. > K<bob> Again, a clear explanation with the underlying physics too obvious to mention. >> You obviously don't understand. You certainly need a MSF refresher course >> or or an introductory course to physics. Beaver's above comment is unwarranted. It's purpose is only to put down the original poster in order to elevate the writer. (And it's incorrect.) >> Countersteering is related to physics, not "precession[?]". Precession: a comparatively slow gyration of the rotation axis of a spinning body about another line intersecting it so as to describe a cone caused by the application of a torque tending to change the direction of the rotation axis. >> Please take an MSF course. The origional poster of >> this article knows what he needs and you need him. Again unwarranted. K<bob> did not earn any abuse. >> --beaver >> {allegra!oliveb, seismo!mordor, ihnp4!nsc, ucbvax}![IN]tolerant!beaver Countersteering works the way K<bob> explained it. Bicyclists use the technique to *swerve suddenly*. (Leaning is adequate on a bicycle in most other situations.) On a bicycle one turns the wheel hard left (without leaning into it.) This causes the bicycle to *fall* right. Then, the bicyclist turns hard right to correct for this fall. Voila! Countersteering. To initiate a hard turn (swerve) on a bicycle, turn the wrong way first. Why use a bicycle in the argument? Because the gyroscopic forces are too small to account for the *quick* change of direction of a much larger mass (the bicycle and rider). F=ma (the "a" includes the time aspect). The gyroscopic effect would produce a slower change (if any) and cannot account for the observed results. Motorcycles (being heavier and resisting the lean of the riders weight) respond better to to countersteering in a much larger domain of conditions. Todd Vierheller Tektronix, Inc Portland, Oregon
stirling@fortune.UUCP (Patrick Stirling) (04/16/86)
In article <329@tolerant.UUCP> beaver@tolerant.UUCP (Robert Beaver) writes: >> Um, what do gyroscopes have to do with countersteering? >> Countersteering is not related to precession. >> >> K<bob> > >You obviously don't understand. You certainly need a MSF refresher course > [...] > >--beaver Now I'm completely confused! Having read beaver's article I don't see where (s)he refutes anything K<bob> said! What I understood K<bob> to mean is that gyroscopic effects are very small (or negligible) in steering a bike, (particularly at low speeds) compared to the effect of the change in position of the bike's center of gravity. beaver then said that if you tilt a spinning wheel, it will precess (i.e tilt at right angles to both its axis of rotation and the initial tilt direction). I would say that both statements are true! Considering the relative forces generated a) gyroscopically by the front wheel and b) by the bike's center of gravity being out of the vertical line of the bike, I would say that the rotational force (b) is greater than the rotational force (a). However both forces act to lean the bike into the turn, so this is really academic! About coming up out of a turn: by Newton's 1st law of motion (Prof. Stirling here!), the bike's natural tendency is to travel in a straight line, so as soon as it's c.o.g is realligned (by uncounter-steering or leaning) it will straighten up. Another point is that I've found that I can steer my bike quite well without counter-steering, i.e. (presumably) without any gyroscopic help. patrick {ihnp4, hplabs, amdcad, ucbvax!dual}!fortune!stirling