Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: Notesfiles $Revision: 1.7.0.10 $; site convexs Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!ihnp4!inuxc!pur-ee!uiucdcs!convex!convexs!bobm From: bobm@convexs.UUCP Newsgroups: net.cycle Subject: Re: Need classroom demonstration gyrosc Message-ID: <800011@convexs> Date: Sat, 5-Apr-86 20:28:00 EST Article-I.D.: convexs.800011 Posted: Sat Apr 5 20:28:00 1986 Date-Received: Fri, 11-Apr-86 00:59:04 EST References: <562@kepler.UUCP> Lines: 40 Nf-ID: #R:kepler.UUCP:562:convexs:800011:000:1887 Nf-From: convexs.UUCP!bobm Apr 5 19:28:00 1986 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