| Author | Message | ||
     Blake |
Okay, I respect your opinion too, eventhough it is wrong.  Greg, apparently you have not read my prior statements that clearly prove that gyroscopic precession hinders the agility of a motorcycle. I will summarize them for you when I get a chance. "I also think you also misunderstand the importance of the gyro effect on stability, without it a motorcycle would be unstable to the point of being impossible to ride at speed." Please explain that ridiculous myth to me. If that is true, how is it that I under perfect control, can slalom water ski "at speed", snowboard at speed, or for that matter control a bike at very slow speeds? What is special about speed that requires gyroscopic action to maintain stability for a single track mode of travel? Please explain that to me. | ||
| Steveb |
Blake, We have some good physics data here and reliable personal experience. I remember that in 1958(?) it was proven impossible to achieve over 160 mph in a 1/4 with a traction coefficient of 1:1. What happened? Did some mathematically challenged racer brake the "barrier" and formulas were rewritten? My point is that although theory sometimes leads results, I think sometimes results leads theory. If you know the answer to the above breakthrough in 1/4 mile speeds, I am interested in the answer. However . . . On the subject of steering, I have ridden an old Gilera that came with skinny tires, but the owner installed a 350 or 400 front tire. The stable gyroscopic stability was much greater, in fact it took a concerted effort to make the bike turn at all. I am guessing that: 1) a spinning wheel has stability against changing direction from off its plane. 2) the more centrifugal/centrepital force (cain't 'member the diff'rence) the greater resistance to change. This would be created by mass and speed? 3)I *think* that precession must overcome the gyroscopic stability. Perhaps that is also why a streamliner steering changes direction around 300 mph. (just a wag) I do know that one finger on the bar end of a bicycle bar provides a huge change in direction compared to a m/c. As to the gyroscopic stability of a spinning wheel, didn't Domokos have a motor spinning his front wheel for stability during his very long wheelies years ago? I have been assuming precession in steering since Navy gyro school in the late 60's, and now your thoughtful arguments have me balled up a bit. When you have time, I also would like to read a short summary of your theory on steering as I am now confused even as to your application or non application of precession to m/c steering. respectfully, steve b | ||
| Hans |
Blake, I have the strong feeling that you know yourself precisely where you are wrong and just beside the point and where you hit the nail on the head. The gyroscopic stability of the turning wheels is the most important help for the biker to keep his balance, even if it that force is very very small as with slow turning wheels at very low speed. For instance: Try keeping your balance on one foot with you eyes closed. Possible but difficult. Now do the same with your pink pushing against the wall with very light pressure: Easy the peasy now. For instance: Artists on shows can do balance tricks on motorbikes without any forward motion: Their wheels are on rolls and a roller under the driven rearwheel is connected with a chain to one of the front rollers which drives the frontwheel. The tricks are easy to do for any biker. Thanks to the gyroscopic stabilisation. The gyroscopic precession is another phenomenon: It is a force perpendicular on the direction of a mouvement on end of the axle of a rotating system and against the direction of rotation. If the force is stopped the loose end of the axle keeps circling around in the other direction as the spinning system. Precession forces are small and not at all important in biking, but the gyroscopic stabilisation is important. The decentralised mass of the wheel brakes hinders the agility more than if that mass was centralised. And skiing ? That will be easy enough on two broad boards, set apart some distance. Ha, try skating.:-) Hans. | ||
| Werewulf |
ref: school of unorthodox riding! the last time that i rode to helen ga had been on the x-1. so yesterday i decided to compare the v-rod to the x-1. its a very twisty mountain road. the rod really felt light and very little pressure is required on the bars to countersteer. much more nimble than my deuce and even easier to push down than the buell. the first sharp turn i went around, i leaned in the traditional manner, the sparks flew and all i could think of was grinding chrome. fortunately it was just the 60 dollar foot pegs. i had heard that the pipes will drag on this bike and i was worried, as i might sell it soon. so i started using the "wulf" lean tecnique. body vertical countersteer only. i did not have one scrape during the rest of the trip. this is basically the same thing as the fat boy at deals gap. i can tell you one thing, the rod is not a great mountain bike! i was sweating for the entire trip that i was going to drag some chrome. i must say that the x-1 really does the job here. im really starting to love that bike! | ||
| Rick_A |
Has anyone seen the ski conversion for mountainbikes? I think that is the closest you'll have to riding a bike with zero gyroscopic effect. Someone buy one and let us know! | ||
| S320002 |
Blake, Its late and I will explain more later but I'll give some things to think about. Can you keep your bike upright at 0 mph? 1 mph? At what speed can you ride in a staight line without wobble? Can you ride at ride at 3 mph with your hands off the bars? Can you ride at 30 mph with your hands off? Think about it. Hard. Also, try the slalom thing with a 4 inch ski. Respectfluly, Greg | ||
| Rashomon |
A late word on countersteering -- it is the only effective way to turn a bike quickly. I've always theorized that most riders do it without realizing it via learned body movements (i.e., leaning left and pushing forward with the left bar end without realizing it.) This is almost surely why so many riders cannot react to situations beyond what their unconscious, learned responses can handle -- as in a decreasing radius corner, that requires a quick steering movement out of the corner to turn the bike in more. The most common single vehicle motorcycle accident is a bike and rider going off tangent to a corner that was passable at the speed the rider entered the corner, but panic and lack of the right reflexes prevented that. Two exercises to demonstrate the effectiveness of counter-steering: 1) ride with the right hand only for awhile, either on a bicycle or a motorcycle, and pay real attention to how the bars turn before the bike leans. If you're one who doesn't believe in counter-steering, you're in for a surprise. 2) Try steering a bike with cruise control or a throttle lock without touching the bars. A big, flat, empty stretch of interstate is the perfect location. Heavy machines respond amazingly sluggishly to even large weight shifts -- the asymmetric aerodynamic forces created by extending a hand far to the side have almost as much effect. And Blake is quite right that the gyroscopic forces increase rapidly with speed. Because of that, both steering effort and potential roll-rate increase rapidly with speed. I once had the privilege of watching Freddie Spencer from up close at a photographer-only location at the Italian GP, and he snapped the 250 Honda he was riding over so hard and so rapidly you could literally see its chassis ring, just as if you'd put a step input into it for a natural frequency test. He was also known to have bent handlebars on Superbikes from his steering inputs on occasion . . . | ||
| Jima4media |
Fast Freddie Sez..... from http://www.fastfreddie.com There's always been quite a debate over the proper way to steer your motorcycle, but here at the Freddie Spencer High Performance Riding school, I teach the exact techniques I used while contesting the 250cc and 500cc Grand Prix World Championships on my way to three world titles. The year I won both the 250cc and 500cc championships, I had to find ways to conserve my energy and strength when running two 50-minute GPs back-to-back, and in doing so discovered that there were multiple ways to affect how the motorcycle steered and transitioned. It was during that time that I began to exploit the same techniques that I now introduce on the first day of every school: the four ways to steer your motorcycle using countersteering, peg weighting, outside knee pressure against the fuel tank and brake/throttle application. What we teach our students is that these are not four independent methods to pick and choose from; each method should be used in conjunction with the other. For now, let's take a brief look at each component: Countersteering Countersteering is the act of pushing on the inside bar (or pulling on the outside) in order to make the motorcycle initiate the corner. Push left, lean left…push right, lean right. The motorcycle's front tire actually turns in the opposite direction of the corner momentarily before falling in and arcing in the direction of the corner. However, a rider that relies solely on countersteering will be at a disadvantage when compared to a rider that uses the four ways we teach. If a rider relies entirely on the movement of the handlebar/clip-ons to turn the bike, he or she must use muscle at a place where you need feel. Let's use a tight left/right s-turn as an example. In order for the motorcycle to transition through the corner using only countersteering, the rider must use a firm grip, forcing the bars and then relaxing. This not only becomes physically tiring when done repeatedly, but also works to upset the chassis if done abruptly. We teach our students to get away from muscling the handlebar. Peg Weighting Think of a motorcycle as a big gyroscope, and at speed that gyro wants to continue moving in a straight line. You've got gears turning, pistons, wheels and brakes…multiple moving parts that make turning the motorcycle all the more difficult. However, the footpegs are set low and act as an inside axle of the gyro, where a rider can maneuver his or her weight and use considerable leverage and pressure to affect how that gyro reacts. But peg weighting is not just about placing the weight there, but when the rider places the weight there -- a discussion we'll have when you sign up for the school. Outside Knee Against the Fuel Tank Using the outside knee against the fuel tank leads to a tightening of the torso muscles, which in turn allows the rider to take the weight off the arms. Why is this important? Because anything that helps alleviate a tense death grip at the handlebar will help the rider receive better feedback from the chassis and tires. And relaxed arms and hands are the direct instruments to have smooth throttle, brake and clutch control. Brake / Throttle The final part of the steering equation we teach at the Freddie Spencer High Performance Riding School involves application of the brake and throttle. We teach that the most important aspect of each corner is the entrance - dubbed Zone 1 in the school - and brake and throttle usage in Zone 1 are essential to successfully navigating the rest of the corner. Both brake and throttle input have a tremendous affect on how the motorcycle steers when used in conjunction with the other methods I've described above. Braking for a corner loads the front tire, compresses the front suspension and tightens rake and trail, allowing the motorcycle to steer quicker. Trail braking well past the turn-in point allows the rider to continue slowing the bike and help it steer, adjusting the line if need be while maintaining the load factor on the front tire. The throttle is used in much the same way; rolling it off and squeezing the brake will cause the motorcycle's line to tighten, cracking the throttle off idle after the brakes are released arrests the bike's lean angle and helps hold the desired line. One of the reasons we use such a diverse methodology when teaching students how to most efficiently steer their motorcycles is because a rider will use different techniques depending on the situation. On the racetrack, a rider can hang off the bike and use body and peg weighting more than on the street. During street riding, more importance may be placed on countersteering and brake/throttle application. But the important thing is to understand how all of these inputs can be best utilized to help maneuver the bike. When you sign up for one of our schools, you will not only get a detailed explanation of each of these methods and how they work in unison, but combined with drills and lots of track time, will see how they improve your riding in a practical environment, on the racetrack and in everyday street riding. The many miles I've covered street riding and the years I spent battling it out with riders like Kenny Roberts and Anton Mang have culminated in a series of techniques that I believe in…techniques I look forward to sharing with you at the Freddie Spencer High Performance Riding School. | ||
| Rashomon |
Jim4media -- using throttle/brake to effect cornering line is certainly effective, and using the outside knee to locate the torso to relieve arm loading and thus allow a lighter grip is also certainly good practice. (As an example, early S1 Buells with the wide bars were very subject to rider overcontrol unless you kept a light grip on the bars, in which case the leverage provided was pretty wonderful. And there's still something to be said for not hanging off during fast street riding so you can keep your torso locked to the chassis, thus allowing a very light, very conscious touch on the bars -- which is why the kind of ground clearance that recent Buells have is also wonderful.) However, I don't understand how peg weighting works or theoretically should work, and suspect it's just another unconscious way of putting a steering input in via the bars. Static net loads on the rear frame unit don't change without rider movement, no matter how the rider distributes his weight between his two legs. However, a redistribution to one leg or another may require the rider to create a torque to hold his position, and I suspect that the upper torso and handlebar are involved in this. Or can somebody here show me a free-body diagram and perhaps explain a dynamic effect that I'm missing? | ||
| Blake |
Rash: Sounded to me like Freddie was talking about shifting weight, as in shifting CG, as in hanging off or putting all your weight on one peg. | ||
| Jima4media |
It sounds to me like the effect you have when down hill skiing. You weight the downhill ski and unweight the uphill ski to turn more easily and quicker. Jim | ||
| Steveb |
Lets see if I've got this right Jim. For a left curve you weight the right peg, apply pressure to the tank with your right knee, and as part of that motion push your butt to the left so you hang off a bit in the turn, and also your trunk and shoulders are pushed to the left causing a push on the left bar and pull on the right. I think I've got it now. Motorcycles must be the most pure form of creation in the world. Everything works together. Dang, when I meet Blake I'll have to wear a steel helmet to protect me from precession concussion. Steve B | ||
| Rick_A |
Ummm...no. You weigh the left peg. It's a lot easier to practice than explain. Just do it  | ||
| S320002 |
Rick, Steve has it right. In addition to the things he mentioned weighting the outside peg gives you slightly more cornering clearance. However at parking lot speeds weighting the inside peg makes for a quicker turn (the bike leans more). Greg | ||
| Blake |
Greg: You weight the "outside" peg? How exactly can you hang off inside with your weight on the outside peg?  I think you are confusing Mr. Code's instructions concerning leveraging off the outside peg upon entry into a curve with what Fast Freddie is saying. Two different things. |
