GuzziMoto Posted October 1, 2009 Share Posted October 1, 2009 No, it was not meant as a joke. Many steering dampers are friction based and not hydraulic. But you could have a valid point about brake away torque, but I think the correct term is breakaway. Selecting a bearing surface with low static friction and high dynamic friction would be ideal for damping purposes but possibly would not work as a durable, low maintenance bearing surface. I do think a bearing surface like Greybeard mentioned would likely work very reliably, but yah, tightening to the point of trying to replicate a damper is probably a bad idea. Also to reduce break away torque the bearing diameter may need to be lesser and the steer stem length may need to be greater.... or maybe the breakaway torque is no big deal??? which is why I ask. Break away torque is a bad thing in steering heads or steering dampers on bikes. It is one of the ways a steering damper can fail, requiring more effort (torque) to begin to turn the forks then it requires to maintain them turning. It leads to weaving and bad handling. I know of no modern steering dampers that are friction based. Yes, they did it back in the before time but they don't do it any more because it is a bad idea. This does not mean the plain bearing idea is a bad idea, but I would rather have a higher quality tapered roller bearing. Plain bearing work well (but often not as well as quality roller bearings) because they use oil pressure to prevent contact between the two surfaces. Something like what Greybeard found would possibly work but I doubt it would work better then a quality tapered roller bearing. Plain bearings biggest advantages are cheap to make and install, quiet, and they last a decent amount of time. But as soon as they loose oil pressure bad things happen. Plain bearing materials that do not require oil pressure (oil impregnated, etc..) are not cheap. Cheaper is not better to me, only to bean counters. Link to comment Share on other sites More sharing options...
Dan M Posted October 1, 2009 Share Posted October 1, 2009 Break away torque is a bad thing in steering heads or steering dampers on bikes. It is one of the ways a steering damper can fail, requiring more effort (torque) to begin to turn the forks then it requires to maintain them turning. It leads to weaving and bad handling.I know of no modern steering dampers that are friction based. Yes, they did it back in the before time but they don't do it any more because it is a bad idea. This does not mean the plain bearing idea is a bad idea, but I would rather have a higher quality tapered roller bearing. Plain bearing work well (but often not as well as quality roller bearings) because they use oil pressure to prevent contact between the two surfaces. Something like what Greybeard found would possibly work but I doubt it would work better then a quality tapered roller bearing. Plain bearings biggest advantages are cheap to make and install, quiet, and they last a decent amount of time. But as soon as they loose oil pressure bad things happen. Plain bearing materials that do not require oil pressure (oil impregnated, etc..) are not cheap. Cheaper is not better to me, only to bean counters. Tapered rollers are perfect for the application. Hard to imagine why you would do anything else. If you want damping a hydraulic damper is far better than friction. Friction has no account for speed. Hydraulic can be valved for firm damping against high speed inputs yet softer on low speed inputs. Not so with friction. That's the whole idea isn't it? As GM said "they did it back in the before time". Why would you go backward now in the after time? Link to comment Share on other sites More sharing options...
dlaing Posted October 3, 2009 Share Posted October 3, 2009 The one superior characteristic of friction damping is that it reduces oscillation when your bars reach the apex of the sine wave going left to right or vice versa. This occurs at the moment where static friction is desirable. Of course static friction is not desirable most of the time, which is why hydraulic damping has become more prevalent. Plain bearings don't need pressurized oil, but a grease fitting or two would certainly ease maintenance. A sintered bronze bearing like Greybeard mentioned is exactly what I had in mind, not a pressurized fluid bearing, like the main crank bearings in the engine. There may even be dry ceramic or teflon bearings that could be even more ideal???? But again, we want low static friction, and I suspect awell greased sintered bronze is more likely to deliver there, not as well as tapered bearing, but the sintered bronze isn't going to develop a notch that increases the risk of tank slappers. Link to comment Share on other sites More sharing options...
Guest ratchethack Posted October 3, 2009 Share Posted October 3, 2009 Uh-oh. . . This looks ominous. . . Could get extremely odious, let alone extremely twitchy. . . Best leave it alone and hope it quietly succumbs to exposure. . . Link to comment Share on other sites More sharing options...
Dan M Posted October 3, 2009 Share Posted October 3, 2009 The one superior characteristic of friction damping is that it reduces oscillation when your bars reach the apex of the sine wave going left to right or vice versa. This occurs at the moment where static friction is desirable. Of course static friction is not desirable most of the time, which is why hydraulic damping has become more prevalent. What? Link to comment Share on other sites More sharing options...
Guest ratchethack Posted October 3, 2009 Share Posted October 3, 2009 Now you've done it, Dan. You've gone and poked it with a stick. It seems to be some kind of a telltale asteroid fragment from the old ceramic and teflon bearing thing on it's cyclical orbit from deep space, coming back around again. . . . How long d'you reckon it'll be before the imaginary 2-part urethane rocket science project without end starts up again?? . . .[sigh]. . . There's gonna be some hell to pay now. . . Pandora's box -- opened up once again. Look! I've already had to get out the blender and mix up a whole new batch of bad metaphors. Link to comment Share on other sites More sharing options...
dlaing Posted October 3, 2009 Share Posted October 3, 2009 What? During handlebar oscillation, the bar travels in one direction and then another, and the velocity is not constant, it is like a sine wave. If the bar shakes and moves 10cm to the left, back 20cm to the right, then back 20cm to the left, and then stabilizes and goes about 10cm to the right all within ONE Second, then the bar has traveled at an average velocity of 60cm per second, but the speed varies from anywhere between 0cm per second and something greater than 60cm per second. At the moment in time that bar has reached maximum movement to left or right, the bar is traveling at 0cm per second and the static friction takes effect, if only for a brief moment in time, helping to break the wave of oscillation. Years ago riders debated the value of steering dampers when friction dampers were the only thing available, yet people still used them, for good reason. Technology has progressed with hydraulic dampers that increase resistance as velocity increases, offering almost no perceptible resistance to the rider. Yet today there are still skeptics that don't see the value of dampers. Comparatively there is no doubt the friction damper is inferior, but it does have advantages like not gushing oil all over when a seal blows, and the static friction does effectively counter oscillation, but the trade off is that the static friction is bad for the handling. Always a compromise, the friction dampers had to set just right. Kind of like the BiTubo dampers, but the BiTubos are superior to the friction damper. An excellent way to test a friction damper and f up your well being is to take the bike up to 120 MPH, take your hands off the bars and then whack the handle bar. Be sure to where a speedo and flip flops while doing this as it will make your death quicker. Link to comment Share on other sites More sharing options...
dlaing Posted October 3, 2009 Share Posted October 3, 2009 What? What don't you understand Dan? Static Friction? Dynamic Friction? Sine waves and velocity? The value of friction dampers? The superiority of Hydraulic dampers to friction dampers? Are you just trolling for an argument as usual? Link to comment Share on other sites More sharing options...
luhbo Posted October 3, 2009 Share Posted October 3, 2009 And while I'm at it, @#!#$# humility. You all revere Roper, and rightly so, but I fitted a Roper plate to Captain Nemo's V11 long before I even owned a V11 or hung out here much.... Ego-problem? Hubert Link to comment Share on other sites More sharing options...
Dan M Posted October 3, 2009 Share Posted October 3, 2009 What don't you understand Dan?Static Friction? Dynamic Friction? Sine waves and velocity? The value of friction dampers? The superiority of Hydraulic dampers to friction dampers? Are you just trolling for an argument as usual? From the bottom up: No argument. Just baffled as usual. Can you find a post where I was trolling for an argument? If you have followed this thread, it was me that said hydraulic was superior to friction. It is about 8 posts back if you can't find it. IMO with modern hydraulic technology there is not much value of friction dampers. Possibly the reason they are no longer used. I know what sine waves are Dave. What I don't understand is you. Are you saying that you've studied handlebar oscillation frequency electronically? Viewed the sine wave on an oscilloscope? Measured the effects of both types of dampers? Also, are you suggesting that the use of roller bearings and hydraulic dampers on motorcycle steering heads is too modern so we should explore outdated methods like plain bearing with grease zerks and friction dampers?? Just looking for clarification, not an argument. Link to comment Share on other sites More sharing options...
CFMAW Posted October 3, 2009 Share Posted October 3, 2009 Link to comment Share on other sites More sharing options...
Dan M Posted October 3, 2009 Share Posted October 3, 2009 one of my favorites - see post 208 of this thread Link to comment Share on other sites More sharing options...
dlaing Posted October 4, 2009 Share Posted October 4, 2009 From the bottom up: No argument. Just baffled as usual. Can you find a post where I was trolling for an argument? If you have followed this thread, it was me that said hydraulic was superior to friction. It is about 8 posts back if you can't find it. IMO with modern hydraulic technology there is not much value of friction dampers. Possibly the reason they are no longer used. I know what sine waves are Dave. What I don't understand is you. Are you saying that you've studied handlebar oscillation frequency electronically? Viewed the sine wave on an oscilloscope? Measured the effects of both types of dampers? Also, are you suggesting that the use of roller bearings and hydraulic dampers on motorcycle steering heads is too modern so we should explore outdated methods like plain bearing with grease zerks and friction dampers?? Just looking for clarification, not an argument. What? Link to comment Share on other sites More sharing options...
dlaing Posted October 4, 2009 Share Posted October 4, 2009 From the bottom up: No argument. Just baffled as usual. Can you find a post where I was trolling for an argument? If you have followed this thread, it was me that said hydraulic was superior to friction. It is about 8 posts back if you can't find it. IMO with modern hydraulic technology there is not much value of friction dampers. Possibly the reason they are no longer used. I know what sine waves are Dave. What I don't understand is you. Are you saying that you've studied handlebar oscillation frequency electronically? Viewed the sine wave on an oscilloscope? Measured the effects of both types of dampers? Also, are you suggesting that the use of roller bearings and hydraulic dampers on motorcycle steering heads is too modern so we should explore outdated methods like plain bearing with grease zerks and friction dampers?? Just looking for clarification, not an argument. OK, excellent. I just think when you reply with What? it is not constructive dialog and leads to an argument. But I will certainly agree that I was not being succinct. What I was trying to suggest, is that the notching effect of ball bearings can be eliminated with a plain bearing, and that the perceived negative effect of comparatively increased static friction would not be such a bad thing if kept to an acceptable level, and it may in fact be a good thing, as evidenced by the history of friction steering dampers and their value. A little bit of static friction combined with a lack of notchiness, could eliminate the alleged NEED for a steering damper. No, I don't think it would be as sweet a setup as a new tapered bearing and HyperPro RSC or Scotts damper with variable high speed damping, but it could it be about as nice as the OEM setup when in perfect condition, but it would be simpler and more problem free than the OEM setup with ball bearings and potentially leaky, jerky, BiTubo damper. Link to comment Share on other sites More sharing options...
helicopterjim R.I.P. Posted October 23, 2009 Share Posted October 23, 2009 It seems like wheelies cause speed wobbles! Helmet cam Link to comment Share on other sites More sharing options...
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