| Author | Message | ||
     Surveyor  |
I'm sure many of you will have seen the photo of slaughter's XB after a high speed off at the track.(see XB frames cracking? thread) The damage seems very light. I also binned my roadgoing XB9R (50mph LHS lowside) at the track last year. Due I suspect to good luck and some minimal precautions my damage was also quite minimal. The bike damage resulted in a new primary side case (because the shift lever pinion stub couldn't be removed),gear shift assembly, and left hand clip-on. The rest of the damage was very superficial despite the fact that my leathers were shredded and knee and elbow armour broken. Even the clutch lever survived!! I had no frame protectors or crash bungs fitted but had removed front turn signals (replaced by nut and bolt) and mirrors (replaced by cable ties). I'd be interested to hear about what other products or tricks people are using to protect against track (or road) damage. | ||
| Glitch  |
I'm using the carbon fiber full frame covers, I got from Daves, Summer before last. And Shred made me a set of swing arm sliders out of some R6 frame sliders we got from Cycle Gear. | ||
| Ingemar  |
Surveyor, I would be interested to hear how much less damage you suspect you'd have if you had the frame pucks and sliders through your wheel axles. Maybe a silly question, but what causes such a violent head shake, and does a steering damper prevent it? | ||
| Slaughter  |
Ingemar, My headshake came when I was doing an outside pass on a Gixxer 1000 (you know how slow those Gixxers are!) - and he came wide and hit my front wheel. I was leaned way over to the right in turn 8 (bad news - actually the fastest place on the track) and when I got hit, it instantly started banging stop to stop til I fell off. The damper DOES help (but in that case, I'd probably still have crashed). Before the damper, I always would get a little shake at the same 3 places on the track - turn 6 when I'd bottom down the hill, entering turn 8 if I used too much muscle entering the turn and btaking/turning into turn 1 (the end of the front straight). With the damper installed, the problem went away. Unfortunately, I don't have speeds but based on gearing, I'd say those speeds were at maybe 80+ mph in turn 6 and 100+ in turn 8 and maybe on the brakes/turning at 90-ish in turn 1. Don't know if it'd be such a problem on the highway. One thing I did do was also to RAISE the front end a little by lowering the fork tubes in the clamps. Under hard braking the forks compress and the angles REALLY steepen. I don't know if doing this without also installing a damper will do any good. I still have the front end raised about 5mm above normal position. Of course all the "manly men" will tell you to just pin the throttle to stop headshake... yeah, Riiiiiight! | ||
| M1combat  |
From what I've felt and learned, a bike in a head shake is just like a plane in an oscillation. The key is to change one or more of the dynamics. I've never been through a violent head shake, but I would imagine that the only control you have left is rear brake, body english (maybe) and you could put pressure on one bar. What if you were to gentle press the rear brake and push the inside/pull the outside bar? I would imagine that the pushing idea would be your only option at the bars if they were really getting crazy though. Someone should run a head shake through a simulator and figure out what the "right" thing to do is. I'm thinking hang on with your legs, let go of the bars and squeeze the rear brake.... I'd probably die though, so don't try that at home  . | ||
| Slaughter |
I really don't think there's time to do anything except get the front end unloaded by pinning the throttle. The wobble is probably 3-5 Hz - too fast to respond directly | ||
| Ben_jamminvfcc |
Tankslappers that people actually fall off from are usually too violent to control with your arms. In fact, trying to do so, usually makes it worse. Heck...too much arm input is what causes a lot of tankslappers. The closest I was was on my SV at about 50mph. I had it leaned most of the way over when I hit a bump coming out of the turn. My arms were too tight on the bars and she started shimmying. So I just slipped the clutch and pulled a sick wheelie and rode it out.....just kidding.... MSF says slowing down...uhhh...slowly, is the best thing to do. And rear brake is a much more feasible idea than trying to apply front brake controllably while it's flinging from stop to stop. Addittionally, it keeps the weight from transferring to far forward. On a V-twin I imagine letting go of the throttle is enough to slow it down respectably fast. | ||
| Buells Rule! (Dyna in disguise)  |
I've never been through a violent head shake, but I would imagine that the only control you have left is rear brake, body english (maybe) and you could put pressure on one bar. I have been through it & let me tell you its one of the scariest things you can go thru. A truly viloent one will be just about impossible to control & you will most likely crash no matter what you do. It happens so fast you really dont have time to think & its all reactive what you do. I was coming around a curve on my HD & must have hit some spilled diesel fuel, the front end slid just a touch & then a violent tank slapper started. I struggled with the bars & am pretty sure I just about got it under control when the rear end decided it wanted to swap places with the front & wham down we went. This all happened within 2-3 seconds. My arms were physically sore from the trashing they took due to the headshake. I dont wish that experience on anyone & for folks that havent experienced it you really have no idea just how hard it is to control. | ||
| Bomber  |
ain't no damper in the world gonna fix head shake like that, induced by an impact from another scoot -- I'm waiting for Erik and Company to address braking induced front end dive -- I'd LOVE to see an alternate front end for East Troy, but, given the lack of success they ahve had in the marketplace in the past, I also hope he doesn't go out on that limb | ||
| Surveyor |
Ingemar, There was virtually no damage to the swinging arm or frame or anything else for that matter. I suspect that if I had had rigid crash bungs on the bike it might have flipped and damage would have been serious. I've had this discussion on another forum and there is a school of thought that says rigid fittings such as non folding rearsets and perhaps even crash bungs can cause damage by digging in and flipping the bike. Fittings that are designed to snap off after initial contact may be better especially if combined with carbon fibre or other protection against sliding. Just about anything that could snap off or fold up did just that in my case. My point is that I'm not sure that all the products that are marketed as providing crash protection actually do so, Slaughter's bike does not appear to have flipped and neither did mine...neither appear to have had rigid crash protectors fitted. Just my thoughts for what they are worth...it would be good to hear others experience. I have experienced the start of tank slappers while braking deep into a corner having raised the forks through the clamps in an attempt to speed up steering under braking... it scared me so much that I raised the front end again. I reckon a steering damper might have improved matters but I never got a chance to test it as I fell off at the next track day!!! | ||
| Blake |
"ain't no damper in the world gonna fix head shake like that, induced by an impact from another scoot" But that is exactly what a good steering damper is supposed to do. They dampen out the high frequency, high rate steering actuation. A car's suspension dampers (shocks) dampen unwanted chatter/oscillations of the wheels do they not? (Message edited by blake on January 06, 2005) | ||
| Cataract2 |
Soooooo, a steering damper is suppose to prevent a tank slapper right? If that's the case could someone point me to a good one that fits the XB9SX? | ||
| Ingemar |
Thanks for the excellent explanations guys! Cataract2, I would highly recommend the XB LSL Steering damper. Several BWB sponsors have them. Wrt bikes flipping after a lowside, isn't the only thing causing a bike to flip once it is sliding, is when the tires touch the tarmac? Wouldn't rounded alu axle sliders create more distance between the tarmac and the tires and therefore lessen the chance of a flip? Personally I don't buy the thought that an axle slider would "bite" into the tarmac and causes a bike to flip. One thing, I would definitely round them off. | ||
| Odie  |
Back in '85 I had a brand new Interceptor and was passing a car when the rear tire broke loose in some sand. It suddenly grabbed so violently that it broke my grip with one hand and I was hanging on with the other. I looked and felt like a rodeo rider trying to get it under control. I finally got it under control- the guardrail I sideswiped stopped the headshake! Needless to say I had a broken foot, ankle, tore off a few toenails, ripped the front off of my military boots and did some damage to the bike. I was scary to say the least......Odie | ||
| Henrik  |
I've read somewhere, that a tank slapper is the castor effect of rake/trail trying to bring the front wheel back in line with line of travel - after say a bump, but over-shooting. Thus, getting on the gas will take some weight, and thereby some "righting" effect off the front wheel. All from shaky memory, mind you. Henrik | ||
| M1combat |
For the most part yes. The simple term is counter steer. Bikes will always countersteer themselves (when left to their own devices) into a straight line (or close to it anyway) due to rake and trail (rake=caster). The problem is that the steering head builds inertia and overshoots the point that it needs to be, so an oscillation starts. | ||
| Slaughter |
On my bike, I'm still experimenting with increasing the compression damping and have already raised the front end (lowered forks) - "slowing" the steering a bit. I don't know what really works well BUT the damper has helped with the shaking that I had been getting. I do know that Fread Finnerty got headshake so bad at Willow that his brakes failed going into turn 1 and he had to ride off at about 90 (he kept it upright!!!) We still couldn't tell if it was air shaken into the lines or the pads beaten back by wheel flex and shake. He didn't have time to think of pumping the brakes before he ran off. Keep in mind, these are track conditions, HARD braking or heavy loading of the front end while turning/bottoming coming downhill. YMMV | ||
| Xbolt12 |
And Fread told me this story while showing me the new damper on his street going xb12r! xbolt12 | ||
| Dropnstyle |
on my 929 i would get headshake doing endos above 45mph. i dont weigh enough to keep pressure on the bars so we fitted a damper and they pretty much went away. just my 2 cents brian | ||
| Gschuette  |
I would just like to tell you guys about an interesting technology that could be adapted to motorcycles to prevent dive under braking. Most mountain bike suspension makers have switched to a stable platform system in their forks and shocks. It functions similiar to a fork with extra low speed compression. On these though they are usually able to be tuned to break open and close when the user wants them to. The technology was first used in Desert trucks and was invented by a guy named Curnutt. His son Charles Jr. teamed up with bike maker FOES and brought it to the bike world. It was originally introduced to combat the suspension moving with each pedal stroke (bob). It works really well. All of my Mountain bikes have it front and rear. The bikes accelerate faster, jump lower, and are far more stable under braking. The extra compression resistance keeps them from diving which gives us more useable travel in the big bumps. I love this technology and think it could only help motorcycles. Search for Curnutt suspension on the net and I am sure you will find more info than I can provide. I hope this is not really old news that has been discussed. I will really feel dumb if some makers already use this technology. | ||
| Gschuette |
Forgot to say that it is all controlled by a small air damper so revalving is not needed for all but the heaviest or lightest users. It also gives better bottoming resistance. | ||
| Buells Rule! (Dyna in disguise) |
Several manufacturers have tried the antidive stuff in the past, I believe Buell even tried it in the early 90's. So far none of it has worked very well. | ||
| Gschuette |
I would like to see what set ups they used and how it compares to the stable platform stuff. Do you have any more info? Names of companies involved? |
