Bill is correct on this and if Rip had ever had a real tank slapper he would know why he is wrong. I had one years ago whilst racing a twin at Cadwell park. It was on the top straight at about 100 mph and the bars moved so fast that there is no way any normal human being could possibly keep hold of them. Even given all new spring strengths etc I think that a modern hydraulic steering damper is a good way to go. And I have no commercial interest in selling them!!
Comet suspension
- Thread starter redbloke1956
- Start date
There does not seem to be any mention of the Thornton springs for Girdraulic forks in this thread, are they no longer the way to go. I was under the impression that Laney Thornton had put in an enormous amount of research and development to finalize on the ideal spring.
Rip,
I have no issue with Phil Irving and it was he that pointed the way to my conclusions. I used his own words as the title to the first article that I wrote on this subject.
Perhaps I did not use the best analogy in explaining my assuptions, but there is nothing personal about it, I just failed to make my point.
David
I was taken wrong.... the best way to get out of a tank slapper is not to get in one by maintaing a solid grip on the bars and being aware of the road conditions that begin one and avoiding them. I have had only one horrendous
tank slapper in my life when I took my hand off the bar to wave at oncoming bikes and at that instant hitting an oblique bump sending the front wheel lock to lock, I fought my way out of it using my legs to to kick the bike up
after each dive..... it happened so fast it was over in an instant and whatever I did was unthinking automatic reflex..... but, I kept the Rap up somehow.
tank slapper in my life when I took my hand off the bar to wave at oncoming bikes and at that instant hitting an oblique bump sending the front wheel lock to lock, I fought my way out of it using my legs to to kick the bike up
after each dive..... it happened so fast it was over in an instant and whatever I did was unthinking automatic reflex..... but, I kept the Rap up somehow.
Peter,
Thornton did an enormous amount of research with Gil Valincourt on the dampers. As I mentioned in my last article on springs, my opinion is that the springs were not developed with the express intent of eliminating tank slappers. The focus of the design was greater spring travel with an end to better ride quality.
When I installed a pair of Thornton springs in the Grey Flash many years ago, I had it jacked up on the work stand. Once installed, I let the jack down. When the front wheel touched the bench nothing happened. With the jack removed the bike sat at absolutely full extension. I did not see how this would work. In defence of the springs, they were designed for the twin and Comets were not contemplated. My solution was to remove one spring. It worked beautifully and I raced it that way for several seasons. I later purchased a Comet racer that had some shorter and lighter prototype Thornton springs in it. They seemed to be better on the single, but what I did not realize is that they were still holding the fork too close to an extended position. While braking on the straight at Deland the bike went into a tank slapper and that settled me on the idea of finding out why. So, Thonton did do development work on the springs, but the springs as supplied did not offer me a solution to my problem.
David
It annoys the hell out of me when people assume. Your experience has nothing to do with my experience..... but the one thing I can say for myself (and folks can have all theories they wish) the tank slapper I had could not have been
worse but I didn't crash..... so that says something!
worse but I didn't crash..... so that says something!
I do not want to hijack Kevin's thread so I will just say that the work I have done was intended to benefit those, like me, who had suffered serious crashes on Vincents from tank slappers. I have spent a considerable amount of my own funds and time on this and I do not sell springs. I have offered the spring designs I have come up with to anyone who asked, including Thornton, because I believe this as a potential safety issue. I am very moved by those who have described their crashes because I understand that it is a real act of faith to get back on a bike that was the cause of so much pain without knowing why it would do such a thing. I think I have answered some of those questions, but I also understand that I do not have all the answers.
David
David
As promissed, I wanted to point to some early photos that provided clues to what I have come to believe is the most practicable set-up on a Girdraulic. This first photo is well-known as the works machine. I have examined the original factory photos and the bike is unladen. I would point out the lower link is parallel with the ground. When the rider is seated, the eccentric is lower than the front spindle. What I found out is that if the suspension is set-up this way then the suspension works independently of the brakes. If the eccentric is higher than the front spindle, like the photo of Kevin's fork showing the bend in the blade, I found that the use of the brakes causes the suspension to seize. It is a progressive effect getting worse as the fork is extended.
I found the photos interesting because they show a set-up that was not available on the production models.
David
I found the photos interesting because they show a set-up that was not available on the production models.
David
This photo shows Grey Flash 3520. The set-up is remarkably similar to the Works Flash.
I have spoken to both riders. Unfortunately I was not smart enough to know the right questions with the first. The second did quite a bit of suspension work. His succint comment was "The fork works much better on compression than extension." The photo is from the cover of 355MPH.
David
I have spoken to both riders. Unfortunately I was not smart enough to know the right questions with the first. The second did quite a bit of suspension work. His succint comment was "The fork works much better on compression than extension." The photo is from the cover of 355MPH.
David
Hey, do you think maybe the rider has something to do with controlling the motorcycle? I have ridden more Vincents for more miles than the lot of the assuming geniuses above and the fact that perhaps I'm a damn good
Vincent rider has something to do with the fact I've never had a tank slapper but one which I controlled. Basically you are blaming the tool.
Vincent rider has something to do with the fact I've never had a tank slapper but one which I controlled. Basically you are blaming the tool.