Danke

"She's a round like my head"

touring919

Okay. I realized my confusion. And a 3 bar linkage wouldn't work. It would be locked in position. Have to have 4. See attachment.

The 919 is a 4 bar linkage. So is a Hossak style deal which is in the middle. A slider link is two seperate links. On a set up like the 919 the spring and damper is combined with the slider links.

My mistake cam with assuming the rear axle would be placed somewhere on link 2 of the hossak style which would have a modified arc that is a function of both the upper and lower link. And it would be a very large arc which would give the benifits of a longer swing arm without actually having a longer swing arm. If Hoever the axle was placed at A. The hossak style or the 919 style would have the same result as far as the wheel motion was concerned making the hossak style rear suspension pointlessly complicated and hard to package.

A CRF is a 6 bar linkage as shown at the bottom. more complex but one can play with the wheel rates (spring rate at the wheel) much more than with a simple 4 bar set up. The CBR has the same basic 6 bar linkage but the top of the slider link is attached to the swing arm (bar #1) instead of ground (the frame)

Attached Images

linkages.jpg (20.2 KB, 16 views)

Danke

I thinky I might see where the confusion is coming from. The shock in the system counts as one part, not two even if it does consist of several moveing parts. The frame isn't counted in this party either.

touring919

Then I better burn my applied kinematic analysis book.

sike

Just don't burn your kimchi, that stuff smells bad enough without adding heat.

Danke

I am going to have to trust what the guy who wrote the bible on this says.

You can check out the software here and read the manual. TONY FOALE DESIGNS - Home page

sike

I'm pretty sure that motorcycles haven't existed that long...

mcromo44

I have Foale's classic book Motorcycle Handling and Chassis Design, and it is excellent.
I see you got a session with Tony at some point ?
Where was that and what was it like ?
How many other disciples sat in ?
Comments ? Observations ?

Danke

A couple years ago he did a seminar in Vancouver. There were under 20 folks in the class. It was 2 days long and an 8-5 affair with a really back in the classroom book learning atmosphere.

That said it was a great experience. He's a real tinkerer, building bikes in the back yard and racing them and he's been in the scene long enough that he can pull out some great stories from the world of racing.

If you have a local club that can pool enough members he'll fly over and run a seminar where you are. If you're into tuning, or building or any of that it's worth it. When I took it the seminar he wanted to see 10-25 folks in the room. Cost was $275 CD for the class or $475 with the book and software.

mcromo44

What a deal for a guy like that !!!!!!!!!!!!!
If you ever hear of him going to Van again, please let us know. I for one would go. I'm going to float something locally here in Alberta based on your info. I'll post it on the motorcyclehq website, not the UK one, the one that caters primarily to the Alberta scene.

touring919

I would love to go to that class. I love going to those types of classes. Always great to pick the brain of guys like that.

I'm going to have to disagree with you Danke on your understanding of the 4 bar system though. Statments like this, "comprehensible to the average reader " from the description of that book scare me. Not saying anyone here is at a low or high ability of undersanding but if a book is dumbed down it may loose something in "translation" so the average joe can undersand it.

Danke

You probably don't want to know this but he did a seminar in Calgary the weekend before the Vancouver one. Steve Dick helped set it up.

Danke

If you're the average reader who enjoys pages and pages of math then you'll be fine. If you're the average reader who likes comic books then you may be at sea. Often the local library has a copy of the book, you could always check it out ahead of time.

touring919

Library. Brilliant. Somehow I doubt my little library will have it but I'll give it a go. I would really love to get my hands on the software but its not in the budget this time of year. Too bad your on the other end of the continent.

I did leaf through some other books I have. BMW paralever system is a 4 bar drawn like the 2nd system in my diagrams. Forgot about that one. Still don't know why no chain drive bikes use something similar.

Good discussion. Glad this didn't degrade to name calling. Even if we didn't agree on anything at minimum I'm sure it got a lot of us thinking, maybe even in different directions than we would have on our own.

mcromo44

Ahhh, Dickey still lives ! I saw him once at Westwood in the early 80s.
And no, I did not know, and I'm OK now knowing.
One way to look at it is this way, if he came once, he's surely to want to come again !

I floated a thread on motorcyclehq yesterday, and will update it today with your intel.
Better yet, have a look at the site and see if you are interested in joining.
It's got a small population of users, mostly the Calgary / Edmonton corridor.
It's a recent start up as initiated by some locals here in town.

mcromo44

Foale's book is a very serious read, and is more of a textbook style writing. It is loaded with info, much of which can be simply "read" without doing any math, but if you want to do math, he gives you that option too. The book is very authoritative and backed up with hard science. Say 200 pages, and not a bit of colour.

touring919

Adding it to the christmas list for next year.

sike

For some reason, this made me think that the only reason forks were inverted was to give nerds another thing to argue about (as if Star Wars and Star Trek wasn't enough). Present company excluded, of course.....

mcromo44

Hypothetical Explorations are the ultimate Bench Racing element. I should know !

Sike, impressed ? Just TWO sentences ! I'm really working on it.

sike

Very impressed. I'm guessing it will give you more time for Star Trek re-runs (or is it Star Wars????).

mcromo44

I must admit, I still do have a soft spot for the original Star Trek TV series !
As for the movies and Star Wars stuff, nah, it would cut into my Bench Racing time far too much.

zaq123

Old thread but just want to add after my USD conversion:

USD forks are more stable period. Not only due to the their stiffness but also because of their different design. Unlike in regular forks, where slider is physically tops out on the very short cartridge spring, USD's slider is basically suspended by the cartridge rod. At the same time cartridge rod is supported by two springs: top/fork spring as we know it and long top-out spring or negative preload spring. That makes front end extremely stable and not very sensitive to bumps in the road during hard acceleration, when front end is getting extended.

It's definitely a different feeling launching front in the air now, that front wheel just stays planted to the surface . No wonder RC51 is so stable with such a steep rake angle, freaking 23.3'.
However RC51's suspension is to light for my weight (197lbs). It's too light on RC and event lighter on 919
(about 10-15lbs heavier). I will be installing slightly shorter top-out springs and new fork springs in the near future.

The Shadow

Good objective observations, Zaq...it can be hard to get past the subjective, "but they look really keen!" observations around here sometimes!








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FloridaMountaintop

It is bad enough the forks leak, I just see puting the fluid on top will make the leaks more noticable when it starts, that is why I like Springer frontends on my Harley, no fluid to leak, hell it leaks enough as it is.................