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Old 11-09-2011, 08:58 AM   #166
Roadracer_Al
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This is probably an OS-dependent function, or a browser-specific function... but on my Mac using Chrome, when I tell it to print a page, there is an option to save the page as a PDF. You still have to print the individual pages, but using Acrobat, you can string them together in a single document. If your system doesn't have that function, I'd be happy to do it for you.
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Old 11-09-2011, 11:17 AM   #167
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I saw part of the Moto2 race at Valencia yesterday. (Probably on tape delay.) Someone (race leader?) got slammed in a really abrupt highside in a lefthander. The rear end stepped out about a foot, then caught and snapped back. Bang. Last I saw of the guy he was face down in the gravel, slowly flexing the fingers of his right hand, probably testing to make sure his appendages still worked.
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Old 11-10-2011, 04:51 AM   #168
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Very interesting. Way beyond my machining/drafting skills. Im paying you attention.
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Old 11-10-2011, 04:42 PM   #169
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Is this an option?

Husky electric bike,


Because all GP and 99.9999% of production race teams use telescopic forks that have a round cross section the only option to introduce lateral flexibility to deal with bumps is to have the entire fork and headstock assembly move. Round cross sections have equal stiffness in all directions since all the material is the same distance from the center of the profile. If you have a plastic pen try to bend it. It provides the same resistance regardless of which direction you try to bend it in. Not try to bend a ruler along its flat direction then along its narrow direction, it provides extremely different stiffness depending on the direction because its profile is not symmetric about its center axis
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Old 11-12-2011, 11:30 AM   #170
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It's true that the dual fork arrangement would result in characteristics similar to what Chris has described, but it's a sub-optimal arrangement that precludes the ability to fine-tune side-flex.

With a Hossack, you only need to machine new legs (i.e. simple slabs of metal, not very high precision sliding cylindrical elements which contain the damping) with a different design to alter side-flex. It is not inconceivable that a Hossack could be designed with bolt-on legs that can be swapped out as easily as a changing tires.

One of the benefits of the Hossack-type front end that hasn't been discussed is that they're cheaper to build **to high levels of performance** than telescopic forks. A good set of forks (amateur racing) from Ohlins might cost $3~5k and a *really* good set of Ohlins (pro racing) might cost $15~20k, and doG only knows what they pay for forks in MotoGP, although at that level, the cost is not so much hardware, it's the engineer & crew -- i.e. institutional knowledge -- that you're buying.

Part of this savings is that the Hossack uses a standard rear shock absorber, which, as technology goes is significantly well-developed and highly tunable. A really good shock is $1.5k.

I don't recall if this has been mentioned, but another big advantage of the Hossack is reduced stiction. One way that you can examine a suspension for build quality is to look at how much stiction it has -- less is better.

Simplistically, It boils down to seals. A shock has a ~15mm shaft and seal. Telescopic forks have TWO ~50mm shafts and seals. Compare the circumferences: the 15mm shaft has 47.1 mm of circumference. The two 50mm forks have a total of 314mm of circumference -- that's nearly 7x more seal area that grips the fork legs, resisting subtle motion.

I mentioned above the idea of institutional knowledge. Race teams that want to win typically take a very conservative approach: they want a 'sure thing' that is supported by institutional knowledge. Right now, that's forks. This is why Chris' work is so important: he's building the base of institutional knowledge which will promote the use of a superior, but lacking in institutional knowledge, technology that resolves many of the core problems with teleforks.
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Old 11-12-2011, 01:15 PM   #171
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thank you!

pure unadulterated bikeporn!!!

Thank you for being, doing and sharing!
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Old 11-12-2011, 01:19 PM   #172
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Alan's firing on all cylinder with that explanation. Thanks. It's rare that I can't add my own $.02 but this is one of those cases.

And his illustrations in the Motorcycle Suspension Bible are excellent. We should all have a copy. Suspension improvement is the most important optimization you can do on a bike. Especially on street and adventure bikes that experience a much greater variety of terrain than a roadrace bike.


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Old 11-13-2011, 04:58 AM   #173
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Quote:
Originally Posted by thecosman View Post

Front wheel chatter (purple) line:


what kind of apparatus did you need to get this sort of data?


(you're my hero.)
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Old 11-13-2011, 10:48 AM   #174
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There are a lot of different data acquisition systems, but the one I'm familiar with due to my work with RaceTech, is of course the RaceTech product, the "Shock Clock". If you hit RaceTech's site, the system is described under one of the tabs on the header bar.

http://racetech.com

Chris, thanks for both the props on my comment, and the plug for the book. I was well prepared to make that comment -- I had exactly this discussion with my best friend, who is a telefork advocate.

I'm obviously biased, but I agree with your assessment -- it's a very useful book, and there is something for every level of knowledge in it -- If you want to understand the theory of how suspension works, that's the first 1/3 of the book (which is where my illustrations live). There is a section of the book which is a photographic step-by-step breakdown of the process of disassembling several different types of current suspension components.
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Old 11-13-2011, 10:51 AM   #175
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I used a Mychron 3 Gold bike with linear potentiometers attached to the front and rear shock. Total system price was about $3k with sensors. Since those days there are many more data acquisition vendors on the market and the price has come down. Mychron is a good mid-level company and has since come out with more advanced systems. Some of the entry level stuff has a lot of features like GPS mapping and wireless PC download. The Starlane stuff (available from Yoyodyne) may not look like an Apple product but has a lot of functionality.

Setup and wiring can take a while but then you have the ability to generate a lot of numbers. What you do with those numbers is another question altogether. There are simple uses like finding the appropriate gearing using the speed/rpm data. It also can do interesting things like show you which rpm ranges the engine spends most of its time in. You can then use this data to tune the engine to suit those areas with intake, exhaust, and cam timing changes all allowing you to reposition the torque curve to where it is most useful. The suspension data can be used in a simple fashion like analyzing suspension movement to determine if the proper spring rates are used to allow correct use of the suspension stroke. More advanced analysis looks at the frequency of the suspension movements to allow you to to energy analyses that take more sophisticated parameters into account. You can also see chatter frequency and change the resonant frequency of the supporting structure optimally to cancel it out. Its why MotoGP teams usually have 2-3 dedicated electronics staff for interpreting the data.


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Old 11-13-2011, 11:53 AM   #176
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There really isn't a way to use a Hossack-style front end on a bike that came with telescopic forks without major frame mods such as relocating the headstock, is there? It seems like there would be a substantial increase in wheelbase, and for a faired bike, internal clearance issues.
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Old 11-13-2011, 01:41 PM   #177
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For a telefork conversion on an existing headstock frame a girder style would make a lot more sense. This guy did a great job but with this much effort to modify the existing frame I think making a new one is not too much more.

Internal clearance issues with either approach definitely need to be considered.


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Old 11-13-2011, 02:15 PM   #178
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Thanks. That looks very cool, but one definitely need to be a fabricator or have buckets of money sitting around, or both.

I realized after I posted that I should have put my question over in the advice thread. Sorry about the minor hijack.
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Old 11-13-2011, 03:17 PM   #179
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Since you mentioned 'hossack' I think this is the right place. And yes, buckets of money helps any of these efforts!

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Old 11-14-2011, 04:04 PM   #180
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I've been using a Racepak IQ3 on my drag boat. It is amazing what they will do. I spend more time going over data now than testing. And have gotten faster and more efficient.

Quote:
Originally Posted by thecosman View Post
I used a Mychron 3 Gold bike with linear potentiometers attached to the front and rear shock. Total system price was about $3k with sensors. Since those days there are many more data acquisition vendors on the market and the price has come down. Mychron is a good mid-level company and has since come out with more advanced systems. Some of the entry level stuff has a lot of features like GPS mapping and wireless PC download. The Starlane stuff (available from Yoyodyne) may not look like an Apple product but has a lot of functionality.

Setup and wiring can take a while but then you have the ability to generate a lot of numbers. What you do with those numbers is another question altogether. There are simple uses like finding the appropriate gearing using the speed/rpm data. It also can do interesting things like show you which rpm ranges the engine spends most of its time in. You can then use this data to tune the engine to suit those areas with intake, exhaust, and cam timing changes all allowing you to reposition the torque curve to where it is most useful. The suspension data can be used in a simple fashion like analyzing suspension movement to determine if the proper spring rates are used to allow correct use of the suspension stroke. More advanced analysis looks at the frequency of the suspension movements to allow you to to energy analyses that take more sophisticated parameters into account. You can also see chatter frequency and change the resonant frequency of the supporting structure optimally to cancel it out. Its why MotoGP teams usually have 2-3 dedicated electronics staff for interpreting the data.


Chris
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