tag:blogger.com,1999:blog-13887692.post5730201764481180089..comments2024-03-13T02:16:08.135-04:00Comments on Cozy Beehive: Dynamic Ride Comfort & Measuring Vibration In BicyclesRon Georgehttp://www.blogger.com/profile/18394865788996482667noreply@blogger.comBlogger17125tag:blogger.com,1999:blog-13887692.post-15314502387170400542009-09-04T09:21:38.326-04:002009-09-04T09:21:38.326-04:00I wonder what a bike would ride like that has been...I wonder what a bike would ride like that has been built with 80% flax, 20% high modulus 3k carbon comboBuilding Materials Supplieshttp://www.cambridge-homeimprovement.co.uknoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-70581464216429525402009-09-01T13:29:16.970-04:002009-09-01T13:29:16.970-04:00Ron, the link is in-plain text right at the bottom...Ron, the link is in-plain text right at the bottom of jaycee's post.<br /><br />www.bikethink.com/Frameflex.htmUnknownhttps://www.blogger.com/profile/00403695097675640092noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-33437355043030279512009-08-28T02:15:51.997-04:002009-08-28T02:15:51.997-04:00Jason, I'd like to see that article. Where are...Jason, I'd like to see that article. Where are you guys reading this from?Ron Georgehttps://www.blogger.com/profile/18394865788996482667noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-60914359839920578492009-08-27T21:54:56.797-04:002009-08-27T21:54:56.797-04:00jaycee,
I find that analysis highly suspect. The...jaycee,<br /><br />I find that analysis highly suspect. The writer performs a purely static analysis at various points in a cycle, demands the reader ignores all those pesky complex forces and then magically comes up with the notion that the spring is giving back to the upward pedal stroke exactly as much as it took and perfectly in phase and in plane.<br /><br />Sorry, but thats called bullshit where I'm from. What happens to all that torsion that is totally out of plane of the bearing surfaces? <br /><br />The way I see the dynamics of the system is that any flex in the BB location causes the force vector of your pedal stroke to move out of plane of the chainring, thus lessening the effective torque you are applying and it is not immediately clear to me that the deflection provides an exactly compensatory restoring force because the force vectors on each side of the BB are actually different because the crankset is not symmetric.<br /><br />Also, the only wheel flex that is not elastic is what goes on in the tires, and the tires will always be significantly more compliant and thus bear the bulk of the deformation even if you make your metal frame a touch more flexyUnknownhttps://www.blogger.com/profile/00403695097675640092noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-19329709637397426982009-08-27T15:56:08.665-04:002009-08-27T15:56:08.665-04:00Good Vibrations:
I hate to state the obvious, but...Good Vibrations:<br /><br />I hate to state the obvious, but all materials have natural damping in them or else they would continue to vibrate for ever. Superior damping characteristics was one of the selling points of magnesium frames when they first came out. <br /><br />http://www.mgbiker.20m.com/mg.htm<br /><br />Also check out Elastic hysteresis as I believe it explains the Bontrager phenomena. <br /><br />http://en.wikipedia.org/wiki/Hysteresis<br /><br />Also see damping:<br /><br />http://en.wikipedia.org/wiki/Dampingalloycowboyhttps://www.blogger.com/profile/14429465662167808264noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-10467940764199290792009-08-27T13:10:03.792-04:002009-08-27T13:10:03.792-04:00Jaycee : I would love to read Bontrager's idea...Jaycee : I would love to read Bontrager's ideas. Could you please link the Wayback archives story here, if you can? Besides, I did not imply frame flex totally 'absorbs' pedaling energy. I mentioned how it acts like a spring in the article. Springs are shock absorbers to a degree because they have a "K" value and a damping "C" value. Now whether it gives some of it back into positive pedaling motion is something to be discussed. Intuitively, I guess one could argue that it is.<br /><br />Jason : You're absolutely right. If there was an Advertising Standards Authority for cycling, perhaps we wouldn't have seen so much of the black art you mention.Ron Georgehttps://www.blogger.com/profile/18394865788996482667noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-57060396896501401442009-08-27T10:43:07.245-04:002009-08-27T10:43:07.245-04:00No one has ever shown that frame flex absorbs peda...No one has ever shown that frame flex absorbs pedaling energy. FEA shows that bike frames act as perfect springs and that the very amount of energy "lost" to the frame is returned. <br /><br />Keith Bontrager argued that some flex increased performance - because the slight smoothing of power reduced lossy flex in the wheels. <br /><br />You'll need to use the Interent wayback machine to see the Bontrager article but you can read about the FEA at www.bikethink.com/Frameflex.htmjayceehttps://www.blogger.com/profile/13022499495647528352noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-65285003278734647792009-08-26T11:37:08.016-04:002009-08-26T11:37:08.016-04:00An extra little precision. FFT just refers to any...An extra little precision. FFT just refers to any computational algorithm used to take a data set and move between time and frequency domains without actually having to do the detailed calculus involved of the DFT - this is great because experimental data sets don't always obey easily fittable functions nor can or do you want to spend time curve fitting in situ (something that is fairly perilous anyway).<br /><br />As to the issue at hand, I think this is a great topic and a very well written post. I'm struck by the complete lack of some common engineering sense in the cycling industry and in the consumer.<br /><br />I'm really amazed how much "magic" and black art the industry has managed to surrounded bike design with regards to stiffness and comfort - all in the name of spoon feeding marketing to the hapless consumer.<br /><br />The engineering system itself might be quite complex, but the basic knowledge behind what needs to be done is not. Without being able to throw in a whole slew of "large displacement" dynamic elements that makes suspension systems comparatively robust it's high time road cyclists accept that there is only so much you can do and that any of it comes at a performance cost.<br /><br />From a structural standpoint having a cushy seat and flexy frame generally will translate to a softer ride and that should be accepted basically as the gospel IMO, something that can probably be rationalized with a simple lumped spring mass damper system (mass of rider + bike), some net vertical compliance of the frame, etc. You're trading power transfer for that comfort every time though, point finale.<br /><br />Other tricks, like zerts which I figure work on the basis of acoustic impedance mismatching and hysteresis might do something but I've yet to see any actual data on how much they do.<br /><br /><br />I think the biggest hoax out of all of this is that I'd bet tire pressure (which is quite simply adding more compliance and a touch of damping) and the wheel set probably does more than switching frames and that riding technique, proper position and a perfected bike fit are all dramatically more important to your long term comfort than a frame ever will be after a certain price point.<br /><br />With regards to bike reviews, I think that any review that does not put quantities (ie 99% of all of the reviews of anything out there) are absolutely useless. Save your money and time and use those to test ride yourself - your LBS ows you at least that much for your continued patronage.Unknownhttps://www.blogger.com/profile/00403695097675640092noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-13284990311365206222009-08-26T10:42:08.066-04:002009-08-26T10:42:08.066-04:00Thanks a lot. Now I can show off I learnt some new...Thanks a lot. Now I can show off I learnt some new words. :0Sprocket_Rocketnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-19279214523813897582009-08-26T00:10:34.106-04:002009-08-26T00:10:34.106-04:00Sprocket_Rocket - That's ok. Let me see if I c...Sprocket_Rocket - That's ok. Let me see if I can explain.<br /><br />Everything around us is in frequencies. Light, sound, colors etc etc. If you turn on a red light in your room, that's a particular frequency. Now if you switch it off and turn a blue light on, that's another frequency. When we analyze a signal and see how it changes with frequency, it is called the frequency domain. If we analyze a signal with respect to time, we're in what's called time domain (this is usually how we analyze things. Example, when you tell someone you work 40 hours a week in your day job, your giving him some data in the time domain...40hours/week...40 hours/time). <br /><br />Fast Fourier Transform allows you to move from time domain to the frequency domain by doing a set of mathematical operations on the time domain signal. We do this because there are many things that could be understood in the frequency domain that you cannot understand or analyze in the time domain. When you do a frequency breakdown of the signal, you're basically breaking down the initial time domain signal into individual component signals that "SWITCH ON" at a particular frequency. All these signals make up the initial signal. Its cool to analyze that!<br /><br />Mr. Fourier was a French mathematician who proved all complex wave forms could be broken down into their individual frequency components mathematically. We use his math to convert time domain signals to frequency domain signals. Since this is a complex procedure to do by hand, there are computer softwares that do all the transformation for us. This is called the FFT operation. Hope that gave you atleast a basic appreciation for this jargon. Its difficult, I know.Ron Georgehttps://www.blogger.com/profile/18394865788996482667noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-34546448665227346412009-08-25T23:46:25.388-04:002009-08-25T23:46:25.388-04:00Hey Ron, sorry but I'm not one of the humans g...Hey Ron, sorry but I'm not one of the humans gifted with brain power. But what's this fast fourier transform?Sprocket_Rocketnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-24039717311704092442009-08-25T23:00:29.319-04:002009-08-25T23:00:29.319-04:00I was wondering would there be any way for the des...I was wondering would there be any way for the designers to do a modal analysis using computers? The only challenge I see here is how to tell the computer that the bike has a special composite material in it?Richardnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-78979520778690206862009-08-25T18:20:45.551-04:002009-08-25T18:20:45.551-04:00Ron their are a couple wild cards in the mix. That...Ron their are a couple wild cards in the mix. That would be rider size, power, and weight. A bike that feels stiff to 140 lb rider may feel like a wet noodle to a rider that weighs 200 lbs. So the bike needs to be tuned to the individual rider. I think the future of frame building is custom composite frames for everyone. Here is how the process will work. "Just add money!"<br /><br />A female frame mold will be rapid protyped based on the riders custom specifications. A ceramic male mold is then created from the female mold using "Advanced Cermacis Manufactering's" Aquacore Premium Ceramic. Then the carbon composite frame will be layed up over the ceramic core and cured in an autoclave. Once the frame is cured the water soluable ceramic core is dissolved away leaving the pure carbon frame now ready for finishing. <br /><br />Rumor has it that Race Face is building its carbon cranks this way.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-60443189062532932802009-08-25T13:37:31.632-04:002009-08-25T13:37:31.632-04:00In every bicycle design, there are tradeoffs. Too ...In every bicycle design, there are tradeoffs. Too much of one good attribute leads to the lessening of others. I think its upto the consumer to make the compromise.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-55125119210484755242009-08-25T13:32:44.216-04:002009-08-25T13:32:44.216-04:00Intereresting posts as always!! The MF5 is an 80% ...Intereresting posts as always!! The MF5 is an 80% flax, 20% high modulus 3k carbon combo. I wonder if its all that flax that makes this bike 'flexy'. FLAX FLEX!!!Ronhttps://www.blogger.com/profile/16268869622833968439noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-29331157541215423552009-08-25T13:21:39.475-04:002009-08-25T13:21:39.475-04:00it's posts like this that make me feel smarter...it's posts like this that make me feel smarter, eventhough i'm really not (well, maybe +/- 5% but that's negligible in the iso's eyes). keep it comin'!acquiesce808https://www.blogger.com/profile/18358706190760979985noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-62032100166306768802009-08-25T07:35:34.110-04:002009-08-25T07:35:34.110-04:00Ron,
Thanks for your post. I think this is one of...Ron,<br /><br />Thanks for your post. I think this is one of the more important issues with bike design & marketing.<br /><br />Most reviewers are told what ride to expect prior to testing & have preconceived ideas of the ride characterists of different frame materials. So developing an unbiased repeatable testing protocol would be a huge leap forward.<br /><br />I'm not sure how manufacturers will react, as I guess not all 'special' design features will be proved to be functional.Jamesnoreply@blogger.com