Wyatt Earp Posted January 4, 2010 Share I'll get the popcorn..... Spidey' date=' I thought you said earlier that popcorn was inappropriate for this thread We need beer and biltong Thanks Jeremy for doing all the calculations . Your answers have come the closest to helping me understand how much of a difference rotational mass makes to cycling performance. [/quote'] Link to comment Share on other sites More sharing options...
GoLefty!! Posted January 4, 2010 Share Edmund R. Burke Ph.D Much like his mentors and associates' date=' Dr. Burke gained worldwide renown. Professionals in the fields of exercise physiology, nutrition and medicine are familiar with his exceptional work ethic and reputation as an author, scientist and educator. His 39 page curriculum vitae speaks for itself as it reveals some of his outstanding career accomplishments, including over 1,000 articles and many book chapters and books that he wrote and published in the areas of health, sport science and applied physiology. He served as Coordinator of Sports Sciences for the U. S. Cycling Team leading up to the Olympic Games in 1996 and was a staff member for the 1980 and 1984 Olympic Cycling Teams. Some of his books: http://www.pickabook.co.uk/typesearch.aspx?Type=authorisbn&Code=9781583331460&Key=Edmund%20R.%20Burke Also: "Kiwi, you posted the full force equation. If you substiture values into this equation for wheels of different Ir (rotational inertia) but the same mass, and calculate acceleration, it will show that Ir has a very very small effect on everything. " Different wheels with different Ir are different because their mass is different. Looking at the table I posted you can see a lighter wheel has a lower Ir and a heavier wheel such as the mountain bike wheel at the other end of the table has a higher Ir. Rotational Inertia and Mass for Various Wheels Wheel Details Ic(kg m^2)Mass(gm)Wire SpokeRear, Std Rim, 700, track, 36 spokes, w/o tire, w/ axle, nuts 0.05281177Wire SpokeFront, Std Rim, 700, 32 spokes, w/ tire, tube, rim strip, axle, skewer0.08851264Wire SpokeRear, Std Rim, 700, 32 spokes, w/12-21 cassette, tire, tube, rim strip, axle, skewer 0.09671804Specializedtri-spokeFront, 700, w/ tire, tube, axle, skewer0.09041346Specializedtri-spokeRear, 700, w/ 12-21 cassette, tire, tube, axle, skewer 0.10321771Specializedtri-spokeFront, 650, w/ tire, tube, axle, skewer 0.06831207MavicFront, Std Rim, 650, 28 Bladed Spokes, w/ tire, tube, rim strip, axle, skewer0.06321179MTBFront, 32 Spokes, w/ tire, tube, rim strip, axle, skewer0.15041847I'm not suggesting anyone should believe me, this is something very easy to find out for yourself. Strap on some wheels in the 1800 gram range, do a race, then strap on something in the 1400 gram range and do a race and you can feel the difference. As I suggested do the above with a power meter and you can measure the difference.[/quote'] funny this, I recently did just that by trying out a pair of american Classic carbon clincer 58 vs my Easton EA90SLX theres a full 500 gr difference between the wheel sets I could feel absolutely no dfference at all. What I could feel is that the AMC carbon 58's rolled nicer than the easton's. This is clearly a scientific arguement for heavier wheels. BTW, I'm with Bornman on this one.Even though differences in Ir and all that makes great calculation and keesp my HP48Gx busy, out on the road those little difference are lost in the total package on the road. Get wheels that are sturdy, and have machined braking surfaces. I've seen so many come a cropper while using carbon tubbie rims and then could not stop because the braking performance was inconsistent. oh btw, Por's are paid to ride their equipment Link to comment Share on other sites More sharing options...
TNT1 Posted January 4, 2010 Share 39 page CV huh? When you're a ponce, you're a ponce... Link to comment Share on other sites More sharing options...
GoLefty!! Posted January 4, 2010 Share like bling, there are no half measure of ponce Link to comment Share on other sites More sharing options...
Barend de Arend Posted January 4, 2010 Share Jules has made the following comments:C: I reckon aerodynamics is a far more important concern than massat the perimeter of a wheel. A: I dare not go into aerodynamical calculations (they arehorrific and usually non-linear and only solvable by numericalmeans)' date=' but I would tend to agree with you here. [/quote'] It's a very different exercise. Aero is squared. Twice the speed is four times the drag. Aero is drag. It needs constant work -- not just to accelerate. That alone should make a bigger impact. Aero changes in crosswinds. In a bunch, aero is less important than solo, or in a break when you're sharing the work. It's not going to make a difference at the back of the bunch. But then you're not attacking, either.Just like weight, aero of the rider has a larger factor than aero of the wheels or bike. I think that the percentages are very different though. ie. aero wheel is a larger percentage of the total package than a lightweight wheel's percentage of total weight.Excellent work! Link to comment Share on other sites More sharing options...
Jules Posted January 4, 2010 Share In a bunch' date=' aero is less important than solo, or in a break when you're sharing the work.? It's not going to make a difference at the back of the bunch.? [/quote'] Yebo yes. I remember Cervelo did some sums showing why their Soloist was faster than the R3 even on steep mountain passes. They said that the aerodynamic advantage of the soloist outweighed the weight advantage of the R3. However, I remember thinking that they did not specify whether they were referring to a rider in a bunch or in a break. Link to comment Share on other sites More sharing options...
GoLefty!! Posted January 4, 2010 Share most aero numbers are quoted from data gathered by testing aero components under static conditions in a wind tunnel. The data does not translate well to the road since effects of wind direction change are not taken into account. At the end of the day, aero, lighter weight are all just tools to get a customer to hand over more money for an item that has low intrinsic value. Just get the goodies that looks the best. I'm all over the proper bike fit thing at the moment. proper fit has a much bigger effect on your performance on the bike than does aero wheels or lighter wheels. Thats the best R250=R450 you can spend. With this information I've come to realise that way too many peopleare willing to spend loads of cash to simply look pro. Thats fine but then why try to get all scientific about looking good? Link to comment Share on other sites More sharing options...
TNT1 Posted January 4, 2010 Share Just get the goodies that looks the best. Spoken like a true roadie. Link to comment Share on other sites More sharing options...
GoLefty!! Posted January 4, 2010 Share well you can't look half pretty can you? does you wife so half her make up? do you get half a hair cut? or wear half underpants? [lightbulb] Link to comment Share on other sites More sharing options...
TNT1 Posted January 4, 2010 Share or wear half underpants? [lightbulb] I second the motion... Is the prototype ready yet? Link to comment Share on other sites More sharing options...
GoLefty!! Posted January 4, 2010 Share it was, but the other half binned them. Said they needed replacing. Link to comment Share on other sites More sharing options...
jmaccelari Posted January 4, 2010 Share BTW' date=' I'm with Bornman on this one.Even though differences in Ir and all that makes great calculation and keesp my HP48Gx busy, out on the road those little difference are lost in the total package on the road.[/quote']And I'd also agree with you. Maths ain't everything. The energy saving really is less than 1%. What you probably noticedwas the inertia of the wheel. This (simplistically) is the resistance ofthe wheel to changes in its rotational velocity (speed). You took more energy (a very small amount) to spin them up and thenit felt more comfortable (like a flywheel) during the race since they continued to roll more easily and smoothly. The whole package is about more than just weight...jmaccelari2010-01-04 21:38:27 Link to comment Share on other sites More sharing options...
epoh Posted January 4, 2010 Share I think it is time to put the biltong, popcorn and coke away. The time has come to print and snort this thread and enlighten ourselves! Link to comment Share on other sites More sharing options...
BikesRxS Posted January 5, 2010 Share Pure Genius Johan, we have been suckered into this weight weenie nonsense for too long and need to change our beers. Well done man, hope some of the hubbers have the cranial capacity to get what you saying Cheers . Excellent start to 2010 ! Link to comment Share on other sites More sharing options...
LazyTrailRider Posted January 5, 2010 Share Hmmm, one question no one has asked yet: what happens when you have a couple of patches on your tube (like I always have) and you ride a R2000 wheelset (like I do), with tyres constantly gunked with dirt? Will I never be able to win a race, ever?! Link to comment Share on other sites More sharing options...
TIMEprb Posted January 5, 2010 Share OK' date=' I think your averages vary far too much. If I work with these I have to ask you how much you accellerated for each attack from 1 to 24. Too much work. Give me an average attack speed and lets pretend on this race the attacks were all equal. Scenarios (actual data)Time (s)Acc m/s2Scenario One 33 to 63 in 30 sec200.277778Scenario Two 33 to 67 in 55 sec250.171717Scenario Three 36 to 72 in 55 sec300.186869Scenario Four 30 to 76 in 65 sec350.324786 Have a look at the far right colum. This is accelleration for the said scenario in m/s/s or m/s2 Choose one and we go with that. [/quote'] Just a little nit picking...<?: prefix = o ns = "urn:schemas-microsoft-com:office:office" /> How the hell did a cyclist accelerate @ 200 m.s^2 when gravitational acceleration is but 9.8 m.s^2 ???? Your calculations are based on a load of bull Mr Wise Guy! Using your most modest figure, this guy completed 90km in 30 sec To clarify s=ut+1/2at^2 (physics law of movement) Say the guy does 0km/h and starts accelerating @ 200m.s^2 u = 0 (initial speed)t = 30 (time)a = 200 (acceleration) Pop those into the equation and you end up with a total distance of wait for it 90 km in 30 seconds amazing!!!! Link to comment Share on other sites More sharing options...
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