#31
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#32
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Fine, but we weren’t supposed to factor aero into it, only weight. The title should have “(Because aero)” appended to it if it came down to just about being aero then. If like you said, the rider with the lighter wheels would inch away ever so slightly, that would matter if the scenario happened directly at the finish line, would it not? Quote:
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#33
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Italian track team had rims weighted with lead long time ago. Helped with inertia. Don't think anybody is doing it now, but for "the hour" it still may help.
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#34
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__________________
It's not an adventure until something goes wrong. - Yvon C. |
#35
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If wheels that spin up fast make me feel faster will I go faster?
I'm inclined to say yes. |
#36
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Perhaps please measure your inclination, extremely precisely, and then post again? Thank you. |
#37
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Anyone can see, nothing really matters...to me
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#38
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But if we want to see what happens if there was no difference in air resistance, then maybe we should use a more realistic difference in weight. The 1 kg (2.2 lb) difference in the exercise is a huge difference in wheel weight. When we talk about the differences between "light" and "heavy" wheels, we're usually talking about differences of only 200 grams or so. So let's see what happens in this case. Because air resistance increases non-linearly with speed, doing the true calculation would require non-linear differential equations. But for simplicity, we can get a ballpark figure by holding the drag constant during the acceleration. The distance traveled D from an intial speed V0 over an amount of time T is: D = V0*T + (A*T^2)/2 Acceleration is F/M (force over mass), so the equation becomes D = V0*T + (F/M)*(T^2)/2 Over a 30 second acceleration with the lighter wheels: D = (9m/s)*(30 s) + (30 N/90 kg) * ( (30 sec)^2)/2 = 420 m With the heavier wheels over the same 30 second acceleration D = (9m/s)*(30 s) + (30 N/90.2 kg) * ( (30 sec)^2)/2 = 419.67 m So, the lighter wheels come out 1/3 m ahead after 30 seconds of acceleration. Given all the other variables that affect bicycle performance, that's pretty small. Other factors will be more important. (Note: The video didn't say changes in rotational inertial will produce no difference at all, it said they will be relatively insignificant). So, if a rider has a choice between two wheel sets, where one is has less air drag but more rotational inertia, the choice is clear - the aero set will be better in just about all cases (including climbing and accelerations). Edit: After pondering a bit more, I realize the simplifications in the calculations above exaggerate the difference in distance traveled. In reality, air resistance will increase as the bike speeds up, and pedal force delivered to the road (for a constant power output) will decrease as the bike speeds up, so the actual acceleration rate will decrease as the bicycles go faster. So in this example, the actual difference in distance traveled will be a bit less than 1/3 me. Last edited by Mark McM; 07-12-2020 at 08:41 PM. |
#39
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Until then I'm sticking to my guns. |
#40
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The key takeaways are simple. This video is literally just a lesson on terminology.
1. Rotational weight is different from weight. 2. Some/Many of us have been erroneously been calling the effects we feel of heavier/lighter wheels due to "rotational" weight, when we should just call it "weight". Every time this topic comes up, I really view it as the terminology police/grammar Nazi coming in to clean up some misnomers. And some people get prickly about it and miss the point. There ARE perceivable and performance differences between wheels of different weight. Period. It's just not due to rotational weight, for the speeds and power put out by a human on a pedal bike. |
#41
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It matters.
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#42
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It’s what they’re counting on |
#43
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__________________
please don't take anything I say personally, I am an idiot. |
#44
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If you take two identical bikes and in one of them you add 400g of lead inside the rims and the other you add 400g of lead inside the frame the result will not significantly show up in any scenario. For every acceleration applied to the pedals from the rider there will be an equal amount of resistance to deceleration whether it's in the wheels or the frame. That's the crux of the video, not whether a lighter combination of bicycle/wheels/rider is faster. |
#45
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how "different" will the feel be of each of those bikes?
flat, downhill, climbing? zero or significant?
Quote:
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Crust Malocchio, Turbo Creo |
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