Trakhak

As demonstrated at the bottom of the post quoted in post 288.

If this thread or one like it is still active, I'll try to remember to provide a link the next time a bass player's forum I look at has a similar "I don't care about the science!" thread going.

My favorite: the guys who claim that older, heavier solid-state amplifiers (a.k.a. "lead sleds") have "heft" and "slam" and that the newer class D amps don't.

Since "heft" and "slam" are (conveniently) not quantifiable because they're undefinable touchy-feely terms, the arguments can go on for hundreds of posts.

When it is pointed out to a heft/slam guy that one of the people they're arguing with has been a professional in the industry for 40 years and that he designed both their favored lead sled and the class D amp they're spitting on, does he back down?

He does not.

venturi95

Thank you for the kind words. Out of 38 people who started the course, two of us finished with "A"s, I was one of them. I did struggle with calculus, but I am able to utilize my modest understanding of what goes on around me very well. I devised an experiment to quantify the errors in our steam sampling method while working in geothermal. This was not insignificant; it was something that the genius (one of two I have known) who ran the show, and the 100 or so guys who worked the job before me never realized.
Less of a fable than the pointy nipple perfection of the model I am countering. In fact, not a fable at all, because if your reading comprehension wasn't challenged you would know I've lived it. No offense, but I'd be willing to bet you engineers have never ridden a seriously light sew-up wheel set in a hill climb competition. There are reasons why we race and don't just sit around a plug numbers into an equation. Show me the math where i'm wrong at time = thrice f'd. PLEASE, GO ON.

tomato coupe

You seem to think you're the only one that has racing experience. You're as wrong about that as you are about the physics of the scenario you painted.

venturi95

Wow, just wow. You got me there, we all know how bicycle racers proceed shoulder to shoulder at a steady pace during a hill climb [Sarcasm alert].
Now you have me wondering if you have ever even seen a bike race? [Not being sarcastic].

venturi95

My scenario in way goes counter to the laws of physics, what the hell are you refering to exactly?

elcruxio

I had an unfortunate typo there that I fixed. All other things being equal the heavier wheel will be slower. But they aren't equal.

Your example left out aerodynamics. Bit of an unfair omission that, because some would say it's a pretty big deal.

tomato coupe

You're arguing that the reduced moment of inertia of his wheels is a factor when the cyclist in your racing scenario attacks on an uphill section and opens a gap. Physics indicates it's an insignificant factor.

PeteHski

Well you've seen from the physics that the magnitude of the cyclical accel-decel is actually reduced with more rotational inertia. So however small that acceleration is, it is going to be even smaller with heavier wheels. The extra wheel mass would of course slow your average climbing speed down ever so slightly (if no aero effect), but there would be less speed variation over each pedal stroke. Or are you suggesting that more speed variation through the pedal stroke might be easier on your muscles? That does sound counter-intuitive to me.

venturi95

Yes, I would say aerodynamics are big deal too, and they still matter, especially for the pros who are of course moving faster. And add to that, many miles of not climbing, but descending or flat (or very close to it) in the Grand Tours in the mountainous stages... I can see the aero wheels being chosen. I just don't see the 7% grade being the trade-off point for this argument, and some accuse me of being a flat earther.

Trakhak

Not an engineer, but I raced hill climbs and time trials in the 1980s on a Columbus SL/SP Bianchi Specialissima Super Corsa, sometimes on Campy wheels with Mavic MA4 wheels with light Barum tubulars and sometimes on Hi-E wheels (their lightest model and the lightest production tubular wheels on the market at the time).

Allowing for wind conditions, etc., my times didn't vary much between the two wheel sets. I did set a course record for a 10-mile time trial using the Campy/MA4 wheels, so there's that.

I finally got rid of the Hi-E wheels because I didn't like the subtle but annoying stop-go feel of having to reaccelerate those wheels with every pedal stroke. (See the larger zig-zag lines corresponding to the lighter wheels at the bottom of the aforementioned post.)

Yes, it was a princess-and-the-pea thing to be annoyed by, but once I started noticing it, it was hard to concentrate on maintaining maximum effort.

PeteHski

The only thing your real world example proves is that you can still win on old equipment if you are a bit stronger than the guy on new equipment. If the average gradient was 7% then lighter wheels are likely to be marginally faster for a non-pro rider. Nobody is arguing about that. It's the part where you were arguing that wheel mass is worth significantly more than static mass due to all these "micro-accelerations". Unfortunately the physics doesn't support that view, regardless of what race experience we all have.

venturi95

How many watts is insignificant?. I would have to educate myself again [Hint: not going to happen] and go over the raw data to believe the Willits numbers posted way back, like I said, hundredths of a Watt? Okay, gradient goes from a low of 6% to a high of 10%, but average is 7%, only difference is the 150 grams per rim. 70 kilos per rider. I have no idea what a pedaling force would be, where the accelerations would be coming at, how to model so I can optimize my argument, minimize my argument, or even an accurate approximation of speeds. I am sure I could not do the math in a timely manner.
Many times I have seen riders who had 2 or 3 pound heavier bikes with heavier wheels ride away from big fields of hard climbing riders. The lightest equipment doesn't guarantee a victory, but you may have 10 or even 20 riders who are physically capable of winning.

venturi95

We need engineers, they make geologists look well-dressed.
In the distant future, a balding, overtly intellectual, skinny old college instructor is giving a physics lecture at a prestigious east coast school:
And here we have venturi's "Thrice F**ked Conundrum" regarding uphill accelerations during cycling competitions.

PeteHski

Uphill accelerations? You mean like accelerating from 9 mph to maybe 11 mph over a couple of seconds? Really you should just give up on this line of thought.

PeteHski

The maths has been done:-

terrymorse 

Yes, the higher inertia wheel decelerates more slowly than a low inertia wheel. But it also accelerates more slowly, which is where the muscle fatigue question arises.

Expanding what I wrote above, pedaling the high inertia wheel is like throwing a heavy ball a short distance, pedaling the low inertia wheel is like throwing a light ball a longer distance, and while the work done is identical, it's not at all clear which one is more fatiguing (or if they're equally fatiguing).

PeteHski

I don't think the difference in this case is significant enough for it to matter either way. At least with the physics it's easy enough to calculate some numbers - even if people are still in denial of the results. In your analogy the differences in both ball weight and distance thrown would be very small. Maybe not even measurable.

HTupolev

Why not? If you did fine through a year of collegiate physics, the relevant material is well within your level of understanding.

What you're questioning are conclusions that are literally derived from just basic high-school-level Newtonian kinematics, a quadratic force formula typically represented with no linear element, and coefficients to that force formula that have been getting measured and published since the 19th century (with respect to tire rolling resistance and aerodynamics) or a couple hundred years earlier (gravity).

Over the past few pages of this thread, you've basically taken a position of "I have a moderate background in exactly the subject matter that's relevant to this discussion, but I refuse to leverage that understanding in assembling my argument."

HTupolev

What terrymorse is getting at is the issue of crank inertial load, or perhaps more generally, "what are the physiological consequences to changing how the pedals respond to pedaling force." Personally I think it's an underexplored realm of cycling performance, but, I'm inclined to agree that rotational inertia from wheel changes is an extremely marginal part of the discussion. It's an incredibly tiny difference compared with, say, the differences between inertial loads while cruising on the flats versus grinding up a steep hill.

PeteHski

Agreed, that's a whole different discussion.

Maelochs

Here is what I see. One poster keeps saying that the difference is force on the pedals as the cranks rotate is a significant source of fatigue---not spinning them, but the uneven resistance through teh rotation---and that heavier wheels produce significantly less fatigue because they damp out variations in the pressure pulses.

Did I get that right?

And at 8- rpm, there would be 160 pulses per minute? and 150 grams or weight on the rim would reduce load, even though obviously it increases load (it Is load) ?

Okay ... show Any test results. Any data. Anything but "I think it must be this."

Nobody really believed Einstein until some photos showing the Sun bending light were published, many years after his paper was published. Why should we believe you when you say that pedal-pulses are a significant source of fatigue?

Test it, explain the test, and show the results

It seems to me the variations are so minor and so frequent that it would be impossible to feel the difference and possibly impossible to quantify the difference. And if ti is not a Significant difference---if you cannot show a whole-number Watts Lost figure--then we are back to arguing that removing even one molecule Makes a Difference,

Show us the money.

tomato coupe

From a physics perspective, estimating the magnitude of these effects is trivial.

RChung

Back in 2011 I worked a little bit on modeling the team pursuit in prep for the 2012 Olympics. (For oddball reasons we worked with the American and Canadian women's pursuit teams). One of the tricky things is that in team pursuit there are pretty wild swings in power (and thus acceleration) as you rotate both through the team and also around the velodrome. Wheel speed actually rises and falls more than center of mass speed since in the turns the bikes lean over so the wheels take a longer path than the rider, and the center of mass drops and then rises as you come out of the turn and onto the straights.

So we knew the geometry of the track and how much each rider would lean at what speed in each turn--and, we knew the wheel weight, and had figured out "where" in the wheel the "mass centroid" was so we could calculate the moment of inertia. We did this because this was one of the first times we were trying to get good high quality high precision estimates of CdA and Crr from field-based tests using power meters. Our model was very good, so once we had proper estimates of CdA and Crr, and using the carefully calibrated power meters, we could absolutely *nail* the speed for power for a rider both on the straight and on the turns. I was agog that my calculations worked so well--I hadn't actually expected that.

Here's the thing: although we had the moment of inertia for the wheels, it quickly became evident that the MOI was a small enough contribution that we could simplify the model and ignore it. Even though the speeds and accelerations were high, our predictions of speed for power didn't significantly depend on it at all.

tomato coupe

Worth emphasizing ...

tFUnK

When you say "...didn't significantly depend on (wheel mass)" do you mean statistically significant or functionally significant?