AIR RESISTANCE: influence of motorbikes, bike position etc

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Just for the lol's I fitted an exponential function to data points generated by the physical relation P(v)=v^3. You start to get a reasonable result (was too lazy to calculate reduced chi squared values to evaluate properly) with 3 degrees of freedom (fit range was 0 to 15), i.e. P_fit(v)=a*e^(b*v) + c
Visually, it looks reasonable although still not perfect. Parameters are: a=133.8 +- 17.4, b=0.2 +- 0.0, c=-223.9 +- 41.9
Parameter c obviously indicates that something is still fundamentally wrong with this fit as it should be 0. You would probably need to add a second summand to your fit function to get a better result. So yeah, you can model a power function with an exp function if you wanted to. That does however not change the fact that the theoretical relation is that of P(v)~v^3, so every attempt to use an exp function is unphysical and not justifiable.
 
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ClassicomanoLuigi said:
Alex Simmons/RST said:
The relationship between speed and power output is a cubic equation (a mathematical power function), and is *not* an exponential equation. Exponential implies something vastly different to a power law.
A cubic equation is an exponential equation, the former type is a subset of the latter.
A third-order power law is also an exponential equation, so the distinction you are trying to make is between the variable and the base ...
Whereas what I said, covers all of the above.
"*not* an exponential equation"
is just untrue, I see what you are saying, though. Better observation would be: that it is a specific kind of exponential function
An exponential function has its variable in the exponent, but a power function has its variable in the base. It is a significant difference.

e.g., where "x" is the variable and "a" is a constant:
exponential function: f(x) = aˣ
power function: f(x) = xᵃ

The physics relationship in play here is a power based relationship, not an exponential relationship. There is no physics involved which invokes an exponential relationship. IOW the variable of velocity would never appear in the exponent.

Where v = velocity, the mathematical relationship between speed and power is of the following form:

Power(v) = av³ + bv² +cv

The cubic part is for air resistance, gravity and rolling resistance are linear parts of the equation. There are very small parts (bearing friction) related to the square of velocity. This is for steady state cycling. For changes in speed then of course the change in kinetic energy is also related to the changes in the square of starting and ending velocities.

Here's the equation from the seminal paper on it:
http://www.aerocoach.com.au/math-model

As a result, solving power from speed(s) is relatively straightforward, provided you have all of the relevant input constants (coefficient of drag, frontal area, coefficient of rolling resistance, gradient, mass, wheel moment of inertia, relative wind velocity etc).

Solving speed from power is (mathematically) much harder.
 
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I'd like to see a study comparing different sized groups. We've all seen small breakaways, say, 10-12 riders, get caught by the peloton. I guess the peloton is driven by fresher riders, but probably no more of them than alternate in the break. If there are two or three of them, the draft advantage would be greater, but the break could do the same thing.

So is it just the fresher legs, or a size advantage?
 
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Merckx index said:
I'd like to see a study comparing different sized groups. We've all seen small breakaways, say, 10-12 riders, get caught by the peloton. I guess the peloton is driven by fresher riders, but probably no more of them than alternate in the break. If there are two or three of them, the draft advantage would be greater, but the break could do the same thing.

So is it just the fresher legs, or a size advantage?
It's not everything in Φ ... φ
 
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Merckx index said:
I'd like to see a study comparing different sized groups. We've all seen small breakaways, say, 10-12 riders, get caught by the peloton. I guess the peloton is driven by fresher riders, but probably no more of them than alternate in the break. If there are two or three of them, the draft advantage would be greater, but the break could do the same thing.

So is it just the fresher legs, or a size advantage?
This was actually (at least in part) explained in the research/interview in the opening post. Whether a bus, car or peloton is riding directly behind a cyclist, as long as it is a "large mass" that displaces air by moving, the rider in front will benefit from it, because it pushes the air in front, forward. Thus "protecting" the leading rider. However, this advantage is obviously a lot smaller than the advantage of riding behind a large mass. See the image with Delgado, chased by cars and motorcycles, and the image with the motorcycle riding behind the cyclist. There's supposedly still a reasonable advantage to be had.

Additionally i believe that even though the amount of riders taking pulls might be the same in both the peloton as the break, that the riders that are in the peloton, might "drop further back" inside of the peloton, and stay a lot more fresh than the riders in the break, even when they're currently not pulling.
 
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sir fly said:
Merckx index said:
I'd like to see a study comparing different sized groups. We've all seen small breakaways, say, 10-12 riders, get caught by the peloton. I guess the peloton is driven by fresher riders, but probably no more of them than alternate in the break. If there are two or three of them, the draft advantage would be greater, but the break could do the same thing.
So is it just the fresher legs, or a size advantage?
Suppose that pulling on the front of a group is (an expectation) to do about 40% more work. The 12-rider breakaway that you mention as an example is becoming dangerous for the win, because if they choose to work together as a rotating double-paceline, each rider only has to take short pulls at the front, 30 seconds is enough, then 30 seconds on the front of the second, regressing paceline, and so it's 1 minute 'on' / 5 minutes 'off'. Lots of time to recover, especially for professionals, they can do that again and again.
The peloton in a mass-start race can't all rotate like that, because a two-lane road is not wide enough, because of lack of coordination between teams or individuals, and not much incentive to be on the very-front leading edge. There will be an arrowhead, phalanx, or echelon type formation on the front, and a broader and more amorphous peloton extending far back, according to the width of the road and the race scenario.
Being in the center of a huge peloton is like being swept along, surrounded, while doing very little work. Some riders could go for hours without having to lead the group at all, so those sheltered people are never 'burning their matches' above a threshold level, nor the slow-burn on/off of the breakaway escapees. Glycogen reserve is limited
Is it just fresher legs or a size advantage - it's both, the larger and more cohesive the peloton is. In a mass-start event. The bad part is being 'boxed-in' - it's becoming a nervous affair when the speed is up, sometimes vague accidental jostling shoulder to shoulder within the group, I can't move straight forward because I will clip someone's rear wheel, and I can't move straight back, because I would cause, whomever is drafting me at the time, that same problem, and they may crash. A good position is: near the front (to avoid the risk of crashes further back) but not on the very-front (thus to avoid work). So in real racing (not amateur like me), teams want to position and protect their GC hopefuls or sprinters like that.
Teams pulling on the front are doing that: to control the pace when strategically they decide that faster / slower pace at that moment is more important than conserving energy for later. Escapees have no choice, relentless, and if they don't all cooperate efficiently as 'frenemies' then they are likely to be caught by the peloton
 
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Merckx index said:
I'd like to see a study comparing different sized groups. We've all seen small breakaways, say, 10-12 riders, get caught by the peloton. I guess the peloton is driven by fresher riders, but probably no more of them than alternate in the break. If there are two or three of them, the draft advantage would be greater, but the break could do the same thing.

So is it just the fresher legs, or a size advantage?
It doesn't happen as much, but you do sometimes see when a well-organized group of 8-10 riders, well-distributed among the teams, and only 1 team has any motivation to chase (say, nobody wants to help set up a sprint, if e.g. Bora or Quickstep have the only top-rank sprinter in the race) and the break stays away. It also happens in shorter stage races with smaller teams, where the chasing teams only have 6 riders, and they run out of manpower sooner.

In those cases, it is just a case of numbers. If a 10 rider group gets caught, it's because there were 3 or 4 teams in the peloton for whom catching the break was important enough to put more than 10 on the front.
 
I'm not sure we could consider this a scientific study but a German tv show for kids/youths did some tests with Ralf Grabsch in a velodrome. The show was called Kopfball, and this episode was aired 27th of March 2007, 11 AM. There used to be a video online of this episode until 4 or 5 years ago but there's no trace of it now.

They measured Ralf Grabsch's power output while he was riding at 45 km/h on the track under different circumstances. Here are the results:

Position Power (w)
Upright 520
Aero 434
Rider on his wheel 428
Behind a rider 282

434 w seems much for 45 km/h by today's standards but this was 2007 and I'm not sure how efficient Ralf's material was back then, and he probably wasn't the very elite of time trialists either (unlike his brother Bert)?

The intersting thing at the time was that one could save 1.5 % power by having a rider wheelsucking!
 
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You wouldn't need to fly closely in front of a rider. First of all, you don't even have to fly "over" the road, you can fly next to it. Camera's will be much more stable than from a bike. Less vibrations and shakes, meaning you can fly farther ahead and zoom closer (which is a problem on a bike due to vibrations). For personal use, check DJI. They have really great quality drones under 1000$ with great image quality.


Camera drones are (just like a motorcycle) operated by two people. One pilotting the drone, one doing the camera. The main hurdles currently are the range of control and battery life. It's probably too soon yet, but technology progresses fast, especially once it hits mass production. Even 1000 dollar drones are used for professional TV reports. Image quality is actually very good, it will be more stable than shot from a motorbike. But i don't know the cost and specs of high-end drones. I know DJI has a pro camera drone (for television) for "only" +/-5000 dollars. Very stable and fast. But maybe there are even better drones for 5x that price, that have longer range and better battery. In theory, you could consider having a bus to operate the drones, riding 100 meters in front of the peloton, and swap batteries every 30 minutes, while staying close to the drone (for range). But i think it's still too soon. I guess they'll start on closed loop competitions first, and maybe start experimenting in 5 to 10 years. I 'm pretty sure they're being used on some CX races already since a few years.

But this is just my personal belief/opinion. I'm neither a drone expert, nor an aerodynamics expert.
You would think costs alone would drive this change. (Pilots, fuel, insurance, etc.)
I would imagine a mix of drones ant copters would do until the technology is proven in this application.
 
Great research. It makes you wonder how much influence motors have had on famous races in the past. Maybe they should use drones to film the race?
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Is using drones really feasible?
I've been thinking about drones for cycling coverage before and in more detail again today after the topic came up again. Been looking at what's on the market currently for professional use. There are some interesting problems to solve for this to become feasible which I'd love to investigate in more detail.
Linking up with the topic of the thread, it would also be interesting to see the effects of a drone flying closely in front of a rider.
You would think costs alone would drive this change. (Pilots, fuel, insurance, etc.)
I would imagine a mix of drones ant copters would do until the technology is proven in this application.
View: https://www.facebook.com/tourdelavenircycliste/videos/733726620402423/
 
I think it's a lot harder to find people who can fly a drone remotely without crashing than people who can ride a camera motor
Yes, I think you will have to develop a system where the drones actually work autonomously. I imagine something where the director instructs the drone to shoot a specific group of riders from a specific distance/angle/whatever and the drone, by having the necessary sensors and a.i. onboard, maneuvers itself into the position to deliver the requested shot.
 
I think it's a lot harder to find people who can fly a drone remotely without crashing than people who can ride a camera motor
I think this is an extremely silly statement.

As someone who got his motorcycle license aged 19, i can tell you there is a huge difference between "being able to ride a (motor)bike" and "riding a camera motor". As a camera motor, you need to be able to ride a massively heavy bike (these are never light bikes, and with good reason), with a cameraman as duo, who is carrying heavy gear, who is constantly maneuvering (sitting up, hanging left, hanging right...) at LOW speeds. Furthermore, you need to be very familiar with the peloton, how riders move, how the peloton flows, when to wait, when you can pass by... This is a VERY small pool of riders who can do both. Safely. Motorpilots from the VRT were hired by other channels not so long ago, to do worldchampionships, TDF etc... simply because it is such a niche.

Camera drones are also operated by a pilot and by a cameraman. They are stuffed with sensors to make sure they don't crash into stuff, safety features to go to certain altitude and keep hovering, in case connection is lost. You don't need to fly directly over the peloton (see the video above). About every production company now has a drone pilot. They don't need to fly "through" the peloton, so there are a lot of safety issues that simply do not apply.
 
I think this is an extremely silly statement.

As someone who got his motorcycle license aged 19, i can tell you there is a huge difference between "being able to ride a (motor)bike" and "riding a camera motor". As a camera motor, you need to be able to ride a massively heavy bike (these are never light bikes, and with good reason), with a cameraman as duo, who is carrying heavy gear, who is constantly maneuvering (sitting up, hanging left, hanging right...) at LOW speeds. Furthermore, you need to be very familiar with the peloton, how riders move, how the peloton flows, when to wait, when you can pass by... This is a VERY small pool of riders who can do both. Safely. Motorpilots from the VRT were hired by other channels not so long ago, to do worldchampionships, TDF etc... simply because it is such a niche.

Camera drones are also operated by a pilot and by a cameraman. They are stuffed with sensors to make sure they don't crash into stuff, safety features to go to certain altitude and keep hovering, in case connection is lost. You don't need to fly directly over the peloton (see the video above). About every production company now has a drone pilot. They don't need to fly "through" the peloton, so there are a lot of safety issues that simply do not apply.
Fact is the camera moto drivers are an established profession in the pro peloton.

I'm all for using drones. It's just that the sport is extremely resistant to change.
 
I agree with that. But i think they can do it gradually. Sports like cyclocross are ideal to start trying out (and they've been doing it there already). Races with local laps of a few km too. And mountain stages like the example above. Mountainbike downhill... Other sports will play their part in making drones a standard as well.
 

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