Bald Paul

So, if I were to toss a bike out of a skydiving plane, it would see acceleration and a change in barometric pressure, along with an increase in wind speed, and read power without me actually being on the bike, pedaling?

grizzly59

Look at the tall weeds, leaves at the tops of trees.

Ogsarg

I like windfinder.com for checking out wind conditions. Shows what is going on in real time and allows you to look forward to any time of day. I ride in the area shown below and the wind direction as well as speed can vary quite a lot. Sometimes I'll adjust the route I take based on what is going on that day. Not sure I see the point of being able to measure the wind speed once you're in it.

WhyFi

No. Why would it?

tessellahedron

sure but the power would be hella negative, just like coasting down the road they built on Everest. I have no idea what the actual power meter would show you. Non military GPS systems are slightly crippled for security's sake. They're programmed not to function above a certain speed or altitude. I thought it was 10,000ft but there are mountains west of here taller than that where people hike so I dunno.

There are very few trees here and tall grass definitely doesn't work. By the time the wind is high enough to produce visible waves in the crops that show its direction its strong enough that I definitely don't need the indicator.

Windfinder.com! Thank you!

sailflow.com and windy.com were also mentioned. So some good came of this thread. I'm going to see if using those sites can help me avoid wind and not care about it when I am out biking.

Bald Paul

Ooooooooooo-kay.

tomato coupe

That hasn't been true for more than 2 decades.

Barry2 

All of them.
Else, the head unit needs to contain the calibration table and do the calculations for the PM.
But that does NOT mean the Power Meter measures degrees Fahrenheit.

Example.
The Gridiron Pendulum used in precision clocks, corrects for the expansion of the metal with temperature.
Yet does not require you to know the type of metal, it's rate of expansion with temperature or even the current temperature!

Barry

imakecircles

The best, cheapest, and easiest to access indicator of wind speed, although it is completely subjective, is the volume of wind noise in one's ears (for those not hearing impaired). If the volume increases, I am either going faster, or the headwind has increased, or some combination of the two. Of course, the inverse is also true. Comparing the wind noise level with my cadence helps to isolate if it's my speed or the wind that's changing. If I'm pedaling the same gear at the same cadence, and the wind volume increases, then I have isolated that the wind has increased.

Different volume levels in each ear also help me ascertain which direction the wind is coming from relative to my vector, ie the volume in the upwind ear will be higher. This is useful for anticipating the wind conditions ahead if the course direction is changing.

After years of riding, I've developed an intuitive sense that above a certain level of wind noise, I should be in the drops and small to the wind or I'm just throwing away watts needlessly (and I don't have any extra to spare).

tessellahedron

you must also know why I learned that in college less than 20 years ago then. Care to share?

tomato coupe

I have no idea what that means.

The U.S. government ceased Selective Availability in May 2000.

tessellahedron

finally another useful suggestion, thank you!

my hearing sucks but with practice maybe I could do it. I will try.

so far all I've noticed is that when I'm going fast and it's really calm there has to be a tailwind.

you just gave me an idea! Multiple pressure sensors in a plane facing away from each other and a tiny little circuit that lights an led to show the sensor with the highest reading. Not quantitative but could be fun. I could measure wind speed by riding with the wind and watching what speed the led changes from back to front at. You might get more information with microphones but probably would need a processor and this was supposed to be simple. Probably won't get around to building this one either.

RChung

Hmmm. Well, part of the calculation requires that you enter the all-inclusive weight, so if you're not on the bike the total mass will be wrong. I recommend that you do this while on the bike.

[Edited to add:] Elsewhere I've posted a list of almost every argument in cycling fora. I believe your post falls under #5.

RChung

Actually, you enter total mass and with the barometric altimeter it can measure free-fall speed; it knows the gravitational constant, and if you do this repeatedly it can refine its assumption of your aero drag. So maybe not the first time but on subsequent jumps it'll know what your terminal velocity is. If you're going faster than that, it'll know that there was some added force; if slower, it knows there was some added drag. So if it knows force, distance, and time, yeah, it can calculate the power.

www.xkcd.com/54

RChung

Early attempts at doing "cheap" power meters were based on altimeters and speedometers. You can see a vestige of that each year during the TdF when guys on the Intertoobs try to infer doping behavior from VAM.

I evaluated both altimeter-based power meters and the inverse thing: how to turn an expensive power meter into a cheap altimeter. That works better.

DangerousDanR

The Airmar WS220WX NMEA0183/2000 is an ultrasound anemometer. Not cheap and you will need to mount it on a mast that is four feet above obstructions to get an accurate reading.
They are used on sail boats to get accurate and precise wind speed and direction measurements. I have used them for other purposes. As I remember, they use a fair amount of electricity so you will need to carry a big battery pack.

tessellahedron

I took a video but you can barely hear me talking at all over the wind, and I can't figure out how to post it anyway. My phone sucks, it took 8 shots to get a 360, but here they are. This is where I turned around this morning, some place in Nebraska.

S

SE

E

NE

N

NW

W

SW
I didn't take the anemometer because I was afraid it would get dirty or damaged before I return it. I wished I'd had it though so maybe a good solution will be a tiny pocket one that I can use on water breaks for my own curiosity.

I'm beginning to doubt that I'll find a way to relate the Google forecast to real world conditions. They may simply be independent. This morning was supposedly light wind, 11 or 12mph, but the roar/howl was pretty consistent and strong enough that riding into it was exhausting. Haven't yet switched to sailflow, windy or windfinder. Probably in the next few rides.

I'm trying out some dirt riding for many reasons but one big one is that I think my speed will be much lower. It seems like the relationship between air speed and aerodynamic drag is non-linear. If that's true, going a little slower should reduce the drag significantly.

I always enjoy new routes but I do feel that I enjoyed this morning's ride more than I would have if I'd been on the highway with that wind.

burnthesheep

It is not for something like casual riding but the aero sensors do this and include a Garmin live data field. Like the Notio. They are more for affordably replacing a wind tunnel session(s) with a sensor. Not casually seeing wind speed. They’re expensive but cheaper than a few hours in a wind tunnel.

RChung

msu2001la

The Dutch Headwind Cycling Championship may be in your future:
​​​​​​https://en.wikipedia.org/wiki/Dutch_..._Championships

dedhed

Selective availability and CoCom limits are two different things.
Cocom limits are 18km altitude AND 1000 knots speed although some receivers do OR

Mojo31

Funny how the wind speed increases the faster you go with that thing mounted like that.

msu2001la

Apparent wind speed vs. true wind speed

https://en.wikipedia.org/wiki/Apparent_wind

mdarnton

https://earth.nullschool.net/
I find this site pretty useful. Once you zero in on your coordinates (I got them for my home from google maps) you can make a bookmark and come back to the same place every time. I generally plan my recreational rides so I'm going out against the wind and get pushed back home by them. The speed it gives is not too far off. My personal limit for fun rides is 15mph.

Mojo31

Having been a sailor for more than 50 years, I am very familiar with both.