Windchill... - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 12 (permalink) Old 03-15-2019, 09:35 AM Thread Starter
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Windchill...

Since I've ridden a few times this month and the temps have started out in the low 40s F. I was curious about windchill.
The attached images are a "translation" of what the temp feels like.when riding a motorcycle.
Your thoughts?

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post #2 of 12 (permalink) Old 03-15-2019, 10:00 AM
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I think the wind chill only applies to exposed skin. Its what the temp feels like, as the air flow strips away and evaporates the moisture level your skin tries to maintain. If you are covered up it does not really apply unless the wind is getting thru your gear. Thats because the outer layer of your gear is going to equal the air temp (unless your gear is wet or its raining...) no matter how much air is hitting it.

another way to say this: the wind chill when its 35F at 25mph is 23. That does not mean if you put a glass of water out in a 25mph wind when its 35 outside, the water will freeze. The water will have some evaporation cooling, but it wont fall far below 35, and it wont freeze. But your expose skin will feel like its 23 because it will keep pumping moisture to your skin and it will keep evaporating and being stripped away. That lost moisture includes the heat your body is generating, and it cant keep up, causing hypothermia.

It would be interesting to see what the wind chill effect is at higher temps. In a car with no AC, when its above 100F sometimes it feels hotter if you have the windows open with the hot air blasting on you, like you are standing infront of a furnace blowing heat on you. There is still an evaporation cooling effect when its hot, and you are usually better keeping covered on a motorcycle, so the wind does not strip all the moisture from your body and leave you dehydrated.

BTW, when it gets cold somehow gloves always seem to be the weak point in the riding gear.

Last edited by KCW; 03-15-2019 at 10:04 AM.
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post #3 of 12 (permalink) Old 03-15-2019, 10:37 AM Thread Starter
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I think the chill is a "feeling" and not an actual temperature.
Like yesterday morning's ride into work. The outside temp was 45. While travel to work at 75-80mph. When I opened my visor, it did feel colder. The chart say 23. And I'd agree with that.

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post #4 of 12 (permalink) Old 03-15-2019, 12:05 PM
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Quote:
Originally Posted by Scrumdown View Post
I think the chill is a "feeling" and not an actual temperature.
Like yesterday morning's ride into work. The outside temp was 45. While travel to work at 75-80mph. When I opened my visor, it did feel colder. The chart say 23. And I'd agree with that.

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No, it’s an actual temperature. That’s why air moving through a metal nozzle from a compressor will accumulate condensation on it. Because it IS colder.
Also, windchill is only a factor up to 45mph. Any faster wind doesn’t bring the temp down any further.
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post #5 of 12 (permalink) Old 03-15-2019, 12:11 PM
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BTW, when it gets cold somehow gloves always seem to be the weak point in the riding gear.
Which is why heated grips are the cats meow! 😁
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post #6 of 12 (permalink) Old 03-15-2019, 12:32 PM
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No, its an actual temperature. Thats why air moving through a metal nozzle from a compressor will accumulate condensation on it. Because it IS colder.
...
its easy to mix up the effects of compressing air and moving air

when its windy out, the air is not being compressed or decompressed to any significant level. The front between a high pressure area and a low pressure area produces strong winds, but the air is not changing pressure fast enough for PV=nRT to have an effect on air temperature.

its not the air moving across a nozzle in an AC unit that cools it, it the fact that the pressure is being reduced. If you reduce the pressure slowly in a big piston, the temp change will be the same. There is no factor for time in PV=nRT.

Humidity can be measured by putting a wet sock over a thermometer and exposing it to airflow, and comparing it to a dry thermometer in the same air. In dry air the water will evaporate off the wet sock faster, leaving cooler water atoms behind.

If you put a wet sock thermometer in the wind, next to a dry one, it will read a few degrees colder, but it will not read the perceived wind chill temperature.

Its an interesting subject, but its really a matter of how fast your metabolism can generate body heat, to replace the warmth being stripped off your bare skin by the wind. That resulting "it feels like...." number is very subjective from person to person. Thats whats on the wind chill factor chart.
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post #7 of 12 (permalink) Old 03-15-2019, 12:33 PM
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Which is why heated grips are the cats meow! ...
I ride with my hands in my pockets

or put them on the cylinder fins when I stop for red light....
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post #8 of 12 (permalink) Old 03-15-2019, 12:58 PM
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Originally Posted by KCW View Post
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Originally Posted by ChiefGunner View Post
No, it’s an actual temperature. That’s why air moving through a metal nozzle from a compressor will accumulate condensation on it. Because it IS colder.
...
its easy to mix up the effects of compressing air and moving air

when its windy out, the air is not being compressed or decompressed to any significant level. The front between a high pressure area and a low pressure area produces strong winds, but the air is not changing pressure fast enough for PV=nRT to have an effect on air temperature.

its not the air moving across a nozzle in an AC unit that cools it, it the fact that the pressure is being reduced. If you reduce the pressure slowly in a big piston, the temp change will be the same. There is no factor for time in PV=nRT.

Humidity can be measured by putting a wet sock over a thermometer and exposing it to airflow, and comparing it to a dry thermometer in the same air. In dry air the water will evaporate off the wet sock faster, leaving cooler water atoms behind.

If you put a wet sock thermometer in the wind, next to a dry one, it will read a few degrees colder, but it will not read the perceived wind chill temperature.

Its an interesting subject, but its really a matter of how fast your metabolism can generate body heat, to replace the warmth being stripped off your bare skin by the wind. That resulting "it feels like...." number is very subjective from person to person. Thats whats on the wind chill factor chart.
Forgot about the decompression factor! Thanks for the reminder. You’re absolutely correct.
Also good point in metabolism. Which is why some are more affected than others.
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Last edited by ChiefGunner; 03-15-2019 at 02:05 PM.
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post #9 of 12 (permalink) Old 03-15-2019, 01:17 PM
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All I know is this morning it was 49 degrees and the faster I went the colder it felt. It could be real or not, my skinny body said it was cold and I should have worn a heavier jacket.

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post #10 of 12 (permalink) Old 03-15-2019, 02:06 PM
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Quote:
Originally Posted by KCW View Post
Quote:
Originally Posted by ChiefGunner View Post
Which is why heated grips are the cats meow! ...
I ride with my hands in my pockets

or put them on the cylinder fins when I stop for red light....
Lol! Yea right. 🤣
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