Understanding the weather...

[Canardly]

Can cope with most things, but wind is the one I dislike most.

 

[Browser]

Personally I wouldn't chance it. Have a go at riding under electricity pylons and you will quickly find out why. If you can get a painful but harmless poke from that, then imagine what would happen if a metal object passed under a charged cloud.

Sorry, are you saying you can get a belt from cycling under a pylon? I walk under the things all of the time at work and have cycled under them hundreds of times, up and including those carrying 400kv, and have never even felt a tingle. I've also had occasion to switch in our 132kv sub in the fog, similar result. You can certainly hear the pan-of-bacon-from-hell crackling from the insulators, but that's about all.

 

[Matthames]

Sorry, are you saying you can get a belt from cycling under a pylon? I walk under the things all of the time at work and have cycled under them hundreds of times, up and including those carrying 400kv, and have never even felt a tingle. I've also had occasion to switch in our 132kv sub in the fog, similar result. You can certainly hear the pan-of-bacon-from-hell crackling from the insulators, but that's about all.

If you don't earth yourself riding under a pylon, the electromagnetic field produced by the current running through the wires will cause you to become electro statically charged, so if you were to earth yourself, say by touching a metal brake lever before the charge had chance to dissipate slowly you will get a static shock. I had it happen to me once, I rode under some electric cable as it crossed a road. Went to touch the brakes and got a bit of a poke from the static. The way I have learnt to avoid something like that is to touch something metal as you ride underneath and it prevents a charge from building up.

 

[jimboalee]

If you take a flourescent tube under a HV cable, you can do a good impersonation of Luke Skywalker.

 

[snailracer]

FL = 0.5 * Q * Cd * A * V^2

Sorry Admin.

V^2, The square of the speed Norm was talking about.

Correct, however:

Power = FL * V

Therefore, power is proportional to velocity cubed.

If you are riding 30mph into a 3 mph headwind (ie almost none), your windspeed increases from 30mph to 33mph, and you would need to put out an extra 32% of power, which is significant.

 

[jimboalee]

Correct, however:

Power = FL * V

Therefore, power is proportional to velocity cubed.

If you are riding 30mph into a 3 mph headwind (ie almost none), your windspeed increases from 30mph to 33mph, and you would need to put out an extra 32% of power, which is significant.

Pf = ( Crr x (W/375) x V ) + ( CdA x (V^2/391) * (V/375) )

How does that grab you?

30 to 33 mph headwind on my Dawes Giro 500 is 30.2 % more power requirement. It is ONLY the Airspeed that is changing. Tyre deformation and geartrain losses remain the same.

 

[darth vadar]

Pf = ( Crr x (W/375) x V ) + ( CdA x (V^2/391) * (V/375) )

How does that grab you?

30 to 33 mph headwind on my Dawes Giro 500 is 30.2 % more power requirement. It is ONLY the Airspeed that is changing. Tyre deformation and geartrain losses remain the same.

Blimey !

I bet the winter nights just fly by in your house.

 

[snailracer]

Pf = ( Crr x (W/375) x V ) + ( CdA x (V^2/391) * (V/375) )

How does that grab you?

30 to 33 mph headwind on my Dawes Giro 500 is 30.2 % more power requirement. It is ONLY the Airspeed that is changing. Tyre deformation and geartrain losses remain the same.

Geartrain losses increase because power has increased.

If the gears are 95% efficient, and 30.2% more power is being transmitted, then the geartrain losses add 0.302 * 0.05 = 1.51% extra.

30.2% + 1.51% = 31.71%

 

[jimboalee]

Geartrain losses increase because power has increased.

If the gears are 95% efficient, and 30.2% more power is being transmitted, then the geartrain losses add 0.302 * 0.05 = 1.51% extra.

30.2% + 1.51% = 31.71%

Oil or no oil?

 

[jimboalee]

This is from a handout I was given before working in Canada.


Deg C Windchill.



0 to -9

Low - Slight increase in discomfort

- Dress warmly, with the outside temperature in mind.



-10 to -27

Low - Uncomfortable
- Risk of hypothermia if outside for long periods without adequate protection

- Dress in layers of warm clothing, with an outer layer that is wind-resistant.
- Wear a hat, mittens and scarf. - Keep active.



-28 to -39

Increasing risk:

- Exposed skin can freeze in 10 to 30 minutes

- Check face and extremities (fingers, toes, ears and nose) for numbness or whiteness
- Risk of hypothermia if outside for long periods without adequate protection

- Dress in layers of warm clothing, with an outer layer that is wind-resistant.
- Cover exposed skin: wear a hat, mittens and a scarf, neck tube or face mask.
- Keep active.



-40 to -47

High risk: exposed skin can freeze in 5 to 10 minutes*

- Check face and extremities (fingers, toes, ears and nose) for numbness or whiteness (frostbite)
- Risk of hypothermia if outside for long periods without adequate protection - Dress in layers of warm clothing, with an outer layer that is wind-resistant.
- Cover all exposed skin: wear a hat, mittens and a scarf, neck tube or face mask.
- Keep active.

WARNING LEVEL**


-48 to -54

High risk: exposed skin can freeze in 2 to 5 minutes*

- Check face and extremities frequently for numbness or whiteness (frostbite)
- Serious risk of hypothermia if outside for long periods

- Be careful. Dress very warmly in layers of clothing, with an outer layer that is wind-resistant.
- Cover all exposed skin: wear a hat, mittens and a scarf, neck tube or face mask.
- Be ready to cut short or cancel outdoor activities.
- Keep active.



-55 and colder

High risk: exposed skin can freeze in less than 2 minutes DANGER!
- Outdoor conditions are hazardous

- Stay indoors.


Riding a bicycle, -9 Deg C windchill is when the ambient is -2 Deg C and the cyclist is travelling at 12 mph.
In the UK, we sometimes get into the -10 to -15 Windchill region.