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  #171  
Old December 23rd 18, 02:14 AM posted to rec.bicycles.tech
Ralph Barone[_4_]
external usenet poster
 
Posts: 853
Default Power on hills.

Mark J. wrote:
On 12/22/2018 11:59 AM, Frank Krygowski wrote:
On 12/22/2018 11:21 AM, wrote:
On Saturday, December 22, 2018 at 3:54:20 PM UTC+1, Ralph Barone wrote:
wrote:
On Saturday, December 22, 2018 at 12:52:51 AM UTC+1, Andre Jute wrote:
On Friday, December 21, 2018 at 8:25:37 PM UTC,
wrote:
At low speeds - those below 100 mph of so, aerodynamic drag really
isn't a large loss unless you're playing for real small power such as
that developed by a human over relatively long periods of time.

Just as a demonstration.

30 square feet of frontal area
coefficient of drag of 0.5
This is similar to a family car

F = 0.5 C ρ A V^2

A = Reference area as (see figures above), m2.
C = Drag coefficient (see figures above), unitless.
F = Drag force, N.
V = Velocity, m/s.
ρ = Density of fluid (liquid or gas), kg/m3. (dry air at 70
degrees F ~ 1.2)

.5 x .5 x 1.2 x 30 x 27 m/s (60 mph) = 243 N
.5 x .5 x 1.2 x 30 x 45 m/s (100 mph) = 337 N


Whereas the power to accelerate the mass of a car which is about 2200
lbs is huge.* KE = ½mv²

Thanks for putting the numbers to my argument, Tom.

Andre Jute
DESIGNING AND BUILDING SPECIAL CARS; Batsford, London; Bentley, Boston

I just reading an aero special article in TOUR magazin. Position on the
bike can save you 54 watts or gaining 3.9 km/hr going from riding on
the
tops to riding in the drops. Clothes can make a difference of up to 27
Watt or gaining 2,3 km/hr in speed. An aero bike saves you 16 Watt or
gaining 1.4 km/hr. This is all at a speed of 35 km/r, a speed not
unrealistic for a lot of us. So putting some estimated numbers in a
formula doesn't do the trick IMO.

Lou


It works better when you do the math properly and get the units
right. :-)

Yeah, that is what you get using Mickey Mouse units. Using feet and
ending up with Watt? WTF. Don't you have a Mickey Mouse unit for power?


Maybe for small amounts, we could use mousepower? It seems aesthetically
related to horsepower.

The U.S. system is so picturesque! Distance in furlongs or chains or
feet; weight in a couple different types of pounds and/or ounces; volume
in gallons or barrels or hogsheads, etc...

And you Euro guys have boring conversion factors - nothing but tens all
up and down the scale. We get lots of interesting ones to remember, and
I'm not even talking about SI to U.S. units. I'm just talking about the
conversions _within_ our system!

I wonder how many people in the U.S. know which U.S. units convert to
other U.S. units by multiplying by 231, or 5280, or 33,000, or 128, or
16, (or alternately 14.58, which is related to 7000), or 778.2, or 36,
or 3.


I used to excuse exchange students from having to learn many of these
(e.g. 5280), but I told US residents they were (currently) stuck with
the system, so yes, it might be on the exam.

Mark J.

PS - 640 (Acres in a square mile)


Some of these are guesses (I avoided consulting Google):
231 cubic inches per gallon?
5280 feet per mile
33,000 ft-lb/min per HP
128 ounces per gallon (US not English)
16 ounces per pint (or ounces per pound)
778.2 grains per pound?
36 inches per yard
3 feet per yard

Ads
  #172  
Old December 23rd 18, 05:24 AM posted to rec.bicycles.tech
Frank Krygowski[_2_]
external usenet poster
 
Posts: 7,511
Default Power on hills.

On Saturday, December 22, 2018 at 7:33:29 PM UTC-5, Mark J. wrote:
On 12/22/2018 11:59 AM, Frank Krygowski wrote:
On 12/22/2018 11:21 AM, wrote:
On Saturday, December 22, 2018 at 3:54:20 PM UTC+1, Ralph Barone wrote:
wrote:
On Saturday, December 22, 2018 at 12:52:51 AM UTC+1, Andre Jute wrote:
On Friday, December 21, 2018 at 8:25:37 PM UTC,
wrote:
At low speeds - those below 100 mph of so, aerodynamic drag really
isn't a large loss unless you're playing for real small power such as
that developed by a human over relatively long periods of time.

Just as a demonstration.

30 square feet of frontal area
coefficient of drag of 0.5
This is similar to a family car

F = 0.5 C ρ A V^2

A = Reference area as (see figures above), m2.
C = Drag coefficient (see figures above), unitless.
F = Drag force, N.
V = Velocity, m/s.
ρ = Density of fluid (liquid or gas), kg/m3. (dry air at 70
degrees F ~ 1.2)

.5 x .5 x 1.2 x 30 x 27 m/s (60 mph) = 243 N
.5 x .5 x 1.2 x 30 x 45 m/s (100 mph) = 337 N


Whereas the power to accelerate the mass of a car which is about 2200
lbs is huge.* KE = ½mv²

Thanks for putting the numbers to my argument, Tom.

Andre Jute
DESIGNING AND BUILDING SPECIAL CARS; Batsford, London; Bentley, Boston

I just reading an aero special article in TOUR magazin. Position on the
bike can save you 54 watts or gaining 3.9 km/hr going from riding on
the
tops to riding in the drops. Clothes can make a difference of up to 27
Watt or gaining 2,3 km/hr in speed. An aero bike saves you 16 Watt or
gaining 1.4 km/hr. This is all at a speed of 35 km/r, a speed not
unrealistic for a lot of us. So putting some estimated numbers in a
formula doesn't do the trick IMO.

Lou


It works better when you do the math properly and get the units
right. :-)

Yeah, that is what you get using Mickey Mouse units. Using feet and
ending up with Watt? WTF. Don't you have a Mickey Mouse unit for power?


Maybe for small amounts, we could use mousepower? It seems aesthetically
related to horsepower.

The U.S. system is so picturesque! Distance in furlongs or chains or
feet; weight in a couple different types of pounds and/or ounces; volume
in gallons or barrels or hogsheads, etc...

And you Euro guys have boring conversion factors - nothing but tens all
up and down the scale. We get lots of interesting ones to remember, and
I'm not even talking about SI to U.S. units. I'm just talking about the
conversions _within_ our system!

I wonder how many people in the U.S. know which U.S. units convert to
other U.S. units by multiplying by 231, or 5280, or 33,000, or 128, or
16, (or alternately 14.58, which is related to 7000), or 778.2, or 36,
or 3.


I used to excuse exchange students from having to learn many of these
(e.g. 5280), but I told US residents they were (currently) stuck with
the system, so yes, it might be on the exam.

Mark J.

PS - 640 (Acres in a square mile)


43,560 square feet per acre. (Why on earth do I have that memorized?)

And I've come across volumes of water measured in acre-feet.

- Frank Krygowski

  #173  
Old December 23rd 18, 05:27 AM posted to rec.bicycles.tech
Frank Krygowski[_2_]
external usenet poster
 
Posts: 7,511
Default Power on hills.

On Saturday, December 22, 2018 at 8:14:13 PM UTC-5, Ralph Barone wrote:
Mark J. wrote:
On 12/22/2018 11:59 AM, Frank Krygowski wrote:
On 12/22/2018 11:21 AM, wrote:
On Saturday, December 22, 2018 at 3:54:20 PM UTC+1, Ralph Barone wrote:
wrote:
On Saturday, December 22, 2018 at 12:52:51 AM UTC+1, Andre Jute wrote:
On Friday, December 21, 2018 at 8:25:37 PM UTC,
wrote:
At low speeds - those below 100 mph of so, aerodynamic drag really
isn't a large loss unless you're playing for real small power such as
that developed by a human over relatively long periods of time.

Just as a demonstration.

30 square feet of frontal area
coefficient of drag of 0.5
This is similar to a family car

F = 0.5 C ρ A V^2

A = Reference area as (see figures above), m2.
C = Drag coefficient (see figures above), unitless.
F = Drag force, N.
V = Velocity, m/s.
ρ = Density of fluid (liquid or gas), kg/m3. (dry air at 70
degrees F ~ 1.2)

.5 x .5 x 1.2 x 30 x 27 m/s (60 mph) = 243 N
.5 x .5 x 1.2 x 30 x 45 m/s (100 mph) = 337 N


Whereas the power to accelerate the mass of a car which is about 2200
lbs is huge.* KE = ½mv²

Thanks for putting the numbers to my argument, Tom.

Andre Jute
DESIGNING AND BUILDING SPECIAL CARS; Batsford, London; Bentley, Boston

I just reading an aero special article in TOUR magazin. Position on the
bike can save you 54 watts or gaining 3.9 km/hr going from riding on
the
tops to riding in the drops. Clothes can make a difference of up to 27
Watt or gaining 2,3 km/hr in speed. An aero bike saves you 16 Watt or
gaining 1.4 km/hr. This is all at a speed of 35 km/r, a speed not
unrealistic for a lot of us. So putting some estimated numbers in a
formula doesn't do the trick IMO.

Lou


It works better when you do the math properly and get the units
right. :-)

Yeah, that is what you get using Mickey Mouse units. Using feet and
ending up with Watt? WTF. Don't you have a Mickey Mouse unit for power?

Maybe for small amounts, we could use mousepower? It seems aesthetically
related to horsepower.

The U.S. system is so picturesque! Distance in furlongs or chains or
feet; weight in a couple different types of pounds and/or ounces; volume
in gallons or barrels or hogsheads, etc...

And you Euro guys have boring conversion factors - nothing but tens all
up and down the scale. We get lots of interesting ones to remember, and
I'm not even talking about SI to U.S. units. I'm just talking about the
conversions _within_ our system!

I wonder how many people in the U.S. know which U.S. units convert to
other U.S. units by multiplying by 231, or 5280, or 33,000, or 128, or
16, (or alternately 14.58, which is related to 7000), or 778.2, or 36,
or 3.


I used to excuse exchange students from having to learn many of these
(e.g. 5280), but I told US residents they were (currently) stuck with
the system, so yes, it might be on the exam.

Mark J.

PS - 640 (Acres in a square mile)


Some of these are guesses (I avoided consulting Google):
231 cubic inches per gallon?
5280 feet per mile
33,000 ft-lb/min per HP
128 ounces per gallon (US not English)
16 ounces per pint (or ounces per pound)
778.2 grains per pound?
36 inches per yard
3 feet per yard


Seven out of eight is pretty darn good! (There are 7000 grains in
a pound, IIRC.)

And there are also 3 teaspoons in a tablespoon.

If I were in charge, I'd have made it a lot more scientific. I'd have
said there are Pi teaspoons in a tablespoon. ;-)

- Frank Krygowski
  #174  
Old December 23rd 18, 05:39 AM posted to rec.bicycles.tech
Frank Krygowski[_2_]
external usenet poster
 
Posts: 7,511
Default Power on hills.

On Saturday, December 22, 2018 at 6:06:38 PM UTC-5, John B. Slocomb wrote:
On Sat, 22 Dec 2018 02:28:15 -0800 (PST), wrote:

On Saturday, December 22, 2018 at 12:52:51 AM UTC+1, Andre Jute wrote:
On Friday, December 21, 2018 at 8:25:37 PM UTC, wrote:
At low speeds - those below 100 mph of so, aerodynamic drag really isn't a large loss unless you're playing for real small power such as that developed by a human over relatively long periods of time.

Just as a demonstration.

30 square feet of frontal area
coefficient of drag of 0.5
This is similar to a family car

F = 0.5 C ? A V^2

A = Reference area as (see figures above), m2.
C = Drag coefficient (see figures above), unitless.
F = Drag force, N.
V = Velocity, m/s.
? = Density of fluid (liquid or gas), kg/m3. (dry air at 70 degrees F ~ 1.2)

.5 x .5 x 1.2 x 30 x 27 m/s (60 mph) = 243 N
.5 x .5 x 1.2 x 30 x 45 m/s (100 mph) = 337 N


Whereas the power to accelerate the mass of a car which is about 2200 lbs is huge. KE = ½mv²

Thanks for putting the numbers to my argument, Tom.

Andre Jute
DESIGNING AND BUILDING SPECIAL CARS; Batsford, London; Bentley, Boston


I just reading an aero special article in TOUR magazin. Position on the rbike can save you 54 watts or gaining 3.9 km/hr going from riding on the tops to riding in the drops. Clothes can make a difference of up to 27 Watt or gaining 2,3 km/hr in speed. An aero bike saves you 16 Watt or gaining 1.4 km/hr. This is all at a speed of 35 km/r, a speed not unrealistic for a lot of us. So putting some estimated numbers in a formula doesn't do the trick IMO.

Lou


One route I used to ride had a long slightly downhill run on the way
home - perhaps a half kilometer and not very steep. It was at the top
of a fairly steep climb so I used to top the hill and then just sit
there and coast - probably 30 kph. Changing from riding on the tops to
riding on the drops gained about 1 kph. I used to change to the drops,
note the increase in speed and then go back to the tops and note the
decrease.


Some years ago, the guys at _Bicycle Quarterly_ paid for wind tunnel
testing of a rider on their favorite type of bike. That bike is
unlike what most of us probably ride. IIRC, wide tires (probably
wider than 32 mm), but drop bars. IIRC they tested changes in rider
position, but also presence or absence of fenders, handlebar bag,
etc.

As I recall they found the strong controlling factor was frontal
area. They said, based on their measurements of frontal area, that
the drag coefficient didn't change significantly. However, I don't
recall what they tested or concluded about clothing. I know loose,
flappy clothing adds drag, and probably without a measurable increase
in frontal area.

I've said for a long time the most significant thing a rider of an
upright bike can do for speed is to ride an aero bar when feasible.
The increase in speed is much more than just changing to the drops.

- Frank Krygowski



  #175  
Old December 23rd 18, 07:06 AM posted to rec.bicycles.tech
John B. Slocomb
external usenet poster
 
Posts: 805
Default Power on hills.

On Sat, 22 Dec 2018 20:39:03 -0800 (PST), Frank Krygowski
wrote:

On Saturday, December 22, 2018 at 6:06:38 PM UTC-5, John B. Slocomb wrote:
On Sat, 22 Dec 2018 02:28:15 -0800 (PST), wrote:

On Saturday, December 22, 2018 at 12:52:51 AM UTC+1, Andre Jute wrote:
On Friday, December 21, 2018 at 8:25:37 PM UTC, wrote:
At low speeds - those below 100 mph of so, aerodynamic drag really isn't a large loss unless you're playing for real small power such as that developed by a human over relatively long periods of time.

Just as a demonstration.

30 square feet of frontal area
coefficient of drag of 0.5
This is similar to a family car

F = 0.5 C ? A V^2

A = Reference area as (see figures above), m2.
C = Drag coefficient (see figures above), unitless.
F = Drag force, N.
V = Velocity, m/s.
? = Density of fluid (liquid or gas), kg/m3. (dry air at 70 degrees F ~ 1.2)

.5 x .5 x 1.2 x 30 x 27 m/s (60 mph) = 243 N
.5 x .5 x 1.2 x 30 x 45 m/s (100 mph) = 337 N


Whereas the power to accelerate the mass of a car which is about 2200 lbs is huge. KE = mv

Thanks for putting the numbers to my argument, Tom.

Andre Jute
DESIGNING AND BUILDING SPECIAL CARS; Batsford, London; Bentley, Boston

I just reading an aero special article in TOUR magazin. Position on the rbike can save you 54 watts or gaining 3.9 km/hr going from riding on the tops to riding in the drops. Clothes can make a difference of up to 27 Watt or gaining 2,3 km/hr in speed. An aero bike saves you 16 Watt or gaining 1.4 km/hr. This is all at a speed of 35 km/r, a speed not unrealistic for a lot of us. So putting some estimated numbers in a formula doesn't do the trick IMO.

Lou


One route I used to ride had a long slightly downhill run on the way
home - perhaps a half kilometer and not very steep. It was at the top
of a fairly steep climb so I used to top the hill and then just sit
there and coast - probably 30 kph. Changing from riding on the tops to
riding on the drops gained about 1 kph. I used to change to the drops,
note the increase in speed and then go back to the tops and note the
decrease.


Some years ago, the guys at _Bicycle Quarterly_ paid for wind tunnel
testing of a rider on their favorite type of bike. That bike is
unlike what most of us probably ride. IIRC, wide tires (probably
wider than 32 mm), but drop bars. IIRC they tested changes in rider
position, but also presence or absence of fenders, handlebar bag,
etc.

As I recall they found the strong controlling factor was frontal
area. They said, based on their measurements of frontal area, that
the drag coefficient didn't change significantly. However, I don't
recall what they tested or concluded about clothing. I know loose,
flappy clothing adds drag, and probably without a measurable increase
in frontal area.

I've said for a long time the most significant thing a rider of an
upright bike can do for speed is to ride an aero bar when feasible.
The increase in speed is much more than just changing to the drops.

- Frank Krygowski


I believe that the RAAM guys use aero bars and I read that one of the
reasons is that they support the upper body on the elbows and, they
say, it is less tiring to ride long distances that way. As well, of
course, the lower wind resistance.


cheers,

John B.


  #176  
Old December 23rd 18, 07:18 AM posted to rec.bicycles.tech
John B. Slocomb
external usenet poster
 
Posts: 805
Default Power on hills.

On Sat, 22 Dec 2018 20:24:38 -0800 (PST), Frank Krygowski
wrote:

On Saturday, December 22, 2018 at 7:33:29 PM UTC-5, Mark J. wrote:
On 12/22/2018 11:59 AM, Frank Krygowski wrote:
On 12/22/2018 11:21 AM, wrote:
On Saturday, December 22, 2018 at 3:54:20 PM UTC+1, Ralph Barone wrote:
wrote:
On Saturday, December 22, 2018 at 12:52:51 AM UTC+1, Andre Jute wrote:
On Friday, December 21, 2018 at 8:25:37 PM UTC,
wrote:
At low speeds - those below 100 mph of so, aerodynamic drag really
isn't a large loss unless you're playing for real small power such as
that developed by a human over relatively long periods of time.

Just as a demonstration.

30 square feet of frontal area
coefficient of drag of 0.5
This is similar to a family car

F = 0.5 C ? A V^2

A = Reference area as (see figures above), m2.
C = Drag coefficient (see figures above), unitless.
F = Drag force, N.
V = Velocity, m/s.
? = Density of fluid (liquid or gas), kg/m3. (dry air at 70
degrees F ~ 1.2)

.5 x .5 x 1.2 x 30 x 27 m/s (60 mph) = 243 N
.5 x .5 x 1.2 x 30 x 45 m/s (100 mph) = 337 N


Whereas the power to accelerate the mass of a car which is about 2200
lbs is huge.* KE = mv

Thanks for putting the numbers to my argument, Tom.

Andre Jute
DESIGNING AND BUILDING SPECIAL CARS; Batsford, London; Bentley, Boston

I just reading an aero special article in TOUR magazin. Position on the
bike can save you 54 watts or gaining 3.9 km/hr going from riding on
the
tops to riding in the drops. Clothes can make a difference of up to 27
Watt or gaining 2,3 km/hr in speed. An aero bike saves you 16 Watt or
gaining 1.4 km/hr. This is all at a speed of 35 km/r, a speed not
unrealistic for a lot of us. So putting some estimated numbers in a
formula doesn't do the trick IMO.

Lou


It works better when you do the math properly and get the units
right. :-)

Yeah, that is what you get using Mickey Mouse units. Using feet and
ending up with Watt? WTF. Don't you have a Mickey Mouse unit for power?

Maybe for small amounts, we could use mousepower? It seems aesthetically
related to horsepower.

The U.S. system is so picturesque! Distance in furlongs or chains or
feet; weight in a couple different types of pounds and/or ounces; volume
in gallons or barrels or hogsheads, etc...

And you Euro guys have boring conversion factors - nothing but tens all
up and down the scale. We get lots of interesting ones to remember, and
I'm not even talking about SI to U.S. units. I'm just talking about the
conversions _within_ our system!

I wonder how many people in the U.S. know which U.S. units convert to
other U.S. units by multiplying by 231, or 5280, or 33,000, or 128, or
16, (or alternately 14.58, which is related to 7000), or 778.2, or 36,
or 3.


I used to excuse exchange students from having to learn many of these
(e.g. 5280), but I told US residents they were (currently) stuck with
the system, so yes, it might be on the exam.

Mark J.

PS - 640 (Acres in a square mile)


43,560 square feet per acre. (Why on earth do I have that memorized?)

And I've come across volumes of water measured in acre-feet.

- Frank Krygowski


I think it is all what you are used to :-)

One of our senior accountants was British. I asked him if accounting
with the British system - penny, shilling, pound and guinea was a
problem and he said "not if you grew up with it" :-)

And, again in G.B., the old folks counted sheep "yan, tan, tethera,
pethera, pimp..."


cheers,

John B.


  #177  
Old December 24th 18, 02:10 AM posted to rec.bicycles.tech
Mark J.
external usenet poster
 
Posts: 840
Default Power on hills.

On 12/22/2018 8:24 PM, Frank Krygowski wrote:
On Saturday, December 22, 2018 at 7:33:29 PM UTC-5, Mark J. wrote:
On 12/22/2018 11:59 AM, Frank Krygowski wrote:
On 12/22/2018 11:21 AM, wrote:
On Saturday, December 22, 2018 at 3:54:20 PM UTC+1, Ralph Barone wrote:
wrote:
On Saturday, December 22, 2018 at 12:52:51 AM UTC+1, Andre Jute wrote:
On Friday, December 21, 2018 at 8:25:37 PM UTC,
wrote:
At low speeds - those below 100 mph of so, aerodynamic drag really
isn't a large loss unless you're playing for real small power such as
that developed by a human over relatively long periods of time.

Just as a demonstration.

30 square feet of frontal area
coefficient of drag of 0.5
This is similar to a family car

F = 0.5 C ρ A V^2

A = Reference area as (see figures above), m2.
C = Drag coefficient (see figures above), unitless.
F = Drag force, N.
V = Velocity, m/s.
ρ = Density of fluid (liquid or gas), kg/m3. (dry air at 70
degrees F ~ 1.2)

.5 x .5 x 1.2 x 30 x 27 m/s (60 mph) = 243 N
.5 x .5 x 1.2 x 30 x 45 m/s (100 mph) = 337 N


Whereas the power to accelerate the mass of a car which is about 2200
lbs is huge.* KE = ½mv²

Thanks for putting the numbers to my argument, Tom.

Andre Jute
DESIGNING AND BUILDING SPECIAL CARS; Batsford, London; Bentley, Boston

I just reading an aero special article in TOUR magazin. Position on the
bike can save you 54 watts or gaining 3.9 km/hr going from riding on
the
tops to riding in the drops. Clothes can make a difference of up to 27
Watt or gaining 2,3 km/hr in speed. An aero bike saves you 16 Watt or
gaining 1.4 km/hr. This is all at a speed of 35 km/r, a speed not
unrealistic for a lot of us. So putting some estimated numbers in a
formula doesn't do the trick IMO.

Lou


It works better when you do the math properly and get the units
right. :-)

Yeah, that is what you get using Mickey Mouse units. Using feet and
ending up with Watt? WTF. Don't you have a Mickey Mouse unit for power?

Maybe for small amounts, we could use mousepower? It seems aesthetically
related to horsepower.

The U.S. system is so picturesque! Distance in furlongs or chains or
feet; weight in a couple different types of pounds and/or ounces; volume
in gallons or barrels or hogsheads, etc...

And you Euro guys have boring conversion factors - nothing but tens all
up and down the scale. We get lots of interesting ones to remember, and
I'm not even talking about SI to U.S. units. I'm just talking about the
conversions _within_ our system!

I wonder how many people in the U.S. know which U.S. units convert to
other U.S. units by multiplying by 231, or 5280, or 33,000, or 128, or
16, (or alternately 14.58, which is related to 7000), or 778.2, or 36,
or 3.


I used to excuse exchange students from having to learn many of these
(e.g. 5280), but I told US residents they were (currently) stuck with
the system, so yes, it might be on the exam.

Mark J.

PS - 640 (Acres in a square mile)


43,560 square feet per acre. (Why on earth do I have that memorized?)

And I've come across volumes of water measured in acre-feet.


Here in the land of hydro-power and mountain reservoirs (Oregon),
acre-feet are in pretty common usage, I think. Pretty sure I've seen
them in the newspapers fairly regularly.

Mark J.
  #178  
Old December 24th 18, 02:42 AM posted to rec.bicycles.tech
John B. Slocomb
external usenet poster
 
Posts: 805
Default Power on hills.

On Sun, 23 Dec 2018 17:10:40 -0800, "Mark J."
wrote:

On 12/22/2018 8:24 PM, Frank Krygowski wrote:
On Saturday, December 22, 2018 at 7:33:29 PM UTC-5, Mark J. wrote:
On 12/22/2018 11:59 AM, Frank Krygowski wrote:
On 12/22/2018 11:21 AM, wrote:
On Saturday, December 22, 2018 at 3:54:20 PM UTC+1, Ralph Barone wrote:
wrote:
On Saturday, December 22, 2018 at 12:52:51 AM UTC+1, Andre Jute wrote:
On Friday, December 21, 2018 at 8:25:37 PM UTC,
wrote:
At low speeds - those below 100 mph of so, aerodynamic drag really
isn't a large loss unless you're playing for real small power such as
that developed by a human over relatively long periods of time.

Just as a demonstration.

30 square feet of frontal area
coefficient of drag of 0.5
This is similar to a family car

F = 0.5 C ? A V^2

A = Reference area as (see figures above), m2.
C = Drag coefficient (see figures above), unitless.
F = Drag force, N.
V = Velocity, m/s.
? = Density of fluid (liquid or gas), kg/m3. (dry air at 70
degrees F ~ 1.2)

.5 x .5 x 1.2 x 30 x 27 m/s (60 mph) = 243 N
.5 x .5 x 1.2 x 30 x 45 m/s (100 mph) = 337 N


Whereas the power to accelerate the mass of a car which is about 2200
lbs is huge.* KE = mv

Thanks for putting the numbers to my argument, Tom.

Andre Jute
DESIGNING AND BUILDING SPECIAL CARS; Batsford, London; Bentley, Boston

I just reading an aero special article in TOUR magazin. Position on the
bike can save you 54 watts or gaining 3.9 km/hr going from riding on
the
tops to riding in the drops. Clothes can make a difference of up to 27
Watt or gaining 2,3 km/hr in speed. An aero bike saves you 16 Watt or
gaining 1.4 km/hr. This is all at a speed of 35 km/r, a speed not
unrealistic for a lot of us. So putting some estimated numbers in a
formula doesn't do the trick IMO.

Lou


It works better when you do the math properly and get the units
right. :-)

Yeah, that is what you get using Mickey Mouse units. Using feet and
ending up with Watt? WTF. Don't you have a Mickey Mouse unit for power?

Maybe for small amounts, we could use mousepower? It seems aesthetically
related to horsepower.

The U.S. system is so picturesque! Distance in furlongs or chains or
feet; weight in a couple different types of pounds and/or ounces; volume
in gallons or barrels or hogsheads, etc...

And you Euro guys have boring conversion factors - nothing but tens all
up and down the scale. We get lots of interesting ones to remember, and
I'm not even talking about SI to U.S. units. I'm just talking about the
conversions _within_ our system!

I wonder how many people in the U.S. know which U.S. units convert to
other U.S. units by multiplying by 231, or 5280, or 33,000, or 128, or
16, (or alternately 14.58, which is related to 7000), or 778.2, or 36,
or 3.

I used to excuse exchange students from having to learn many of these
(e.g. 5280), but I told US residents they were (currently) stuck with
the system, so yes, it might be on the exam.

Mark J.

PS - 640 (Acres in a square mile)


43,560 square feet per acre. (Why on earth do I have that memorized?)

And I've come across volumes of water measured in acre-feet.


Here in the land of hydro-power and mountain reservoirs (Oregon),
acre-feet are in pretty common usage, I think. Pretty sure I've seen
them in the newspapers fairly regularly.

Mark J.


Most trades or industries have their own esoteric language. Irrigation
is often described in acre-feet, horses race over furlongs, bicyclists
describe their power output in something other then the traditional
"horse power" :-)

cheers,

John B.


  #179  
Old December 24th 18, 02:48 AM posted to rec.bicycles.tech
AMuzi
external usenet poster
 
Posts: 13,447
Default Power on hills.

On 12/23/2018 7:42 PM, John B. Slocomb wrote:
On Sun, 23 Dec 2018 17:10:40 -0800, "Mark J."
wrote:

On 12/22/2018 8:24 PM, Frank Krygowski wrote:
On Saturday, December 22, 2018 at 7:33:29 PM UTC-5, Mark J. wrote:
On 12/22/2018 11:59 AM, Frank Krygowski wrote:
On 12/22/2018 11:21 AM, wrote:
On Saturday, December 22, 2018 at 3:54:20 PM UTC+1, Ralph Barone wrote:
wrote:
On Saturday, December 22, 2018 at 12:52:51 AM UTC+1, Andre Jute wrote:
On Friday, December 21, 2018 at 8:25:37 PM UTC,
wrote:
At low speeds - those below 100 mph of so, aerodynamic drag really
isn't a large loss unless you're playing for real small power such as
that developed by a human over relatively long periods of time.

Just as a demonstration.

30 square feet of frontal area
coefficient of drag of 0.5
This is similar to a family car

F = 0.5 C ? A V^2

A = Reference area as (see figures above), m2.
C = Drag coefficient (see figures above), unitless.
F = Drag force, N.
V = Velocity, m/s.
? = Density of fluid (liquid or gas), kg/m3. (dry air at 70
degrees F ~ 1.2)

.5 x .5 x 1.2 x 30 x 27 m/s (60 mph) = 243 N
.5 x .5 x 1.2 x 30 x 45 m/s (100 mph) = 337 N


Whereas the power to accelerate the mass of a car which is about 2200
lbs is huge. KE = mv

Thanks for putting the numbers to my argument, Tom.

Andre Jute
DESIGNING AND BUILDING SPECIAL CARS; Batsford, London; Bentley, Boston

I just reading an aero special article in TOUR magazin. Position on the
bike can save you 54 watts or gaining 3.9 km/hr going from riding on
the
tops to riding in the drops. Clothes can make a difference of up to 27
Watt or gaining 2,3 km/hr in speed. An aero bike saves you 16 Watt or
gaining 1.4 km/hr. This is all at a speed of 35 km/r, a speed not
unrealistic for a lot of us. So putting some estimated numbers in a
formula doesn't do the trick IMO.

Lou


It works better when you do the math properly and get the units
right. :-)

Yeah, that is what you get using Mickey Mouse units. Using feet and
ending up with Watt? WTF. Don't you have a Mickey Mouse unit for power?

Maybe for small amounts, we could use mousepower? It seems aesthetically
related to horsepower.

The U.S. system is so picturesque! Distance in furlongs or chains or
feet; weight in a couple different types of pounds and/or ounces; volume
in gallons or barrels or hogsheads, etc...

And you Euro guys have boring conversion factors - nothing but tens all
up and down the scale. We get lots of interesting ones to remember, and
I'm not even talking about SI to U.S. units. I'm just talking about the
conversions _within_ our system!

I wonder how many people in the U.S. know which U.S. units convert to
other U.S. units by multiplying by 231, or 5280, or 33,000, or 128, or
16, (or alternately 14.58, which is related to 7000), or 778.2, or 36,
or 3.

I used to excuse exchange students from having to learn many of these
(e.g. 5280), but I told US residents they were (currently) stuck with
the system, so yes, it might be on the exam.

Mark J.

PS - 640 (Acres in a square mile)

43,560 square feet per acre. (Why on earth do I have that memorized?)

And I've come across volumes of water measured in acre-feet.


Here in the land of hydro-power and mountain reservoirs (Oregon),
acre-feet are in pretty common usage, I think. Pretty sure I've seen
them in the newspapers fairly regularly.

Mark J.


Most trades or industries have their own esoteric language. Irrigation
is often described in acre-feet, horses race over furlongs, bicyclists
describe their power output in something other then the traditional
"horse power" :-)

cheers,

John B.


You left out gear inches.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


  #180  
Old December 24th 18, 05:33 AM posted to rec.bicycles.tech
Ralph Barone[_4_]
external usenet poster
 
Posts: 853
Default Power on hills.

John B. Slocomb wrote:
On Sun, 23 Dec 2018 17:10:40 -0800, "Mark J."
wrote:

On 12/22/2018 8:24 PM, Frank Krygowski wrote:
On Saturday, December 22, 2018 at 7:33:29 PM UTC-5, Mark J. wrote:
On 12/22/2018 11:59 AM, Frank Krygowski wrote:
On 12/22/2018 11:21 AM, wrote:
On Saturday, December 22, 2018 at 3:54:20 PM UTC+1, Ralph Barone wrote:
wrote:
On Saturday, December 22, 2018 at 12:52:51 AM UTC+1, Andre Jute wrote:
On Friday, December 21, 2018 at 8:25:37 PM UTC,
wrote:
At low speeds - those below 100 mph of so, aerodynamic drag really
isn't a large loss unless you're playing for real small power such as
that developed by a human over relatively long periods of time.

Just as a demonstration.

30 square feet of frontal area
coefficient of drag of 0.5
This is similar to a family car

F = 0.5 C ? A V^2

A = Reference area as (see figures above), m2.
C = Drag coefficient (see figures above), unitless.
F = Drag force, N.
V = Velocity, m/s.
? = Density of fluid (liquid or gas), kg/m3. (dry air at 70
degrees F ~ 1.2)

.5 x .5 x 1.2 x 30 x 27 m/s (60 mph) = 243 N
.5 x .5 x 1.2 x 30 x 45 m/s (100 mph) = 337 N


Whereas the power to accelerate the mass of a car which is about 2200
lbs is huge.* KE = mv

Thanks for putting the numbers to my argument, Tom.

Andre Jute
DESIGNING AND BUILDING SPECIAL CARS; Batsford, London; Bentley, Boston

I just reading an aero special article in TOUR magazin. Position on the
bike can save you 54 watts or gaining 3.9 km/hr going from riding on
the
tops to riding in the drops. Clothes can make a difference of up to 27
Watt or gaining 2,3 km/hr in speed. An aero bike saves you 16 Watt or
gaining 1.4 km/hr. This is all at a speed of 35 km/r, a speed not
unrealistic for a lot of us. So putting some estimated numbers in a
formula doesn't do the trick IMO.

Lou


It works better when you do the math properly and get the units
right. :-)

Yeah, that is what you get using Mickey Mouse units. Using feet and
ending up with Watt? WTF. Don't you have a Mickey Mouse unit for power?

Maybe for small amounts, we could use mousepower? It seems aesthetically
related to horsepower.

The U.S. system is so picturesque! Distance in furlongs or chains or
feet; weight in a couple different types of pounds and/or ounces; volume
in gallons or barrels or hogsheads, etc...

And you Euro guys have boring conversion factors - nothing but tens all
up and down the scale. We get lots of interesting ones to remember, and
I'm not even talking about SI to U.S. units. I'm just talking about the
conversions _within_ our system!

I wonder how many people in the U.S. know which U.S. units convert to
other U.S. units by multiplying by 231, or 5280, or 33,000, or 128, or
16, (or alternately 14.58, which is related to 7000), or 778.2, or 36,
or 3.

I used to excuse exchange students from having to learn many of these
(e.g. 5280), but I told US residents they were (currently) stuck with
the system, so yes, it might be on the exam.

Mark J.

PS - 640 (Acres in a square mile)

43,560 square feet per acre. (Why on earth do I have that memorized?)

And I've come across volumes of water measured in acre-feet.


Here in the land of hydro-power and mountain reservoirs (Oregon),
acre-feet are in pretty common usage, I think. Pretty sure I've seen
them in the newspapers fairly regularly.

Mark J.


Most trades or industries have their own esoteric language. Irrigation
is often described in acre-feet, horses race over furlongs, bicyclists
describe their power output in something other then the traditional
"horse power" :-)

cheers,

John B.


Horsepower is simply too embarrassing of a unit to be used by any cyclist
with an ego. We suffer badly by comparison with horses. That's why Watts
are so popular, although I wonder why ergs per second never caught on.

 




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