Is body weight equivalent to bicycle weight?

Mark Hickey wrote:

Thing is, since you can give a loose wheel a spin with a finger and
easily get it up to "sprinting speed", it's pretty clear that this
"acceleration tax" is minimal.

Quite true... as it also takes little energy to toss a wheel and tire
across the room. They just don't weigh that much compared to the 180+
lb (for most of us), bike/rider system.

Bruce W.1 wrote:
Is body weight equivalent to bicycle weight? In other words, would
riding a bicycle that's five pounds lighter be the same as losing five
pounds off of your body weight?

There's an old Army saying; one pound on your foot (boot weight) is
equivalent to five pounds on your back. But I'm not sure what this has
to do with anything.

Thanks for your help.

Not taking into consideration the value of being lighter, that is, less
fat, the energy it takes to accelarate the bicycle is the mass of the
bicycle and rider, so, a 185 pound guy on a 20 pound bike will take the
same energy as a 190 pound guy on a 15 pound bike.

Wheel rotation type stuff exists but since the acceleration is so
small, it is a teeny part of the equation. Fly wheel affect really is
lost in the noise(hello wheel marketeers!!)

"Joe Riel" wrote in message
...

If all the mass of the wheel is at the rim (worst case), then k=1 and
we get the factor of 2 previously mentioned.


Now figure it out for typical acceleration rates for cyclists and you'll see
that Paul was effectively correct.

-Andy B.

"C" wrote in message
...
In article ,
Bruce W.1 wrote:
Is body weight equivalent to bicycle weight? In other words, would
riding a bicycle that's five pounds lighter be the same as losing five
pounds off of your body weight?

Depends on where the 5 pounds comes off your body. If you lose muscle
as well as fat, then you are losing strength.

For endurance cycling, better performance comes generally from being
lighter (up to a point). Losing strength is not such a big deal. Power
to weight or power to drag ratio is much more important.

Phil H

writes:

(If you're not sure about the odd business of the foot
coming to a halt with every step, even at Olympic sprinting
speeds, step through a puddle and then look back at your wet
footprints. They show that your foot never slipped when it
was touching the ground, just as the wet track left by your
rubber tire will show that your tire was not slipping when
it touched the pavement at 20 mph. If the feet and the tire
weren't slipping against the ground, then they must have
been equally motionless.)

If one is interested in the dynamics of the system it makes a lot more
sense to use a reference frame centered on the body. The foot does
not stop.

Jim Smith wrote:
writes:

(If you're not sure about the odd business of the foot
coming to a halt with every step, even at Olympic sprinting
speeds, step through a puddle and then look back at your wet
footprint s. They show that your foot never slipped when it
was touching the ground,

If one is interested in the dynamics of the system it makes a lot more
sense to use a reference frame centered on the body. The foot does
not stop.

Imagine you have a (let's say small) bicycle wheel which you can hold
up in the air by a handle attached to the axle on the left, and which
has a handle on the right attached to the rim which you can use to
crank the wheel up to speed. You then crank in uniform circular motion.
Now, start running forward at the same time: even more motion. Finally,
at the same time as all this, slowly lower the wheel down so that the
tire touches ground. If you get the timing right, it will roll along
the ground with no slippage.

You can think of this as one reason why, in problems with systems that
both rotate and translate- like the leg system while running, or a
bicycle wheel, or for that matter, a person leaning over- neither the
ground coordinate system NOR one attached to the body is adequate. One
uses both: one attached to the ground, and one attached to the center
of mass of every rotating system.

On 24 Jul 2005 07:33:23 -0700, "41"
wrote:



Jim Smith wrote:
writes:

(If you're not sure about the odd business of the foot
coming to a halt with every step, even at Olympic sprinting
speeds, step through a puddle and then look back at your wet
footprint s. They show that your foot never slipped when it
was touching the ground,

If one is interested in the dynamics of the system it makes a lot more
sense to use a reference frame centered on the body. The foot does
not stop.

Imagine you have a (let's say small) bicycle wheel which you can hold
up in the air by a handle attached to the axle on the left, and which
has a handle on the right attached to the rim which you can use to
crank the wheel up to speed. You then crank in uniform circular motion.
Now, start running forward at the same time: even more motion. Finally,
at the same time as all this, slowly lower the wheel down so that the
tire touches ground. If you get the timing right, it will roll along
the ground with no slippage.

You can think of this as one reason why, in problems with systems that
both rotate and translate- like the leg system while running, or a
bicycle wheel, or for that matter, a person leaning over- neither the
ground coordinate system NOR one attached to the body is adequate. One
uses both: one attached to the ground, and one attached to the center
of mass of every rotating system.

Dear 41,

Sounds like a reasonable approach, since the foot stops once
with every step from the point of view of the ground
(inchworm), and twice with every step from the point of view
of the hip (pendulum).

Carl Fogel

Carl Fogel

"41" wrote in message
oups.com...


Jim Smith wrote:
writes:

(If you're not sure about the odd business of the foot
coming to a halt with every step, even at Olympic sprinting
speeds, step through a puddle and then look back at your wet
footprint s. They show that your foot never slipped when it
was touching the ground,

If one is interested in the dynamics of the system it makes a lot
more
sense to use a reference frame centered on the body. The foot does
not stop.

Imagine you have a (let's say small) bicycle wheel which you can hold
up in the air by a handle attached to the axle on the left, and which
has a handle on the right attached to the rim which you can use to
crank the wheel up to speed. You then crank in uniform circular
motion.
Now, start running forward at the same time: even more motion.
Finally,
at the same time as all this, slowly lower the wheel down so that the
tire touches ground. If you get the timing right, it will roll along
the ground with no slippage.

You can think of this as one reason why, in problems with systems that
both rotate and translate- like the leg system while running, or a
bicycle wheel, or for that matter, a person leaning over- neither the
ground coordinate system NOR one attached to the body is adequate. One
uses both: one attached to the ground, and one attached to the center
of mass of every rotating system.


I agree but I think your description is too broad to be useful for a
specific sport.

Now, "get back to your oar 41"....bonus points for the movie and actor
quoted.

Phil H

Depends on where the 5 pounds comes off your body. If you lose muscle
as well as fat, then you are losing strength.

Not necessarily. There are many riders who lose mass, including
muscle, as they get stronger from spring to summer. In a trained
cyclist (10% fat, competing, 300+ miles/week) a 5 pound reduction
in bodyweight can improve performance the same as 10 or more pounds
off the bike.

The primary determinant is not muscle mass but rather efficiency.
Efficiency is difficult to measure but almost always increases
exponentially to weight decreases independent of composition. This
is because of several factors: 1) the stress of digestion,
especially during recovery, 2) circulatory demands from both muscle
and non-muscle tissue, and 3) innumerable micro-metabolic processes.

Philip Holman wrote:
For endurance cycling, better performance comes generally from being
lighter (up to a point).

Endurance or otherwise that point tends to be around 6% bodyfat for most
(male) cyclists.

--
Roger Marquis
http://www.roble.net/marquis/

Quoting Eric Hill :
The rule of thumb that I've been told goes, "an ounce off the wheels
equals a pound off the frame."

But that's obviously completely bogus. Even if all the mass of a wheel
was at the very edge, which it's not, it would be only twice as hard to
accelerate as non-wheel mass; and of course only a small proportion of
energy goes to acceleration anyway.
--
David Damerell Distortion Field!
Today is Gaiman, July - a public holiday.