Maximum power output for a human for short periods?



R

Robert Clark

Guest
I'm interested in producing human powered vehicles. I copied below a
proposed method for generating 1800 watts of human generated power for
a period of say 1 minute. Some references suggest you might only be
able to get up to say 1,000 watts for over a minute. They say
cyclists might be able to get up to 2,000 watts but only for short
bursts. But I need this over a minute or so for my purposes.
Have their been weightlifting instances where the lifter uses both
the upper and lower body and is able to get high reps at a total
lifted weight of over 3 times their body weight?
Also, I might need the power generation to be continuous in both the
positive and negative directions. Then could a lifter pull back with
as much force when reversing a leg press as when he extended his legs?
And could he pull back with his arms when reversing a bench press with
as much force as when he extended his arms?


Bob Clark

=============================================================
Newsgroups: sci.astro, sci.physics, sci.space.policy, sci.engr.mech
From: Robert Clark <[email protected]>
Date: Tue, 13 Nov 2007 13:42:05 -0800
Local: Tues, Nov 13 2007 4:42 pm
Subject: Re: Proposal for hovering flight.

On Nov 11, 2:36 pm, "CWatters" <[email protected]>
wrote:

> news:[email protected]...


> It's interesting to take a look at how man powered flight has been
> achieved - bear in mind that racing cyclists can only put out about a third
> of a horsepower continuously...


> http://en.wikipedia.org/wiki/Man-powered_flight


> I believe the prize for a man powered helicopter is still unclaimed although
> some have managed to get off the ground on less than one horsepower!>http://www.humanpoweredhelicopters.org


....
Thanks for those links on human powered flight. I found this link
that suggested top cyclists could generate 500 watts continuously and
900 watts peak (though perhaps with some chemical augmentation ;-) )

Olympic Human Powered Flight
Human Powered Flight Undergoes Renaissance With Olympic Competition.
"//humans can produce about 100 watts continuously, with peaks of 400
watts or more// That may be so on average, but for a trained cyclist
those stats are quite low. I'm at 300 watts continuous / over 900
peak
with moderate training. Lance Armstrong somehow manages 500
continuous. It's probably safe to say Olympic cyclists can maintain
at
least 400 watts."
http://www.halfbakery.com/idea/Olympic_20Human_20Powered_20Flight

The prize discussed on the human powered helicopters site only
requires that the craft hover at 3 meters under human power only for
one minute.
A fit male probably could do leg presses of twice his body weight
for
several reps and bench presses of his weight for several reps. These
would only have to be done for 60 seconds.
To see these are reasonable capabilities note that in climbing
stairs
we're actually supporting our weight most of the time on one leg.
We're using both legs only for the short time when we're switching
from one leg to the other. So just climbing stairs we're doing the
equivalent of supporting twice our body weight. A normal fit person
climbing stairs certainly could go up one stair in one second, with
the stairs being about 8 inches, 20 centimeters high. Then a good
athlete could do the equivalent of 100 centimeters, one meter, per
second up the stairs if only for one minute.
For the bench press, a normal fit male could do several reps of
push-
ups, which is supporting your weight with your arm and chest muscles,
once each second. The distance would be about 2 feet. Then a good
athlete should be able to raise his weight in a bench press 1 meter
once per second for several reps for a minute.
Note for both of these I'm assuming that both the positive and
negative directions count as a single repetition, not a full cycle,
as
in normal exercising. This corresponds to how this would be useful
for our scenario since both the positive and negative directions
could
be used for driving the craft.
However, there is a question of whether both the upper and lower
body
could be used at this intensity at the same time. I think for the top
athletes this could be possible at least for one minute. Then we may
suppose a top athlete raising and lowering 3 times his weight 1 meter
once per second, that is, a full up-down cycle taking 2 seconds, for
60 seconds.
For a small 60 kg athlete, this would be 180 kg raised 1 meter per
second or 1800 N over 1 m per second, or 1800 watts. For the weight
of the person of 60 kg, this is a weight to power ratio of 33 to 1. I
will assume that the canopies and the shell holding the craft can be
made quite light, and will take simply the total weight to be 60 kg.
Remember now that the weight to power ratio is 100/v. So v is 3 m/s,
for the speed at which the canopies are brought down. Then plug this
into the equation for the drag produced to see how large the canopy
has to be raised 60 kg. We need to produce 600 N of force. This
requires a canopy diameter of about 6.6 meters.


Bob Clark
==============================================================
 
On Nov 16, 12:25 am, Paul Cassel <[email protected]>
wrote:
> Robert Clark wrote:
> > I'm interested in producinghuman poweredvehicles. I copied below a
> > proposed method for generating 1800wattsof human generated power for
> > a period of say 1 minute. Some references suggest you might only be
> > able to get up to say 1,000wattsfor over a minute. They say
> > cyclists might be able to get up to 2,000wattsbut only for short
> > bursts. But I need this over a minute or so for my purposes.
> > Have their been weightlifting instances where the lifter uses both
> > the upper and lower body and is able to get high reps at a total
> > lifted weight of over 3 times their body weight?
> > Also, I might need the power generation to be continuous in both the
> > positive and negative directions. Then could a lifter pull back with
> > as much force when reversing a leg press as when he extended his legs?
> > And could he pull back with his arms when reversing a bench press with
> > as much force as when he extended his arms?

>
> I doubt a human can produce a kw for even very short periods and surely
> not a minute much less 1.8kw. What you can try is to have your human
> operating at a lower output for a time but store some of that energy in,
> say, a flywheel and then harness the flywheel's kinetic energy when you
> need 1 minute of 1.8 kw.
>
> Try asking at a bicycle group such as rec.bicycles.tech. Many of the
> guys there are quite familiar with human energy output capacities. A
> typical civilian thinks he's working hard at 150watts.
>
> -paul


Producing 1800 watts for a few seconds should be within the range of
the best power lifters and perhaps for up to a minute. Remember 1 watt
means applying a force of 1 newton through a distance of 1 meter in 1
second. So if you lifted 1 kg, that's 9.8 newtons of force, about 10
newtons, for 1 meter in 1 second, that would be 10 watts. So lifting
180 kg, 1 meter high in 1 second would be 1800 watts.
The best power lifters can do squats of several times their body
weight for 1 rep. Let's say the power lifter weighed 100 kg, about 220
lbs. He might be able to do 3 times his weight for a single rep. That
would be 300 kg. But remember he's actually raising his own weight as
well. So he's actually lifting 4 times his weight, 400 kg for this one
rep. For a male of average height, he might be raising this over a
distance of 1 meter.
So doing 1800 watts of power for one minute would be like giving this
power lifter a weight of only 60 kg (for a total weight of 180 kg) and
doing squats with this light weight for the high number of reps of 1
per second over one minute. I think this would be possible for a
weight so much lighter than their usual 1 rep maximum weight.



Bob Clark
 
"Paul Cassel" <[email protected]> wrote in message
news:[email protected]...
> Robert Clark wrote:
>> I'm interested in producing human powered vehicles. I copied below a
>> proposed method for generating 1800 watts of human generated power for
>> a period of say 1 minute. Some references suggest you might only be
>> able to get up to say 1,000 watts for over a minute. They say
>> cyclists might be able to get up to 2,000 watts but only for short
>> bursts. But I need this over a minute or so for my purposes.
>> Have their been weightlifting instances where the lifter uses both
>> the upper and lower body and is able to get high reps at a total
>> lifted weight of over 3 times their body weight?
>> Also, I might need the power generation to be continuous in both the
>> positive and negative directions. Then could a lifter pull back with
>> as much force when reversing a leg press as when he extended his legs?
>> And could he pull back with his arms when reversing a bench press with
>> as much force as when he extended his arms?
>>
>>

> I doubt a human can produce a kw for even very short periods and surely
> not a minute much less 1.8kw. What you can try is to have your human
> operating at a lower output for a time but store some of that energy in,
> say, a flywheel and then harness the flywheel's kinetic energy when you
> need 1 minute of 1.8 kw.
>
> Try asking at a bicycle group such as rec.bicycles.tech. Many of the guys
> there are quite familiar with human energy output capacities. A typical
> civilian thinks he's working hard at 150 watts.
>
> -paul


A human is good for about 1 hp for 12 seconds. Max continous is probably
around 1/2 hp.

Bob
 
Robert Clark wrote:
> I'm interested in producing human powered vehicles. I copied below a
> proposed method for generating 1800 watts of human generated power for
> a period of say 1 minute. Some references suggest you might only be
> able to get up to say 1,000 watts for over a minute. They say
> cyclists might be able to get up to 2,000 watts but only for short
> bursts. But I need this over a minute or so for my purposes.
> Have their been weightlifting instances where the lifter uses both
> the upper and lower body and is able to get high reps at a total
> lifted weight of over 3 times their body weight?
> Also, I might need the power generation to be continuous in both the
> positive and negative directions. Then could a lifter pull back with
> as much force when reversing a leg press as when he extended his legs?
> And could he pull back with his arms when reversing a bench press with
> as much force as when he extended his arms?
>
>

I doubt a human can produce a kw for even very short periods and surely
not a minute much less 1.8kw. What you can try is to have your human
operating at a lower output for a time but store some of that energy in,
say, a flywheel and then harness the flywheel's kinetic energy when you
need 1 minute of 1.8 kw.

Try asking at a bicycle group such as rec.bicycles.tech. Many of the
guys there are quite familiar with human energy output capacities. A
typical civilian thinks he's working hard at 150 watts.

-paul
 
On Nov 15, 4:45 pm, Robert Clark <[email protected]> wrote:
> On Nov 16, 12:25 am, Paul Cassel <[email protected]>
> wrote:
>
>
>
> > Robert Clark wrote:
> > > I'm interested in producinghuman poweredvehicles. I copied below a
> > > proposed method for generating 1800wattsof human generated power for
> > > a period of say 1 minute. Some references suggest you might only be
> > > able to get up to say 1,000wattsfor over a minute. They say
> > > cyclists might be able to get up to 2,000wattsbut only for short
> > > bursts. But I need this over a minute or so for my purposes.
> > > Have their been weightlifting instances where the lifter uses both
> > > the upper and lower body and is able to get high reps at a total
> > > lifted weight of over 3 times their body weight?
> > > Also, I might need the power generation to be continuous in both the
> > > positive and negative directions. Then could a lifter pull back with
> > > as much force when reversing a leg press as when he extended his legs?
> > > And could he pull back with his arms when reversing a bench press with
> > > as much force as when he extended his arms?

>
> > I doubt a human can produce a kw for even very short periods and surely
> > not a minute much less 1.8kw. What you can try is to have your human
> > operating at a lower output for a time but store some of that energy in,
> > say, a flywheel and then harness the flywheel's kinetic energy when you
> > need 1 minute of 1.8 kw.

>
> > Try asking at a bicycle group such as rec.bicycles.tech. Many of the
> > guys there are quite familiar with human energy output capacities. A
> > typical civilian thinks he's working hard at 150watts.

>
> > -paul

>
> Producing 1800 watts for a few seconds should be within the range of
> the best power lifters and perhaps for up to a minute. Remember 1 watt
> means applying a force of 1 newton through a distance of 1 meter in 1
> second. So if you lifted 1 kg, that's 9.8 newtons of force, about 10
> newtons, for 1 meter in 1 second, that would be 10 watts. So lifting
> 180 kg, 1 meter high in 1 second would be 1800 watts.
> The best power lifters can do squats of several times their body
> weight for 1 rep. Let's say the power lifter weighed 100 kg, about 220
> lbs. He might be able to do 3 times his weight for a single rep. That
> would be 300 kg. But remember he's actually raising his own weight as
> well. So he's actually lifting 4 times his weight, 400 kg for this one
> rep. For a male of average height, he might be raising this over a
> distance of 1 meter.
> So doing 1800 watts of power for one minute would be like giving this
> power lifter a weight of only 60 kg (for a total weight of 180 kg) and
> doing squats with this light weight for the high number of reps of 1
> per second over one minute. I think this would be possible for a
> weight so much lighter than their usual 1 rep maximum weight.
>
> Bob Clark


The information you want is mostly here: http://www.velocitynation.com/article.aspx?ID=108&CID=56
Besides power, weight, or rather lack of it, is important if you are
considering flight.
"Marty Nothstien weighted 220 pounds or 100 kilos in the 1996
Olympics, it takes a lot of power to get that much weight up to 45+
MPH but with maximum power at over 2200 watts at peak his engine was
more than big enough. That's well above great road sprinters who are
comparatively small like Cipollini (1900 watt max) or Pettachi
(reported 1700 watts). Conversely Chris Boardman was able to produce
over 440 watts for an hour to break the hour record but his top power
in a sprint was only 1000 watts, not enough to win a cat 5 sprint at
Floyd Bennett Field. "
 
On Wed, 14 Nov 2007 16:17:41 -0800, Robert Clark
>
>> I believe the prize for a man powered helicopter is still unclaimed although
>> some have managed to get off the ground on less than one horsepower!>http://www.humanpoweredhelicopters.org


>
> The prize discussed on the human powered helicopters site only
>requires that the craft hover at 3 meters under human power only for
>one minute.


Don't forget that you have to get up to 3 meters first then stay there
for a minute. Also getting up to that height will require considerably
more energy than hovering there.