Why not measure the HR of the engine? I've read that the well trained
athelete can output something in the neighborhood of 1/4 HP. All the
variables of measuring the work accomplished would not change the power
rating of the motor, if it is power you are after! TnT

On 27 Feb 2005 06:35:50 -0800, "Tinkerntom" wrote:

Why not measure the HR of the engine? I've read that the well trained
athelete can output something in the neighborhood of 1/4 HP. All the
variables of measuring the work accomplished would not change the power
rating of the motor, if it is power you are after! TnT

Different muscle groups may output different amounts of energy/power,
whatever the potential of the CV system.

Happy trails,
Gary (net.yogi.bear)
--
At the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom

"Kieran" schrieb im Newsbeitrag
news:nK2Ud.65307$8a6.4571@trndny09...
Hey there, sorry for the cross-post!

I might be taking on a project where we try to determine the power
(force and velocity) developed by a kayaker while paddling. I'm
wondering if anyone out there knows of any research that's been done
like this. I know that it is a fairly common thing for rowing crews to
be "instrumented" with strain guages on the oars, and potentiometers on
the oarlocks, to get force/time curves for on-water rowing. So, I'm
wondering if anyone is aware of this sort of study having been done on
kayaking or canoeing.

The obvious problem with kayaking and canoeing, is that the paddle has
no fixed pivot point, like a rowing shell does. So most likely some
sort of video kinematic analysis will be necessary. We have the
capability to set this up, although I think the physics will be
complicated (i.e. statically indeterminant problem). I've done a search
of the scientific journal literature (Medline) and haven't found any
published papers on this topic, but that doesn't mean the work hasn't
been done at some National training center, or product development
center somewhere... or that it's in a very obscure journal that Medline
doesn't cover.

I'd appreciate any thoughts or hints on who might have done this sort of
work in the past. I'd rather not re-invent the wheel, if I can maybe
work on just improving it! :-)

Thanks,
Kieran Coghlan

Look for

http://www.fes-sport.de/kanu.htm

But I am not sure how much of their work is published

Eberhard

Excuse me for my stupidity . . . How about a spring scale on a boat
and the paddler paddling with comparable strain to what would be a
normal paddle effore for an hour watch the weight and average it. For
the strain at the hand use the same scale or replace it with a preasure
scale ( bathroom scale ) and again replicate the average paddle strokes
preasure.
Just a thought.
Or if you are good at math you can nick someone elses work.
Sorry, Kieran; I am that simple .
Alex McGruer

Peter wrote:


If you just want average power generated then you could use some of the
test and model data from Sea Kayaker magazine in their kayak test
reports that shows the drag force of each boat model at various speeds.
Combine this with measured speeds of paddlers in races and it should
give an idea of the effective paddling power.


Actually, we want direct measurement of force through the paddle,
applied by the paddler. This way, we can not only determine the overall
power, but also do an inverse dynamics analysis of the joint forces in
the paddler's arm and shoulder.

-Kieran

Bob Arledge wrote:
Why not put a strain gauge on the paddle shaft just below the paddler's
hand. This would give you the moment at that point, so the force would be
the moment divided by the distance between the strain gauge and the centroid
of the paddle blade.



That's the general idea, but because the paddling motion is 3-d, it's
not very easy to determine power just from the strain in the paddle
shaft. You need to know instantaneous velocity (direction and
magnitude) at every moment. In a fixed-pivot environment like rowing,
you can just put a potentiometer on the oar-lock. But the kayak/canoe
paddle has no fixed pivot point. So, I imagine that a virtual pivot
point would have to be derived via 3-d kinematic video analysis.

I haven't yet sat down and done a free-body of the system, but in my
head, it seems like it's going to be an indeterminant system... not fun.

Thanks,
-Kieran

"Kieran" wrote in message
news:j1tUd.66306$8a6.13749@trndny09...
Bob Arledge wrote:
Why not put a strain gauge on the paddle shaft just below the paddler's
hand. This would give you the moment at that point, so the force would be
the moment divided by the distance between the strain gauge and the
centroid of the paddle blade.

That's the general idea, but because the paddling motion is 3-d, it's not
very easy to determine power just from the strain in the paddle shaft.
You need to know instantaneous velocity (direction and magnitude) at every
moment. In a fixed-pivot environment like rowing, you can just put a
potentiometer on the oar-lock. But the kayak/canoe paddle has no fixed
pivot point. So, I imagine that a virtual pivot point would have to be
derived via 3-d kinematic video analysis.

I haven't yet sat down and done a free-body of the system, but in my head,
it seems like it's going to be an indeterminant system... not fun.


Actually, it should be quite managable, seeing as how the paddle is a line.
You only need two points to track all the motions of the paddle shaft, and
two more on the sides of the blade to track the feather. Everything else
follows.

Seems like someone out there must have some sort of pressure plate: two
sheets of material with a lor of sensor points between. Put one on the blade
and get a readout of the water pressure against all points of the blade at
all times. If all you are interested in is the resultant force, put a
potentiometer on the bow and brace it against a wall.

--riverman
(I love trying to sound like I know what I'm talking about)

Might be worth looking at the reaction forces on the boat - ie/
footrests/seat, as these would be relatively easy to measure, and with
a bit of meathematical modelling could probably give you a fair amount
of information about paddle force & direction.

riverman writes
"Kieran" wrote
Bob Arledge wrote:
Why not put a strain gauge on the paddle shaft just below the paddler's
hand. This would give you the moment at that point, so the force would be
the moment divided by the distance between the strain gauge and the
centroid of the paddle blade.

That's the general idea, but because the paddling motion is 3-d, it's not
very easy to determine power just from the strain in the paddle shaft.
You need to know instantaneous velocity (direction and magnitude) at every
moment. In a fixed-pivot environment like rowing, you can just put a
potentiometer on the oar-lock. But the kayak/canoe paddle has no fixed
pivot point. So, I imagine that a virtual pivot point would have to be
derived via 3-d kinematic video analysis.

I haven't yet sat down and done a free-body of the system, but in my head,
it seems like it's going to be an indeterminant system... not fun.


Actually, it should be quite managable, seeing as how the paddle is a line.
You only need two points to track all the motions of the paddle shaft, and
two more on the sides of the blade to track the feather. Everything else
follows.

Seems like someone out there must have some sort of pressure plate: two
sheets of material with a lor of sensor points between. Put one on the blade
and get a readout of the water pressure against all points of the blade at
all times. If all you are interested in is the resultant force, put a
potentiometer on the bow and brace it against a wall.


Since it is more the reduction in pressure on the convex back of the
paddle which moves the boat than the increase on concave face, you'll
need a sensing surface on both faces. Even then you'll measure pressure
but not shear (frictional) forces.

Might be better to measure the forces at the paddle neck directly by
means of strain-gauge rosettes. Then there's angle of shaft, direction
& velocity of blade motion & (variable) location of centre of pressure
to consider.

Sounds a nice easy problem, only slightly more difficult than the one
about life, the Universe & everything. Have fun, Keiran!

Cheers -
Carl

--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)

"Carl Douglas" wrote in message
...
Since it is more the reduction in pressure on the convex back of the
paddle which moves the boat than the increase on concave face...

Huh?

Isn't it the force of the paddler's butt, feet, or whatever other
parts are in contact with the boat that propel it?

Wolfgang