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A hunting bow is a highly progressive spring, its pull going from very easy to very difficult just before release. A compound hunting bow uses cabling through a series of eccentric pulleys in order to convert the pull from a progressive rate to single rate, finally using a camming slope on the pulleys
to "lock" the spring so that very little pull at all is required to maintain full tension prior to release. It's a brilliant idea and a wonder that it wasn't conceived of earlier by someone like Da Vinci. But then only more people would have been slaughtered in war, so it's just as well I guess.
Why not adopt the idea to an oar for rowing? Many of the same advantages would seem to apply. There are varying degrees of input efficiency between arm/torso position and the angle at which the paddle 'attacks' the water. A well engineered oar making use of eccentric pulleys and cable similar to a compound bow could be designed to put optimum human effort into propulsion.
Wait a sec..., almost forgot my bakery manners. This could also be used for compound prosthetic beauty queen waving arms, prosthetic ballet limbs, rentable enhancements for seniors during extended hours at the slot machines, devices for teens working summer jobs slinging clay at skeet shooting facilities...
Oar-driven pump
Oar-driven_20pump
Another possible use for this technique. [csea, Dec 07 2009]
[link]
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If you're after true propulsive efficiency, better a bicycle frame and a well-contoured propeller. An oar is nothing more than an intermittent-immersion paddle wheel, which are rather inefficient compared to propellers. |
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...Amish butter churns... |
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Can we adapt it for mousing to minimize the range of movement required? |
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//A hunting bow is a highly progressive spring, its pull going from very easy to very difficult just before release// |
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Actually a clever bowyer will build [I forget the term, um, "thingy"] into the limbs. A compound can go to nearly full force almost immediately and hold it until the let-off valey starts (this optimises the energy imparted to the arrow by making every inch of draw hold as much force as possible). A clever recurve maker will do something similar with the recurve limbs so they "stack" (I remember the term now), and go to full force earlier in the draw cycle, but it won't have any let-off. |
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Anyhoo, what I'm getting at is I imagine expensive and high tech oars (such as those used for competitive rowing) - are most probably not as rigid as possible, rather sprung at an appropriate rate to optimise force transfer and maintain blade angle. If they don't, they should. |
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You should check out the exotic drive systems on modern sea kayaks. Some use recumbant bicycle type pedals to drive vertical under-keel blades that move in a complex pattern to optimise thrust. It's not oars, but it's definitely pulleys, etc. Not baked, just a different idea with the same goal. |
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And I've seen a canoe/kayak set up witharticulated oars so that it's optimised for the rower/s to be facing forwards rather than backwards. Presumably that arrangement has some kind of science behind the geometry to optimise the use of the oars... |
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A good traditional 12' spruce oar bends through the stroke, building up energy, then releases it back into the water just before the back stroke to give a little acceleration to help carry you through the backstroke. |
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I wish I could give two separate croissants, one for the first
two paragraphs, and a whole 'nother one for the last. |
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Thats probably what the regular bow folks said about the compound bow. And the spear folks said about the bow. And the sharp rock folks said about the spear. |
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This is great stuff. I wonder if rowing competitions mandate regulation oars? |
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I also like this device as the hurling arm for a pumping chucking catapult. |
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