How do angles of waterwheel affect angular velocity

  • #1
Hello, I'm currently writing a high school academic paper on waterwheels. One of the things I want to find out is whether the angle of paddles of the undershot waterwheel affects the angular velocity.
So here is my question:
How do the different angles of the paddles in a waterwheel affect it's angular velocity, and why?
Thanks
 

Answers and Replies

  • #2
Danger
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Hi. I'm not quite sure what you mean by the question. A paddle has no angular velocity unto itself, since it is a rigid structural component of the wheel. Do you mean how the angle affects the efficiency of capturing energy from the water?
 
  • #3
Hi. I'm not quite sure what you mean by the question. A paddle has no angular velocity unto itself, since it is a rigid structural component of the wheel. Do you mean how the angle affects the efficiency of capturing energy from the water?
Oooops! Thats what I mean. I'm still kinda new to physics, but I'm guessing it has to do with free body diagrams?
 
  • #4
Danger
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Truth be told, young dude, I really have no idea what a "free body diagram" is. We never did any of that kind of stuff when I was in school. I still can't get used to seeing the terms "Newtons" and "bars"; I was taught in foot-pounds, horsepower, and pounds-per-square-inch. (And that was in physics class, not just auto shop.)
What effect the "angle of attack" of the paddle has will partially depend upon how it fits into the overall structure of the wheel. (ie: is it a flow-through design, or does it form an enclosed "bucket" or maybe a "catch-and-release" system..?
I won't be able to provide any meaningful assistance once you get to your exact question, but I hope that perhaps I can help you get to it.
 
  • #5
Doug Huffman
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Paddle angle does not appear in power or efficiency calculations. As the angle tends away from zero the resultant force has a larger useless component side loading the bearings.
 
  • #6
Danger
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Paddle angle does not appear in power or efficiency calculations. As the angle tends away from zero the resultant force has a larger useless component side loading the bearings.
Side loading? How does that come about? :oldconfused:
 
  • #7
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An angled paddle deflects the force of the water. When you row a boat you want the paddle flat vertical to the water, if you tilt the top in the direction you are rowing the paddle wants to climb out of the water "side loading" the oar pivots.
 
  • #8
Doug Huffman
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LOL When I was in school we were required to learn in the units of the founder of the field. There has not been, that I know, an error of magnitude caused by mistaking the system of units ETA in my field.
 
Last edited:
  • #9
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an error of magnitude caused by mistaking the system of units.
The next time they update SI maybe it will be all I use. :-p
 
  • #10
Danger
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if you tilt the top in the direction you are rowing the paddle wants to climb out of the water "side loading" the oar pivots.
Thank you for that explanation. I had misinterpreted the the term "side" as meaning that it was trying to pull the wheel's shaft out of the housing (so as to need a thrust bearing instead of just a rotary one). Sorry about that.

ETA in my field.
Oh, great... clear up one question and raise another. :oldgrumpy: Ex-pilot here... in my field, ETA means when you plan to put your ass on the grass. What is it in this context?

In reference to the former, though... how does "useless" enter into it? Doesn't more side-force indicate that more work is being done upon the wheel, and thus giving a greater output? (Or is it a matter of decreasing efficiency as opposed to actual loss?)

edit: Edited the above to add the last sentence.
 
  • #11
Paddle angle does not appear in power or efficiency calculations. As the angle tends away from zero the resultant force has a larger useless component side loading the bearings.
Yeah, I thought that when the angle of the paddles change, there would be energy wasted. But I have no clue how to calculate that component.
 
  • #12
An angled paddle deflects the force of the water.
But is it possible for me to calculate the force deflected?
 
  • #13
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I don't think so because it doesn't just affect the force on the wheel, it also disturbs the flow of the water.
 

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