Tuesday, February 27, 2007

Whirligig Plans

 

If you would like full size plans and material lists to any of the whirligigs shown in my blog and my Youtube Channel, [http://www.youtube.com/chuckdunbar], leave a message. They will cost $10 US.

Posted by Chuck at 08:39:08 | Permanent Link | Comments (0) |

Blade Hubs

I have shown the steps for making a whiriligig propeller hub with metal rod arms. (Whirligig Blade Hub, 1-26-2007) In the coming week I'm starting a whirligig the blade hub of which will have the wood blades directly attached to the hub. I'll post photos showing each step to making the hub.
Posted by Chuck at 08:27:28 | Permanent Link | Comments (0) |

Saturday, February 24, 2007

Mechanism for Whirligig #36

 
 
 
Cam to Create a Wagging Circle, cam diameter 2 1/8" (5.7 cm)
 
 
Several sketches led me to this simple mechanism for Whirligig #36. There are two problems to solve. First, the cam needs to be counter weighted (balanced) so that it doesn't shake and not much force (from the wind) is needed to turn it. Second, how much blade surface area is required to generate the needed force to turn the cam at low windspeed. There are formulas to calculate this, but I would have to spend a lot of time reviewing math from a long, long time ago. Instead I'm eyeballing it. Weighting the cam involves changing the cam's center of gravity so that when the linkage is in the top position, gravity acting on the descending weighted linkage provides enough force to turn the cam. Once in the bottom position, the adjusted center of gravity of the cam will raise the linkage to the top position. That is what the 1/4" dia. brass rods inserted into the cam are doing. The drawing shows what the finished mechanism will look like. I'm going to design the whriligig so that if the initial blade arrangement is not adequate to run the mechanish, I can replace them with bigger blades. I also need to find any easy way to measure the force needed to turn the cam. Then I can begin to accumulate some data relating the force to turn the cam and the surface area of the blades.  Go to my Youtube Channel to see the mechanism in motion.  (Address in the column to the right.)
Posted by Chuck at 23:29:17 | Permanent Link | Comments (2) |
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