Post
by Balsa Man » April 2nd, 2010, 4:16 am
Here's one way-
Use a piece of brass rod - we're using 3/32nd - 1/8th would be ok, too. Mount the fan up near the top of the box. The rod (initially) stands up vertically. Make a pivot at the bottom end. Put a ....paddle at the top end. That paddle goes in front of the fan. We're using a piece of 1/16th sheet balsa, about the size of the fan. Align the bottom so that the rod is just past vertical when the paddle is resting against the fan- that is, its leaning against the fan, just slightly. When the fan comes on, blows against the paddle. All it has to do is move it past vertical, then it falls on its own. For the electrical connection that the falling rod breaks, get some fairly thin brass sheet (Hobbytown), cut a couple strips, oh, 1/8th wide, couple inches long. Solder a wire to each. Set them up (we use a little block of balsa) so that the rod (when vertical) is between them - the strips aligned so that they are parallel to each other, with the distance between just a bit less than the diameter of the rod- so you get good contact without putting too much.....drag on the rod. Rod falls, breaks contact.....
Len Joeris
Fort Collins, CO