PHD 

This is for the turbine only and not jar test experiment pdf generator itself. The main photo you see is the goal. Shown below are several botched designs.

All four are attached to the drive shaft of a 24-volt DC battery-operated lawn mower. The vertical bar you see is an allthread bar that is attached to the motor shaft. The galvanized metal is half of a dryer vent tube. The first design would turn half way and then stop because of the resistance of the back side of it coming into the wind. I then added a top disk and attached a number of 2-liter soda bottles and some 1-gallon milk jugs to a disk on top. The second design is all cardboard and looked really sharp.

In the third one I added parts of the dryer vent tube to the cardboard mill and that worked a little bit but there was resistance on the back side coming into the wind. At this point, I decided that I had to go back to the drawing board with a simple model to see what had a chance of working. What you see in the photograph are the pieces you are going to cut out of the cardboard. You can also see the knitting needle with some rubber bands on it. Cut 4 strips of cardboard 4″ x 10″.

These notches will be located 1 inch from either side of the ends of paddles. You will need to cut two disks 10 inches in diameter. Since I flunked kindergarten, I found this somewhat of a challenge. Trying to draw a true circle without a decent compass is tricky.

Then after you have drawn it and cut it, finding the true center is also difficult. Here’s an easy way to do it. Cut a 10×10 inch square of cardboard. On all four sides make a mark half way between the edges. That mark will be 5 inches from the corners on each side.

Use a ruler to draw lines that connect opposing 5 inch marks through the center of the square. Where these lines intersect, that’s will be the center of the circle. Use a compass if you have one and jab it into the center and expand it out to end of one of the radius lines. Now draw a full circle with the compass. I’m not sure school compasses are big enough to do this.

An alternative might be to get a ten-inch bowl or something like that and lay it over the square and trace the lines. You can also simply eye-ball it and make an arc from the center of one side the the center of the next. Take a look at the first image. Notice that there is an Angle A and sides a, b, and c. Side c is the line that we want the paddle to line up with. Where we draw it depends on angle a.

To do a little geometry on this let’s cheat and use a web-based right triangle calculator. I chose to make side a 2. Accoding to the calculator, this makes angle A 24 degrees. Going with my 24 degrees configuration, make a mark along side a 2. 25 inches from the center of the circle and then draw side c. Now do that with the other three radius lines.

After that is done, do the same thing with the other disk. Notice that there are short cuts in the disk at angle A on each radius line. The pupose of these cuts is dock the paddle to the disks. The cuts should be about a half inch and should follow the path of line c. Double or triple up one of the rubber bands and push it up the axis rod to within about 2 inch from the top. The purpose of this and the other rubber band is to anchor the rod to the disk via friction. The also help to keep the turbine from slipping up and down.

Push the axis rod down through the center of one of the disks. I suggest that you keep the side of the disk with the angles drawn facing up for easlier alignment of the paddles. Push the rod through the center of the second disk with the side of the disk with the drawn angles facing down. Slid the disk up the rod to within about 8 inches of the top disk.

Slide the second rubber band up the rod to within an inch of the lower disk. Push one of the paddles onto upper and lower disks so that the notches on the paddle dock into the angled notches on the upper and lower disks. You might want to temporarily tape the paddle into place from the top and bottom. Mount the other three paddles in same way. Push the rubber band on the bottom up the rod so that it sits firmly up against the lower disk. As an alternative, you could use a glue gun to glue the paddles in place.

News Reporter