In this tutorial we will be using welds and a motor to make a working windmill:
First, insert a new part for the pole of the windmill. Use the Scale tool to make it narrow and tall.
Next, insert a part which we will use as the shaft of the windmill. It should be a small, almost square, box. Eventually it will need to be moved next to the top of the pole, but for now use the Move tool to keep it suspended in midair.
Click on the Surface tool and select Motor. Then click on one of the sides of the shaft. You will see a small axle sticking out the side of the part. This motor will be what turns the windmill.
Move the part next to the pole so that the axle of the motor goes into the pole.
Click on the Surface tool again and this time select Add Weld. Then, click on the four outer sides of the shaft; These welds will be used to hold the vanes in place.
Insert a new part and use the Scale tool to make it long and thin; This will be one of the windmill's vanes. Move it so it is on top of the shaft.
Copy and paste the vane, then move the copy underneath the shaft.
Copy and paste one of the vanes again. Use the Rotate tool to put it on its side, then use the Move tool to move it to the side of the shaft. Repeat this process for the other side.
If you press Play or Run, the windmill will now rotate like this: