702. Cylinder hone









703. The puzzle is to remove the dowel from the cube without touching either piece. The answer is to blow sharply across the top of the cube, which will cause the dowel to jump out. This is a good demonstration of Bernoulli's principle. I was skeptical that this would work until I did it myself, the dowel can actually be made to jump a full 6" out of the cube. A video of a similar puzzle being solved can be seen here.

Update: Though the Grand Illusions web site states that Bernoulli's principle causes the dowel to jump out of the cube, it most likely works with the aid of the Coanda effect by the deflection of air down the side of the dowel, based on the weight of the dowel and the fact that blowing slightly down works much better than blowing air directly from the side.








704. Paint brush spinner, used to spin brushes dry when cleaning them, the clamps both spin together.









705. Rope bed key, used to tighten the ropes.






706. Roof turbine vent












707. Longford knife sharpener























Last week's set is seen below, click here to view the full post: