I once found the impeller from a tiny oil pump that I would play with quite a bit. It was about an inch in diameter. For those of you who no idea what I'm talking about, let me describe it.
The housing:
One steel disc about an inch across and with a thickness of approximately .25 inches. The interior of this disc is machined to form the shape of an 8 sided star with rounded lobes.
The impeller:
Into this disc fits the actual impeller, which is somewhat smaller, yet of the same thickness. The outer surfaces machined to correspond with the mating surfaces on the interior of the impeller housing. However the impeller has 6 sides instead of 8.
This ensures that a rotary cam action is induced when the impeller is spun against the interior walls of the exterior housing. Through the center of the impeller was a shaft journal of approximately 1/8". This journal was also surrounded by 1/8" holes which correspond to the lobes of the star.
Sound stupid to you? It probably is but it was great mindless entertainment for idle time, and a great stress releiver.
Also, anything that can produce an interesting sound, such as a squeaky hinge, or drawer, or what have you.--Unfortunately, a lot of 'found sounds' seems to annoy other people to no end.
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When There's No There to get to, I'm so There!