References for Building Blocks

Here are some of the missing references for the last post.

1) Nifty materials that are solid if you move fast, but liquid if you move slowly:
Some of this used to be sold under the name "Silly Putty" in the US. If seemed to have the consistency of chewing gum, but if you hit it with a hammer it shattered instead of slashing, then all the chunks sort of melted in place and became gooey again.

Here's a link to a marvelous YouTube video of some young people with a huge hot-tub sized vat of such a substance, demonstrating that you can run across the top if it if you move fast, but you'll sink into it if you stop moving. The YouTube description says:

They filled a pool with a mix of cornstarch and water made on a concrete mixer truck. It becomes a non-newtonian fluid. When stress is applied to the liquid it exhibits properties of a solid.

Wikipedia: http://en.wikipedia.org/wiki/Non_Newtonian Fluid

2) Stirling Engines

Again, Wikipedia has a very nice article on "Stirling Engines", along with a fully animated
diagram. One of the figures is shown here. There are two cylinders, one touching something that's hot and one touching something cold. Each cylinder has a piston, connected to a common flywheel. The connections make the two pistons move out of phase, so they are not both fully down at the same time. The connected cylinders are filled some gas, which could be just air.

The engine converts that temperature difference into a rotational motion of the flywheel. There are no other key parts required, no spark-plugs or valves.

If you go to Google Images, you can see many photographs of actually constructed Stirling engines. Another nice animation from MIT is here with a slightly different design.