Hero's Engine with a drinks can
After breakage of our official Hero's engine, I decided to try a cheaper version.
First, take one 330 ml drinks can. Over a sink, make two holes in opposite sides with an optical pin (or other long pin/needle). Bend the holes with the pin so the vents are opposing. This rough sketch shows you how to shape them. DO NOT open the can using the ring pull. Other than the two holes, the can must remain a sealed vessel.
When the holes are made, the drink will drain naturally. To aid this, one can shake the can. Beware as this can get messy!
Once most of the can is empty, you need to suspend the can from a clamp stand. I used a rubber band to give friction and then tied a fine and light thread to it. The can will twist, so you need something which will take a lot of twist before it starts to correct itself. It is worth checking the condition of the thread before each use as continued twisting will weaken it, and a spinning can falling ontop of a lit spirit burner could cause a minor fire.
Something like this:
The can should then be immersed in a beaker of water, and tilted to allow water to flow in one side. The amount of water isn't critical - somewhere around 50 ml at a rough guess (perhaps someone could try different amounts and add it to this?) You want enough to boil, and not to allow the can to boil dry too quickly, but not enough to make it prohibitively weighty.
We used a spirit burner to heat the can as we felt this was the safest option. Care should be taken, as this involves naked flames and an essentially pressurised container, so a risk assessment should be carried out prior to use. A safety screen would be advisable. The can should be suspended so that the flame touches the bottom. Several tea lights could also be used.
As the water heats up, the can will begin to steam and the steam will drive the can so it spins.
This is a cheap and cheerful alternative to an expensive and, as we found out, delicate piece of apparatus. It takes minutes to make and is surprisingly effective as a demonstration of energy conversion.
--Beaky 15:23, 21 May 2009 (UTC)
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