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With your coffee cup engines how can you calculate the power output
(W) with only a thermometer

You can't use only a thermometer. In fact you don't even need a thermometer. Rig up a thread and a tiny weight to a pully and set the engine up so it raises a weight. Measure the time it takes to raise the weight. Look up the exact formula for measuring power this way in a physics book (I forgot it at the moment) make sure your units are correct and you'll get an accurate power output.

Brent Van Arsdell

Using Brent's extremely simple and correct method:

w = d * m * 9.81 / t

where d = distance, expressed in metres that the weight was lifted; m = mass of the weight, expressed in kilogram; t = time it took to lift the weight, expressed in seconds; 9.81 = gravity constant, m/sec2

result w = result in Watt aka Joule/sec

I supposed that d is much smaller then the earth radius to simplify the formula

# dirk