Stirling Engines are a fun project and I have built three successful versions. The first, the Mk1, was more of a test bed. It was built using aluminium Coke cans and to my surprise, it worked first time. When I built the Mk2 and Mk3 I retained some of the components from the Mk1.
Stirling Engine Mk2:
This engine was made using steel Pepsi cans. These are more difficult to work with, but give much better operation. In order to work this engine needs a 40 degree centigrade temperature difference between the bottom and the top of the bottom can.
Stirling Engine Mk3:
This engine was also built with steel Pepsi cans, but had a cooling jacket made from a tuna can with the bottom cut out.
The cooling jacket seemed to increase the efficiency of the engine, but the thermal difference was still 40degrees centigrade. I measured the thermal difference with a non contact Infra Red thermometer. Once the engine was running properly I measured the temperature of the bottom pressure can, about 1cm up from where the fire box connected to the bottom can. I then measured the temperature just below the bottom of the cooling jacket. Subtracting one from the other gave me the thermal difference of 40 degrees.
There is a definite advantage in using steel Pepsi cans and the engine runs for much longer. The way I connect the bottom pressure can to the diaphragm container is different to that normally used, I use a soft silicone tube about 8mm diameter epoxy resined into the the top of the pressure can. This can be seen in the YouTube videos. I also use small plastic adaptors used to fit 4mm diameter hole wheels onto 2mm shafts. I find this gives more even movement of the shaft.
A good example of plans for a Stirling Engine are shown here: