The picture shows the different engines we made, started on the left side by the first one, which was in theory great but in reality useless. The second engine was the first one with two different parts, the pipes were sealed on, but the sealing was not possible, that was the reason for the failure of this engine. The third one would probably work great, but the head part of the engine was to hard and the put put effect could not be reached. And then the final version of the engine which was sealed with epoxy and actually worked.