Mike i can tell by your answer that you are away ahead of me when it comes to the sums. My real reason for asking the question is i have a few of these small engines lying in boxes doing nothing and i would like to try and make them do something i tried with the Stanley but that`s now on hold until the summer. Looking at Nicks small car i assume the bore is similar to the small twins that i have and if that is the case then it would only run for 3 1/2 mins using the same boiler in the case of the Stanley it took 16mins to burn off 30mls of water using 5mls of meths give or take. My object now is to try an make a platform as small as i can but must be able to run for at least 5min minimum. There are some really nice American cars around the 1906 era.
Regards
RON