Gentlemen,
While I was waiting for aluminum to be delivered I needed something to keep my hands occupied. When the thread about the Huff and Puff steam engine was started by Doc I went to the link to have a look at the original that Phillip Duclos created. I took all the dimensions and as has become my habit I scaled them down to 3/4 of the actual dimensions. That gave a bore and stroke of .1875 x .094. The small hex bolts that hold the front head and the cylinder to the base are M1.0 x .25 and the bolts that connect the rod and valve strap are M.08 x .20 (.032 diameter) The base is .785 long and overall it's 1.25 long.
I built everything to the drawings and it would barely run so I had a look at the valve and changed the timing on it. Doc, you might have a look at it before making yours.
It will run by breath but just barely although I had it well oiled for running on the video.
gbritnell