WOW It is starting to get shape! Well done and good looking!
To bad that the thread: four cylinder Heisler was not stored in pdf form, photos are lost.
About the cylinders and the power of steam:
Do you use or imply formulas to calculate the size and stroke, the free swing(the back pressure of "old steam") ect or just copy the real life size and scale it down?
Perhaps i am over complicating.
I don't think it is doable to buy for every project different sized reamers.
What is your tolerance between the piston and cylinder walls?
And why dont you use ?gasket/gaschecks? around your pistons
It seems to me also that you have a solid "recipe" for the cylinder and valve sizes.
Your valve, the steam regulator on top of the cylinder is also a very tight fit, or you have a blade spring mounted on top of it?
Probably you wrote a thread on it, i did not have a lot of time lately to read all of your fine threads.
A bold question:
Do you have by chance of this built some pictures of the "fresh steam supply/connection" to the cylinders?
I fully understand the technical working principle of real live steam engines, per part and the whole machine, but i must work on my technical English for this subject, all my study books are in my native language sorry i hope you understand what i am trying to translate

Scale models are a bit different than there real life working counterparts

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Thanks in advance, Best Igor