I don't have a double cylinder engine yet.
I'd like to get one (boiler optional) and ideally double expanding. Anybody makes those reasonably priced? My preference is non oscillating but oscillating will do
As for simple twin cylinder engines in my price range, I see PM Research's twin cylinder kit (is this reversible?), Jensen 55, or Wilesco twin cylinder marine engine.
I've been doing a lot of reading about steam engines. The more advanced ones double or triple expanding.
The Märklin 16051 is a double expansion. From what I've read typically (at least 1 example), the high pressure HP cylinder has a diameter of 3 and the low pressure LP cylinder has 5. Which corresponds to a low pressure cylinder with 3 times volume.
However, the Wikipedia article states: In non-condensing engines, the HP:LP volume ratio is usually 1:2¼.
But one can assemble expansion engines with same size cylinders, I've read somewhere that some just dumped the steam from the first HP into 2 LP cylinders. Which backs the ratio from Wikipedia. (So just use 3 Mamod cylinders?)
If the cylinders are 180 degrees out of phase (Woolfe compounding), then the plumping is simple.
But for self starting, one needs 90 degrees phasing with buffers called receivers.
http://ecoursesonline.iasri.res.in/mod/page/view.php?id=2450In order to reduce this pressure variation, the receiver is made at least 1.5 times the H.P. cylinder volume.