I've been working on this model for a long time. My wife was ill and there were a couple of years that I never touched it, and once you get out of the 'habit', it is difficult sometimes to get back in the harness again.
One thing that is a bit different about the Mery ... although it has one cylinder, the piston rides in the middle with an explosion chamber on each end of the cylinder, so it fires at both ends. The influence of steam engines during those years can readily be seen in the design of this engine.