You totally missed the point in this project. This was intended to be a fit-check of the parts before machining out of metal. Further, it was used as an educational aid to show my son how steam engines work and how they can be reversed. This was never expected to be a practical "Steam" driven engine. The fact that it runs on compressed air doesn't make it less of a "Steam" engine. If you are going to play word games, you can discuss it with the dozens of 3D printed "Steam" engines shown on YouTube. Have you printed a working "Steam" engine? For an "Engineer-In-Training", you should show more respect to those of us that have been doing this for a long time, even though my expertise is as a EE not a ME. As an engineer, I hope you pay closer attention to the details of your projects than this. I would say it's sour grapes, but I think it's just chicken.