I've loaded a few of my Sketchup drawings for a model steam engine here.

 Any of the photos will expand if clicked.

 I'm currently making drawings for a model stationary vertical steam engine. Bore and stroke .75 inches. I've got the  steam chest, slide valve, eccentrics, linkages and a lot of other bits yet to go. All the dotted lines are  guide lines that help to keep things aligned while they're being moved around and assembled. These lines will be removed later.

Here's the crank assembly, seen also in the previous photo.

The connecting rod was for some reason exceedingly difficult (for me anyway) to draw. I'm hoping that it won't be as difficult to build. This is actually an assembly drawing of one connecting rod and two rod bearings.

Here's another photo of the cylinder, this time (finally) drilled with steam ports.

The assembly drawing has been updated with the drilled cylinder and a new valve eccentric, and it's eccentric follower. All that's left to finish is the slide valve and the valve linkages. They're about half completed now. Getting the valve geometry right has been a challenge.

All of the engine parts have been drawn here and added to the assembly. The valve components were the last bits to be added. Note there is now also a flywheel. Sketchup does a great job of sticking components or parts together magically. In the real world fasteners are required, and I have work to do figuring out what size to use, where they will go, and what size holes to drill and tap. Oh, all those guide lines have now been removed, and the internal components are now easier to see.

Here's the last image, showing the assembly with holes drilled for the required fasteners.