Root's Engine - Model Steam Engine

based on drawings for a working demonstration of a Root's steam engine. I'm not sure exactly how the crank will turn out, but different production methods should be able to be used to reproduce this model once completed.
the models are "drilled" but not tapped.

The OpenSCAD source is included.

sizes from the drawings are:
Cover to Valve cover setscrews, tap #4-40x 0.19" deep TYP x 8
Exhaust ports, tap .25-28 NF x 0.25" deep TYP x 2
Pressure port, tap .25-28 NF x 0.25" deep TYP x 1
Valve Cover to Body set bolts, tap #6-32 x 0.31" TYP x 12
Valve to Valve Shaft grub screw, #4-40 TYP x1

The only component not shown in these STL files is the SPACER.
OD 0.5" x ID 0.32" thickness to suit.
Not yet assembled to verify what size or thickness this should be to complete the model.

Added 20141207
spacer, which is a piece that sits between the valve cover and the valve to provide thrust support on the side of the valve. This will need a slight adjustment to tune to yo