Press-Fit Piston Air Engine

Print Settings: (Across all parts, specifics per part in stl description)

.1mm layer height

4 perimeters 

15% infill (50% NEEDED for crankshaft, ran out of space in notes)

supports ONLY on bottom faces of crankshaft 

Assembly: (for V1 version, no VCT)

Push the closed end of the connecting rod into the gap on the underside of the piston; line up the hole in the piston with the hole in the connecting rod.

Drop the wrist pin into the hole thru the piston, circular side first. Make sure the point on the rear side of the wrist pin is aligned with the point in the hole thru the piston. Ensure that the connecting rod can swing freely on the wrist pin while holding it up by the piston.

If necessary, sand the top flat face of the end of the connecting rod and/or the insides of the gap in the piston to ensure there is not excessive friction.

Once the rod can swing freely below the piston, push the the wrist pin back out of the piston (it should fall out easily with the points aligned, if not, leave it!), and then reinsert the wrist pin, again circular side first, but this time do NOT align the points, you want the pin to stick. Use the corner of the block to push the pin in from the pointed side; make sure it does not stick out at all past the piston edge.

Sand the seams on the piston and cylinder wall at minimum, entire cylinder wall recommended.

Clip the crank holders onto the outside journals of the crankshaft; there is an angular cutout in each holder, make sure they both face in. Ensure they spin freely, you may have to sand the seam on the crankshaft.

Clip the connecting rod and piston on the center journal of the crankshaft; again ensure it spins freely and sand seams down as needed.

Push the flat end of the valve up into the slot on the block, it should not be able to get suck at the top; if needed, lightly sand the flat top edge of the valve and round out the corners and edges on the valve or very lightly file the inside of the valve slot on each face.

Set the block on a flat surface with the cylinder facing up. Drop the valve flat end down into its slot. Take the crank/piston/holders assembly and guide the piston into the cylinder first with the cam aligned above the valve slot and then start to align the pins on the crank holders with the slots on the block. Make sure you press down on the holders, NOT on the crankshaft when pressing the assembly into the bottom of the block; it will take a decent force to get in but should not need a hammer.

Done! Hold the motor right side up, blow through the small air hole in the top of the block, and quickly spin the flywheel clockwise* to start the motor! (*when viewed from flywheel face, rotation marked on face by arrow)

Notes: 

ONLY print ONE crankshaft option (labeled A and B, which are 1 and 2 parts, respectively). Only print option B if you plan to design your own cam lobe; there's not much room at all to adjust the timing and the motor still run.

sanding down the seams on the cylinder wall and the piston with a fine grit paper is recommended, the top of the valve may need to be sanded to slide freely, and it may not hurt to run a thin file up the channel the valve sits in to prevent a stuck valve.

If you print the version 0 motor, I highly recommend replacing the v0 valve with the v1c valve as it is shorter and allows the motor to run with your finger holding the valve in place from the top. I would also recommend replacing the v0 crankHolders with the v1 as they require much less force and/or sanding to press into the bottom of the block.