Although it is possible to print complex shapes in one go there usually is a significant penalty in the print quality.
My solution was to print parts with each orientated for print quality and designed to fit exactly so they can be simply glued together.
The component parts of a 9 cylinder radial based on the P&W Cyclone.
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To complete each cylinder needs 7 parts with 2 for the crankcase that surround the motor.
So 54 parts to arrive at this:
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It is printed in the appropriate colour PLA so no painting is required.
It has a substantial printed tapered motor mount that will be fixed to the firewall.
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All surrounded by a printed cowling.
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And fixed to the front of my Depron Antonov AN2.
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Of course much of the engine detail is hidden (and not even accessible!) but I do have the satisfaction of knowing it is there.
I did wonder if it would be possible to 3D print the parts to make a
working steam engine but of course running on compressed air.
After much trial and error and several smaller prototypes the final result.
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A twin cylinder double acting 'vertical' engine. It uses the same 'multiple parts glued together' principle.
It runs too.