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I 3D printed a V4 compressed air engine of my own design that runs on breath power (1" bore x a little over 1" stroke to give you a sense of scale). It runs fine but I've noticed I'm losing a lot of air to blow-by around the pistons into the crankcase area. Currently the crankcase is just open - imagine an engine without an oil pan. How can I reuse this air?
I tried rings but they just added way too much friction and the engine wouldn't run. I've thought about maybe adding an "oilpan" with a fitting that connects it to the intake air, so as to reuse it. But then the air pressure in the crankcase would be equal to that in the intake and the pistons wouldn't move.
Maybe I could use it to drive a turbocharger? I wouldn't think the air pressure would be enough to generate any appreciable pressure out of the impeller though. Blow on your hand as hard as you can. About half of that is what I feel blowing past the pistons at mid-RPM.
What if I made my piston tops concave? Would I at least get more efficiency with the same idea as a hemi head?
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Here's a simplified drawing of what I have. It's actually 4 cylinders in a V configuration with 180° crank angles, but you get the idea.
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What if I did something similar to a carburetor, minus the venturi?
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>>1072117
better tolerances, polished surfaces, maybe make the rings out of some other plastic with less friction.
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If you seal or restrict the crankcase pressure in any way, the input will require more pressure to overcome the backpressure.
>>1072195
>better tolerances, polished surfaces
THIS
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>>1072195
>better tolerances, polished surfaces
and a drop of light oil
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>>1072221
Gun lube is working well for oil. I can't think of any way to polish the plastic. Currently file-fitting everything works well enough. The main problem seems to be that the layers of opposing surfaces try to interlock, even after filing them flat.
Could I rub them with wax to fill the small gaps? Or would the wax just rub out?
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>>1072226
work through sandpaper grits, then felt wheel on a rotary tool with some polishing compound
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Could you add a water trap like hookahs? Water would lubricate rhe piston and it would filter the air back into rhe system
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>>1072226
you will have to print them over sized and with more perimeter layers
if you use ABS you can smooth them with acteone and that will make a super smooth slick surface as well as remove any ribbing on the part
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>>1072117
Teflon tape along the piston until the friction gets too big and the amount of air too small
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>>1072117
How the fuck would a turbo help a compressed air engine?
How would you build it anyway if your tolerance is so poor making a piston fit a bore I think you should stay clear of impellers
Thread posts: 13
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Thread images: 3