3d Printed Double Acting Engine

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a41capt

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I recently completed a 3d printed double acting steam engine with my Creality printer. Other than a couple issues with tolerances (probably due to using mixed filament types, PETG and PLA+), I believe it turned out very well. Credit to the designer palexander609 distributed for free on Thingiverse (SINGLE CYLINDER WORKING DOUBLE ACTING STEAM ENGINE by PALEXANDER609) for a really good design!

I haven’t shot any video of it running yet, it does run on the pressure of me blowing into the intake port, but as soon as I can get a smaller source of compressed air I will update the thread. Anybody have an idea for an appropriate aquarium air pump? Humans are only capable of exerting 1.5 to 2.5 PSI from their lungs, so an aquarium air pump might provide enough pressure, but I’m unsure about volume. I could use some enlightenment from the learned members regarding how to run an “air” engine relatively quietly.

Thanks in advance,
John W
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a41capt

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That is a great looking engine !!

.
Thanks! It runs great too, but I haven’t plumbed it so I can get a video. Currently it takes two hands to get air to it and hold it. All REAL credit belongs to the original poster, palexander609 for his design on Thingiverse.:)

This is a relatively new venture for me, I’ve been working on CAD putting together files to build Elmer’s Geared Engine. I’m no CAD guy so it’s slow going!

I’ll get a video of this engine to share as soon as I get it on air.

John W
 

rleete

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I've tried an aquarium air pump, and it didn't put out enough volume to run my rocking piston engine. I can run that engine on breath power easily.

A larger pump may work better, but I used what I had on hand.
 

a41capt

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I've tried an aquarium air pump, and it didn't put out enough volume to run my rocking piston engine. I can run that engine on breath power easily.

A larger pump may work better, but I used what I had on hand.
Thanks, perhaps I’ll find some info on a pump that’s big enough to do the job, quiet enough to keep from overshadowing the engine itself, but still small enough to put in the base under the engine when on display.

Time to keep looking!

John W
 

DrMike

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Maybe a bicycle tire pump or a foot pump made to blow up pool toys?
Won't run for a long time per stroke but you'll be able to adjust flow and pressure.

With a bit of valve trickery you could pump up a bicycle inner tube and then switch it over to run the engine until the inner tube is exhausted. Exactly how long will of course depend on the displacement of the engine.
 
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Rich N

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You might be able to use an airbrush compressor. See them cheap online and at Harbor Fr...
 

a41capt

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You might be able to use an airbrush compressor. See them cheap online and at Harbor Fr...
I gave one to my son awhile back, but it’s very noisy. The aquarium pumps are generally less than 40dB, and while still noisy, they’re easier to muffle.

Thanks for the thought though!
JohnW
 
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John W: just about any compressor that will inflate a car tyre will run a small engine like this - maybe slowly, but that's the best way to see the motion of piston versus valve gear. I have a fridge compressor - salvaged back in the 1970s! and that runs my steam engines up to 1" bore and stroke. - But slowly. When "new" it would make 90psi... But now (well worn in a non-standard environment - my garage which has air not dry CFC for pumping - the compressor makes 30psi on a good day. But the displacement is everything. A fish-tank compressor would need to be huge to match the volume of air you will use, at (say) 300rpm.
But even if you only have a foot pump for car tyres, you can inflate the spare, and make a valve so you can bleed off the air from the tyre for maybe 5 or 10 minutes running of your engine? - Or use a large Lemonade bottle inflated to maybe 10 psi, and that may give you a minute of running? - I fitted a car tyre valve into the screw cap of a 3l plastic bottle had that was my temporary air receiver when I first started using my fridge compressor for running engines at around 10psi. (Now I use a steel ex. gas cylinder).
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A cautionary note for anyone using compressed air (or other gas) without knowing the dangers...
A "common" idea is to test the pressure by putting a finger on the end of a nozzle to "feel" the pressure. Health and Safety advised (at work) that it is possible (I.E. it has happened!) for the compressed air to blow through the skin into a blood vessel, forming a bubble in the blood stream that can cause a heart-attack when it reaches the heart....
So Do NOT try and feel the pressure, just to be safe.
Also, any blown dust or swarf can easily puncture the eye ball and lodge inside the eye, possibly leading to blindness. So please use a brush instead of blowing stuff away.
K2
 

a41capt

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How about an old, small fridge/freezer compressor, the ‘canister‘ type? Virtually silent when running. You could control the output by using a ‘bleed’ valve to adjust engine speed?
Doug.
That’s a good idea Doug. I’ll have to cruise the local junk yard and see what’s lying around!

John W
 

a41capt

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John W: just about any compressor that will inflate a car tyre will run a small engine like this - maybe slowly, but that's the best way to see the motion of piston versus valve gear. I have a fridge compressor - salvaged back in the 1970s! and that runs my steam engines up to 1" bore and stroke. - But slowly. When "new" it would make 90psi... But now (well worn in a non-standard environment - my garage which has air not dry CFC for pumping - the compressor makes 30psi on a good day. But the displacement is everything. A fish-tank compressor would need to be huge to match the volume of air you will use, at (say) 300rpm.
But even if you only have a foot pump for car tyres, you can inflate the spare, and make a valve so you can bleed off the air from the tyre for maybe 5 or 10 minutes running of your engine? - Or use a large Lemonade bottle inflated to maybe 10 psi, and that may give you a minute of running? - I fitted a car tyre valve into the screw cap of a 3l plastic bottle had that was my temporary air receiver when I first started using my fridge compressor for running engines at around 10psi. (Now I use a steel ex. gas cylinder).
K2
I will look at the local Harbor Freight store for one of the large capacity air tanks commonly used to inflate car tires. I believe their pressure rating will be high enough, and with that volume and a small regulator left over from my cabinet shop days, I should be able to get quite a long run at 200-300 RPM.

Thanks!
John W
 
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That’s a good idea Doug. I’ll have to cruise the local junk yard and see what’s lying around!

John W
The cases also contain a lubricant which gets pumped around the system with the refrigerant, (To lubricate the pump). When you open up the system you will, over time, lose this, and will need to ‘Top’ up with a suitable oil. You can use a moisture separator/filter to catch this, but running a steam engine on air, it could well be beneficial to have a bit of extra cylinder lube!
 

Scott_M

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Hi John
Could you possibly measure something for me ? What is the largest part?
I have a rather small printer. 150mm square or 6" square envelope.
Will it fit on my printer?

Thanks in advance!! Looks like a fun print, I would like to try it.

I remember seeing a foot operated bicycle pump that was rather large. 4-5" bore with a similar stroke. A big pedal to stand on to pump. You could hook that up to your tank. And then put the foot pump in front of the table at shows :) Make the kids pump it up. I'll see if I can find a picture of one.

Scott
 

kiwi2

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Hi John,
Do you have a garden sprayer of the type with an air pump on the top which pressurizes the liquid. If so, you can use it to run your engine. The easiest way is to run the sprayer empty a few times to ensure only dry air is coming out the tip, then connect the tip to your engine using silicone tubing. The tubing is available from car parts shops in various diameters as petrol lines. Doing it this way means you can use the valve on the sprayer to turn the air on and off and throttle it to a certain extent. I have modified an old one to run some of my engines.
Regards,
Alan
 

DrMike

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I have some experience with 3D printed cylinders and pistons. The models are nice, but running them presents two problems - wear and heat.

If the pistons and cylinder are left as-printed, they are anything but smooth, even in the best, most finely tuned printers. Running the model in this condition will very quickly wear the piston/cylinder to the point where they won't hold air at any pressure. Even operating the the model by hand will put it into this condition fairly quickly.

It will help some to smooth (drill, turn, ream, bore, hone, depending on the quality of the model) the cylinder, and to a lesser extent the piston, and to plan for a lubricated O-ring piston ring or two to get the longest useful life out of the model. At this point the model isn't entirely 3D printed, rather enhanced after printing, but is certainly a better model. If you are going to this trouble, enhancing the rotating joints with metal pins is also a good idea.

If the model is run fast (more than say 10 rpm) for too long (more than say 10 seconds at a time) the friction will cause the cylinder/piston plastic will melt and seize together, ruining the model. Remember that you are dealing with plastics that are designed to melt at very low temperatures (relatively speaking). It doesn't take long to build up this heat with friction.

I have successfully "run" models that are entirely 3D printed for a few seconds at a time, at very low speeds, using bicycle or foot pumps, and only to illustrate how they work. Even at low speeds, an entirely 3D printed model has a total useful run time of maybe 10-20 minutes.
 

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