Diaphragm Air Engine

this engine is powered purely by pressurized air which sounds awesome but in reality it's just a well-timed valve that synchronizes a burst of air with a piston moving up and down just look at that performance because the piston and cylinder are just plastic parts rubbing against one another the engine is far from being airtight it's like trying to inflate a punctured tire it's going nowhere but i think i have a solution this video is sponsored by kiwiko more about them later a diaphragm is a disc of flexible material that is fixed around its outer edge but is free to flex back and forth almost like a trampoline but with an airtight seal this means we can make a diaphragm move by changing the pressure on either side and i'm thinking this can be used to drive a piston inside of an engine this would remove the issue of a non-airtight engine as the diaphragm will contain all of the air but this also presents another issue we need to somehow control the air pressure above the diaphragm perfectly in sync with the piston without breaking the air tight seal of the cylinder head so between the air supply and the diaphragm we need to design an inlet and exhaust valve that operates with low friction and are 100 airtight one idea i have for exhausting the gas is to make a small hole in the diaphragm which will be sealed shut by the piston then if we adjust the piston travel to be slightly further than the stretch of the diaphragm it will separate from the diaphragm and break the seal this hole also allows for access to the cylinder head which can be used to operate an inlet valve the only engine i've designed in the past with an airtight inlet valve was my very first version because it didn't use any camon pushrod valves like my later versions instead it used a spring on top of the piston which would operate a ball valve in the cylinder head keeping the ball valve closed as the piston traveled up and open whilst the piston traveled down and this was the same design as the original air hogs planes air hogs speak to the revolutionary red engine so air hogs need no gas no batteries just pump it up and of course i had to build a plane myself the only issue with this engine was the spring as they would often bend or break resulting in reliability issues there it goes here it goes come on which i really want to avoid with this new engine so here is my new concept to start the engine the output shaft on the right must be turned by hand which through the gearbox moves the piston to the left the gearbox isn't necessary but allows for speed or torque adjustments if needed the piston then seals against the diaphragm as well as this brass tube sealing with this first o-ring this is part of the inlet valve process which works similar to a two-step airlock door where only one door can open at a time so after the brass tube closes the right-hand valve the thinner pin opens the ball valve which is holding back the high pressure air supply the air then fills this volume inside of the cylinder head but is prevented from pressurizing the diaphragm by the right hand valve then as the piston travels back towards the gearbox the ball valve closes and the valve to the diaphragm opens allowing the stored high pressure air to enter the cylinder this pushes the diaphragm against the piston which accelerates it towards the gearbox then when the diaphragm can't stretch any further it separates from the piston and vents the remaining air through the center hole which then flows through channels around the piston and out through holes in the gearbox this is still a concept as i haven't seen a valve design quite like this before but if it works it will make many sleepless nights worth the effort so let's build a prototype i 3d printed the parts using pla filament supplied from 3d prints uk with a standard 0.4 millimeter nozzle this required the layer lines in the cylinder and piston to be sanded but at least the tolerances don't need to be perfect with the diaphragm design the gearbox was also 3d printed and ran surprisingly smooth considering the small size of the gears brass inserts were made for the connecting rod between the piston and crankshaft to reduce friction and wear on the plastic this could then bolt straight to the large gear and then the main cylinder can be attached which makes for an intriguing mechanism to spin the shaft at one end and see the piston oscillate at the other i then use the drill as a makeshift lathe to smooth the tip of a small brass tube and glued it on top of the piston as well as a thin wire which will both be used to operate the inlet valve working our way up the engine i then cut around the cylinder head to produce a circular diaphragm and use the hole punch to make a four millimeter hole in the center the reason i chose this rubber sheet is because it expands a reasonable amount with just 30 psi of pressure though it can't handle much more but when it's contained inside of the engine cylinder it should be capable of much higher pressures i then installed the o-rings in the cylinder head which will work as the seals for the two-step valve and positioned a ball bearing inside of the top valve which was held in place by a pneumatic fitting that will connect to an air supply i then clamp the diaphragm between the cylinder head and the rest of the engine and we're ready for a test the issue i'm having is finding the correct length for the brass tube and thin wire on top of the piston if the thin wire is too long the ball valve will open early causing air to flow straight through both o-rings and the diaphragm if the wire is too short the ball valve won't open at all if the brass tube is too long the right hand valve will open too late in the engine cycle and the diaphragm won't be pressed against the piston and finally if the brass tube is too short it won't seal the right hand valve and the high pressure air will flow straight into the diaphragm causing the engine to backfire after many many modifications the engine was starting to show some potential so now my new engine design runs but if it's going to outperform my previous engines it needs a large boost in performance fortunately there are a number of things that can be easily changed after three full redesigns i increased the volume in the cylinder head by 300 percent changed to a one-to-one gear ratio and reduced the piston travel by two millimeters this not only reduced the size of the engine but also increased its performance but we all know that noisy engines don't always go faster so i built a test stand to hold the engine which through a lever arm transfers its thrust force into a load cell and we can then measure how much thrust the engine produces [Music] for the air supply i used a two liter bottle pressurized to 0.41 bar or 60 psi so there is always a consistent amount of air for testing the engine's efficiency after running the test three times the measurements can be used to plot a thrust versus time graph which when averaged out gives us an idea for the engine's max thrust as well as its run time with a peak thrust of roughly 0.87 newtons or equivalent to 88 grams it seems reasonable as the engine weighs just 72 grams but how does this compare to my old engine this test was done with the same propeller and pressurized bottle which revealed some surprising results that's right my previous best performing air engine produced nearly a third of the thrust of this new one and if we measure the area under each graph we get the engine's impulse which can be used to compare the efficiency of each engine almost like it's miles per gallon but instead it's thrust time per 2 liter bottle at 60 pounds per square inch which shows the new engine to be 366 percent more efficient due to being fully airtight i also tried the old engine with the smaller propeller it was originally designed for which increased the rpm and run duration but actually performed worse due to less thrust being produced also the reason i kept the gearbox even after switching to a one-to-one ratio is because i can easily design a thread into the cylinder head that allows for mounting straight to a bottle which makes for a perfect way to power a model aircraft this engine probably won't power the future of our world but it's this sort of problem solving that will lead the next generation to work on something that will kiwi co creates super cool hands-on projects designed to expose kids to concepts in science technology engineering art and math and are a great resource for learning at home each monthly crate is very well designed with an easy to follow instruction manual and educational magazine which i personally really like as building something is only half the fun finding out how it works can be just as fun if not more and did i mention they don't require any extra supplies so there's no need to go to the hardware store relevant to my interest in pressurized air engines this specific project produces its own pressure through a chemical reaction which is released in an instant to launch a rocket skyward what better way is there to learn whilst having fun other than kiwi coats crates which are also a great gift option for the holidays so go and check out kiwi co at kiwico.com forward slash tom50 to get 50 off your first month of any crate the link will be down in the description below thank you very much for watching this video if you enjoyed this video it'd be great if you could leave a thumbs up down below and if you're new to my channel and want to see other projects similar to this then please click subscribe down below a massive thanks to all of my supporters over on patreon.com for making these projects possible i honestly couldn't do without your support so thanks once again thanks again for watching and i'll see you in the next video goodbye

Channel: Tom Stanton

Views: 3,318,792

Rating: 4.943152 out of 5

Keywords: engine, air engine, 3D printed, pneumatic, pneumatic engine, compressed air, diaphragm pump, diaphragm, pump

Id: 5B1H5syp4PM

Length: 10min 8sec (608 seconds)

Published: Mon Nov 23 2020

Reddit Comments

[u/nateguy]

Get me 6 muscular dudes and some bike pumps and we'll propel a plane outfitted with this engine with arm power alone!

[u/84thProblem]

It looks like he could gain some efficiency by providing a better exhaust port. It seems that once the piston is separated from the membrane it just goes to pressurize the crankcase, making it sightly harder for the piston to move.

Also, he could lose some mass and drag with that 'piston'. Maybe a thin sheet of polytetrafluoroethylene and/or an open cage rather than the cylinder walls.

Criticisms aside, I enjoy his videos. I don't actually know his background, so maybe he really has more knowledge going into his projects than he lets on, but I really like to watch his trial and error problem solving as he works toward his goals!

[u/alex_sl92]

This guy is going places.

[u/suckbothmydicks]

Did this guy just reinvent the engine?

[u/Hamperstand]

This is how some paint sprayers work.

[u/8-bit-brandon]

I built a steam engine out of a weed eater engine that was pretty close to this design.

[u/Napalm_Oilswims]

I wonder if there is a verson that can recycle the vented air pressure?

[u/TheWhiteRose000]

Now this is some good original content.

[u/1rustySnake]

Very impressive stuff, would be nice to have airflow control so that duration can be extended.