Was about to make the same suggestion. There are lots of videos where people blow up bottles like that with just a little dry ice. You would think that that could run the engine for a fair amount of time.
I wonder if the cold gases would make the PLA brittle. I know its not liquid nitrogen cold, but I wouldn't rule out things like the piston con rod cracking. Even if there is a relief valve though, you should still probably hide your balls behind some plywood lol. With that said, this could totally work.
Biggest issue would be to control the rate at which the dry ice is "melting", as too fast and it will pop the bottle. Also as has been said before, Dry ice is not easy to come by in the UK. Other solutions could be possible though that produce gasses in the more controllable manner.
This version looks really efficient, based on how little pressure it runs at. With that huge propeller, I don't see why you couldn't get the plane to fly. It looked like it produced a lot of thrust and ran for a ridiculous amount of time. It sounds pretty amazing too.
Can you push one of those engines to its max? like increase pressure until it breaks (in a safe way) maybe using the bike pump while running method while standing behind something?
I'd like to see a fail test, hook it up to an air compressor and see how much rpm it can hold up to until it fails. Might wanna swap the prop to a simple flywheel though :D
Fistly - Were you never tempted to try running it from a Co2 bulb such as you get for soda syphons? Tiny size, high pressure - which I'd guess would need to be regulated down via a choke constriction to the pressures your plastic components can survive for more than several runs before failure? Secondly - with a hobby lathe you could machine up some aluminium components, get more rpms etc etc, more time in the air, better performance from greater pressure, improved aerodynamics from not having a blimp of an air bottle that's got to be strangling the aircraft's progress through the atmosphere? Thirdly - I'm surprised at the sluggish pick-up when nearly stalling and give a shot of air, the cylinder charging must be inefficient at those low pressure. Fourthly - very entertaining watch, this.Thankyou for posting all these videos.
Ian Gourlay I don’t think he would machine parts as the point of the engine is to make a 3d printed engine with the least amount of non-printed parts but cool idea anyways
Ian Gourlay He’s not out to reinvent the expansion engine. First would be a bored cylinder and turned piston. Which he should do even with printed components. All he has done is print and sand. It’s a hand-on learning exercise.
Nice build Tom! I couldn't resist and made a couple of replacement parts for a 5cylinder radial engine and I am actually printing the parts at the moment. I can send you the design files if you are interested! The design is mostly copied from your files apart from: Crank case, crank shaft, Piston (minor tweak) and piston rods. They are designed to be compatible with the other motor parts.
Have you put any thought into what you're going to use for the compressed gas source for the car? Without the weight restriction of the plane I'm thinking you could get very creative. If you changed to PVC pipe fittings and placed your pneumatic press fit into a 2" cap, you could make a nice chamber to fill with dry ice (just make sure you include an over-pressure vent). Or what about a peroxide and potassium permanganate, or baking soda and vinegar? Lots of really interesting combinations you could add to a chamber like that. Watching you sand away the piston also got me thinking - why not flange the top and bottom of the cylinder so you don't have to sand the whole face? It will decrease the bearing surface too so you'd get less piston friction as well as being much easier to size to the bore. I'd print oversize and use the time saved in sanding a whole piston face to make sure the bore fit was very close running.
the best solution would be a small pressure tank with a regulator to drop the pressure for the engine. the engine uses air too quickly for something like dry ice or any other chemical reaction.
Like other comments have said: These videos are such a treat.Your in-depth knowledge lets you explain everything in simple terms, which makes watching you making progress very engaging, because we actually understand what's going on. It's super nice, and your passion and fascination for the project becomes very contagious :) Keep it up!
to make the soft drinks bottles hold up to 120psi you can wrap them with duct tape for more rigidity, I have personally got my bottle to hold around 100psi for my diy tubeless tire set up
The problem is that they'll take like 150psi at least, but only once. Plastic like this fatigues over time, so if you continuously use a high pressure it will eventually fail catastrophically. The bottles are designed for a maximum of 100psi (which is a full, shaken bottle, in a hot car), so I'm not sure why he doesn't just use 100psi constantly and swap the bottle out after a dozen or so pumps (isn't like they're expensive). The duct tape would contain the shrapnel if it exploded at 150psi, but being that this is for an aircraft, the weight would be a pretty big downside.
You and everyone in the comments are so smart. This makes these videos so interesting and entertaining to watch. If I've a question pop-up, most of it is already answered, or questioned for that matter, in the comments. Keep it up Tom and the community!
Look at the Bumble Bee gas engine.0.049 The throttle is controlled by opening and closing the exhaust port. Thanks for the quality family entertainment.
Petras L You got me curious too. It was so he could have the connecting rod off-center in the piston; so he could reduce the overall length of the engine, and eliminate one of the bearings. th-cam.com/video/FoQUwpfFnnE/w-d-xo.html at 3:40.
Yep, its true also, but if i noticed properly, now rod right in the middle. And by having square piston, it should be very hard to make precise corners, like Tom mentioned, the same radius/shape to avoid air leakage there. By having round piston it should be possible to mount it, lets say, on the drill and grind it like with lathe. But lets see where "natural selection" will bring Tom's motor ;) Good luck! Its really interesting to follow this series!
I think round piston would be better, too. A circle has better perimeter to area ratio (around 3,5) than a square (4). That means, when you use a round cylinder, there should be less space for air leaks. Edit: these numbers are only for 1 cm2 pistons, but I think you get my point.
Round would have less leakage and less friction. Seems like the difficulty of manufacture is a no-brainer here, the engine would just run better once it was dialed in.
@@owenps6944 Not with common FDM 3d printers like most budget and mid-range printers from folks like Creality. Now, RESIN-based 3d printers especially those at folks like Shapeways is another story!
You should try and go up in bore, this should help you get less friction vs force that the piston exerts on the crank, because friction rises linearly with bore, but the force rises quadraticaly. I'd go for a slightly oversquare engine (~1.2 bore:stroke). Maybe have the crankcase split into 2 parts horizontaly (like a gas engine splits the bearings in two) and try a 2 main bearing version? BTW what is your rod to stroke ratio in the engine, you should aim for 1.75 (connecting rod 1.75 times longer than stroke), it's the optimum ratio.
RedKugelblitz The cylinder head has a lot of stress when the engine runs, and it turns really rough to the piston, and forces it down fast and it slowly decreases speed per revolution. On a opposed piston engine the energy is all used, because the cylinder head isn't dispersing any energy. Also, leaks wouldn't be a problem, since you would still produce twice the Torque in the output shaft (two crankshafts). You can also gear it and make the output shaft rotate twice as much faster by using a smaller gear on the output shaft. Also, the torque curve ( change of speed of the piston per revolution , since the the energy is being displaced softly and constant, because there isn't any over pressure on the intake) is smoother, making the engine run better. And you can also use a rotary valve. The leaks could be a problem. You could come with an increase of about +30% on an internal combustion engine (without the losses by the leaks, 30% has the friction "included"), that with the leaks would be 20-25%. If this air engine had 5-6% efficiency, this design could get it up to 10%, or even more. I'm a ic engine designer, you can trust. I'm basing on the two stroke Diesel opposed piston engine, if you were wondering.
RedKugelblitz You don't need any gearbox if you connect the output shaft With gears, as it is supposed to. And it doesn't have much more moving parts, so doesn't have much more friction. What I have said is that the cylinder head suffers from a lot of stress, and there is a lot of pressure there before expansion, so the pressurized airflow is reduced after the start of the expansion, since you can't get as much air, and the power curve is unbalanced and rough. The advantage in this design is that it can still run with the ball system, but is really hard to do that, but rotary valves are pretty good and much more efficient in this design, and believe me, with proper lubrication, that engine will run for a long time.
RedKugelblitz I don't have any of the opposed cylinder engine Design, but I do have one of the normal one . Also, if you search for " Lego opposed piston vacuum engine" you can see some videos of a similar design of mine. I couldn't record it, because camera seems to be epileptic and everything comes black, so I could only record the single piston. My design of the opposed piston is much faster than on those videos on TH-cam, and has high torque. Unfortunately I don't have it anymore, my little brother destroys everything!
It would be cool to implement a throttle body with just a simple butterfly valve, or a ball valve. This works off the theory of, just because my car's gas tank is full, doesn't mean I run it all out immediately. You could control rpm, make the air last longer, and not have to worry about the psi, you're putting through it as you can control how much air gets to the engine, not via a bike pump and a water bottle. This would be very easy to add, and wouldn't take more than $5 and 5 minutes.
Por que no los dos? regulator and valve. The membrane valve he built worked for demonstration, but would be almost useless in any actual use case. You can hook a servo to a ball valve.
Go to a shop with a large air compressor and a pressure valve and hook it up and do an endurance test! Maybe find a way to continuously oil it? Oil drip? Super cool man!
clavo Yeah! I'm super curious to what the lifespan is on something like this. I'm guessing it it'll run for several hours BUT become very inefficient. I think the plastic piston and cylinder would start to wear down and air would start to go around it. Maybe he needs to figure out how to make piston rings.
Parker - I've been reading comments for about 3 hrs now! One guy suggested a dry lube like graphite. It makes good sense. I gotta get some sleep but this level of thinking is so dang fun!
tom, this video is mostly for the 0.01 percent of people that will actually attempt to make this engine, most of us are here kinda for the engineering of this beautiful air engine, or simply show the build part of the engine at the end
The insides of the cylinder still look a bit rough and uneven. I'd imagine you want to get it as perfect as possible to minimize friction and get a better seal. Have you thought about splitting the cylinder into 4 parts so the inside surfaces can be printed laying flat on a perfectly smooth printing surface? Or 2 corner shaped parts that can be easier and more accurately be sanded flat and then gluing the cylinder pieces together?
I reckon access to desktop injection moulder would assist in the speeding up of these projects, slicing down time to the bare minimum and allow you to put out a boat load of more work and ideas. Maybe there is a generous engineering/moulding company out there willing to help even if they offered the loan or gift a machine as part of a maker space donation it would help projects like this no end. Where are you generous desktop moulder manufacturers and can you help!? Another great vid, Tom. Always enjoy your work.
Maybe Ryanair will install those engines in they planes, to cut the costs. Then every passenger will get his own pump. And there will be new motto "Pump harder, fly faster".
Hey Tom, hopefully you read this comment because I have an interesting idea. I suggest you put a fair amount of dry ice in the bottle and see how long the propeller will spin for. If not enough pressure is available at any given time, crush up the ice to increase its surface area in order to increase the rate of evaporation.
Just fantastic work, man. Something I was thinking about... There are dc motors air pumps... I don't know if any of them is strong enough, but... It may worth looking at. 😊
Possible, one could keep air pumping into it continuously... but like the person above said, yes, inefficient. You might as well power it by a battery motor instead of an air engine at that point.
Good, back to basics on the build, looking very good. If you found a smaller diameter aluminum cylinder in the area of 40-50 mm diameter and say 300-400mm long, you could run the pressure up to 120 psi or higher and place a regulator set at 60 psi and the engine would run at air speed for much longer. In your tests before, at 60 psi the plane wanted to fly with the larger propeller, but the pressure died off so quickly it couldn't make it. This design is the best, IMO. The next step is to add 2 cylinders in order to get more torque, but then you would use twice the air volume...
Tony - There is a comment on here that suggests wrapping the plastic soda bottle with duct tape to get 120 in that bottle! I'm thinking the new Gorilla Tape would even allow higher PSI. I liked your comment.
clavo Thanks! My idea about the small diameter aluminum tube would give less air drag. I think the tape would allow more pressure in the bottle, but you stil have all that large diameter surface as drag.
Tony: absolutely right about the drag. I like your tube design in that aspect but balancing, costs and tooling intelligence needed; I wonder of a 2" pvc plumbing pipe would work?
clavo Yes the PVC would work at 120 psi and is a great idea. The limitations on PVC is right at 120 psi for schedule 40. It should work fine though for this application. I am not sure about the weight comparisons from PVC to a thin wall aluminum tube though, I would think the aluminum would be a tiny bit lighter in weight. The other side is as you say, fitting the aluminum would require special tooling and abilities. I like the PVC idea a lot. I should mention that the limitations on the pressure of PVC is the joints, not the tube wall. Having worked with PVC in compressed air systems shows that the failure is typically in the joints and where the failure is in the tube, other factors exists such as cantilever or external forces cutting the tube.
Tony - Just for grins; What would you think of Tom making a air compressor; almost identical to the motor, that would run off his bicycle back tire the way old mini electric generators did years ago? He could set the back axle on a stand to let the rear wheel freewheel as he pedaled to run the compressor. Again he could use PVC pipe (3") for a storage tank.
A great feeling when it starts to come together. When do you get to sleep? Have been thinking of a double length (in the shape of a U) rubber powered glider driven through a gear box of some kind to extend duration and be could be braked in some manner to give multi starts while in the air. It pays to keep the old brain working eh! Thanks once more.
TALK TO AvE!!!! He does fluid mechanics for a living and I'm sure he will be able to help you. AvE literally just did a video creating an air pump with an old hydraulic pump that was greased up. I'm serious dude, get in contact with him and he will tell you tons of things that would take you weeks to figure out on your own and all the things he says are funny anyways.
i wonder if a classical pneumatic motor would be more effective? or maybe a turbine style engine? would be much easier to build and propably much less internal power loss due to friction
That's a very good question. Why were some heavy lift winches in old welding shops piston type pneumatic motors? Higher torque at low pressure, I think.
i recon that those classical air fin models rely heavily on a combination of flow rate and pressure, where a piston engine only relys on pressure to build up torque, but it would be really interessting to see a direct comparaison between the two, maybe tom does it :)
Harold S. - Yes. The low rpm torque is better in a piston engine; but, in industry, most application use high rpm and the vane motors are more efficient and most common. If you see an industrial piston air motor, it is in an antique shop!
I wonder if you could fill the bottle half way with coke/diet coke and drop a few Mentos in, seal it up and run the engine on the released gases? Of course, you'd want to be careful and get the ratio low enough for the pressure not to blow the bottle ;-). Maybe baking powder and water might be safer?
that would probably work, although I'd reckon you'd have to put some form of filter to prevent the coke/water to foam up and gunk up the engine. Maybe it's not needed if he uses sparklnig water and mentos
True; however, sloshing could be baffled to minimize and 'unnecessary' in this case could be subjective. Either way, it's an easy thing to test/play with and see what happens.
If you have trouble with the cylinder head screws stripping, you can always print the holes longer, and then to start with, use shorter screws. That way, if you strip the thread, you can use a longer screw which will bite into new material. I designed this into a commercial product that used an extrusion and after a few services, the holes were stripped so I just advised to use longer screws and that fixed it!
Yes, I think tom was talking about this in the last video. How the crankcase negative pressure is making it use some of the air pressure to make a full revaluation, if it was an opposed cylinder engine, it would stay neutral, if when one cylinder us tdc the other is bdc..
Phil theVwGuru I ment to put another cylinderhead on the crankcase. But that could be unefficient because the crankcase is too big so much air isn't used.
Seems like push/pulling the same piston as you are suggesting could be done just with some valving modifications of the same one cylinder head, combined with the valve as per old train steam engines. A "D valve"? Actually it's a push/push.
Tom OKAAAY! Well done young man. You have an inquisitive mind and you enjoy the positive feedback from successful projects that began as hypothetical or theoretical propositions. Here's a theoretical proposition: make your motor run on that soda/Mentos experiment. You'll need to make a removable Mentos dropper or depositor and plumb the hose to your motor as normal but because of the added viscosity you may be able to use thinner hose; or You may HAVE to use larger diameter hose for the same reason. Maybe glue or attach a bottle cap that will just barely snuggly hold the mentos pill so that you can urge it to drop by tapping the cap. If you need sketches let me know. I have many other questions and suggestions but don't want this to be too long. I see there are many similar and better suggestions already. It's amazing how many thoughtful creative people are commenting.
That's awesome!! It's clear to see the amount of effort put into developing that engine - thank you for all the videos on it's progress, they've been really interesting to watch!!
Please still make a multi cylinder. It would sound so cool. And you might be able to run a bigger prop. Not sure just guessing but I think it would be awesome
Depends on the pressure of the water and how well the piston seals. It would probably be fine if you allowed for leakage around the piston, which is does as seen by the daylight coming through the sides of the piston while it's inside the cylinder.
Great videos mate, really shows how much thought you put into everything, you back your successes and failures exactly how a good inventor should. Keep it up 👍
JJtheone123 It's a good idea, and it would benefit it but I doubt it'd be nigh impossible with PLA plastic. Even if he could the endurance of rings would suck ass from how thin they'd be. Plus square piston, lul.
Great work Tom, if you hooked up a little infrared sensor you could make a little solenoid controlled idle valve to have the engine operate a the low rpm and pressure bursts like you were doing- just an idea.
Would there be any benefit to filling the crankcase with a light oil just up to the cam? You might be able to run the dual push rod version if that would reduce push rod/cam friction
You should mount this engine on a thrust measuring jig! You can get some data for the thrust curve as psi drops through the duration. Might be useful to understand the "useful" duration of the flight, which would be how long the propeller spins above a certain RPM where thrust is too low to sustain flight.
I've really enjoyed watching you improving this project over time man! I simply love it, I'm so glad I subscribed. It's such a unique thing you do, and the videos are so well made! Please make MORE :)
You can try using propane to make the engine run, it's pressure is low enough and since it's liquid under pressure, the run times can be greatly increased with a small LPG tank,( I'd use copper tubing and solder one together)
Could you convert it to run backwards? With a large propeller acting as a wind turbine pumping bubbles into a fish tank maybe? If this was put outside in a light breeze it could work quite effectively
Very good stuff Tom - this is impressive! If you can get the shaft straighter and balance the prop, you'll be surprised the difference it makes. Good luck!
Super job i have ever seen in TH-cam videos.....air compress to dynamically change..... you become a good scientist in future. Love you become your friend.
If you made it larger, would you be able to integrate a starter valve to just basically flip a switch on a Solenoid and have it start itself? Also, this is rather impractical, but would you be able to hook it to a compressor and have the crankshaft running to an alternator like in a car to essentially make it self-sustaining?
I have thought of two potential things that might be cool. First, as the PVC tubes are flexible, would it be possible to just put two of the cylinders together with a new inner part to make an O-type flat twin? Also, would building some king of 3D printed air compressor and hooking it up to the engine make it run longer. It might even be possible to have the compressor supplying air to the engine while being run by the engine. Great videos, keep them coming!
Thanks for the files! I printed one from aramid-reinforced nylon copolymer weed trimmer line, and it seems to be able to handle all the pressure I can throw at it! I'm thinking of making an inline-6 version, putting it in an R/C Spitfire (Span ~1000mm) with a 5 blade prop from Hobbyking, and powering it with a paintball gun tank and regulator.
Love your air engine series. I'd also like to see a turbine type 3D printed air engine. Should be very simple from a no. of parts perspective, but may be tricky to have its air supply last long enough.
I wish I had a 3d printer because I'd like to run it off my big compressor with some sort of air regulator. I could start off at a low pressure and see how high it can go until it blows the head off. It would also be cool (albeit perhaps too heavy) to copy the dimensions and machine one from aluminum to see how much farther I can push the pressures. Making it out of aluminum would also allow me a wider range of lubricants and possibly smoother surfaces and tighter tolerances.
If you tape the sand paper to a 1/4" thick glass you will get a much smoother and even result, for best results get a lapping surface (can be pricey hence the glass)
Have you considered sanding the cylinder less and then wearing the engine in with some polishing compound to get a better cylinder seal? Not sure if it would work.
Excellent! Do you think a little 6-volt air pump could be attached to the bottle in order for longer running? Those little tyre pumps, when stripped down, are very small but deliver a good bit of air. A small 6-volt motor would run one so it could work on an RC plane.
Have you thought about using an epoxy resin to coat the cylinder and then sanding that down? It'd be easier to sand/less time consuming and provide a less porous surface for a better seal. I know that fdm printing layers arent always perfectly air tight.
Its been such a plessure following along with this series :) I have CAD stuff started for my own version with the double expansion idea mentioned in past videos. With ur STLs i may just try and modify yours to have my additional parts. As yours is already very very nice. Great work!
I wonder if you've tried having multiple bottles pressurized and opening them one at a time. Like if you make a 4 bottle air powered car and as the PSI in the bottle before gets low you flip a switch and open the next one, giving you a boost of power! I've only recently started seeing your videos but this engine is awesome!
I think you should try going back to a round piston and cylinder. When you design the piston, make 2 channels/groves around it so you slip a couple o-rings around it. Then it would seal like a real compressor or engine would, since they use piston rings for the seal. That way you don't need the piston and cylinder to be completely perfect to get a good seal. You could even make the piston a bit smaller than the cylinder and use a thick O-ring in the grooves to fill the gap. You should get a much better seal that way.
What about adding a co2 type filling device, like are used to fill bicycle tires, to provide a boost after the tank empties? You could run a simple servo to one of your extra remote switches. It might be too heavy for a plane.
Capture the exhaust air via a pnumatic fitting, hose and a check Valve and exhaust it back into the bottle, endless air. You can then create a dump valve to bleed off the air to stop it. The check Valve would prevent a suction lock (like a vapor lock). The check valve would be a simple chamber with a o-ring and a ball, the vacuum caused by the cylinder would suck the ball back on to the o-ring for a seal.
I like this engine design, and most of all I like the adjustable valve. But I do have a couple of ideas for you to try, one might already work with your design. Firstly, can you fit the tool inside the hose end to adjust the valve without taking the head off? If not maybe trying to make a housing for the valve that makes it possible to do so. And secondly, where the push rod rubs on the crank shaft, I feel like this price will wear out quickly, I would put a bushing around that pare of the crank and bottom of the push rod to make it last longer. Good job, this design looks and runs good.
For the RC car where weight isn't a huge factor, have you thought about using something like a high pressure scuba tank with a pressure regulator to provide a constant psi for an extended amount of time?
Try using mix of citric acid and baking soda as a gas source. Can be set off with just a couple drops of water and then will continue till the reagents end. I think this one will have much higher volume/mass density than compressed air tank. Also you can smooth PLA using ethyl acetate.
Apologies if already suggested, have you thought of investigating/experimenting with "Compounding"? That is using the exhaust gas on a second lower pressure cylinder. This was used in steam engines for example to extract more energy from the available pressure.
Try using pressurized CO2 bottles instead of a plastic bottle. They hold much more gas compared to their size and CO2 has one of the highest expansion rates. I don't know if the pressure would be too much for your engine, but I suppose you can use a pressure regulator for that.
Have you considered using dry ice or some other gas producing chemical to supply a constant pressure source (with a relief valve of course!)
Had the exact same idea!
Was about to make the same suggestion. There are lots of videos where people blow up bottles like that with just a little dry ice. You would think that that could run the engine for a fair amount of time.
I wonder if the cold gases would make the PLA brittle. I know its not liquid nitrogen cold, but I wouldn't rule out things like the piston con rod cracking. Even if there is a relief valve though, you should still probably hide your balls behind some plywood lol. With that said, this could totally work.
Biggest issue would be to control the rate at which the dry ice is "melting", as too fast and it will pop the bottle. Also as has been said before, Dry ice is not easy to come by in the UK. Other solutions could be possible though that produce gasses in the more controllable manner.
Diet Coke and Mentoes ??
Honestly, these air engine videos are the TH-cam highlight of my week. Keep them coming!
This version looks really efficient, based on how little pressure it runs at. With that huge propeller, I don't see why you couldn't get the plane to fly. It looked like it produced a lot of thrust and ran for a ridiculous amount of time. It sounds pretty amazing too.
USWaterRockets hmm 12 hours early
Patreon innit?
How are you 12 hours early?
patreon
not enough thrust. planes need a ton of thrust.
Can you push one of those engines to its max? like increase pressure until it breaks (in a safe way) maybe using the bike pump while running method while standing behind something?
shinevision sv he could also replace the propeller with a wooden plate as flywheel wich has less airfriction
Yeah! great idea, but maybe testing it with a prop also to see how much you can push it if you use it as a plane :P but yeah, both ideas sound cool!
This should be the next (or maybe reserve it for the last?) video for the series, a completely destructive test
Metzger
A proper flywheel and a pulley. Then measure the work output that generates.
shinevision sv what if he put dry ice in the bottle, would live to see how long it would run for then.
I'd like to see a fail test, hook it up to an air compressor and see how much rpm it can hold up to until it fails. Might wanna swap the prop to a simple flywheel though :D
if you add a regulator you can pressurize the bottle much higher and get much much longer running time.
I want it to be driven to it's max so badly. Please blow one up.
Now that you have your flexible air feed you could easily create that multi cylinder engine that everyone is so keen to see you do.
I think he should make a right angle fitting so the hose can be optionally routed close to the head depending on the need.
Fistly - Were you never tempted to try running it from a Co2 bulb such as you get for soda syphons? Tiny size, high pressure - which I'd guess would need to be regulated down via a choke constriction to the pressures your plastic components can survive for more than several runs before failure?
Secondly - with a hobby lathe you could machine up some aluminium components, get more rpms etc etc, more time in the air, better performance from greater pressure, improved aerodynamics from not having a blimp of an air bottle that's got to be strangling the aircraft's progress through the atmosphere?
Thirdly - I'm surprised at the sluggish pick-up when nearly stalling and give a shot of air, the cylinder charging must be inefficient at those low pressure.
Fourthly - very entertaining watch, this.Thankyou for posting all these videos.
Ian Gourlay I don’t think he would machine parts as the point of the engine is to make a 3d printed engine with the least amount of non-printed parts but cool idea anyways
Ian Gourlay
He’s not out to reinvent the expansion engine. First would be a bored cylinder and turned piston. Which he should do even with printed components.
All he has done is print and sand.
It’s a hand-on learning exercise.
CO2... Have you ever heard about climate change?! 😉
How is the exhaust arranged by the way?
Nice build Tom! I couldn't resist and made a couple of replacement parts for a 5cylinder radial engine and I am actually printing the parts at the moment. I can send you the design files if you are interested!
The design is mostly copied from your files apart from: Crank case, crank shaft, Piston (minor tweak) and piston rods. They are designed to be compatible with the other motor parts.
Very impressive, crazy how low of rpm it will run!
Awesome video now getting mini CO2 regulator and make it run off of a 12 gram CO2 cartridge
It looks like that thing has way more torque than it needs, would you consider adding gear reduction? That could be enough to go airborne
I love it that you look/get so happy when something is working as it should. It shows you have a TRUE interest in what you are doing! Kudos!
Have you put any thought into what you're going to use for the compressed gas source for the car? Without the weight restriction of the plane I'm thinking you could get very creative. If you changed to PVC pipe fittings and placed your pneumatic press fit into a 2" cap, you could make a nice chamber to fill with dry ice (just make sure you include an over-pressure vent). Or what about a peroxide and potassium permanganate, or baking soda and vinegar? Lots of really interesting combinations you could add to a chamber like that. Watching you sand away the piston also got me thinking - why not flange the top and bottom of the cylinder so you don't have to sand the whole face? It will decrease the bearing surface too so you'd get less piston friction as well as being much easier to size to the bore. I'd print oversize and use the time saved in sanding a whole piston face to make sure the bore fit was very close running.
the best solution would be a small pressure tank with a regulator to drop the pressure for the engine. the engine uses air too quickly for something like dry ice or any other chemical reaction.
This is absolutely amazing - the part where you pump air into the bottle as the engine runs is my favourite. Bravo!
That engine is oddly extremely efficient.
Tom has hit a sweet spot of medium-tech engineering. It is so fun to think at this level!
maybe you could try using a additional layer of paint primer/filler after sanding to get it even smoother and maybe get the gaps smaller.
Andi - Yup good idea. Spray paint would be best I think. Plus there is that Krylon stuff that turns wood into acting like lubricated metal.
Like other comments have said: These videos are such a treat.Your in-depth knowledge lets you explain everything in simple terms, which makes watching you making progress very engaging, because we actually understand what's going on. It's super nice, and your passion and fascination for the project becomes very contagious :)
Keep it up!
to make the soft drinks bottles hold up to 120psi you can wrap them with duct tape for more rigidity, I have personally got my bottle to hold around 100psi for my diy tubeless tire set up
Daaamn! Creative.
The problem is that they'll take like 150psi at least, but only once. Plastic like this fatigues over time, so if you continuously use a high pressure it will eventually fail catastrophically. The bottles are designed for a maximum of 100psi (which is a full, shaken bottle, in a hot car), so I'm not sure why he doesn't just use 100psi constantly and swap the bottle out after a dozen or so pumps (isn't like they're expensive).
The duct tape would contain the shrapnel if it exploded at 150psi, but being that this is for an aircraft, the weight would be a pretty big downside.
Jacob T: Daayyaammn good critical data! Lesson learned.
You and everyone in the comments are so smart. This makes these videos so interesting and entertaining to watch. If I've a question pop-up, most of it is already answered, or questioned for that matter, in the comments. Keep it up Tom and the community!
Hier D. - Yes, totally agree.
You should put a small metal flywheel on it, that should make it run for longer and smoother.
Icehawkson i agree
Look at the Bumble Bee gas engine.0.049 The throttle is controlled by opening and closing the exhaust port. Thanks for the quality family entertainment.
Could you remind me, why did you choose square shape of piston and not round?
Petras L You got me curious too. It was so he could have the connecting rod off-center in the piston; so he could reduce the overall length of the engine, and eliminate one of the bearings. th-cam.com/video/FoQUwpfFnnE/w-d-xo.html at 3:40.
Sanding a flat surface is easier than round.
Yep, its true also, but if i noticed properly, now rod right in the middle. And by having square piston, it should be very hard to make precise corners, like Tom mentioned, the same radius/shape to avoid air leakage there. By having round piston it should be possible to mount it, lets say, on the drill and grind it like with lathe. But lets see where "natural selection" will bring Tom's motor ;) Good luck! Its really interesting to follow this series!
I think round piston would be better, too. A circle has better perimeter to area ratio (around 3,5) than a square (4). That means, when you use a round cylinder, there should be less space for air leaks. Edit: these numbers are only for 1 cm2 pistons, but I think you get my point.
Round would have less leakage and less friction. Seems like the difficulty of manufacture is a no-brainer here, the engine would just run better once it was dialed in.
This video is great, even thou I don't own or got access to a 3D-printer I'm really happy that you help the people that do, and will in the future.
You should print the casing out of clear material.
lowtus7 clear filament doesn’t usually come out clear, you wouldn’t be able to see anything
@@owenps6944 Not with common FDM 3d printers like most budget and mid-range printers from folks like Creality.
Now, RESIN-based 3d printers especially those at folks like Shapeways is another story!
You should try and go up in bore, this should help you get less friction vs force that the piston exerts on the crank, because friction rises linearly with bore, but the force rises quadraticaly.
I'd go for a slightly oversquare engine (~1.2 bore:stroke).
Maybe have the crankcase split into 2 parts horizontaly (like a gas engine splits the bearings in two) and try a 2 main bearing version?
BTW what is your rod to stroke ratio in the engine, you should aim for 1.75 (connecting rod 1.75 times longer than stroke), it's the optimum ratio.
akkudakkup - Great lesson/comment. I know I appreciate it. Rod to stroke? did you by chance mean stroke to bore ; or, bore to stroke?
Hey Tom! In terms of efficiency, I found out that opposed piston engines are the most efficient! You should try build one, it's easier than it looks.
RedKugelblitz It only has one cylinder and two pistons. It's much more efficient.
RedKugelblitz The cylinder head has a lot of stress when the engine runs, and it turns really rough to the piston, and forces it down fast and it slowly decreases speed per revolution. On a opposed piston engine the energy is all used, because the cylinder head isn't dispersing any energy. Also, leaks wouldn't be a problem, since you would still produce twice the Torque in the output shaft (two crankshafts). You can also gear it and make the output shaft rotate twice as much faster by using a smaller gear on the output shaft. Also, the torque curve ( change of speed of the piston per revolution , since the the energy is being displaced softly and constant, because there isn't any over pressure on the intake) is smoother, making the engine run better. And you can also use a rotary valve. The leaks could be a problem. You could come with an increase of about +30% on an internal combustion engine (without the losses by the leaks, 30% has the friction "included"), that with the leaks would be 20-25%.
If this air engine had 5-6% efficiency, this design could get it up to 10%, or even more. I'm a ic engine designer, you can trust. I'm basing on the two stroke Diesel opposed piston engine, if you were wondering.
RedKugelblitz You don't need any gearbox if you connect the output shaft With gears, as it is supposed to. And it doesn't have much more moving parts, so doesn't have much more friction. What I have said is that the cylinder head suffers from a lot of stress, and there is a lot of pressure there before expansion, so the pressurized airflow is reduced after the start of the expansion, since you can't get as much air, and the power curve is unbalanced and rough. The advantage in this design is that it can still run with the ball system, but is really hard to do that, but rotary valves are pretty good and much more efficient in this design, and believe me, with proper lubrication, that engine will run for a long time.
RedKugelblitz And you just have a central intake, so yeah. I've tried this with Legos, it's pretty nice.
RedKugelblitz I don't have any of the opposed cylinder engine Design, but I do have one of the normal one . Also, if you search for " Lego opposed piston vacuum engine" you can see some videos of a similar design of mine. I couldn't record it, because camera seems to be epileptic and everything comes black, so I could only record the single piston. My design of the opposed piston is much faster than on those videos on TH-cam, and has high torque. Unfortunately I don't have it anymore, my little brother destroys everything!
I was just as excited as you while seeing that engine running on such low pressure and RPM!! Good job!
It would be cool to implement a throttle body with just a simple butterfly valve, or a ball valve. This works off the theory of, just because my car's gas tank is full, doesn't mean I run it all out immediately. You could control rpm, make the air last longer, and not have to worry about the psi, you're putting through it as you can control how much air gets to the engine, not via a bike pump and a water bottle. This would be very easy to add, and wouldn't take more than $5 and 5 minutes.
He already made a membrane valve for one of his engines
Yep do this!
What he really needs is a pressure regulator so that he can have a high pressure reservoir last longer.
Por que no los dos?
regulator and valve. The membrane valve he built worked for demonstration, but would be almost useless in any actual use case. You can hook a servo to a ball valve.
Squat251 aluminum high pressure cyl hooked to a pressure regulator then a ball valve servo setup.
Longer run time with controllable throttle.
Go to a shop with a large air compressor and a pressure valve and hook it up and do an endurance test! Maybe find a way to continuously oil it? Oil drip? Super cool man!
OOh ooh Great idea Parker! how about throw a balloon with oil in it into the air bottle and use a tiny hose to spray oil into the air stream?
clavo Yeah! I'm super curious to what the lifespan is on something like this. I'm guessing it it'll run for several hours BUT become very inefficient. I think the plastic piston and cylinder would start to wear down and air would start to go around it. Maybe he needs to figure out how to make piston rings.
Parker - I've been reading comments for about 3 hrs now! One guy suggested a dry lube like graphite. It makes good sense. I gotta get some sleep but this level of thinking is so dang fun!
but we need multiple cylinder
plz
Moosh we need something that works best and not something that is "cool"
The cool part comes later. We didnt start building supercars after inventing the engine either.
I want a V8. 😐
MC's Creations watch the videos of motores patelo
Joschi I was just kidding! 😉
tom, this video is mostly for the 0.01 percent of people that will actually attempt to make this engine, most of us are here kinda for the engineering of this beautiful air engine, or simply show the build part of the engine at the end
can you build a silencer for it? also wondering if there be a hand squeeze or giant air filled bag to sleep on that powers something
Why would you want to silence it? The sound is half the enjoyment for me lol.
Ionic, ok, then maybe make it louder then?
The insides of the cylinder still look a bit rough and uneven. I'd imagine you want to get it as perfect as possible to minimize friction and get a better seal. Have you thought about splitting the cylinder into 4 parts so the inside surfaces can be printed laying flat on a perfectly smooth printing surface? Or 2 corner shaped parts that can be easier and more accurately be sanded flat and then gluing the cylinder pieces together?
I'm printing this engine in resin, the tolerances i can get with dlp are out of this world, no sanding just curing.
Hello Tom,
can you try to measure the power output of your engine?
Love your Work!
Best regards from Germany
I would have never thought of that ball air inlet,
such a genius! keep it up.
Try to run it on steam.
xXMountain DewXx : Just a quick reminder: This is 3D printed.
do it anyway
xXMountain DewXx maybe with metallic parts but getting them would be the problem however I agree with you, it'd be cool if he gets to run it on steam
i wonder how the gameplay would be
Not with PLA. It will just melt
I reckon access to desktop injection moulder would assist in the speeding up of these projects, slicing down time to the bare minimum and allow you to put out a boat load of more work and ideas.
Maybe there is a generous engineering/moulding company out there willing to help even if they offered the loan or gift a machine as part of a maker space donation it would help projects like this no end.
Where are you generous desktop moulder manufacturers and can you help!?
Another great vid, Tom. Always enjoy your work.
Maybe Ryanair will install those engines in they planes, to cut the costs. Then every passenger will get his own pump.
And there will be new motto "Pump harder, fly faster".
It would be difficult to get the passengers to buy the pumps!
Hey Tom, hopefully you read this comment because I have an interesting idea. I suggest you put a fair amount of dry ice in the bottle and see how long the propeller will spin for. If not enough pressure is available at any given time, crush up the ice to increase its surface area in order to increase the rate of evaporation.
Just fantastic work, man. Something I was thinking about... There are dc motors air pumps... I don't know if any of them is strong enough, but... It may worth looking at. 😊
MC's Creations fun but very inefficient lol
Possible, one could keep air pumping into it continuously... but like the person above said, yes, inefficient. You might as well power it by a battery motor instead of an air engine at that point.
perhaps too heavy?
Robbie Boehmer It depends on what you use the motor for. If it's for an airplane, probably. But for a car?
As a rule, air under pressure will be a more efficient storage mechanism than a battery, by weight.
Good, back to basics on the build, looking very good. If you found a smaller diameter aluminum cylinder in the area of 40-50 mm diameter and say 300-400mm long, you could run the pressure up to 120 psi or higher and place a regulator set at 60 psi and the engine would run at air speed for much longer. In your tests before, at 60 psi the plane wanted to fly with the larger propeller, but the pressure died off so quickly it couldn't make it. This design is the best, IMO. The next step is to add 2 cylinders in order to get more torque, but then you would use twice the air volume...
Tony - There is a comment on here that suggests wrapping the plastic soda bottle with duct tape to get 120 in that bottle! I'm thinking the new Gorilla Tape would even allow higher PSI. I liked your comment.
clavo Thanks! My idea about the small diameter aluminum tube would give less air drag. I think the tape would allow more pressure in the bottle, but you stil have all that large diameter surface as drag.
Tony: absolutely right about the drag. I like your tube design in that aspect but balancing, costs and tooling intelligence needed; I wonder of a 2" pvc plumbing pipe would work?
clavo Yes the PVC would work at 120 psi and is a great idea. The limitations on PVC is right at 120 psi for schedule 40. It should work fine though for this application. I am not sure about the weight comparisons from PVC to a thin wall aluminum tube though, I would think the aluminum would be a tiny bit lighter in weight. The other side is as you say, fitting the aluminum would require special tooling and abilities. I like the PVC idea a lot. I should mention that the limitations on the pressure of PVC is the joints, not the tube wall. Having worked with PVC in compressed air systems shows that the failure is typically in the joints and where the failure is in the tube, other factors exists such as cantilever or external forces cutting the tube.
Tony - Just for grins; What would you think of Tom making a air compressor; almost identical to the motor, that would run off his bicycle back tire the way old mini electric generators did years ago? He could set the back axle on a stand to let the rear wheel freewheel as he pedaled to run the compressor. Again he could use PVC pipe (3") for a storage tank.
You should try to build V-twin air engine! if it is possible it would be very interesting
A great feeling when it starts to come together. When do you get to sleep? Have been thinking of a double length (in the shape of a U) rubber powered glider driven through a gear box of some kind to extend duration and be could be braked in some manner to give multi starts while in the air. It pays to keep the old brain working eh! Thanks once more.
TALK TO AvE!!!! He does fluid mechanics for a living and I'm sure he will be able to help you. AvE literally just did a video creating an air pump with an old hydraulic pump that was greased up. I'm serious dude, get in contact with him and he will tell you tons of things that would take you weeks to figure out on your own and all the things he says are funny anyways.
If the engine didn't run at all, it sounds like you made it 100% efficient. Good job!
i wonder if a classical pneumatic motor would be more effective? or maybe a turbine style engine? would be much easier to build and propably much less internal power loss due to friction
That's a very good question. Why were some heavy lift winches in old welding shops piston type pneumatic motors? Higher torque at low pressure, I think.
i recon that those classical air fin models rely heavily on a combination of flow rate and pressure, where a piston engine only relys on pressure to build up torque, but it would be really interessting to see a direct comparaison between the two, maybe tom does it :)
Pneumatic motors are usually vane motors.
Harold S. - Yes. The low rpm torque is better in a piston engine; but, in industry, most application use high rpm and the vane motors are more efficient and most common. If you see an industrial piston air motor, it is in an antique shop!
Vane motors need more pressure than he could easily supply with a 2L bottle. Otherwise they're superior in every way.
Rather than a propeller could you connect the drive shaft to a pump to self add air to the tank. Sort of perpetual motion machine?
I wonder if you could fill the bottle half way with coke/diet coke and drop a few Mentos in, seal it up and run the engine on the released gases? Of course, you'd want to be careful and get the ratio low enough for the pressure not to blow the bottle ;-). Maybe baking powder and water might be safer?
helicopter coke bottle
that would probably work, although I'd reckon you'd have to put some form of filter to prevent the coke/water to foam up and gunk up the engine. Maybe it's not needed if he uses sparklnig water and mentos
If he were to use that in a plane, it would just add unnecessary weight and on a car it would lead to worse handling due to the liquid sloshing around
True; however, sloshing could be baffled to minimize and 'unnecessary' in this case could be subjective. Either way, it's an easy thing to test/play with and see what happens.
Jason: well done. But; Ratsies I just made the same suggestion thinking it was original!
This is so cool! You inspired me to try to design my own line of air engines, and so far I have two fully functional engines. Thanks a bunch!
Why don’t you add lubricant into the bottle so when it runs it’s constantly lubricated and in theory increase the life of the engine
mental mtb like a two stroke
Thinking exact same.
Air and wd40 don’t mix effectively
If you have trouble with the cylinder head screws stripping, you can always print the holes longer, and then to start with, use shorter screws. That way, if you strip the thread, you can use a longer screw which will bite into new material. I designed this into a commercial product that used an extrusion and after a few services, the holes were stripped so I just advised to use longer screws and that fixed it!
I just had the idea to use the area under the the cylinder (crankcase) as a "second" cylinder.
Yes, I think tom was talking about this in the last video. How the crankcase negative pressure is making it use some of the air pressure to make a full revaluation, if it was an opposed cylinder engine, it would stay neutral, if when one cylinder us tdc the other is bdc..
Phil theVwGuru I ment to put another cylinderhead on the crankcase. But that could be unefficient because the crankcase is too big so much air isn't used.
Seems like push/pulling the same piston as you are suggesting could be done just with some valving modifications of the same one cylinder head, combined with the valve as per old train steam engines. A "D valve"? Actually it's a push/push.
clavo I didn't knew that something like that exists but I think that adds to much complexity.
Joschi
Dual action cylinder steam engines were standard for high output like trains and ships.
That might strain 3D printing ability
Tom OKAAAY! Well done young man. You have an inquisitive mind and you enjoy the positive feedback from successful projects that began as hypothetical or theoretical propositions. Here's a theoretical proposition: make your motor run on that soda/Mentos experiment. You'll need to make a removable Mentos dropper or depositor and plumb the hose to your motor as normal but because of the added viscosity you may be able to use thinner hose; or You may HAVE to use larger diameter hose for the same reason. Maybe glue or attach a bottle cap that will just barely snuggly hold the mentos pill so that you can urge it to drop by tapping the cap. If you need sketches let me know. I have many other questions and suggestions but don't want this to be too long. I see there are many similar and better suggestions already. It's amazing how many thoughtful creative people are commenting.
Wow this looks so promising, any practical applications?
Toys :p
That's awesome!! It's clear to see the amount of effort put into developing that engine - thank you for all the videos on it's progress, they've been really interesting to watch!!
Please still make a multi cylinder. It would sound so cool. And you might be able to run a bigger prop. Not sure just guessing but I think it would be awesome
i think it would suck, you dont need more \\power\\ and you will run out of fuel way faster.
Great progress. I was glad to see a new video. I am happy to see the new engine running so good.
Boat propeller would be cool.
ukulelefatman Not a bad idea, just would need a sealed bearing and make it airtight completely.
awesome job. looks like the same fittings some paintball markers use. you can get them at 90 degree angle to put the hose away from the prop.
Can that engine run on water?
Great hypothesis!
Depends on the pressure of the water and how well the piston seals.
It would probably be fine if you allowed for leakage around the piston, which is does as seen by the daylight coming through the sides of the piston while it's inside the cylinder.
Great videos mate, really shows how much thought you put into everything, you back your successes and failures exactly how a good inventor should. Keep it up 👍
Fish taco - Good comment! Ever try frozen fish sticks sauteed till cooked and then toss in an egg and scramble? Makes on ok taco.
The engine could probably benifite from gas rings on the piston
At the price of friction
aren't gas rings just relief cuts in the piston? how would that increase friction?
will hicks they do add surface friction, but they also seal off the piston better with enough pressure.
JJtheone123 It's a good idea, and it would benefit it but I doubt it'd be nigh impossible with PLA plastic. Even if he could the endurance of rings would suck ass from how thin they'd be. Plus square piston, lul.
The Bait that is Natori why did he make the piston square anyways?
Great work Tom, if you hooked up a little infrared sensor you could make a little solenoid controlled idle valve to have the engine operate a the low rpm and pressure bursts like you were doing- just an idea.
your window in the background lol
Would there be any benefit to filling the crankcase with a light oil just up to the cam? You might be able to run the dual push rod version if that would reduce push rod/cam friction
No, petroleum based oils will degrade the PLA plastic. Also what you're saying will increase friction.
Who are the 13 ppl that down voted this??? born haters.
What's a down vote????
Dislike @@MeloettaDash
I always loved your approach mate! RnD exactly as it should be done! Keep up the great work and content.
You should mount this engine on a thrust measuring jig! You can get some data for the thrust curve as psi drops through the duration. Might be useful to understand the "useful" duration of the flight, which would be how long the propeller spins above a certain RPM where thrust is too low to sustain flight.
I've really enjoyed watching you improving this project over time man! I simply love it, I'm so glad I subscribed. It's such a unique thing you do, and the videos are so well made!
Please make MORE :)
The idea is excellent, thankyou for providing the free STL files😊
You can try using propane to make the engine run, it's pressure is low enough and since it's liquid under pressure, the run times can be greatly increased with a small LPG tank,( I'd use copper tubing and solder one together)
Could you convert it to run backwards? With a large propeller acting as a wind turbine pumping bubbles into a fish tank maybe? If this was put outside in a light breeze it could work quite effectively
Super cool creative thought.
Very good stuff Tom - this is impressive! If you can get the shaft straighter and balance the prop, you'll be surprised the difference it makes. Good luck!
you should do a Q & A video. I see people have a lot of questions and suggestions. Good job. Keep it up mate.
Super job i have ever seen in TH-cam videos.....air compress to dynamically change..... you become a good scientist in future. Love you become your friend.
If you made it larger, would you be able to integrate a starter valve to just basically flip a switch on a Solenoid and have it start itself?
Also, this is rather impractical, but would you be able to hook it to a compressor and have the crankshaft running to an alternator like in a car to essentially make it self-sustaining?
I have thought of two potential things that might be cool. First, as the PVC tubes are flexible, would it be possible to just put two of the cylinders together with a new inner part to make an O-type flat twin? Also, would building some king of 3D printed air compressor and hooking it up to the engine make it run longer. It might even be possible to have the compressor supplying air to the engine while being run by the engine.
Great videos, keep them coming!
Thanks for the files! I printed one from aramid-reinforced nylon copolymer weed trimmer line, and it seems to be able to handle all the pressure I can throw at it! I'm thinking of making an inline-6 version, putting it in an R/C Spitfire (Span ~1000mm) with a 5 blade prop from Hobbyking, and powering it with a paintball gun tank and regulator.
Love your air engine series. I'd also like to see a turbine type 3D printed air engine. Should be very simple from a no. of parts perspective, but may be tricky to have its air supply last long enough.
I wish I had a 3d printer because I'd like to run it off my big compressor with some sort of air regulator. I could start off at a low pressure and see how high it can go until it blows the head off. It would also be cool (albeit perhaps too heavy) to copy the dimensions and machine one from aluminum to see how much farther I can push the pressures. Making it out of aluminum would also allow me a wider range of lubricants and possibly smoother surfaces and tighter tolerances.
I like that you are pumping by hand!
If you tape the sand paper to a 1/4" thick glass you will get a much smoother and even result, for best results get a lapping surface (can be pricey hence the glass)
Have you considered sanding the cylinder less and then wearing the engine in with some polishing compound to get a better cylinder seal? Not sure if it would work.
Excellent! Do you think a little 6-volt air pump could be attached to the bottle in order for longer running? Those little tyre pumps, when stripped down, are very small but deliver a good bit of air.
A small 6-volt motor would run one so it could work on an RC plane.
Have you thought about using an epoxy resin to coat the cylinder and then sanding that down? It'd be easier to sand/less time consuming and provide a less porous surface for a better seal. I know that fdm printing layers arent always perfectly air tight.
Its been such a plessure following along with this series :)
I have CAD stuff started for my own version with the double expansion idea mentioned in past videos.
With ur STLs i may just try and modify yours to have my additional parts. As yours is already very very nice.
Great work!
I wonder if you've tried having multiple bottles pressurized and opening them one at a time. Like if you make a 4 bottle air powered car and as the PSI in the bottle before gets low you flip a switch and open the next one, giving you a boost of power! I've only recently started seeing your videos but this engine is awesome!
I think you should try going back to a round piston and cylinder. When you design the piston, make 2 channels/groves around it so you slip a couple o-rings around it. Then it would seal like a real compressor or engine would, since they use piston rings for the seal. That way you don't need the piston and cylinder to be completely perfect to get a good seal. You could even make the piston a bit smaller than the cylinder and use a thick O-ring in the grooves to fill the gap. You should get a much better seal that way.
What about adding a co2 type filling device, like are used to fill bicycle tires, to provide a boost after the tank empties? You could run a simple servo to one of your extra remote switches.
It might be too heavy for a plane.
Having this with transparent PLA would be awesome! seeing the inner workings of the engine
Capture the exhaust air via a pnumatic fitting, hose and a check Valve and exhaust it back into the bottle, endless air. You can then create a dump valve to bleed off the air to stop it.
The check Valve would prevent a suction lock (like a vapor lock). The check valve would be a simple chamber with a o-ring and a ball, the vacuum caused by the cylinder would suck the ball back on to the o-ring for a seal.
Awesome as always! Need possibility to fine tuning ignition timing without unscrewing head of the cylinder IMHO))
I like this engine design, and most of all I like the adjustable valve. But I do have a couple of ideas for you to try, one might already work with your design.
Firstly, can you fit the tool inside the hose end to adjust the valve without taking the head off? If not maybe trying to make a housing for the valve that makes it possible to do so. And secondly, where the push rod rubs on the crank shaft, I feel like this price will wear out quickly, I would put a bushing around that pare of the crank and bottom of the push rod to make it last longer. Good job, this design looks and runs good.
For the RC car where weight isn't a huge factor, have you thought about using something like a high pressure scuba tank with a pressure regulator to provide a constant psi for an extended amount of time?
Try using mix of citric acid and baking soda as a gas source. Can be set off with just a couple drops of water and then will continue till the reagents end. I think this one will have much higher volume/mass density than compressed air tank.
Also you can smooth PLA using ethyl acetate.
Apologies if already suggested, have you thought of investigating/experimenting with "Compounding"? That is using the exhaust gas on a second lower pressure cylinder. This was used in steam engines for example to extract more energy from the available pressure.
Try using pressurized CO2 bottles instead of a plastic bottle. They hold much more gas compared to their size and CO2 has one of the highest expansion rates. I don't know if the pressure would be too much for your engine, but I suppose you can use a pressure regulator for that.