Water Air Engine

It's insane how you can make that engine run at such low pressures

My suggestion would be lubrication of the moving parts. Using something like dry Teflon lubricant, graphite, or even a pencil I imagine can make a difference when the air pressure drops even more. Also, real internal combustion engines use a weighted flywheel to smooth themselves out and keep their rotational inertia going between ignition strokes, since in a normal single-cylinder four-stroke engine, there's quite a lot of time between ignition because the piston has to go up and down three more times until the next power stroke. When the air engine slows down and starts oscillating, it's likely because it loses inertia and needs something to keep it spinning in one direction, not to mention smoothing it out. Something heavier than a carbon fiber propeller like an aluminum disc.

The last person who made an engine run out of water mysteriously died

Awesome build! It’s really cool to see the ways you were still able to squeeze higher efficiencies from the motor even after all of the iterative work you’d done to improve it in the previous video!

Love the engine designs! The modification processes and changes over time have been really interesting to watch. Thanks for the great content!

That is honestly the cleanest looking DIY I've ever seen. Good job, Tom!

the solution to your issue is to add more cylinders :3 being able to apply at different stroke phases will enhance efficiency as the blade wont be accelerating and slowing down as often (which is how the change in direction occurs), and the resulting increase in total diaphragm area will allow it to run better at lower pressures. Have you considered adding some intertial mass (flywheel) to the system to also help balance out the power application of the motor to stop the accel/decell issues it has?

I don't know exactly what it is, but I could watch your air engines puffin away for HOURS without getting bored! This must be the most wholesome and entertaining piece of tech I ever saw coming out of a 3d printer and I am kinda sad, that I lack the technical knowhow and equipment to do stuff like that. Thank god for people like you who can scratch that itch for me anyway :D

Wonderful! You could add a floater into the tank to that automatically blocks the outlet as soon as the water reaches the top. That way you don't have to worry about flooding the engine.

You can do the same thing with running water for infinite compressed air using something called a trompe. Mines and other industries that use a lot of compressed air have used this technique for creating compressed air for nearly as long as the need for compressed air has existed. All you need is plenty of water and a change in elevation. Also worth noting is that you get more air pressure from a trompe then you do from a static column of water thanks to the inertia of the water as it falls similar to how a ramp pump provides more pressure out than the input pressure.

My dad told me a few years ago that my grandpa actually used air engines to run a pump when he was working which I find fascinating. I had first heard of these when I was going to school for drafting, I had built a design for one and played around with a 3d print as well. At that time I didn't think that it was anything more than just a representation of what could be done if you play around with physics but since then I have been absolutely obsessed with these

This is like a fluid over air cylinder in automation for industry. They do work really good at lower pressures. I hardly had any problems with them in my previous encounters as a maintenance employee at a large automotive plant.

Fun fact, having an open system like that with a tank on the loft, is actually how you pressurized the central heating system in houses back in the day 😄 Here in Denmark they used to measure the water pressure in the system in mVs (meter vand søjle) meaning “meter water height” I suppose. Basically one meter is equal to .1 bar of pressure :)

Please be careful with acrylic pressure tanks. They tend to fail catastrophically. Not a problem at those low pressures but once you go above that, add a layer of translucent tape around it that keeps the acrylic parts from flying everywhere in case of failure.

I can see more opportunities to increase the efficiencies. A couple of guides extending into the chamber and corresponding tabs on the piston. Should introduce more stability at low cost of friction. A little lubricant would also help. You could tinker away for a long time just experimenting with what improves performance. Maybe "borrow" a regulator from a compressor to stabilize the minimum pressure. One learns so much from iterative development. Thanks for the video!

At that low speed, the sound of the pin hitting the ball is very close to the sound of injector ping on a diesel. Beautiful engine, masterful engineering, as always

You don't need a larger ports to reduce you're losses from the water flowing through the tube. If you put an adapter on the inlet to the pressure chamber and the outlet of the upstairs tank that adapts to a larger diameter tube, you will increase your flow rate even without changing threaded port size. This is because most of your losses are not coming from the simple restriction of the flow cross section, but rather from the friction against the wall of the tube. In fact, in hydraulic engineering (ie engineering of any fluid conveyance system) the losses due to flow restricting components are referred to as "minor" head loss while those due to wall friction are "major" head loss because of how much higher they usually are. If you look at the equation for major head loss you'll see it is the Darcy Friction Factor (usually given the symbol f with subscript D) multiplied by the tube or pipe length, divided by the hydraulic diameter (just the inner diameter in the case of circular cross sections). This means that you can reduce your major head loss significantly by simply adapting to a larger tube diameter, and then just accept that the minor head losses from the comparatively undersized ports at either end.

The flow rate is limited much more by friction losses in the long tube than by the size of the fittings. If you printed some adapters and replaced the tube with one that has a larger diameter, the pressure probably would stay at a value much closer to 0.6 bar.

Very cool. I'd enjoy seeing some more refinements to the engine to reduce losses (more polishing of the piston and bore? More efficient diaphragm materials? Maybe route the exhaust air to act on the rear of the piston for a combined double-expansion double-acting action? (using the pressure left in the exhaust to help power the return stroke so less prop momentum is lost to that) and optimize the geometry. It's really entertaining to see you develop and test refinements. A small air pump connected to the air tank outlet would let you push the water back up to the storage tank and save some trips up the stairs carrying water.

Brilliant! And you could also use an old hot water tank as a reservoir, maybe even using collected rain water pressure, from a rooftop reservoir, via a regulator, to fill it, before using the water for other purposes such as cooking, washing, flushing the loo and watering the garden. If you were careful to use all of the water for other purposes, you could even use mains water. Finally, make a wind- or solar-powered pump to take water to an upper reservoir. Thanks Tom. 🙂👍