Air-Powered Top Only Possible on a 3D Printer

One of the major reasons anyone would turn to a 3D printer, even if they have access to a machine shop, is that there are some shapes that are not possible to make with conventional “subtractive manufacturing” techniques. There are a few more obvious reasons a lot of us use 3D printers over conventional machining such as size and cost, but there’s another major reason that 3D printers are becoming more and more ubiquitous. [Crumbnumber1] at Make Anything’s 3D Printing Channel shows us how powerful 3D printers are at iterative design with his air-powered tops. They incorporate fan blades that allow you to spin the top up to very high speeds by blowing air down onto it.

Iterative design is the ability to rapidly make prototypes that build and improve upon the previous prototype, until you’re left with something that does the job you need. Even with a machine shop at your disposal, it can be expensive to set up all of the tooling for a part, only to find out that the part needs a change and the tooling you have won’t work anymore. This is where 3D printers can step in. Besides all of their other advantages, they’re great for rapid prototyping. [Crumbnumber1] made a box full of tops and was able to test many different designs before settling on one that performed above and beyond everything that came before it.

The video below is definitely worth checking out. The design process is well documented and serves as a great model for anyone looking to up their rapid prototyping game.

25 thoughts on “Air-Powered Top Only Possible on a 3D Printer

    1. The pressure of your air compressor is largly irrellevant.
      The amount of air (and therewith the airspeed) going through the spinning top will be the most important factor.
      If you know that, then you can calculate the (approximate) speed / rpm by the geometry of the top.
      See the parrallellogram below for an indication of how to calculate.

      1. Wouldn’t the pressure determine the airspeed? Seems to me, the lower the pressure, the slower the airspeed would be. I’m also fairly certain that 120PSI would deliver far more volume of air and much faster than one could produce with their lungs. A little tesla turbine I made, I could get it up to about 10,000 RPMs with my breath, but over 40,000 with an air compressor.

        1. 120PSI tells you how much pressure your compressor can put behind the air, not how much air it can move. It’s kinda like voltage and current. The equivalent for current with an air compressor is the rate of flow, usually measured in CFM, or cubic feet per minute.

        2. No. Bernoulli’s principle. Pressure is inversely proportional to velocity, which means pressure at the exit of an orifice is lower as velocity is higher. What you are missing is that as you squeeze air through tight space, the pressure will drop. This leads to an increase of air speed. Think of it this way: if you turn on a water hose and pinch the hose off, the pressure in the hose will be at the supply pressure. Releasing the pinch and allowing the water to run out of the hose resolves into less pressure as the water has a place to go, so it runs and thus moves at a higher velocity than the water that was held in the originally pinched water hose. Pinching the water hose is the equivalent of creating a venturi effect, so water must speed up to pass through the narrow passageway as long as pressure is available to push it forward. At the pinch, the pressure drops, and velocity increases. I hope this explains things a little.

    1. I know right, and could have been iteratively developed with computational fluid dynamics instead of pure luck and guesswork driven 3D Printering. It’s not like there’s a decent failed print shredder and recycler to turn it back to filament. Sure they’re great tools, have many uses, but seem to lead to lazy thinking. I think it’s the absolutes of “impossible without 3D printing” that are really annoying here. Many ways for folks with an ounce of workshop sense to achieve similar results.

      1. I wonder, if they know, how such “impossible” parts are made for turbochargers and jet engines? Or how the engine block, certainly a complex shape hard to machine is made by casting?
        3D printing is great if you need one, custom part or replacement. Using it for “iterative design” is a waste of time, money and filament. Especially when one can simulate the behavior of part in CAD/CAM/CAE software.

  1. Some of his later iterations are coming close to a centrifugal compressor you’d find in a turboprop such as the P&W PT6 or an automotive turbocharger. Might be worthwhile places to look for inspiration for refining the shape of these tops.

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