Turbojet engines are an incredible piece of 20th century engineering that except for some edge cases, have mostly been replaced by Turbofans. Still, even the most basic early designs were groundbreaking in their time. Material science was applied to make them more reliable, more powerful, and lighter. But all of those incredible advances go completely out the window when you’re [Joel] of [Integza], and you prefer to build your internal combustion engines using repurposed butane canisters and 3d printed parts as you see in the video below the break.
To understand [Integza]’s engine, a quick explanation of Turbojet engines is helpful. Just like any other internal combustion engine, air is compressed, fuel is burned, and the reaction produces work. In a turbojet, a compressor compresses air. Fuel is added in a combustor and ignited, and the expanding exhaust drives a turbine that in turn drives the compressor since both are attached to the same shaft. Exhaust whose energy isn’t spent in turning the turbine is expelled and produces thrust, which propels the engine and the vehicle it’s attached to in the opposite direction. Simple, right? Right! Until the 3d printer comes in.
Sadly for 3d printed parts, they are made of plastic. Last we checked, plastic isn’t metal, and so 3d printing a turbine to give the extremely hot exhaust something turn just isn’t going to work. But what if you just skipped the whole turbine part, and powered the compressor with an electric motor? And instead of using an axial compressor with tons of tiny blades that would likely be impossible to 3d print with enough strength, you went with a sturdy, easy to print centrifugal compressor? Of course, that’s exactly what [Integza] did, or we wouldn’t be talking about it. The results are fantastic, especially considering that the entire machine was built with 3d printing and a home made spot welder.
Turbochargers as used on cars bear some similarities with jet engines. Fundamentally, both contain a turbine that harvests energy from hot gas, using it to spin a compressor which sucks in fresh air for combustion. Thus, turning a turbocharger into a jet engine is entirely possible, and [HRom] decided to have a crack at it.
The build starts with a turbo that appears to have been used on a diesel engine from the Volkswagen group. The first step was to cut the integral exhaust manifold off the turbo housing. A combustion chamber is then added which takes in fresh air from the compressor housing, and delivers hot combustion products to the turbine inlet. The homebrewed jet engine burns propane as fuel, introduced into the chamber via a nozzle.
The initial test failed as combustion was occurring at the turbine exhaust rather than in the combustion chamber, likely due to the lack of a proper ignition source inside the combustion chamber. A redesign employed a bigger combustion chamber built out of a fire extinguisher, with smouldering wood pellets inserted inside to get the injected propane burning.
The redesign works, and the turbocharger jet engine releases a thunderous scream as it turns at ever-increasing speed. However, with no oiling system or any way of controlling air or fuel flow in the engine, it eventually stops in a huge puff of smoke. Regardless, the engine did run in a sustained manner even if the ignition method was rudimentary.
We’ve seen similar builds before, and the rudimentary construction means they’re typically nowhere near being flight-weight engines. They are incredibly cool, however, and a great way to learn the basic principles of how jet engines work. Video after the break.
The development of the turbojet engine was a gamechanger in aviation, as no longer would aircraft designers have to struggle with ever larger and more complex piston engines, nor would propellers keep planes stuck below the speed of sound. However, the turbojet is an exacting device, demanding the utmost of materials in order to work successfully. [Integza] discovered just this in his quest to build one at home.
Unlike most home jet engine builds, this one doesn’t use a turbocharger or go with a simpler pulse jet design – though [Integza] has built those, too. This is a proper radial-flow turbojet design. The build uses a 3D-printed compressor, which is possible as it doesn’t have to deal with much heat. However, for the turbine, [Integza] realised that plastic wouldn’t cut it. After experiments with ceramic resins failed too, a 3D printed jig was instead built to allow sheet metal to easily be crafted into a workable turbine. Other internal components were made out of concrete for heat resistance, and a combustion chamber welded up out of steel.
Jet engines are known to be highly demanding machines, requiring the utmost attention to tolerances, material specifications, and operating regimes. If any of these parameters are ignored, failures can be catastrophic and expensive. Despite these exacting requirements, it is possible to build a jet engine in the home workshop – and using a turbocharger is a great way to do that. (Video also embedded after the break.)
[Tech Ingredients] does a great job of discussing the basic concepts behind the turbocharger jet engine build, and how various parameters impact performance and efficiency. Through the use of various rules of thumb, developed over years of experimentation by home builders and engineers alike, it’s possible to whip up a functioning engine without too much trial and error. The video breaks down and discusses the thermodynamics at play, as well as practical considerations like cooling and lubrication, in several easy to digest steps.
This week’s Hacklet focuses on two wheeled thunder! By that we mean some of the motorcycle and scooter projects on Hackaday.io.
We’re going to ease into this Hacklet with [greg duck’s] Honda Sky Restoration. Greg is giving a neglected 15-year-old scooter some love, with hopes of bringing it back to its former glory. The scooter has a pair of stuck brakes, a hole rusted into its frame, a stuck clutch, and a deceased battery, among other issues. [Greg] already stripped the body panels off and got the rear brake freed up. There is still quite a bit of work to do, so we’re sure [Greg] will be burning the midnight 2 stroke oil to complete his scooter.
Next up is [Anders Johansson’s] jaw dropping Gas turbine Land Racing Motorcycle. [Anders] built his own gas turbine engine, as well as a motorcycle to go around it. The engine is based upon a Garrett TV94, and directly powers the rear wheel through a turboshaft and gearbox. [Anders] has already taken the bike out for a spin, and he reports it “Pulled like a train” at only half throttle. His final destination is the Bonneville salt flats, where he hops to break the 349km/h class record. If it looks a bit familiar that’s because this one did have its own feature last month.
[GearheadRed] is taking a safer approach with FireCoates, a motorcycle jacket with built-in brake and turn signal indicators. [GearheadRed] realized that EL wire or LED strip wouldn’t stand up to the kind of flexing the jacket would take. He found his solution in flexible light pipes. Lit by an LED on each end, the light pipes glow bright enough to be seen at night. [GearheadRed] doesn’t like to be tied down, so he made his jacket wireless. A pair of bluetooth radios send serial data for turn and brake signals generated by an Arduino nano on [Red’s] bike. Nice work [Red]!
[Johnny] rounds out this week’s Hacklet with his $1000 Future Tech Cafe Racer From Scratch. We’re not quite sure if [Johnny] is for real, but his project logs are entertaining enough that we’re going to give him the benefit of the doubt. Down to his last $1000, [Johnny] plans to turn his old Honda xr650 into a modern cafe racer. The new bike will have electric start, an obsolete Motorola Android phone as its dashboard, and a 700cc hi-comp Single cylinder engine at its heart. [Johnny] was last seen wandering the streets of his city looking for a welder, so if you see him, tell him we need an update on the bike!
While [Mike]’s junkyard jet made the rounds on the Internet over a decade ago, the theory behind the homebrew turbojet is still sound. After pulling a turbo out of a 1983 Nissan Pulsar, [Mike] built a combustion chamber out of 2-inch pipe fittings. The propane fuel is ignited with a simple motorcycle spark plug and produces a hot and powerful blast of air twenty feet from the exhaust.
We suppose [Mike] wasn’t satisfied with such a puny engine made out of junk, so he decided to step it up a notch and improve his engine. After some development, [Mike] managed to build another jet out of a larger turbo that doesn’t require a constant spark. The newer engine produces ‘hurricane force wind’ 10 feet from the exhaust. We’re not sure how much thrust that translates into, but we’re a little surprised this engine hasn’t been mounted to a go-kart yet.
Check out the walk through and demo of the junkyard jet after the break.