Engine Hacks

163 Articles

Prototyping A Turbojet Engine In The Home Shop

March 16, 2021 by 21 Comments

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.

The engine did run after several attempts, albeit for just ten seconds before components started to melt. While the engine is a long way off being flight ready, it goes to show just how hard it is to build even a bench-running turbojet. Even major world powers have struggled with this problem over the years. Video after the break.

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The Rotary-X Engine Is A Revolution In Thermodynamics

February 15, 2021 by 119 Comments

If you’re running an army, chances are good that you need a lot of portable power for everything from communications to weapons control systems. When it comes to your generators, every ounce counts. The smaller and lighter you can get them, the better.

Connecticut-based company LiquidPiston is developing a high-powered generator for the US Army that uses the company’s own rotary x-engine — a small, light, and powerful beast that sounds like a dream come true. It can run on gasoline, diesel, natural gas, kerosene, or jet fuel, and is scalable from 1 to 1,000 horsepower (PDF).

Co-founder and CEO Alex Schkolnik describes the design as a combination of the best parts of the Otto and Atkinson cycle engines, the Diesel, and the Wankel rotary while solving the big problems of the latter two. That sounds impressive, but it doesn’t mean much unless you understand how each of these engines work and what their various advantages and disadvantages are. So let’s take a look under the hood, shall we?

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Steam Engine Replica From LEGO

January 25, 2021 by 25 Comments

If engineering choices a hundred years ago had been only slightly different, we could have ended up in a world full of steam engines rather than internal combustion engines. For now, though, steam engines are limited to a few niche applications and, of course, models built by enthusiasts. This one for example is built entirely in LEGO as a scale replica of a steam engine originally produced in 1907.

The model is based on a 2500 horsepower triple-expansion four-cylinder engine that was actually in use during the first half of the 20th century. Since the model is built using nothing but LEGO (and a few rubber bands) it operates using a vacuum rather than with working steam, but the principle is essentially the same. It also includes Corliss valves, a technology from c.1850 that used rotating valves and improved steam engine efficiency dramatically for the time.

This build is an impressive recreation of the original machine, and can even run at extremely slow speeds thanks to a working valve on the top,  allowing its operation to be viewed in detail. Maximum speed is about 80 rpm, very close to the original machine’s 68 rpm operational speed. If you’d prefer your steam engines to have real-world applications, though, make sure to check out this steam-powered lawnmower.

Thanks to [Hari] for the tip!

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A 136 Euro Pulse Jet For Some No-Firework Lockdown Fun

January 15, 2021 by 21 Comments

With the aim of reducing virus transmission due to gatherings during the pandemic, the Dutch government have banned fireworks. The people of the Netherlands like their noisy things so we’re told that the ban has been widely flouted, but [Build Comics] are a law-abiding group of workshop tool heroes. For their lockdown noise, they created an entirely-legal pulsejet. The interesting part is that it was made entirely using fairly basic tools on a minimalist budget, with TIG and MIG eschewed in favour of a mundane stick welder.

The form of the pulse jet will probably be familiar as it has been taken from other published designs. A long tube is bent back upon itself with a combustion chamber placed in one of its arms such that the jet forms a resonant chamber that produces continuous pulses of exhaust gas. This one is made from stainless steel tube, and the exhaustive documentation should be worth a look for anyone tempted to make their own. Welding thin sheet with a stick welder requires quite a bit of skill, and in a few places they manage to burn a hole or two. One requires a patch, but the time-honoured technique of running a bead around the edge manages to successfully close another.

Their first attempt to fire it up using a leaf blower with a 3D-printed adapter fails, but following the construction of a more resilient part and a more efficient gas injector the engine starts. It’s then taken out on a farm for some serious noise without too many angry neighbours, as you can see in the video below the break.

The hero tools of Build Comics have appeared here before, most recently with an analogue meter clock.

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Coil On Plug Ignition For Tiny Engines

December 21, 2020 by 40 Comments

The spark plug was a key invention in the history of the internal combustion engine, allowing combustion to be easily controlled and engines to rev faster than messy earlier designs. Mid-century cars tended to rely on points ignition with a distributor and coil, however more modern designs place a coil on top of each individual spark plug. [Roger Moore] decided to build a similar setup for a small model engine on his workbench.

The rig is built with an Arduino, a flyback transformer, a smattering of MOSFETs and passives, an IGBT and a capacitor. The Arduino outputs PWM through a MOSFET which is stepped up through the transformer, and then charges the capacitor. The capacitor is then discharged into a coil mounted on top of the sparkplug of the single-cylinder engine, which fires the spark. The timing of the spark is determined by a Hall effect sensor reading a magnet placed on the flywheel.

Later development aims to shrink the system further to fit on a V10 design [Roger] is planning to make. It’s been done on a small scale before, and we’d love to see another tiny engine with way too many cylinders. Video after the break.

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SLA 3D Printed Vortex Cooled Rocket Engine

December 8, 2020 by 16 Comments

3D printing is an incredible tool for prototyping and development, but the properties of the materials can be a limiting factor for functional parts. [Sam Rogers] and colleagues at [AX Technologies] have been testing and developing a small liquid-fueled rocket engine and successfully used vortex cooling to protect a resin 3D printed combustion chamber. (Video, embedded below.)

Vortex cooling works by injecting oxygen into the combustion chamber tangentially, just inside the nozzle of the engine, which creates a cooling, swirling vortex boundary layer along the chamber wall. The oxygen moves to the front end of the combustion chamber where it mixes with the fuel and ignites in the center. This does not protect the nozzle itself, which only lasts a few seconds before becoming unusable. However, thanks to the modular design of the test engine, only the small nozzle section had to be reprinted for every test. While this part could be manufactured using a metal 3D printer, the costs are still very high, especially at this experimental stage. The clear resin parts also allow the combustion observed and more accurate conclusions to be drawn from every test.

This engine intended to be used as a torch igniter for a much larger rocket engine. Fuel is injected into the front of the combustion chamber, where a spark plug is located to ignite the oxygen-fuel mixture. The flow of the oxygen and fuel is controlled by two servo-operated valves connected to a microcontroller, which is mounted with the engine on linear rails. This allows the test engine to move freely, and push against a load cell to measure thrust. The spark is created before the valves are opened to prevent a delayed ignition, which can blow up the engine, and getting the valve sequence and timing correct is critical. Many iterations and destroyed parts later, the [AX Technologies] team achieved successful ignition, with a clear supersonic Mach diamond pattern in the exhaust.

This is just one more example of 3D printing and cheap electronics allowing impressive progress on a limited budget. Another example is [Joe Barnard]’s progress in getting a model rocket to land itself with a solid fuel engine. Companies and organisations have been using 3D printed components in rocket engines for a few years now, and we’ve even seen an open source version.

Fridge Compressor Turned Into Capable Little Four-Stroke Engine

December 2, 2020 by 18 Comments

Never underestimate the power of a well-stocked junk bin. Along with a TIG welder and mechanical ingenuity bordering on genius-level, all of which come to bear on this fridge compressor to four-stroke engine build.

The video posted by [Let’s Learn Something] is long, but watching it at double speed doesn’t take away much from the enjoyment. By using a piston-type compressor, a lot of the precision machining is already taken care of here. Adding the intake and exhaust valves, camshaft, timing chain, carburetor, and ignition system are still pretty challenging tasks, though. We loved the home-made timing chain sprockets, made with nothing more than a drill and an angle grinder. In a truly inspired moment, flat-head screws are turned into valves, rocker arms are fabricated from bits of scrap, and a bolt becomes a camshaft with built-up TIG filler. Ignition and carburetion are cobbled together from more bits of scrap, resulting in an engine that fired up the first time — and promptly melted the epoxy holding the exhaust header to the cylinder head.

Now, compressor-to-engine conversions aren’t exactly new territory. We’ve seen both fridge compressors and automotive AC compressors turned into engines before. But most of what we’ve seen has been simple two-stroke engines. We’re really impressed with the skill needed to bring off a four-stroke engine like this, and we feel like we picked up quite a few junk-box tips from this one.

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