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.
I’m sorry but M18 Dromader with ASz-62 engine (same as in Antek An-2) is probably simpler to service and maintain than BMW M57. I have Daewoo Lublin van with 4C90 diesel engine registered for 3500 kG max but in reality once I drove from Garwolin to Kleszczele with over 6000 kG of load in the back (used engine blocks and other metal parts). Advantage of simple spring suspension rather than independent one which will break when overloaded or hole in road.
Looking at articles on the home page, I think you managed to post on wrong website. Quite a feat. Have you tried to move some electric engines with turbojet powered Lublin to Szczebrzeszyn? ;)
In the end you just have to use the right materials, people have been building these engines at home for 25-30 years now. If you build an engine for model aircraft use the rules state that your turbine has to have passed x-ray inspection. Something about spinning at 60k plus and flying apart being bad. Which luckily I dont think he got anywhere near that speed. I woudnt be standing anywhere to the side of that engine. There is a heck of a lot of energy stored in that wheel.
Indeed, not wearing a face shield – nor even a safety tie – IMO sets a bad example to his viewers.
I have had to go to hospital to get a piece of angle grinder grit dug out of my eyeball, and I can assure everyone it was not a pleasant experience.
And I was wearing safety glasses, as luck would (not) have it the fragment passed through the small gap between the glasses and my respirator mask nosepiece. Now I wear a full face shield when I wear a mask.
Your mention of a safety tie caused an immediate google – seems you can buy them and I just did :)
Need a new full face shield/powered respirator. Present one is in tatters after years of protecting eyeballs/lungs. Sadly they’re the wrong price, so shall put up with it and continue looking like some sort of post apocalyptic metalwork tramp. But with a nice new Furze tie.
One very good use for rare earth magnets.
For steel shards maybe, for the grit off the wheel they’re going to do nothing. (Like ze goggles)
60k? Maybe the gas generator for a Bell Jet Ranger, definitely not something that pushes small models around, those easily touch 200k
yeh, the Allison 250 engine is ~50krpm compressor/turbine and ~35krpm powerturbine
It is indeed a very challenging task.
Modern turbojets use an axial flow design, which is significantly harder to do in a model engine. I don’t think I have seen any in production for hobbyist use.
an axial compressor need many stages to get a deacent pressure ratio, it is hard enough to get a single stage centrifrugal compressor to work
Interesting build but I wonder about the printed compressor’s ability to spool up to really high revs.
Thomas Kamps, whose original book on building a model jet turbine kicked off the DIY turbojet hobby, used a centrifugal compressor made from thin plywood. Then he wrapped and epoxied carbon fibre filament around the circumference which kept it together at 100,000 RPM. His turbine was sheet steel with the blades twisted to the correct angle in a jig.
Schreckling’s design (published in 1992 per my copy) used the carbon-fiber-reinforced plywood compressor wheel, Kamps’s design used one from a small turbocharger. Both good booklets for anyone interested in model-scale gas turbines.
Ahh you are completely correct sir or madam. It _was_ Schreckling. I have both Schreckling’s and Kamps’ books on the bookshelf (bought years ago), do you think I bothered to walk over to the bookshelf and actually verify my statement before I posted? Sadly not, so thanks for picking this up.
I am looking for a motor for a BD5 aircraft
Reysayre at yahoo
Thx
The off the shelf solution is to use a PBS TJ-100 turbojet, as used in the SubSonex, which has nearly identical performance compared to a BD-5J. Last I looked, these engines cost around $60,000 USD, brand new.
What if you put a narrow tube around the shaft between the compressor and the burner section, make the whole thing longer with a neck in the middle like an hourglass figure, so the combustion chamber doesn’t heat up the compressor?
Maybe he could also use a high bypass design and inject the bypass air into the engine between the combustion chamber and compressor? It might loose him power but better a weaker engine than a molten puddle.
It is a tough home project simply because turbojets combine high RPM, high heat, and tight clearances. Balancing compressor blades that you manufacture yourself would be quite challenging. So is modeling the airflow through any turbojet engine. As the author said, countries have struggled to produce turbojets and very large countries like China have struggled to produce supersonic turbojet engines.
I also wonder if the concrete is helping or hurting him. It may be keeping heat inside the engine that might have radiated from the casing. Also, its an evolutionary dead end because obviously thrust to weight is an important factor and concrete won’t make the cut unless the engine is destined for stationary (generator) application.
He could use it as a gas turbine to propel a concrete ship!