The Recycled Jet Engine

Step 2 Gathering Materials

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I looked around me, all materials already at my disposal, waiting to be transformed into something incredible.

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The things I used for this project are as follows:

• An assortment of tin cans
• A coat hanger
• Some brass tubing from the local hobby store
• JB Weld
• A dremel tool
• A leatherman multi-tool
• Sandpaper
• Electrical tape
• Rubber Bands

I personally believe that in order to do any project you are forced to innovate. You probably won't have the exact same materials to work with, but use your imagination to pull this off with what you have around you!

The only thing that I don't think you can do this without is the JB Weld, which is why it's bolded above. I used this to attach just about everything together, so I don't think you can go without it.

Comments

[fozzy13]

I haven't, as I didn't know there was anything called stove glue, but I believe most any fuel will still burn hotter than that..

[n108bg]

Well, that's where you may be wrong. A lot of people have copper fuel lines and copper nozzles in their working truck turbocharger jets. Epoxies have a questionable working temp, somewhere between 150 and 300 degrees farenheit. A glue like stove glue is designed to work in extreme temperatures, well in excess of what the metal can do. I would question highly whether the JB weld could hold up to that kind of temperature (which is over 300 degrees for everything aft of the fuel ring.)

[turbojet]

Actually, fuel lines are external to the combustion chamber. Mainly the parts disposed of flames are the combustion chamber itself including the flame holder, the internal fuel injection nozzles and ingnitors, the exhaust the turbine and the housing around them. A usual EGT value is from 500 to 700 in celsius, so for at lest the above parts, you should use materials only that are guaranteed to resist 700 preferably 900°C. I am not sure if foodcans are able to handle that. Also, I don't know what amount of heat the stove glue can take, however if you tell me "up to 1000°C" that means it's probably not safe enough for the critical components.

fozzy13 got stuck mostly because of erratic design. The very first thing that shows up is that there is no compressor in his build. This is essential to get the fuel burned (and thus the work done). The project would have to meet the following, very minimal, and by no means complete list of requirements:

- Air gets sucked into the air inlet
- Air gets compressed by the compressor (slowing down the flow raises pressure, however under a certain flow-speed-limit, the compressor will "stall")
- Pressurized air (rich in oxygen) gets into the combustion chamber
- Fuel gets "sprayed" in the pressurized air
- The mixture burns due to the present heat or ignition
- Expanding gases exit through the exhaust
- Flow from the exhaust of the combustion chamber pass through the turbine
- The turbine forces the compressor to continue its rotation
- Gases leave the engine (intake must not exceed outlet or flow will stop because of air jam)
- All the parts starting from the combustion chamber and its components must me made of a highly heat-resistant material (Preferably the whole engine)
- Rotorblades/Fans must be well-balanced

[fozzy13]

Wow lots of information there! I have been considering starting another attempt at a jet engine soon, but we'll see what kind of time I have.

Thanks for the comment!!

[turbojet]

OH! I forgot another important warning. Looks like it isn't mentioned in the docs here. Rotating speed of your fans must be restricted under MACH 1, otherwise the parts will break off causing serious damages, injuries or even death. Thus you must keep you fans under (20417.7 / (fan_daimeter_in_meters * 3.14)) RPM for the above security reasons.

For example if you choose the Cummins ST-50 to make your jet out of, it has a diameter of about 5 inches, so for simplicity, let's say this matches the diameter of the compressor. Then, your diameter is 0.127 meters, so the max RPM should be under 20417.7 / (0.127 * 3.14) RPM, that is 51174.4548 RPM

Actually the centrifugal compressor of the turbo seems to be resistant to the sound barrier (as people often mention 100000 RPM operations), however a 5 inch axial compressor would possibly "explode" above 51174.4548 RPM
This is not mandatory of course, but it is wise to keep in my when experimenting. Supersonic fantips must withstand the extreme conditions...

[esimendi]

i m interested with th theories & calculations to design the jet. so can u tell me what do u mean by the above no: 20417.7 ?

[turbojet]

To be honest, it was quite a time ago and I don't remember where (or out of what) I've found this value. If I put it simply, you have a 0.127 metres diameter, which in turn gives you a circumference of 0.39878 (around 40cm).
This, to reach 340m/s (the speed of sound) needs to have an RPM of 852 so I really don't know. I've abandoned researching this stuff long time ago. My apologies.

If you would like to build one, buy a turbocharger first and then look around for info on how to attach a combustion chamber to it, give it a fuel and oil supply and always wear some ear protectors.

Regards

[turbojet]

I feel it impotant to warn you: I'm new to this stuff. The things I mentioned above are those I found out till now, and far less than complete. I've even omitted some details in order to keep the comment as short as possible.

This thread can help you a lot (as driving you through the steps of making a simple home made jet engine):
http://www.instructables.com/id/How-to-build-your-own-Jet-Engine/

Unfortunately the workaround of attaching a shaft to get power out from the engine is not described here, so it is up to you. If you want to simply use the thrust, then this is a complete step-by-step tutorial for you. It works with nearly any fuel of your choice. (I didn't try it because I don't have funds to buy a turbocharger and a welding machine).
You can find lots of vids about these jets made out of a turbocharger on youtube. I warn you again: These stuff are extremely loud, so never experiment without a good hear-protection.

Also check out this one: http://www.instructables.com/id/Design-a-Jet-With-The-Unknown-Basics/

It's got a lot of important basic information that helps thinking around your project.

Good luck!

[n108bg]

Have you considered using stove glue? It can stand up to 1000 degrees celsius. Back when i tried to build mine, i used this glue with questionable results, since it never fired.