How to make a real homemade minijet engine. Part 3 (completion and commissioning)

After having the support ready and waiting, and the combustion chamber ready to be filled with fuel, the only thing left to do is to prepare the start-up of the minijet rocketTherefore, a structure without an entrance for the air and fuel is of no use, so we can get to work on this part to create the inputs for these fluids.


Materials for the minijet

Fuel injector for the minijet

  • Strong metal glue (Nural type).
  • Thin rubber tube for carrying fuel. Can be used for garden drippers.
  • Fuel valve with nut or use glue to secure it (optional).
  • Thin copper tube.
  • Plastic bottle of baby cologne or similar in which we can store the fuel and inject it. This can be a good method of calibrating the fuel input manually without a valve.
  • Spark plug or the spark mechanism of a cigarette lighter.

Note: All measurements are detailed in the following image.

Click on the image to enlarge it


We are now closer to culminate our designSoon you will be able to start the engine for the first time and hear its characteristic sound and check its power, so take heart! Before following the steps I would like to clarify that there are several methods to proceed, as the original designer does it or modify it to make it easier. I think it is more practical to modify the design to make it easier and to better find the right materials (there are certain valves that are more difficult to find and not everyone has a bottle of oxygen or compressed air at home).

  • Now we proceed to create a hole behind the grille. This can be done using a drill with a metal drill bit. This hole will be used to insert the spark plug or spark mechanism which ignites the fuel mixed with the oxidant in the combustion chamber.

Hole for cigarette lighter or spark plug.

  • Now insert a spark plug to spark the spark in the previous hole or use an electronic device to generate a spark when you want to start the engine. Another easy and inexpensive option is to use the spark mechanisms that can be found on the engine. inside some lighters or kitchen.

Spark plug in place

  • Another hole must also be drilled just in front of the grille, in the area of the reactor intake nozzle. In this hole, a metal valve or metal tube will be inserted, which will be used to connect a rubber will carry the fuel into the reactor. The pipe should be thin so that not too much fuel can pass through at once, but it should be long enough so that it is not too close to the engine and risk burning. The other end of the hose can be connected to a plastic canister containing the fuel (e.g. paraffin). The tube should be flexible so that it can be squeezed by hand to help the liquid to penetrate. Propane gas can also be used, but it is more difficult to find and much more dangerous to handle.


  • To insert the air, we can continue our work by drilling small holes with an awl, so that they are aligned side by side and then levering them out to create a groove in the aluminium of the reactor body. The groove should be right at the back of the reactor and before the grid. The copper tube should be long enough to protrude from the reactor support to connect the tube that feeds air to the reactor. At the other end, it must penetrate a little into the reactor structure and the shape at this end must be flattened (the shape of the groove can be created by hitting the end of the copper tube with a hammer until the required shape is achieved). This will narrow the tube in this area and create the necessary compression effect. Remember seal around the tube so that there are no holes through which leaks can occur.

Air slot

  • The author's method of injecting air involves compressed air or oxygen cylinders, which are difficult to find and dangerous to handle. A simple alternative to the use of gas cylinders is the use a blower The blower will generate sufficient air flow to feed the reactor and allow combustion. The blower will generate enough air flow to feed the reactor and allow combustion. What can be done is to adapt the mouth or outlet of the blower to the copper tube from the previous step, so that the blower will pass the air through the copper tube and compressed air will be injected into the combustion chamber.
  • Other modified models of the reactor include structures that allow the air entering the inlet to be compressed and directly use the blower directed at the inlet without the need to create the orifice and place the tube described in the previous step.

Finished minijet rocket

Finally we have our homemade minijet finished. You should go through the steps to see if you have forgotten anything and check for manufacturing defectsThe glued joints are the most important ones. Afterwards you should take appropriate security measuresThe following are some of the measures to be taken, such as anchoring the engine mount to a rigid platform that can withstand the thrust of the jet, isolating all flammable materials around the engine before starting it for the first time, preparing fire extinguishers in case of an uncontrolled fire and keeping a safe distance from the jet, especially at the rear of the jet where the jet exits.

Once everything is ready, to start it up, we have to prepare the blower just in front of the intake in order to put air inside the jet, then we will inject the fuel and we will make the spark to generate the combustion. If all goes well, the minijet will start to roar and run. Controlling air and fuel flow the power can be controlled.

According to the tests, this ramjet could reach the Approximately 193 kilometres per hourWhat was your result, did you find any modifications or improvements that would benefit the design? All your comments are welcome.

More information - How to make an authentic homemade minijet engine. Part 1 (support), How to make a real homemade minijet engine. Part 2 (diffuser and combustion chamber)

Source - Cottrill Cyclodyne

34 thoughts on “Cómo fabricar un auténtico motor minijet casero. Parte 3 (terminación y puesta en marcha)”

  1. Gonzalo Aguilar Lopez

    This experimental engine is incomplete, and does not meet the characteristics of a stator type engine, what was built here is a gas flame torch assisted by an air blower like the ones my grandfather used to use. Nothing happened here
    The key to the experiment is to test the compression of the air by constricting the cylinder until its temperature is high enough to ignite the fuel without the need for a spark, only a real flight needs an ignition spark because of its initial velocity which is zero.
    The most important thing is to determine ....
    1. how many times must the area of the cylinder with the central cone be reduced?
    2. what air velocity is required to obtain the necessary compression.

  2. I have a question. If I have the necessary motors, could I have enough power to lift a person?

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