REVERSE ENGINEERING OF A FRENCH ENGINE I read that the inventor of this jetpack in 1969 used a WR-19 engine with a thrust of 350-400 kg. Ten years ago, I found books online on the calculations of turbojet engines from the last century. I created an Excel program that, depending on initial conditions and numerous experimental coefficients, calculated the geometric dimensions of the compressor, combustion chamber, and turbine. Since these coefficients had wide ranges, the output values ​​fluctuated over an even wider range. Currently, calculations are made using a mathematical flow through the three engine components—compressor, combustion chamber, and turbine. But even with powerful software, the development time for a new engine can reach 10 years. I have no experimental data or coefficients, and no one will share them with me because they are proprietary to the manufacturer. Therefore, my calculations for six months reached a dead end. By chance, I found numerous photographs of the compressor of the French TRI-60 engine with a thrust of 400 kg online. I've been adjusting the coefficients numerous times (throughout 2017) to get close to the geometric dimensions in the photo. My opinion is that if I estimated the dimensions correctly, then the calculations were also accurate. Unfortunately, I never learned the truth, even though I sent the work to the French company Safran, but never received a response. I'm not offended, because I'm proud of this work, which I consider beautiful. Judge for yourself: Reverse engineering is the reverse design of a product that, for various reasons, must be replicated. To replicate a mechanism, the geometric dimensions of the sample and its component parts are measured. A set of production drawings is prepared, alternative alloys and materials are selected, and, if possible, technical specifications are recorded on a test bench. Currently, a 3D scanner is used to create a 3D model. Coordinate measuring machines are also used. There are examples of reverse engineering of mechanisms in many countries, but in all cases, the objects were real, tangible specimens. My question is this: is it possible, given only photos, video stills, overall dimensions, technical data—in short, media sources for the product—to obtain reliable dimensions for cloning? At the same time, to theoretically calculate a similar device? Since the photo sources depict a three-dimensional object on a plane, the image dimensions are distorted due to projections, perspective, unknown scale, and the lack of a reference size (for example, a matchbox of known length or a measuring ruler for estimating dimensions). Moreover, the quality of the photographic materials leaves much to be desired. To measure the geometric dimensions, a raster photo was loaded into AutoCAD and Photoshop, a segment was used as a reference, the image was scaled, and, if necessary (required for distorted images), deformed relative to the reference. Lengths were measured using the measuring tools included in these software. To verify the values ​​and the calculation methodology, I used the relevant theory. If the calculated and measured values ​​are close (within the required accuracy), then the value is accepted. If there is a significant difference, then the coefficients in the calculation were adjusted (within the specified range) to obtain a value close to the measured one. I worked primarily in AutoCad, so the examples include screenshots from that program. There's quite a bit of information online about the French TRI-60 engine. The first engine appeared in 1974 and was manufactured by Microturbo (now Safran Helicopter Engines). This single-shaft engine has a three-stage radial compressor and a single-stage turbine. Wikipedia states that the engine consists of only 20 major components. It has a low cost, ranging from $52,000 to $83,000. Modifications with increased thrust from 350 kg to 440 kg are available: -1; -2; -3; -5. Some users purchased decommissioned engines and posted their test results online. This involved using engine information from China, a French brochure, and the internet. Engine data varies across sources, due to both commercial and military secrets, as well as misinformation. The same applies to the turbojet diagram; the dimensions are likely distorted vertically and horizontally, and there was also a slight offset. However, all sources state the maximum diameter as 330 mm. This value was the primary reference. Initially, the plan was to calculate the entire engine—the compressor, combustion chamber, turbine, and nozzle. To test the idea, I limited myself to just the compressor. Initial data: 1. Air consumption – 6.28 kg/s; 2. Compression ratio – 3.76; 3. Gas temperature before HPT – 1240 K (obtained by calculation, sources give a different value); 4. Rotation speed under normal conditions (15 С, 101325 N/m^2, H = 0 m) – 21665 rpm; 5. Diameter – 330 mm; 6. Sources indicate different lengths – 749 mm, 757 mm, 880 mm, 52 inches = 1320.8 mm, etc. Fig. 1. Photo from the exhibition. The YouTube video quality is poor. I spent a long time choosing a reference, evaluating the size of the white stand, but ultimately based the cap length on other photos. It's clear that the compressor sections are approximately 100 mm in size, which was confirmed in other photos. Fig. 2. Photo from YouTube. I tried to use the size of a white ad as a reference, probably A3 format. The nozzle section served as a reference. The size was taken from another photo. Fig. 3. Photo from YouTube. Reference: palm near the cap. Fig. 4. Photo from YouTube. The standard was a white medium stand. I estimated the longitudinal dimensions very roughly, but the dimensions "flowed." Fig. 5. An American user of a decommissioned engine. Palm-based assessment. The hubcap on this model is longer than others – 271 mm. Fig. 6. The standard diameter is 330 mm. Fig. 7. Transverse dimensions. The compressor is designed using the Dk = const scheme. The Excel figure shows that the calculated and measured values ​​are virtually identical. The three compressor stages are highlighted in different colors. Another image of the blade calculation The figure below shows a compressor flow chart. The 256.52 mm diameter is the HPC inner diameter. The 162.1 mm diameter is the spigot diameter. Compare this with the measured values ​​shown in Figure 8. There, the inner diameter is 256.81 mm, here it is 256.52 mm; the spigot diameter at the inlet is 161.11 mm, here it is 162.1 mm. In other words, the calculated values ​​are close to the measured ones!!! The profiling of the working blades was performed using an analytical method. Using the methods described in the books, I couldn't confirm the actual number of blades—the resulting figures were inflated. Apparently, smaller gas turbine engines require a different approach. The number was determined from photos: compressor 1 working wheel – 22 blades; 2 working wheel – 26 blades; 3 working wheel – 31 blades. THANK YOU FOR YOUR ATTENTION! I'd be grateful to anyone willing to contribute to my work (not this one, I have other interests at the moment) with any amount. It will serve as additional incentive for me to continue my research. If you want to help, please write to me: proxyda@hotmail.com All the best to you!

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