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Geoff_H last won the day on April 30 2017

Geoff_H had the most liked content!

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  1. Actually as a general rule speed harmonics tend to reduce dramatically as the number of cylinders increases. I remember being taught in 3rd year of degree that a V12 was regarded as the first "fully" balanced engine, well the vibrations were considered insignificant. I don't know about this engine but I am not about to get the books out to calculate the effectiveness of this configuration. Interesting to note that there is a theory that a 'square 4" with contra rotating shafts should be considered extremely well balanced,. mmmm how heavy would that be?
  2. Props change their section as the diameter changes. The Reynolds number also changes according to, among other things, that is a function of lineal speed the position on the prop. These things change the drag of the prop at a point along the shaft, the overall torque required by the prop is the integral of the torque along the entire length of the prop. This should match, or be slightly lower than the available engine torque. This should be analysed for the aircraft to ensure that the aircraft can get into the air. At max aircraft speed the prop angle of attack to the air vector, this should be the best lift/drag ratio for the aircraft ( lots of factors affect what ratio is best). The best technique for prop design is to use finite element analysis for the aerodynamics of the prop. I created a crude finite element program some years ago. It generally produces results that are close to operating wings (actually it was designed for helicopter blade design but is the same as prop design). It also calculates stress along the prop. An important factor.
  3. The Cri Cri design used a homemade style of dynamometer. A piece of square section of wood. It has been designed and "calibrated ," to test each engine. It provides enough air for cooling and enough ploar moment of inertia for testing. Not sure of size details but maybe a safer option as I think that the diameter of the wood maybe less than a prop. The square section provides drag, the HP of the engine is determined by the max speed that the engine can get to. If I remember rightly the HP is a function to a power of around 5. Not sure anymore, old age 😀, this maybe of help in testing. If it is interesting and relevant, and you want me to, I could look up the function.
  4. Many years ago I owned a Cherokee. I could not really afford it then. I opted to insure the passenger liability for $250,000 a seat. At the time I was told by the insurance agent to make sure that I killed passengers and didn't maim the that was much cheaper.
  5. Sorry Nev, I was replying to the radio controlled turbo
  6. A scaled up version could be quite cheap. But it is very inefficient. You could expect fuel consumption to be many times what a Rotax would burn for the same kw. Efficiency depends upon the compression ratio, here I expect about 4:1, and the turbine inlet temperature TIT. The higher temperatures that your blades could take the more efficient. I expect that a turbo prop would be many orders of magnitude higher in cost.
  7. My preferences are for gas turbines. Simple design, very light for the power output if compression ratio is high. With metal 3d printing the number of parts could be reduced to very few. 60%efficiency has been obtained with high temperature turbine blades. They can run on virtually any fuel. Even coal!!!!! On India a gas turbine station was built using coal, well it made coal gas first, fed that to a bank of gas turbines then burner the coal char in a fluidised bed boiler they generated using steam turbines. A small gas turbine with high efficiency would be either very heavy or very expensive. But I would love to power my project with one. You can also get two stroke engines that run on diesel with low pressure injection. Light weight high output. Not sure of the efficiency
  8. The seat would weigh more than the aircraft. But love the thought. Unfortunately the seat in the aircraft forms part of the structure as a bulkhead, yes single seat. Love your comment lol
  9. I like the idea of testing a design, even if it has little chance of final success, you always learn something. Knowledge is never a load to carry. Many years ago I read of people experimental Rotary engines that tacked a third rotor onto the Mazda Rotary, apparently easily done. Obviously a new design of output shaft is required. The reports that I read said that they were having trouble with shaft breakage. The light weight for power would mayke such an engine attractive,even if fuel consumption is higher at high rpm.
  10. For my own design I am installing a parachute! And wearing one! I am also looking at explosive devices to disconnect the wings from the aircraft in case of uncontrollable spin. It has a sidestick so I may, in military style, strap my arm in place with some sort of quick release. Of course A full 150% load testing with sand bags etc will.be done first. Also looking a racing car helmet and brace in case the nosewheel breaks on landing and diggs in. I do expect problems, I am trying to design control of failures into aircraft. I suggest that one reads the reports of all failures reports that you can get your hands on and see if they are applicable to one's design and work out what to do to mitigate that failure should it happen to you
  11. Someone said mirror. When I bought my outback going Mooney the guy that owned it before me had a super shinny piece of metal, quite thin, rather than glass that could fracture in case of accident. I always carried oil on trips across Australia, never know when oil consumption may increase.
  12. This part was 3d printed. A test piece. Each end was bent to 12 mm deformation. It maintained its integrity. More interesting it returned to near its original Shope over the next few minutes. It is very tough, it didn't delaminate. This is so encouraging for the future of 3d printed parts. It weighs 13grams. Is 65x25x12. Carbon infused nylon.
  13. When making parts for the inside of the aircraft be aware that PLA (made from corn starch) will soften an temperatures that are common in summer. ABS is the plastic often used in motor vehicles, use it by preference. I used PLA for some support pieces for a bird restricted system, a week later had to make the 50 odd pieces out of ABS
  14. Having owned a Mooney M20J for many years I can only say that he must have gone into the side of a mountain of something head on. Mooney's are surprisingly survivable. They have a steel space frame cabin, single piece wing spar that attaches under the rear seat and a monocoque tail that moves up any down pivoting about a "hinge" at the rear of the space frame. The Mooney web sites over the years have shown Mooney crashes that were not fatal. I have transited Coffs Harbour many times. I always took the sea path in the control zone. The inland is just too dangerous in IMC. Such a tragedy,.
  15. Landing gear support. Green is proof of design, it was too small and was increased. White part should have been a straight nylon part, it failed impact testing
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