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Geoff_H

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Everything posted by Geoff_H

  1. Geoff_H
    A properly crimped joint is a galvanic bond and will only corrode around the edges. High voltage (330/500kv)I we are crimped, often near salt water, they are not known to collapse from corrosion of the joints.
  2. Geoff_H
    A properly done crimp does.
  3. Geoff_H
    Yesterday I had my latest encounter with soldered joints failing. A classic mini that had an upgrade to a solid state fuel pump, one we often see in aircraft. The short leads from the pump had an extension soldered to extend their length to a plug. Sitting near the rear suspension the pump even has its own vibration isolation mount. The joints (positive and negative) had heatshrink around them. Finally failed several years after installation. Unfortunately 200km from home. I am just glad it was not an aircraft. A motor mechanic soldered a new pump in, he did not realise what the failure really was. The owner and I have a date to replace the soldered joints with crimped ones. With a professional crimp tool!
  4. Geoff_H
    Surely everyone knows that space aliens actually gave them antigravity stuff to build the pyramids. 😳
  5. Geoff_H
    I think seals will be a problem. The surface velocity looks like it will be high, this will contribute to wear. Air cooling claim was suspicious, and we only saw the engine with apparently no load. However the concept fascinated me. I have an unusual curiosity, just ask the wife.😏
  6. Geoff_H
    Not defending it but there is video at the end of the clip that shows something like this running. I don't think that the wear at the max speed would be acceptable. I just found it an interesting concept.
  7. Geoff_H
    https://thekneeslider.com/omega-1-internal-combustion-engine-is-light-powerful-efficient-and-clean/ This engine is very interesting.
  8. Geoff_H
    I did heaps of calculations on which is lighter an epoxy/ cloth design or aluminium. Strangely aluminium was the lightest, for a very unusual reason. The shear stress of aluminium is around 60%of the UTS. With any epoxy/cloth the maximum shear is the shear stress of the epoxy, after all that is in shear between the layers without cloth holding it together. When I designed the main spars they were heavier than aluminium by a significant amount, just to ensure that the spar would not fail in shear. A lighter spar could have been made using a carbon/Kevlar intertwined cloth. Still a little heavier than aluminium. The monocoque shell needed a foam core to get a good Euler's buckling force. Boeing don't use epoxy, a much high strength "glue". I am however a proponent of FRP.
  9. Geoff_H
    To convert to RSS what are any additional costs to flying instructions?
  10. Geoff_H
    Skippy You are after a high performance cooling system, one which cools the engine continually but presents the least drag on the aircraft. In my 50 years as an engineer I have not seen a totally new design be got right on the first design. What I think that you will need is to make a cowling then instrument it and data log the data probably including spaces inside the cowling when miscellaneous equipment such as fuel lines may lurk. Amongst the temperatures that would need to be monitored is all cht, inlet air temperature exit, air temperatures air flow measurements etc. I worked on the design of the fluidised boiler at Redbank Power Station, the first of its kind in the world, we changed that design many times over a year or more before we got it as good as it could be without tearing it down. But I do wish you the best of luck with what you choose. Geoff
  11. Geoff_H
    My cri cri similar project just puts the cylinder fins in the airflow, hopefully enough flow at idle. Much simpler, more drag, as said earlier it's all a compromise.
  12. Geoff_H
    "That's all fine but the math doesnt lie." That is if you have the right maths. After years of calculations and observations of actual air flow in ducts believe me it is far more complex than simple maths. Everything from zero wall velocity to air viscosity etcetera. Best idea is to observe what works on a similar installation and copy it
  13. Geoff_H
    Personally I think it is but I am not writing from any point of knowledge. It definitely has more strength at temperature. 95% of what I use is epoxy.
  14. Geoff_H
    Many years ago the epoxy landing gear on the Cost IV often sagged with time. The cure was to 'cure' the epoxy by constraining the legs and heating them for several hours without any load on them. The suggestion was to stop them in black plastic and put them out in the summer sun. It was claimed that there was no sag on undercarriage legs so treated. I don't have details not numbers. It does make a little sense when you look at prepeg fibreglass with uncured fibreglass is placed in a mould then heated to cure it.
  15. Geoff_H
    It is a polyurethane foam with glass/ epoxy skins. Attachment to the glass epoxy using a glass balls/epoxy mix, that never failed. The foam failed in shear at the centre. I have searched for data on composite strengths, the best advice I got was that data was very expensive to get and guarded very much. Some years ago I had organised to do a Master's in Aeronautical, my project would be to determine a calculation system for composites. I got a contract just as I was about to start, never got back to it. Too old now.
  16. Geoff_H
    Thanks, great information. I am only aware of people making composite aircraft using a skin of epoxy glass or foam with a fibreglass double skin. With the exception of the very advanced aircraft construction similar to the Boeing aircraft. I have been building using a foam covered with glass/epoxy. I have been unable to determine the strength of the combination by calculation. I quess a combination, construct it and then test to destruction and use the values found in the test as the value for design. I think that finite element analysis maybe the way to go. All my tests have failed by shear stress at the centre of the foam. The layers of glass/epoxy remained intact in the testing, but it was deformed. But will the structure take significant cycling? Will it fatigue? Maybe I should make a test rig.
  17. Geoff_H
    Thinking about the fatigue in aircraft brings another question to mind. The designer of the Cozy IV stated that composite fibreglass does not fatigue. I don't know that I believe him. Anybody know anything about composite aircraft fatiguing?
  18. Geoff_H
    There are several kits to build your own EFIS at home. There are also EFIS' for your smartphone. Anyone have any experience in any form with these?
  19. Geoff_H
    Steel has a stress level below which fatigue does not exist. Aluminium does not have any point at which does not fatigue. The design level is statistically derived with a nice safety margin....however is your aircraft aluminium as per design? Inspections are important. As Nev commented salt erodes aluminium and I think that it reduces the fatigue failure points (not sure).
  20. Geoff_H
    It is not the wires melting that the current rating is based on it is the maximum temperature that the insulation can stand. With the Tefzel wire (a Teflon like product with less lethal gasses given off in a fire), you can use a smaller gauge wire, a weight reduction. Digital signals don't require a high current, not even the power supplies, but you never know what will go wrong. Murphy was an optimist!! I would never again solder, I had so much trouble, even with heat shrink, then I was told to crimp....now I always crimp. Only use non oxidation gold connection. In my younger days we carried ink erasers to clean dirty signal connections. Gold was a saviour. No good getting a failed digital signal for lack of quality connect systems.
  21. Geoff_H
  22. Geoff_H
    I think that you are right Nev. I should have researched a little more. I was so pissed about my car I was on the verge of demanding my money back when they fixed it
  23. Geoff_H
    When I picked up my car in 2019 the 3G and GPS were interfering with each other. Data was being stopped and the GPS had me in the middle of McCarrs creek. The two antennas are in the only little enclosure at the rear of the roof. Overseas did not have this problem, so they said. In Australia we often use the lower end frequencies of 4G as their range is better, especially near where I live. Well some Germans came out with a lot of test gear and it looks like the problem is solved. The FAA is worried that 5G will interfere with their GPS equipment as I believe that the frequencies are very close.
  24. Geoff_H
    My Mooney had gap seals. They appear to work very well.
  25. Geoff_H
    I sure do. 74. It was Matt Hall's dad that tried to make me sick with aerobatics. Never a moment of sickness, loved every second of it.
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