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Bruce Tuncks

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Everything posted by Bruce Tuncks

  1. Bruce Tuncks
    Sorry about the mucked up posting.... I left the thing to look up how to spell bouyant, then had trouble getting back to the start again.
  2. Bruce Tuncks
    thanks nev for that tip about altering nuts for adjusting the torque . I agree about air pockets.... they are actually areas of lift and sink, thermals and sinking air. flying though them with a winged plane will cause extra lift and downwards "lift " as they are encountered. Yes, flying into a sharp-edged bit of sink can seem like you have flown into a vacuum, but that is not the case. Thermals have been extensively studied, mainly in Germany, and one of the surprising things, for me anyway, was that the air is more bouyant
  3. Bruce Tuncks
    Gosh, I hope that they really are pro-trump climate change deniers. How do they explain how their evangelists did not help? Will the price of planes increase as a result?
  4. Bruce Tuncks
    thanks nev for that tip about altering nuts for adjusting the torque . I agree about air pockets.... they are actually areas of lift and sink, thermals and sinking air. flying though them with a winged plane will cause extra lift and downwards "lift " as they are encountered. Yes, flying into a sharp-edged bit of sink can seem like you have flown into a vacuum, but that is not the case. Thermals have been extensively studied, mainly in Germany, and one of the surprising things, for me anyway, was that the air is more buoyant in a thermal if it has water vapour in it. ( molecular wt of water vapour is 18, while nitrogen is 28 and oxygen 32 ). We see this effect on some summer days when the cu are only over the areas of scrub, where the deep roots are sucking water.
  5. Bruce Tuncks
    There could be some lesser heating just from the flexing of the prop, but this is beyond me to work out.
  6. Bruce Tuncks
    yes it would if there is any movement permitted. The slightest looseness, which is not discernible on the ground, will provide the relative motion and energy = force times distance . The energy from this friction will become heat. This is what caused the prop hub to go burnt black on our first Jabiru. I reckon we were lucky in that the flywheel bolts stayed good. The lesson is... Make sure your prop is on tight, and as I said, an indicator blob will help. The dried blob will crack if there is relative movement.
  7. Bruce Tuncks
    OME had it right. The variations in rotational speed come primarily from the pulsations from the power strokes. 4 cylinders are worse than 6. The worst I have ever come across was a single cylinder 4 stroke model plane engine. Just imagine... power for every 45 degrees in 720 degrees. Apparently with high-speed photos, you could see the prop bent one way on the power strokes and (less so ) the other way for the rest of the cycle. Here, the prop acted as the flywheel. It sure would on a big plane engine too.
  8. Bruce Tuncks
    I've seen a Jabiru prop hub that has been made black by the relative movement between the prop and the driving flange.... and this was on a prop with driving bushes . There was a letter from Jabiru where this movement could have been responsible for the trouble with fracturing flywheel bolts. A hammering at one end of the crankshaft was transmitted to the other end. On reading this, I used epoxy to take out any play in the driving bushes and also used a trace-glue ( nail polish ) to show if there was any movement going on... yes, I did need to use a bit of heat to remove the bushes later, but this was not much. You can't tell by turning on the ground if there is any play... so I recommend the nail polish between the driving flange and the prop, and only use epoxy if you have to.
  9. Bruce Tuncks
    Those bolts marked "8.8" are a metric bolt and pretty good too. I don't think Bolly would provide crook ones. In general, the higher the number, the better the metric bolt is. I'm mystified by the references to nyloc nuts though. I've never heard of one coming loose, but I agree they are not used on Jabiru props. Personally, I would use some low-strength loctite and adjust the torque to suit the changed friction when tightening. If you use cotter pins and castellated nuts, you have to live with the thought that these items do nothing until the bolt has come loose a bit.
  10. Bruce Tuncks
    Gosh, here am I thinking the 230 is a big and heavy plane... the sk jabiru was as heavy as the gliders I used to fly, and the 230 is heaps heavier. But my flight in a chipmunk sure told me that the dark side has easier landings. And easier flying, with no cht instrument to worry about.
  11. Bruce Tuncks
    Yep, after flying a Jabiru SK for years, I was amazed at how easy a chipmunk was to land.. inertia and big oleos sure helped. So, maybe for the first time, I fully agree with turbs. Maybe years of landing taildragger gliders helped with the transition to the Jabiru. But whatever it was, the Jabiru is not easy to land nicely every time.
  12. Bruce Tuncks
    Thanks mike and matt, I didn't know about them and they are good stuff.
  13. Bruce Tuncks
    I need to fly so I can answer that question turbs. I think so . What I try and do is to get the mains at about a foot high and then try to keep them there, in other words I try and NOT land. I reckon there is room for improvement in my judgement of the 1 ft high though. Sometimes the arrival is harder than I'd like. I do remember a couple of late afternoon glider landings, where you could feel the wheel being spun up from the tips of the little weeds, as the speed washed off, and you fed in more elevator to keep this going.
  14. Bruce Tuncks
    I'll let you guys know as soon as I get to try it out. But knowing if your mains are 2 ft or 1 ft above the runway does seem like useful information at this stage. A big unknown is how the system will handle the approach over the scrub... will it take the scrub tops or see through to the ground below? AND, how will the technique of landing be altered to suit if it does work? Right now, the setup is not on the plane .... the easiest place to put it is on the floor just behind the pilot's seat. This means making 3 holes, the big one for the lidar to look through and the 2 smaller ones for the attach screws.
  15. Bruce Tuncks
    I am planning to connect the lhs to : Red and yellow wires.... 12 volt temporary supply. Blue wire ( lhs audio output ) to pin 6 of micro-air radio.At first, this will be through a resistance box, with the initial resistance well over 1000 ohms. Yellow wire ( the negative voltage wire ) to pin 11 or 12 on the micro-air . I am quite scared of doing the wrong thing and causing smoke to appear. References... enginebridge Landing Height System 200-B manual and micro-air 760 manual.
  16. Bruce Tuncks
    I have just got one of these in the mail. It only weight about 200 gms and it tells you just how high ( down to one foot ) your wheels are off the ground. You can see it working on the net. My problem now is how to install it on my J230 plane, complete with microair radio. The radio has an aux input .( pin 6 of DB15 connector according to p14 of microair manual ) The manual says to only use a headset audio and so my plan is to use a resistor at least at first between the lhs audio and the radio. Does anybody know about these things? I would ideally like somebody who has installed one on a Jabiru 230 to help, but this may be asking for too much.
  17. Bruce Tuncks
    AND I'll be self-sufficient with a tent n stuff.
  18. Bruce Tuncks
    Good onyer OME. Just tell me where and when.... I'll be there if weather permits.
  19. Bruce Tuncks
    Mike, the only person who I know who has landed in scrub said that when the wings were ripped off, the plane stopped. I take this to mean. that if you keep flying enough to aim the fuse between trees, this will be mighty helpful.
  20. Bruce Tuncks
    I reckon 500 ft is too conservative, But you can find out for yourself at a safe height. An important factor is how long it takes you to begin the turn-back.
  21. Bruce Tuncks
    Gosh, that is an impressive plane. I wonder if they are relying on better batteries by then.
  22. Bruce Tuncks
    Good onyer Meglin
  23. Bruce Tuncks
  24. Bruce Tuncks
    SAorry, I wanted to fly from Edenhope on Friday. Don't think it is going to happen.
  25. Bruce Tuncks
    I thought there were more Rotax engine failures in the last lot???
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