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Thread: Gyro Design Question - Puller Engine Positioned At Rear Of Craft

  1. #1

    Gyro Design Question - Puller Engine Positioned At Rear Of Craft

    I'm a tinker type and been wanting to build a gyro for some time now. Been doing a lot of research and it seems the greatest safety factor (aside from the pilot) is longitudinal stability. Secondarily seems to be rotor impact on the air frame or prop.

    Generally I tend to think if nobody's doing it then it's likely not a good idea - pioneers tend to get their wagons burned. But I have to ask the experts. Why doesn't anyone mount the engine in the rear but with the prop in front more towards the horizontal cg?

    It seems having the weight (pilot and engine) coupled near the horizontal cg would tend to negate the potential for the weight to counteract PIO. I'm not an engineer but it seems moving the pilot and engine weight outward toward the respective front and rear would increase longitudinal stability as long as the horizontal cg is properly managed. It also seems having the prop positioned mid-craft would lessen it's potential to induce PPO and essentially eliminate prop strikes.

    Am I crazy, ignorant or suffering from some other defect?

  2. #2

    Wahoo, somebody who is crazy like I am. Umm, I hope you don't take offense. I don't have the faintest idea what the effect, if any, of moving the prop towards the CG would be. But I have a practical thought. All designs I know of place the variable weights, passenger and fuel, at the CG so that they don't change the balance when varied. Put the prop there and what do you do with them?
    Magni has a simple and effective solution to stability. They have moved the tail back significantly to give it a longer arm so more leverage, more authority. I have thought, why not move it back even more? A fixed wing has a lot more. But then, they're pretty smart guys, and surely they would do a lot of testing to find the sweet spot. Am I likely to find something better? Still, like you, I just wonder. Why didn't somebody else think of that a long time ago?
    Then again, a lot of designers have picked up Ernie Boyette's tall tail, but not many seem to have moved to the tail farther back, which would seem to be a thing rather hard to patent and maybe easy to mimic. Maybe it's hard to get a good feel for it just from pictures, usually taken from an angle.


  3. #3
    No offense taken - I like to look at all angles of a problem and some of them are downright crazy. But sometimes 'crazy' is just the first label applied to a breakthrough. I appreciate the reply and insight. I have to admit I'm a bit disappointed at the lack of discussion happening on these forums.

  4. #4
    Our members have tried your quite a few things in the past. twin engine, pushers, pullers, one rotor blade, jet engine, turbine engine, jet tipped rotors, extended tails, horizontal stabs in all configurations, and even installing a canard wing.
    Remember, PRA members has been around for over 50 years. Our members have experimented with most first thought ideas.

    the propeller has nothing to do with CG. The top rotor is the main concern with CG.

    Ernie's tail is from the Sarrowhawk design. It works well. If it's moved back in reference to fixed wing. It would become much more difficult to trailer.
    Last edited by BRENT DRAKE 38604; 08-23-2017 at 08:12 AM. Reason: Added

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