Your opinion on the Tractor Style Gyrocopter?

Discussion in 'Hangar Flying' started by cheapracer, May 4, 2017.

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  1. May 8, 2017 #61

    cluttonfred

    cluttonfred

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    Very cool, I don't know the design but it looks like it might have a mid-fuselage-mounted engine with a long shaft to the prop. I am not sure what's up with that nosewheel, though!
     
  2. May 14, 2017 #62

    Grelly

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    Hi Cheapracer,

    I notice nobody has mentioned the CarterCopter. It isn't a tractor, but does mix wings and rotors, so I thought it might be of interest: http://www.cartercopters.com/

    Grelly
     
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  3. May 14, 2017 #63

    cheapracer

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    Thanks Grelly, yes it is interesting and would certainly suit someone's purpose. To me it looks messy, too much going on.

    What a shame the first one crashed and set it back some, because, wait for this one, the pilot didn't put the landing gear down during a landing gear test!
     
  4. May 15, 2017 #64

    rtfm

    rtfm

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    Hi guys,
    Great to see a gyro discussion on HBA. I've not been here for some time, so this was a welcome read when I returned this morning.

    Tractors vs pushers. For me there's no contest. Pushers all look a bit weird, to be honest. I really like the look of tractors. However, I am definitely not in the nostalgia time-warp. I like modern and pretty. So, based on the Pitbull (the nicest of the tractors, IMO) I started designing a little tractor of my own.

    Now, before someone says - there goes Duncan again - off on a new tangent. Let me remind you that I am hard at work on my AeroMax kit, which is progressing nicely. But there is LOTS of time in the evenings when one can't work on the plane, so at times like these, my mind turns to designing planes.

    Here's my current concept.

    RTFM tractor gyro sketch 1.jpg

    It is small, light and simple. A basic aluminium tube keel, triangulated mast, and two composite fuselage half-shells. Canopy optional. Couldn't be simpler to build. Cost of materials would also be minimal. How gyros can cost upwards of $100k is absolutely beyond me. To supply any/all of the already cut AL tubing, head, rotors and landing gear would be pretty simple. The fuselage is two half-shells with an (optional) canopy. Once the mold is made, production is pretty straightforward also.

    RTFM tractor gyro sketch 4.jpg

    Up front: 100hp Simonini (or similar)

    Other features:
    • Semi-powered rotor. Either by a Dick De Graw differential system, or a separate rotor-dedicated motor on an overrun clutch. Apparently, to keep the rotors spinning at about 220 RRPM one would need about 10hp. Easy enough. Why? Well, you need a good pre-rotator anyway, and if you keep the rotor powered to 220 RRPM during flight, the airflow only has to provide the extra 20 or 30 RRPM - meaning the disk angle is greatly reduced. And that means less drag and faster forward speeds.
    • Tricycle gear. There are some issues with rotors on tail dragger gyros, as Ron Herron has pointed out. So why add yet another barrier for potential users who see tailwheel ground handling as a major issue?
    • Stub wings (8ft span. Mainly acting as gas tanks, but producing about 100lbs of lift at cruise.) And not big enough to interfere with the rotor downwash. And the wings aren't big enough to obscure the downward view too much either. And relieving the rotor of 100lbs in the cruise is a great idea.

    My main problem is that I can't draw very well, and really struggle with creating 3-D fuselages. So for the moment, I'm having to content myself with a spindly 2-D side-view of the fuselage. Not ideal, but at least it does help to conceptualise the thing.

    As to why tractors are so unpopular? I think what the gyro world (small as it is) needs is a sexy looking, cheap and easy to build tractor to lure them. Enough already with the nostalgia - which appeals to a sub-niche of a sub-niche of a very small segment of the flying/building public. With stub wings it even looks like a plane. Get rid of as many barriers as possible.

    My 2c
    Duncan
     
    Last edited: May 15, 2017
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  5. May 15, 2017 #65

    BJC

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    Of the several people that I have known who were interested in homebuilt gyros, all but one wanted the simpliest, cheapest, easiest to fly, easiest to build flying machine possible. The bolted-together pusher configuration, a la Benson, seems to meet that criteria far better than the tractor configuration. And the one tractor devotee has had his under construction for almost 20 years now.

    The tractor configuration certainly has appeal as a retro (think 1930's) symbol of wealth and adventure.


    BJC
     
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  6. May 15, 2017 #66

    Grelly

    Grelly

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    :nervous: Bet he doesn't mention that on his CV!
     
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  7. May 15, 2017 #67

    cheapracer

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    Yes I understand that POV, also sadly has given any startup now a bad name before they even start due to the high incident rate in their history.
     
  8. May 15, 2017 #68

    spaschke

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    I think an electric motor would make a great pre-rotator. Power it from the alternator, gear it down so you can use a smallish motor. In an engine out situation, you could power the pre-rotator (off battery) for a minute or two to slow decent even more.
    I would like a closed cockpit Gyrocopter. I think I lean a little towards a tractor layout.
    I want something to go on cross country trips. Visit backcountry strips (fields). I wouldn't need as long a runway as a standard cessna. Might work with floats.
    I like the CarterCopter. I would think small wings would help the stability at cruise speed, but may hurt performance at low speed.
     
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  9. May 15, 2017 #69

    cluttonfred

    cluttonfred

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    Personally, I think this idea of using the pre-rotator to power the rotor in flight is a solution in search of a problem. Powering the rotor in flight to keep it at a low angle of attack means playing dangerously close to the edge of negative flow through the rotor, which could quite literally be deadly, not to mention introducing torque effects that would result in additional trim drag from the rudder and strong yaw forces with changes in speed. Existing gyros can already land safely in very small areas, far smaller than they can use to takeoff, no power assist required. If an electric pre-rotator is lighter than a mechanical one, which I doubt, then great, but it should only be used as a pre-rotator on the ground.
     
    Last edited: May 15, 2017
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  10. May 15, 2017 #70

    cheapracer

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    Quite a few do it already with starter motors.

    There's a Russian guy on the net with a Subaru powered Gyro who has hooked a power steering pump to an aircon pump electric clutch pulley for easy electric switch on and off, and it drives a servo pump up on the mast.

    Well there you go, I book marked it ...

    [video=youtube;DcaEx_jjqbQ]https://www.youtube.com/watch?v=DcaEx_jjqbQ[/video]
     
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  11. May 16, 2017 #71

    rtfm

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    Hi BJC,
    If you have in mind the Little Wings type tractor, then I agree with you wholeheartedly. They are actually full fixed wing aircraft without the wings. Very complex to build. But I am talking about a simple bolt together frame...

    RTFM tractor gyro frame.jpg

    Even if you have to cut and drill these seven pieces of aluminum tube yourself, it is the work of a morning.

    The undercarriage is a simple triangulated affair, attached to each side of the keel with standard criss-cross bracing as seen on hundreds of light planes. Like this Cub.

    Bungee undercarriage.jpg

    So far, there is nothing different from a Bensen-type pusher.
    • Where to put the engine is essentially immaterial as far as construction goes.
    • Rotor/rudder controls are the same for either configuration.
    • Likewise for the tail feathers, seat, windshield (which very easily attaches to the triangulated masts), rotor head and rotor blades.

    So now we have:

    RTFM tractor gyro frame2.jpg

    So now we add the tail feathers (which pushers have to have also). And like many gyros, these can be either be flat plate affairs put together by the builder himself, or churned out in my molds and bolted on.

    RTFM tractor gyro frame3.jpg

    You could now hop on and go fly. What is more complicated build-wise than your typical Benson-style gyro?

    Except that, of course, you can add to this basic design by adding stub wings (which are optional, of course). They are just a convenient place to store the gas, but another arrangement could be made. They also provide some lift during cruise, essentially making the gyro about 100lbs lighter, which is a bonus.

    RTFM tractor gyro frame4.jpg

    You could now go fly, and have a more satisfying experience.

    And if/when you decide to add a little sexiness/cold weather comfort, you can bolt on the two molded pieces of the fuselage shell (left/right, popped out of my molds). The cowling is also in two pieces (top/bottom).

    RTFM tractor gyro frame5.jpg
    Or with the canopy...
    RTFM tractor gyro frame6.jpg

    If, as you say, cost, and simplicity are the major factors considered by gyro builders, then surely this hits the mark also?

    Regards,
    Duncan
     
  12. May 16, 2017 #72

    KAF

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    "Stub wings (8ft span. Mainly acting as gas tanks, but producing about 100lbs of lift at cruise.) And not big enough to interfere with the rotor downwash."

    I'm no rotary wing expert, but I think a gyro copter only has upwash. Someone on here who is smarter than I am can explain all the differences between upwash and downwash and how a true helicopter can experience both.
     
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  13. May 16, 2017 #73

    Tiger Tim

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    RTFM, take a good long look at the Pit Bull gyro. They did exactly what you're proposing and if you're serious it would be worth studying what worked for them and what didn't.
     
  14. May 16, 2017 #74

    cheapracer

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    Acts like a wing that happens to be spinning, so it's primarily deflecting air downwards. You need to see that it isn't like a helicopter that's powered and forcing the air in suitable directions.

    gyro heli.jpg
     
  15. May 16, 2017 #75

    rtfm

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    Hi,
    That's exactly what I did. My first sketches were as near to the Pitbull as I could get. But thre is almost zero technical data on the Pitbull. I've searched high and low - even to find some basic measurements (beyond length - which seems to differ for every Pitbull I could find).

    I then read a few of the NACA reports related to gyros, especially with respect to wings, otors and the interference between the two.

    Finally, I noticed that my drawings had morphed into their own thing. But such is life. It is early days yet, and by the time I actually get round to bolting the frame together, fitting a seat and putting the craft onto wheels, I'll be able to make a better judgement call on the length/shape of the fuselage shell. It's an iterative process, but one I enjoy very much.

    I really like the look of the BTTB Pitbull. I suspect my little design will morph back into something more resembling that gem.

    PitBull-Landingpage_v1s_r1_c1.jpg

    Duncan
     
  16. May 16, 2017 #76

    cluttonfred

    cluttonfred

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    Yes and no. I absolutely agree that the rotor "acts like a wing that happens to be spinning" so it creates a downwash in its wake. Unlike a fixed wing, however, the gyro rotor must always maintain upward flow through the rotor, in other words a positive angle of attack, since downward flow from a negative angle of attack will try to stop the rotor, then bad things happen. That and pitch damping are why the horizontal tail on a decent arm is so important and why the Bensen-style gyros have such a bad reputation.

    There is also the special case when the gyro can "fake" being a helicopter by trading rotor energy for lift with no forward motion, no wind. You can see that in practice when a gyro does a spot landing with the engine off or at idle and the in the final flare will appear to hover or even climb a little at the last second and the pilot will see the rotor RPM drop. It's not sustainable, just a few seconds, but it's clearly not something a fixed wing could ever do.
     
  17. May 16, 2017 #77

    cheapracer

    cheapracer

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    Of course, it wouldn't spin otherwise. But it's never forcing air through other than on occasions of inertia, as you point out, it's being forced through the air and being deflected upwards as it moves forward.

    I will eventually get my CFD guy to do a sim.
     
  18. May 17, 2017 #78

    Tiger Tim

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    RTFM and Cheapracer, you guys both seem like folks who want to run airplane kit companies. What advantage do your tractor gyros offer over, well, anything that would get enough folks laying down cash to keep your operations going? I'm not asking this just to crap on either one of you, I'm just curious what got you going down this path.
     
  19. May 17, 2017 #79

    rtfm

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    Hi,
    As far as I'm concerned, I enjoy designing/building more than anything else. I'm not looking to make this a business, but if I go to the trouble of building molds, and figuring out how to get everything to work the way I want it to, then I might as well offer the fruits of my labour to others. I don't want to make a loss, but I also don't see this as a full-time business either.

    Regards,
    Duncan
     
  20. May 17, 2017 #80

    deskpilot

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    Duncan, you can design whatever you like with Sketch-up. All it needs is practice and experimentation. there are loads of tutorials on the web. Sure, some things are harder than others but perseverance will get you there.
     

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