Aluminum Tube & Gusset Airbike / Legal Eagle / Parasol Thread

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Victor Bravo, Oct 8, 2019.

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  1. Oct 17, 2019 #241

    proppastie

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    just stretch one cell end till you get the length you want,...probably need thicker tubes,wire, and perpendicular supports at intervals to cut down on the Euler length of the tubes. Now this needs 3D to design.
     
  2. Oct 18, 2019 #242

    FritzW

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    If you did it right you'd only have to loosen one turnbuckle and your airplane could fold up a fit in the trunk of your car (we'll... not quite, but it could still be pretty handy).
     
  3. Oct 18, 2019 #243

    ScaleBirdsScott

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    Tensegriplane? Crazy house!
     
  4. Oct 18, 2019 #244

    Vigilant1

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    We had a useful thread a couple of years ago--it started with "how to make a steel tube frame without welding" but morphed into discussion of AL frames. Some snippets:
    Comparing steel tube vs AL tube (in reference to my comments about crashworthiness), cheapracer wrote in part:
    Autodidact also made a comparison spreadsheet between AL and steel tubing, the post is here.

    Many other good comments and pictures are there.
     
  5. Oct 18, 2019 #245

    ScaleBirdsScott

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    Longevity and just straight up class/quality/etc can be a factor here where those numbers don't always add up. I feel like it probably goes something like: If pragmatism is the rule, aluminum is cool. If you're making one for the ages, steel earns its wages.

    Or something, I don't know, it's late.

    Figure if I want a fun little runabout I'm all about the aluminum T&G. It's light, it's easy, it's affordable. I don't expect the light, low cost machine like that to be flying for 30 years. It's something for now, and eventually I'd do something different. If I was making a serious machine that was going to be a real money sink of a project, and it was a tube frame design, I'd be looking at steel because you'd never worry about it.

    In the middle, a utility plane that might still cost money, require real performance, and see some punishment, but it doesn't matter what it's made of from an... appreciation standpoint. So whatever is most pragmatic. I'd probably explore Aluminum.

    Of course this is strictly a tube-frame type design scenario. Once you get into aluminum skinned it's all sorts of a different equation.
     
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  6. Oct 18, 2019 #246

    TFF

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  7. Oct 18, 2019 #247

    litespeed

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    Not that I mind thread drift.

    And I must admit to drooling over many a early design.........

    I think we are getting away from our desired construction technique.

    Ideally we just want as much material as possible in one type for the airframe, for speed of build and predictable loads. Also it tends to be a lot cheaper, which is either time or tools/machines or money. We want to utilise the best available methods and materials for a 2019 aircraft that is homebuilt and cheap, and fast to build for a novice builder.

    The use of cables should be a last resort and only in critical bracing loads like the tail and wings. Ideally streamlined alloy tube is far better. But I would never want a fuselage that had wires to hold it together. I would use cables for control surfaces but only where absolutely needed for a design.

    I know wires are usual in old and also very light built wing designs but we should aim for as little if any wire. Unless it it for electrons.

    The design should take all the loads in easily designed and built materials- that means tube and gusset. The wires on WW1 replicas are there for retro looks and old school thinking. Any wires just ups the cost, time and skills to build. The ability to fine tune a airframe with wires is a plus, but its easily done on the build table of a good T&G frame and with adjustable struts etc.

    If a design for our mission needs a heap of expensive wire and crimped ends, extra tools, fittings, design gussets that take those loads plus hold tubes etc....................

    And ignores the flying elephant in the hangar of drag for the exposed stuff. We want as much performance and little drag as our design allows.

    We should burn that design. As Maxwell Smart would say "missed it by that much"
     
  8. Oct 18, 2019 #248

    SlowFlight

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    Bicycle spokes are available in lengths and quantity at reasonable prices made of many materials with many material fittings at both in a variety of styles suited for aluminum or CF rims. Also consider dissimilar material interface, use of isolating washers.

    lightest aviation fitting I've observed was an internal drag wing truss block cap outside the truss on the CF cub. Think triangle top to outside with a flat bottom facing the top of the compression strut. So rather than a turnbuckle, it is two nuts on either side of the top of the triangle and were nuts. Load path crossed in centerline fore/aft, but side by side on top of the compression strut. Other heavier alternates would be a strap over the inside of the compression strut between the longeron, through bolted through the longeron pinning the strap and applying a flat compression load to the compression strut. Cable ties on both ends of strap. Does not compress longeron, does not apply shear load to rivets.

    Tension can be set using a bicycle spoke tensioner. Noise Harmonics can be attenuated at tie cable crossings together at the X, with rubber pinched in-between. Frame flutter Harmonics will change with temperature tension unless the materials are the same.

    From my understanding tube compression failure is usually the earliest. Tube length key. As a primary load component two spokes might be considered instead of one.
     
  9. Oct 18, 2019 #249

    Aerowerx

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    Have you seen the NASA morphing wing? Yes, it is real. Not flown yet, but they have a prototype.

    Seems like a short jump to having a plane that can be folded flat and carried on your luggage wrack like a set of skis.:D
     
  10. Oct 19, 2019 #250

    bifft

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    I did compare that as well, my recollection is it added about 1.5 lbs compared to the straps. Still quite a bit lighter than the steel one. Not as fiddly to build as the strap idea.

    Thinking about straps so as to make weight in a 103.
     
  11. Oct 26, 2019 #251

    FritzW

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    It might just be brain damage but: After hitting my head (many times) on a 701 stabilizer that's in the way, of everything, in the hangar I had a vision of a single seat T&G 701 using VB's orphan 701 wings and tail feathers. With some clever trickery even the landing gear could be reused. It'd be light, cheap, simple and very cool.

    ...a Graham Lee 701/Savanna.
     
  12. Oct 26, 2019 #252

    plncraze

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    FritzW, when you are thinking of tube and gusset construction do you imagine two or three generic gusset shapes that one could make as when making stick ribs?
     
  13. Oct 26, 2019 #253

    FritzW

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    I imagine individual gussets specific to one cluster. The gussets get laid out on one "cookie sheet" (in CAD) and the sheet gets drilled and cut on a CNC machine. ...or, the cookie sheet gets printed on paper and glued to the aluminum sheet and cut with tin snips. Hand cut gussets would probably need to be match drilled to the tube.

    Weather the gussets are cut out on a machine or with tin snips they still need to be cut out. I don't see any advantage in trying to make them "one size fits all". Weather the gussets all the same or all different, if your using tin snips it's still going to take two pots of coffee and 1/2 box of band-Aids to cut them out.
     
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  14. Oct 26, 2019 #254

    plncraze

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    Coffee! Yes! Thanks for the quick response. But after two pots of coffee it couldn't be slow. LOL
     
  15. Oct 26, 2019 #255

    Aerowerx

    Aerowerx

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    If I tried to cut gussets with tin snips after 2 pots of coffee,they would end up looking like they were made from an old rip saw blade!;)
     
  16. Oct 27, 2019 #256

    litespeed

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    Gussets are fun and have a large blood to cut ratio.

    My trick is never use cheap aviation snips. They do awful things to alloy and leave a ragged edge. Quality snips do quality work. Powered ones are great too if you have spare cash.

    I also use a small 3 in 1 bending/brake/roller that sits on a bench. Allows nice straight easy cuts and bends. Or even rolled in the middle for round tubes.
    [​IMG]

    A cheap one can be had from the usual suspects.

    Another tool is a curving shear cutter which allows nice rounded cuts with ease.

    [​IMG]
     
  17. Oct 27, 2019 #257

    FritzW

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  18. Oct 27, 2019 #258

    Vigilant1

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    That's an amazing outcome, given what we see in the video.
     
  19. Oct 27, 2019 #259

    plncraze

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    All the heavy stuff in the airplane is ahead of the pilot and it did not look like it was going all that fast. Hitting at 60 mph requires two feet of deceleration room to be survivable I believe. And no fire!
     
  20. Oct 28, 2019 #260

    Victor Bravo

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    Change of sub-subject:

    Saturday I had the chance to see one of the tiny little Verner 3 cylinder radial engines in person. A friend had just bought one of the last two or three engines that was available from one of the first batches of 10 engines that reached the US, I believe.

    It was still in a molded styrofoam shipping block. My friend is scratchbuilding a TEAM Airbike for it.

    Wow, what an absolutely adorable little jewel. Looked very well made, although we did not remove it from the foam. Very compact. This one uses three of the (Honda or similar) V-twin industrial engine cylinders I was told.

    The engine's new owner had done the research and reported to me that this engine would be essentially a direct replacement option for the Rotax 503 weight-wise, when you compare apples to apples (installed weight with exhust system, as opposed to bare engine brochure weight).

    It makes 42 HP on takeoff and something like 36 HP continuous. The exceptional torque would allow it to swing a fairly large propeller,and deliver close to equal real-world thrust. It wiwll use significantly less fuel than the 503, apparently.

    Really neat, and a viable option for some of the tube and gusset ideas being thrown around in this thread.
     
    Last edited: Oct 28, 2019
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