Re: Stan40353's "Challenge to you all"

Discussion in 'The light stuff area' started by Autodidact, Sep 12, 2011.

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  1. Sep 12, 2011 #1

    Autodidact

    Autodidact

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    I think the best construction method would be pop riveted aluminum tube like the Airdrome replicas, only not a replica of anything. People turn these things out pretty quickly and they have the potential to look pretty good. Something similar to a Buhl Pup maybe? Light enough and clean enough and you could have reasonable performance from a relatively unmodified B&S or Honda or Generac direct drive.
     
  2. Sep 12, 2011 #2

    PaulS

    PaulS

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    Autodidact,
    I like the light weight of aluminum but I don't like that it begins to fatigue the first time it is under stress. I think a light weight (thin wall) 4130 steel tube would last a lot longer with very little weight penalty. I am working on my 6th incarnation of a low cost, easy to build and fly ultralight. Working through design changes and lightening the airframe. Mine will have a one piece high wing, pusher prop, tricycle gear and an enclosed canopy. I would be happy to share the design whether it is used as designed or just a platform for further development. I don't plan on selling plans or kits so there is no need for secrecy. Right now I am only finalizing the design and have very few details worked out or fitted for the plane.
    Paul
     
  3. Sep 12, 2011 #3

    inventing_man

    inventing_man

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    Pauls ,What is your frame member joining method with 4130 ?
    If you have the skill to oxy-acetylene weld And are good at tubing notching / fitting, you could have good welds, with no other process needing to be done . If you MIG or TIG , there are other steps in heat treating to normalize the entire frame to prevent weld cracks.
    The thinner the tubing is, the more critical the heat treating becomes. Welding 4130

    Having said that, suspose one were to build 4130 tubing connectors where Aluminum tube ( or even 4130 tube) was slipped over or in the 4130 connectors and bolted in place . That way when a airframe piece ( tube or connector ) is suspected of fatague , it could be replaced . heat treating a connector to proper specs would be a lot easier to control than an entire frame . Just a thougt here .
    But really everything has a useful life span , flex is all a part of it . In the long run Alum or steel will ware out . Its how you build it so you can easily replace those parts that ware (flex) the most, that will make your design more user friendly and economical to own
     
    Last edited: Sep 13, 2011
  4. Sep 12, 2011 #4

    inventing_man

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    Dont think you really want to direct drive a prop off a crank shaft on these motors . . As they are not designed for direct push or pull forces a prop generates . They are designed for the side loading of belts or chains , .In Direct drive such as PTO drive shaft, these is still no push or pull loading on the crank shaft. The Equipment being operated by the drive shaft is stationary such as a pump or gen set .
    Also you loosing a grate oppertunity to gain thrust by reduction
     
  5. Sep 12, 2011 #5

    Autodidact

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    A redrive would be much better, I agree with you there, but these engines have been used direct drive with some success. The performance is lower and the type of flying is more sedate. If you don't make quick angular direction changes the gyroscopic forces are kept low and the thrust forces won't be more than 300 lb or so, probably much less. Corvair engines fly reliably on Pietenpols without the extra bearing because the don't fly aggressively. It would be nice if the engine only needed a prop hub and a lightweight flywheel added, the redrive is added cost and complexity. The pop rivetted construction reduces the complexity as well and can be designed with fatigue in mind. Also, if it flies well on a heavy, low powered engine it would be that much better with a lighter more powerful one. Some more information on the durability of these engines used direct drive would be helpful in choosing the type of engine, though.

    Another option for steel tube would be the old Heath parasol bolted joint type construction which was pretty light.

    Love to see a pic or drawing of PaulS's airplane.
     
  6. Sep 12, 2011 #6

    mstull

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    I've been using pop-riveted gussets for many years on my U/L designs, with no problems with fatigue. If exposed to enough vibration, the pop-rivets can gradually loosen up. But I've found that spacing the pop-rivets a little closer together will counter that. I use 2024-T3 for all my structural parts, allowing about 1/3 thinner walled material than 6061-T6, thus saving weight. But 2024 costs thrice as much.


    Parts near the engine should be a little more robust to take the vibration loads. But it is possible for a part far from the engine to resonate at some RPM and fatigue and fail. It makes a difference what engine you choose, and how you mount it. I started using compliant sandwich mounts to better isolate the airframe from engine vibration.


    You can get a very light frame using thin walled 4130 if it's well engineered. There's nothing wrong with that, other than all the added work of welding all the little pieces of tubing into nice trusses, and having an engineer determine the ideal diameter and wall thickness of each piece to keep the weight reasonable. With aluminum, you can make the whole frame out of a few simple large triangles. It's real quick and easy.
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    I've heard the industrial engines can take a thrust load okay too... at least some of them. The gyroscopic loads aren't a problem. And the harmonic resonances won't be a problem as long as you use a wood prop. You will get a lot more thrust with a reduction drive and much larger prop. But that adds a lot of weight to an already heavy engine. It's hard to get a decent power to weight ratio from one of those engines, since weight wasn't even a consideration in their design.
     
  7. Sep 12, 2011 #7

    BBerson

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    About 300 complete airplane kits were shipped with an Onan industrial engine in late '70's and early '80's from the Quickie Aircraft Co.
    The engine weighed 80 lbs direct drive. The thrust bearing is huge, I just disassembled an old Onan to inspect the inside.

    Direct drive usually makes sense for faster designs.
    But even some ultralights can use direct drive such as the half VW powered Legal Eagle, for example.

    Lastly, steel tube fuselages do not need any post weld heat treatment.
    BB
     
  8. Sep 13, 2011 #8

    stan40353

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    looks like i put it in the wrong area to start with lol. sorry about that, here is a repost in case other gets deleted. so what i would like all of you to keep talking about is what would work and be very inexpensive,and the 4130 sounds like a pretty good tube to use, and i am telling right now, this site will come up with a new aircraft design. and pauls what is the estimated finish weight? fly ready.and a 2 axis would help cost and simplicity of building right?

    a challenge to you all

    there look to be some good minds on this site.from what i read here alot of you are very knowledgeable. so i got to thinking, the purpose of a site such as this is to bring people with the same interest together and help the members of this site.so i have a challenge to put toward each and everyone of you.the cheapest way to fly is by far with ultralights.there are lots of kits out there that cost many 1000.00s of dollars.and the name of this site is homebuilt airplanes.so why not put the minds of the people here to come up with a truly unique design of an ultralight. a new aircraft that anyone can build and be much much cheaper than the kits you can buy.make it affordable to the average American worker, lets face it, not all of us have great paying jobs, and some are single parents such as myself. money is tight.but we have a passion as well to fly. i think it can be done way cheaper than the kits,and be a safe aircraft. so work on it and tell me what you come up with.remember,least amount of cost as possible.something some one could build without a big financial burden over the winter. if i get enough ideas i will build it myself.if fly safe we can share the plans with the world for free! any concept or configuration. lets do this people!!! you do not have to have a complete set of plans, just a part,like for the wings and main body, whatever it is, post it here, lets build something together!!! and KEEP COST DOWN!!! lets make this for everyone.! happy thinking!
     
  9. Sep 13, 2011 #9

    Autodidact

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  10. Sep 13, 2011 #10

    stan40353

    stan40353

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    very nice vids!! it flew!! that put a smile on my face to see that.
     
  11. Sep 13, 2011 #11

    inventing_man

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    Depends on the metal used , And the method of welding . If its 4130 and Mig or Tig-ed it certainly Will need more heat treat work . If Not ,The cracks will appear in the parent metal just before or after the weld every time . The welds will be fine though. The tube cracks ! And this is talking about places where there will be a high concentrations of vibration or flexing . in other areas it may last the life time of the aircraft with out proper heat treating ..all depends,
    If its OX welded and welded by a pro , most likely not.
     
  12. Sep 14, 2011 #12

    BBerson

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    Nobody in the light aircraft industry building with light tubing does any post heat treating for MIG or TIG because it is impractical and unneeded. (just my observation, having been in the light aircraft industry myself nearly 40 years)
    BB
     
  13. Sep 14, 2011 #13

    deskpilot

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    The word Super should never be used for this aircraft. What a pathetic performer. A real live Pelican strapped to the wings would probably get into the air quicker :roll:
     
  14. Sep 14, 2011 #14

    PaulS

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    72InchAirfoil.jpg Sketch001.jpg I am recovering from back surgery (due to a car accident not an aircraft) so I am not getting on here as much as I would like and sometimes I can only stay for a short period.
    I am trying to make this plane easy to build without welding if possible. I am trying to keep in mind that I want novices to be able to build it.
    Joining the tubing is a challenge (under those constraints) but a slug and saddle attachment should be as stong as welding - with a slight weight gain.
    I haven't had the time to calculate weight yet but I am figuring 80 lb. max for the engine which will mount on the floor behind the firewall that the seat back will come close to. The prop shaft will be about 24 inches above the crankshaft (center to center) and run 1:1 with a four foot prop. I have attached the overall scetch and the airfoil with construction plans and dimensions.
    I am hereby releasing this aircraft design as open source so that it can be used and modified freely by all of us.
    In the sketch the red members are the major compression members when landing - the vertical black member in the middle is the firewall.
    Paul
     
  15. Sep 14, 2011 #15

    PaulS

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    I should add that I am already re-thinking the crossed rear horizontal members and crossing the ones just ahead of them instead. It should make the placement of the prop shaft supports easier.

    Paul
     
  16. Sep 14, 2011 #16

    Hot Wings

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    Joining the tubing is a challenge (under those constraints) but a slug and saddle attachment should be as stong as welding - with a slight weight gain.

    Have you considered brazing? It's not skill or equipment intensive. As long as the joint is designed with that method in mind it's perfectly satisfactory. This generally means making some gussets, similar to pop riveted aluminum tube construction, but they are easy and quick to make.
     
  17. Sep 15, 2011 #17

    stan40353

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    i like the design. its a very good start. like i said, we can build something together, many minds on a project. ends with a finished product.
     
  18. Sep 15, 2011 #18

    Autodidact

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    A company called Arrowprop makes redrives for v-twin engines from 15 to 40 hp, the darn things weigh 19 lb and cost $690.00. At 1.69 ratio you could use a pretty big prop. I like redrives but they are expensive and it seems hard to find a good one. Who makes a good redrive for v-twins that's cheap AND light? A ppg engine would be great but they are kind of expensive, I guess there may be no way around it. Generac makes a single cylinder 15 hp engine that would weigh about 45 lb stripped and has pressure lube where others are splash lubed, not sure if that really makes a lot of difference, though.
     
  19. Sep 15, 2011 #19

    inventing_man

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  20. Sep 15, 2011 #20

    PaulS

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    Brazing (oven brazing) is often used to join 4130 in all kinds of high stress applications but a first time airplane builder may not have the skill or even the Oxy/Acet torch. That is not to say that brazing or welding could not be used to replace the slug and saddle joints just I would like to make this as simple as possible for a novice to build. The other consideration is repair of damaged tubing. If the junction is bolted together it can more easily be inspected and replaced than a welded or brazed joint. Having had a career where soldering, welding and brazing was integral it would be easy for me to use any type of joining - like many of you - but the idea is to make it possible for a complete novice to put the aircraft together without having the possibility of poor skills causing a disaster later on. The open source nature of this plan set makes modification easy but allows for a base that can be used "as is" for those less "talented" shall we say. Taking as much risk out of the project as possible without taking away from the economical and fun nature of flying will get more people involved in the ultralight field. (hopefully while making it safer too)
    Paul
     

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