Single engine 300-400hp pusher

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by KC135DELTA, Jan 29, 2010.

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  1. Oct 7, 2010 #41

    Mac790

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  2. Oct 7, 2010 #42

    autoreply

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    I don't see the torsional vibration issues of the engine taken into account in either of those. Since that's by far the most critical issue, I guess those documents aren't that relevant after all, but thanks for the link nevertheless.

    Personally I'd be very interested in the Stemme S10VT:
    [​IMG]
    [FONT=Trebuchet MS, Arial, Helvetica]1> Propeller blades extended,[/FONT]
    [FONT=Trebuchet MS, Arial, Helvetica]2> Reduction gearbox limits the propeller speed & noise,[/FONT]
    [FONT=Trebuchet MS, Arial, Helvetica]3> Flexible coupling,[/FONT]
    [FONT=Trebuchet MS, Arial, Helvetica]4> Carbon-Fibre driveshaft contained in a Kevlar tunnel,[/FONT]
    [FONT=Trebuchet MS, Arial, Helvetica]5> Splined sliding joint,[/FONT]
    [FONT=Trebuchet MS, Arial, Helvetica]6> Torsional Vibration Absorber ensures smooth, quiet running,[/FONT]
    [FONT=Trebuchet MS, Arial, Helvetica]7> Centrifugal Clutch avoids stop/start shock-loads,[/FONT]
    [FONT=Trebuchet MS, Arial, Helvetica]8> Engine – Turbocharged Rotax 914 – Flat 4, Twin-carb., Water-Cooled, dual ignition
    (The earlier S10 & S10-V models use the Limbach L2400)
    [/FONT]


    It's one of the very few operational, certified aircraft with a driveshaft. Especially the details of item 3 and 6 would be very interesting.
     
  3. Oct 7, 2010 #43

    Mac790

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  4. Oct 7, 2010 #44

    PeterJC

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    Hi, some of you already know this text, but I post it here anyway since it's relevant to subject :)

    No Short Days:
    The Struggle to Develop the R-2800
    "Double Wasp" Crankshaft

    Piston Engines
     
  5. Oct 7, 2010 #45

    autoreply

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  6. Oct 7, 2010 #46

    Mac790

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    Thanks, I've never heard about that pusher either :), it reminds me Vk-30 with different tail and wings shape. Wonder which one was reverse engineered :roll:.

    I've found one more pic of Stemme back coupling pix1, one thing only makes me wonder did they use something else, in a car between the engine and the gearbox, there is a clutch with springs (for obvious reason), it would be nice to see also Porsche 928 "installation" (it has engine at the front and gearbox at the back).

    After looking at Stemme pix2, "ultimate" pusher pix3, and helicopter boom pix4 (of course different RPM, different loads/forces, etc), one thing coming to my mind, wouldn't be easier to build the front section of a pusher plane out of composites and the tail section (with an engine mount) out of 4130 tubes? It would be easier to calculate and design for sure, better maintenance (removable tail section shells), etc.

    edit
    After looking at the manual, seems that there is a kind of centrifugal clutch? there, page 4 http://www.stemme.de/man/s10vt/mm_uk/amendment13.pdf

    Seb
     

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  7. Oct 7, 2010 #47

    billyvray

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    Gentlemen, there is another pusher homebuilt out there as well. The Orion G-801, and a link to view a page about building/flying one:

    Orion G-801 - HomePage -
     
  8. Oct 7, 2010 #48

    Mac790

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    Thanks Billy, we've heard about that one before, it's a pity that plans for this plane are not available anymore. The propulsion system was close to that in Mini Imp, if I remember correctly.

    Seems that they don't use any elastic coupling besides flexidine.

    Seb
     

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  9. Oct 7, 2010 #49

    wsimpso1

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    Turboprops have already had a lot of the work done on beating resonance issues, but if the designer was going to use a shaft to extend the prop aft, you get to start over.

    In turboprops, it is not a matter of there are no vibes to beat. While the blade passing freq's are very high, you do have tooth frequencies, accessories, and if you extend the prop aft, you will get vibe inputs as the prop blades cross the wake of the wing, engine air inlets and outlets, and the tailplanes.

    It will likely be easier than with a piston engine, but don't believe that there are no vibe issues possible.

    Billski
     
  10. Oct 7, 2010 #50

    TFF

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    Some Rotax 912/914s have an overrun clutch in the gearbox; tension check at certain intervals. All the ones I have worked on, a big two, do not have them. I dont know what the original applications like the Stemme is using. 2 VK30s at my airport, one a reck with a turbine Alison and one being built with Cont. Turbo Voyager 6. I know the VK30 needs respect, 50% of completed planes have crashed.
     
  11. Oct 7, 2010 #51

    Mac790

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    Thanks TFF, seems that some Rotax has overload clutch but Stemme has centrifugal clutch probably something similar to this one centrifugal the point of it is because Stemme has retracted propeller, I'm guessing that at the idle the prop doesn't turn.

    Seb
     
  12. Oct 8, 2010 #52

    TFF

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    I guess the advantage is you can stop the prop where you need to to stow without having to turn the engine against the compression to line it up.
     
  13. Oct 8, 2010 #53

    Mac790

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    We were calculating, and also lab testing (critical speeds, etc), only let's say "conventional" (metal) drive shafts, but the general rule was, if the drive shaft is going to be longer than 1.6m (if I remember correctly, that was 2 years ago), you have to divide it (and use support/bearing). The Stemme drive shaft has 1.9m.

    Seb
     

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  14. Oct 8, 2010 #54

    TFF

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    The advantage of 2 piece is only one side needs to be phased as the other is fixed straight. Advantage of the one piece is lighter weight. Having owned a bunch of different cars, European cars usually have 2 piece and American ones have one piece; always exceptions. American cars of the 60's and 70's have driveshafts around 6 ft. The VK30 has one about 8 ft.
     
  15. Oct 8, 2010 #55

    Mac790

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    TFF, hmm, it's very strange, I've seen dozens maybe even hundreds different drive shafts, and I don't remember anything longer than 1.6m.
    I think that those cars had low RPM V8 engines.

    But it's not only about cars, if you take a look at helicopter booms, you won't see shafts longer that 1.5m which is unsupported or/and divided. I think that those guys know what they are doing.

    But didn't you say that 50% of them crash, (I'll take a look at NTSB reports), something was wrong with VK and something is wrong with Stemme if they have to overhaul shaft after 400h, the strange thing is that those rubber couplings (at the ends of the shaft) you have to replace every 10 years or so, in cars those elements last shorter than shafts.

    Seb
     

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  16. Oct 8, 2010 #56

    autoreply

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    I don't understand what you're saying by "one side needs to be phased". Can you explain?



    I don't understand the difference between those 2:
    Anybody has a clue?
    Because, if both are similar to what 3%3E%20Flexible%20coupling,%206%3E%20Torsional%20Vibration%20Absorber%20ensures%20smooth,%20quiet%20running,[/quote]"]Mac posted, well, apparently it's pretty straightforward to just use automotive stuff.

    AFAIK, the clutch on the Rotax is pretty standard and is to avoid shock-loading (PSRU and maybe prop) when starting the engine. It has nothing to do with prop extension, one has to shift the nosecone before even thinking of starting the engine.
    If one is going to a have shaft bearing and such in the tail? Certainly. For a pusher, with the engine, just aft of the spar and a single shaft though I'd still favor load-bearing composite shell.
    Well, everything can be scaled up. If we take into account that carbon is about 3 times as light as steel (and the same strength) I'd say you can go at least to 2.77m And actually, I don't see a problem in a long, unsupported shaft if you have a big diameter. A 5" thick, 10' long carbon shaft, with a wall thickness in the order of 1/4th of an inch doesn't seem unrealistic.



    Billski, help!

    :speechles


    :gig:
     
  17. Oct 8, 2010 #57

    Mac790

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    Looking at the picture which I posted in post 43 it seems like there is no difference between those two. Maybe they just use different names for it.

    It seems that there is nothing special between the engine and the shaft (save an enlarge picture) Stemme-UMS:*Sagem-Patroller.

    Personally I'm not obsessed with pushers, I have obsession about loud engine in front of me, which enclose my vision, etc. I really like Stemme solution to that problem, I would also prefer to see what is going on with my prop, just in case of bird strike, etc.

    But if a shaft like that fail for what ever reason, it will cut your entire tail section clean off :). I would really prefer to have smaller diameter and supported shaft front of me, rather than behind me.

    Seb
     
    Last edited: Oct 8, 2010
  18. Oct 8, 2010 #58

    TFF

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    The phased side is the one with the universals or CV joints. On a two piece you build on section straight in line with the power output to the hanger bearing; then the side with the u joints can be short to deal with the bending. To keep the bending down, the operating angles of the joints need to add up to 180 or a straight line. If one side the joint is at 80 deg, the other side needs to be at 100 deg. CV joints of course dont have to be in line but the joints are not as strong and still do better when run straight. The rubber disks European cars use are a cool way to get a simple CV, but you will rip them out if you dont keep up on them.
    My day job is working on helicopters and yes the drive shaft is supported in short spans, but it is also a 1" dia .050 4130 tube driving something that is using about 20% of the engine horsepower; those American car driveshafts are 4-5"dia. tubes moving 4000 lbs. When those are not in phase it is spectacular to see the damage.
    The VK is a higher performance aircraft than most owners want to admit. Most seem to want to come out of an Arrow when they really should have jet time. You can see the engineering fingerprints between the VK 30 and the SR20/22. The wing is very close but what they learned with the VK was they made it too complicated; SRs are much a simpler airframe. The VK driveshaft is about 7" dia. composite. There was one at Oshkosh and he had 800hrs on his, so it can work.
     
  19. Oct 8, 2010 #59

    autoreply

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    I think everybody that has an "obsession" with a certain kind of configuration is following the wrong path. Having said that though, each configuration has its plusses and minus. Since I stopped working on my push-pull design I started working on something like the Vmax probe, albeit much roomier interior, Rotax-powered and much friendlier behavior, so not a nec-plus-ultra design that one was. (Decent stall speed, a bit of room for luggage roomy cockpit and so on)
    For my criteria this configuration seems a good idea.
    Nope. A 5" diameter shaft @ 2500 rpm "flies" at 60 km/h (40 mph). That's easily contained in a layer or 2 of kevlar, as in the Stemme. Mass for a long shaft is also really low, on the order of 20-50 lbs:
    Source
    [/SIZE][/FONT]
    Ah, great, now I understand, thanks :)
    So would a simple rubber disk be sufficient to couple engine=>shaft=>prop axis if all are aligned straight as in - for example - the Vmax Probe?
     
  20. Oct 8, 2010 #60

    Mac790

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    Thanks for those numbers, and nice to know when you work if I have a question in relation to helicopters I know who I should ask:).
    Speaking about that 20%, I was expecting it, that is way I put also pix of CH-47 Chinook.

    Would it be possible for you to make a few pixs, of propulsion system (couplings,etc).

    Seb
     

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