Turbo

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Everything posted by Turbo



  1. Turbo added a post in a topic Compression numbers ?   

    Egp8111, I'm a bit the newb here, but isn't 6500 static a bit high?  From what I understand, 6200 to 6300 is the rpm range to shoot for statically, so when you're moving thru the air, and the prop is unloaded somewhat, you aren't in danger of exceeding redline.  Now, I may be idiologically mistaken, comrade, but I see the compression test as only a crude indicator, since the engine in operation is turning way faster than even an electric starter can crank it, so any leakage past the rings will be fractionally way less.  I have read that worn-out 2-stroke engines become hard to start.  I'm sure there are folks on this site that have way more 2-stroke experience than I do.  What other symptoms say a 2-stroke engine is ready to suddenly stop running due to wear?  That IS the main concern, right?
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  2. Turbo added a post in a topic Compression numbers ?   

    Comparing both carbs, all the floats seem to be low riders!  Dried and shook them, and none had fuel sloshing inside.  One float bowl had the requisite half-inch level from the rim, the other less.  I am thinking that I just need to "rebuild" the bad carb, and of course clean them both.  Seems like the float-bowl level cutoff valve is the culprit for the bad carb.  Could just have a tiny piece of debris on the seat.  Sorry to have misappropriated the thread!
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  3. Turbo added a post in a topic Compression numbers ?   

    Mine tested at 115psi and 118 psi.  Only one problem.  My bowl floats are sinking!  Holy Moly are they pricy little buggers!  Is there another way out here?  Are the Bing 54 carbs used on snowmachines or something without wings?
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  4. Turbo added a post in a topic Compression numbers ?   

    O.K., so what to do if you have the pull-starter?  Hard to get a consistent compression value if you can't crank at a consistent rpm.  Facing my first conditional with a guy who doesn't have experience with 2-strokes.  Hopefully demonstrating 6200 rpm static full throttle will do, along with appropriate temps.
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  5. Turbo added a post in a topic Folding wings an Avid idea?   

    Nice 2-1/2-cell sesquiplane design.  Spars can be quite minimal as they don't really have to support much bending.  Optimal airfoil thickness for fabric-covered wings (no laminar flow) is around 13%, though, which of course favors monoplanes where you can take advantage of deeper spars.
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  6. Turbo added a post in a topic Curious fawns   

    OOOPS!  Hundreds of MILLIONS of years!
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  7. Turbo added a post in a topic Curious fawns   

    Adorable baby bird.  Those guys put us human fliers to shame though!  Hundreds of years of evolution compared to only 115 for us as fliers.  I am awed with what birds routinely pull off.
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  8. Turbo added a post in a topic Ever wonder what it's like to...   

    Hey Joey,
    Is it true that B-1 drivers always have a dirty windscreen from fuel splatter upon disconnect?  Aerial refueling is so cool, and I'll bet the receivers appreciate that KC-10 with its bigger extension range, envelope, and fuel flow, over the antiquated KC-135!  The big guys just need to keep their T-shaped tailfeathers out of #2's exhaust plume!  The KC-45 will solve that problem (or will it, with the 767's wing engines so close together?).  We, McDonnell Douglas Boeing, had an internal hu-hu with the Boeing Wichita folks, who wanted to warm over the -135 boom for the KC-45.  I got dragged into the early phases of that design activity.  But there was no saving a bad, 1st-gen design!  We almost lost the tanker to Aerbus!  Fortunately, that KC-45 now sport a modified KC-10 boom,  and on some versions 3 (count 'em 3) hose drogues!  3 times the fun!  Anyway, thanks for what you do, and enjoy your "retirement"!
     
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  9. Turbo added a post in a topic Leaning the carbs for altitude - on the cheap   

    Good question.  Since the oil is ostensibly less atomized with the OI system, maybe it won't be any worse.  Same relative motion, same friction, same temperatures, same lubrication. Sounds right to me.  Beats hell out of potentially under-lubricating the engine.  What say y'all with leaned, high-altitude time running premix?
     
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  10. Turbo added a post in a topic Leaning the carbs for altitude - on the cheap   

    Rfphtmfxr, I agree with you in that there is a difference between OI and premix wrt leaning. With premix, less fuel means less lubrication when leaned out at altitude despite essentially the same cruise rpm, whereas with the oil injection you should be getting the same oil flow at all altitudes.  I think this is an advantage for the OI system over reverting to premix.
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  11. Turbo added a post in a topic Leaning the carbs for altitude - on the cheap   

    My mistake!  I did originally mention a direct-leaning approach.  Cowlove's point regarding same is taken.  
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  12. Turbo added a post in a topic Leaning the carbs for altitude - on the cheap   

    Cowlove, I like your solution!   BTW, we were t alking about a float bowl vacuum leaning system; that's what the hacman system is, but based on the carb throat as the vacuum source.  Where did you find the vacuum pump?
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  13. Turbo added a post in a topic Leaning the carbs for altitude - on the cheap   

    My understanding is that the OI system responds to two things only: throttle slide position and engine rpm.  How rich or lean your air/fuel mixture is should not affect engine oiling.  It seems to me that you're good to go.  Of course, you'll be watching EGT and coolant temp. - Turbo
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  14. Turbo added a post in a topic Fabric touch-up   

    Contrary to the standard wisdom, there apparently is such a thing as a too-dumb question.  Well, I went for it anyway.  The result, while practical, isn't pretty.  Mine's not a show-bird, and I'm a pragmatist.  The magic, it's ability to fly, is unaffected.  Superstition likely would suggest that a fancy paint job is a groundloop invitation anyway, and who wants that?
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  15. Turbo added a post in a topic Blocking off the Oil Injector 582   

    Shockaroo!  No plastic gear behind the panel/flange.  Lots of 2-stroke oil escaped when I cracked it open, indicating that a few squirts of same when installing the gear and pump will be in order. Looks like I'll be running premix for now.  Hey Vance, does your offer still stand? Might that include the plastic drive gear?  I'm game enough to make a road trip out of picking the parts up in Post Falls; that way I get to meet you in person!  Just a short trip from the gorge.
    I'm moving closer to a condition inspection then first flight.  Exciting times!
    Best regards to all,  Art
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  16. Turbo added a topic in Technical tasks   

    Fabric touch-up
    Hey y'all, my bird has the classic butyrate dope-with-aluminum-powder finish, but time and chance have taken their toll, and I see a couple of spots where touch-up would be highly desirable.  One is on the top of the wing, where some kind of solvent spill has lessened he UV protection in one local area.  Others just look like the typical hangar rash.  So is touch-up with a soft artist's paintbrush feasible?  I don't have any of the equipment needed for spraying, and to me this would feel like gross overkill.  I've got a quart of Rand-o-fill and a quart of thinner.  Should I just go for it?
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  17. Turbo added a post in a topic Blocking off the Oil Injector 582   

    O.K., so new question:  I'd like to take the oil pump off so I can inspect and test it.  That includes the plastic drive gear.  I hear there's a second cover plate that comes off so the gear can be removed.  If I take this off, am I going to affect the rotary valve and its lubrication?  I have no idea how the rotary valve lubrication works, but I understand the layout.  I don't want to end up having to take the engine off so I can refill the rotary valve's oil tank and lines without leaving a fatal air bubble in the line.  The Avid's engine is plugs-down.  Thanks in advance, guys!
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  18. Turbo added a post in a topic Blocking off the Oil Injector 582   

    Thanks, NLappos, but I have a good oil tank.  Actually I have two of them, but only one appears to fit easily in between the frame tubes.  This is weird, since they look identical.  Man, is everything a tight fit in these birds!
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  19. Turbo added a post in a topic Blocking off the Oil Injector 582   

    Hey, thanks NorthIdahoAvidFlyer!  I may take you up on this.   My first orders of business involve some kind of trim system, and cabin heat!  After that, I am keen to get the OI sytem up.  I have no idea what kind of shape my oil pump is in, and in fact don't know if there is any timing issue with the gearing.  Since it's a piston pump, one would think that it should squirt the oil just as the air/fuel mixture rushes in thru the carb.  Maybe it doesn't matter at all.  I just don't know.  Anyway, thanks for your generous offer.  I'll let you know.
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  20. Turbo added a post in a topic Blocking off the Oil Injector 582   

    Thanks, guys!  
     
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  21. Turbo added a post in a topic Blocking off the Oil Injector 582   

    Seems like this thread has gone cold.  I finally have the bird in hand (well, garage really), and am preparing to, among other things, put the oil injection system back in play.  The Rotax engine diagrams appear to indicate that if you try to take off the oil pump, the nylon gear is too big to extract through the hole.  Is this true?  In my case, the pump was not removed when the engine was set up for pre-mix.  The oil inlet tube is sealed off, that's all.  There's a crack in one of the injection lines, so I will have to replace them.  Are these lines just 3/32" tygon spaghetti tubing, or urethane?  Can I expect the oil pump to still work?  I would think that the engine's internal oil fog might keep it from seizing.  
    Of course, I'll bleed the system and run premix until I'm sure it's working.
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  22. Turbo added a post in a topic CG Excursion   

    Adding a leading-edge extension shouldn't change the CG position much at all, since the moment arm of that weight is so small, but will change the aerodynamic center, shifting it forward.  This reduces static margin, so your aft CG limit will come forward.  (Forward limit too, but no biggie.)  Be careful!  Stay away from the original aft limit until you know where the new aero center is.  With the LEX are you re-referencing all your weight moment arms to the new LE location, or keeping the front edge of the front spar as the reference?  That could account for differences in your values vs. Others.
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  23. Turbo added a topic in Avid Model C   

    Engine cooling
    My model c has the belly radiator and no provision for cabin heat.  There apparently have been several arrangements for in-cowl radiators.  The one that I currently favor has one radiator mounted behind the starboard-side motor mount strut.  This allows a  simple radiator mount, along with a very neat setup for cabin heat - just a little valve-box/dump on the firewall.  But man, that rad is darn close to the firewall!  Does anybody have this arrangement, and how well does it work?  What are the specs for the radiator?  It's clear to me that a good in-cowl arrangement will save drag and fuel over the belly rad.  I'm also thinking that instead of a fixed gill to exhaust the hot air out the bottom, a sort -of  variable cowl flap could reduce cruise drag while allowing for lots ot airflow for climb.  Of course it would likely make removing the cowl kind of a pain.  Gotta work on that.  I'm not too keen on the dual-rad-in-nostrils approach.  Vibration, and so many opportunities for leaks.
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  24. Turbo added a post in a topic Solo bungee wrapping   

    I'm not convinced we all have this "double-bar" config under the seat.  I know the Avid doesn't.  The axe-handle approach won't work for me.
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  25. Turbo added a post in a topic INVERTED TAIL RIBS QUESTION   

    CL of 4 is possible with slats and flaps.  For a single-element airfoil the max is around 2.2 for Reynolds numbers of interest to us.  A former colleague, Bob Liebeck, used variational methods and boundary layer theory to develop a series of airfoils that establish what is possible.  Even worse than the 5-digit NACA airfoils, they have a very nasty stall..  They lose a lot with just a few bug-splats, and are not suitable for use on fabric-covered wings.   
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