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Thread: Two cycles, Boy some folks sure hate them

  1. #11

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    Hey Bob, I just wanted you to know I for one am interested in the experimental side of EAA (unlike some others who need to stick with certified rigs)and have flown behing a 2 stroke, I was a skeptic but after selling it and aquiring a "reliable" continental powered aircraft, I have realized that all that reliability hinges on the owner. The Rotax I flew with is a reliable design and after I purged the previous owners influence on it it was a fantastic engine, but I was swayed by the crowd to get a "real" airplane and engine. The Continental failed at 75 hrs, less than 200 since major once again the previous owner's influence not the design. With my practical experience having flown behind one and having done all the set-up and maintenance, I say the 2 strokes are a fine choice for a lightweight powerplant. As long as the EGT's are monitored during tuning and proper maintenance done there is no secret to the 2 strokes operation if you run it lean it will melt.

  2. #12
    steveinindy's Avatar
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    "GOOD LUCK!" to everyone on the ground.
    The risk to folks on the ground is so low as to be negligible. One researcher put the odds of a given person being killed by a crashing aircraft while not involved in aviation related activities at roughly the same likelihood as being struck by lightning while holding the day's winning lottery ticket.
    Unfortunately in science what you believe is irrelevant.

    "I'm an old-fashioned Southern Gentleman. Which means I can be a cast-iron son-of-a-***** when I want to be."- Robert A. Heinlein.



  3. #13

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    Just a quick point of clarification:
    The DA-20 was powered by the normally aspirated 80 hp 912, not the more high tech 115 hp turbo 914 engine.

    Where the A&Ps were trained to understand the water cooling and the different metallurgy, the engines and schools
    ran fine. I can cite Diamond Aviation at KSQL in the 1990s as an example. Not so much high tech as just different tech.

    From what I saw and heard along the way, treating a Rotax like a Lycosaurus respects neither and is a sure path
    to trouble. This seemed to happen in lots of places where factory training was not taken.

    How often do you hear of a 4 stroke Rotax throwing a rod? Or a Lyco floating and crushing its valves at 6000 rpm?

    Back to 2Strokes, I have never used them in aircraft, only in yard tools.
    Engineering is always compromise, in this case reliability exchanged for weight and performance.
    I have ocassionally had my 912s take me on 2000 mile round trips, some thing I would not contemplate with a
    two stroke.

  4. #14

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    Quote Originally Posted by rampil View Post
    Back to 2Strokes, I have never used them in aircraft, only in yard tools.
    Engineering is always compromise, in this case reliability exchanged for weight and performance.
    I have ocassionally had my 912s take me on 2000 mile round trips, some thing I would not contemplate with a
    two stroke.
    Well without having flown behind one, kinda quick to not contemplate, you pointed out others that probably haven't owned a 912/914 pointed out problems with them,pot.....kettle???

  5. #15

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    Quote Originally Posted by turtle View Post
    There is no disrespecting ultralights here. They serve a purpose but they do have a higher risk. I don't think anyone will deny that.
    I personally felt safer in my ultralights than I do flying my Sonex. Yes, I had 10 "emergency" landings in ultralights over the years, but because they land so slow and in such a short distance and because you only fly ULs over "safe" terrain there was never any fear of damage or injury. Basically, the engine quits and you land.

  6. #16
    steveinindy's Avatar
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    Likewise. I'd take an engine out in an UL aircraft any day over a Sonex.
    Unfortunately in science what you believe is irrelevant.

    "I'm an old-fashioned Southern Gentleman. Which means I can be a cast-iron son-of-a-***** when I want to be."- Robert A. Heinlein.



  7. #17
    bwilson4web's Avatar
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    I finally got around to weighing the 60 hp, 1835cc, HAPI VW engine: 172.6 lbs. This is about 20 lbs heavier than the 'dry weight' in the Sport Aviation article. This weight includes the starter, cooling baffles, intake manifold, magneto, backup electric ignition, and second spark plugs. It did not include the 1.3 lb Ellision and 7.0 lb exhaust stacks for an all-up weight of 179.9 lbs. BTW, I will be selling the HAPI but not the Ellison, yet.

    The BSR straps can run from the engine mount points along the fuselage and back to the wing cover. Replacing the VW engine means the 'side cheeks' are no longer needed or could be replaced by something more functional:

    For example, ducts that carry radiator plumbing and BSR stainless steel cable.

    One radical thought is the BSR might fit in front of the firewall. This improves the CG by moving it forward and putting the rocket on the other side of the firewall. In fact, a canister BSR might fit:

    A lighter, 60 hp engine means the engine mount needs to extend forward to maintain CG. This increases the space between the firewall and engine and possibly allowing a BSR canister to fit. This space might compete with a radiator and ducting but there is a more radical solution.

    The coolant hoses could route outside the sides of the fuselage back to a rear mounted radiator and ducting in the fuselage behind the wing drag bulkhead. This avoids running plumbing through the cabin and bulkheads. Jon Finley did this with his Subaru powered, Q2 running the pipes under the fuselage.

    The radiator hoses could be encased in functional, external duct(s) on each side with a profile no worse than the 3" x 9" side cheeks. The side cheeks could be the front anchor for aluminum ducting. Run the BSR straps or stainless steel cable along the duct top and two problems are solved. A rear, P-51 style, radiator offers the possibility of reduced cooling drag. Both options need to be modeled.

    Bob Wilson

  8. #18

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    2-cycles

    Bob:

    2-cycle engines of today are much better than in previous years due to being designed and built for aviation use specifically. The improvements include automatic oil injection to eliminate mixing errors with fuel, dual electronic ignition, and gear-driven PSRU"s to slow the prop speed down and eliminate drive belt failures.

    I have flown 2-cycle engines in ultralights and homebuilts since 1980 and I have personally experienced engine failure while airborne. My experience is definitely skewed due to the fact that many of these failures
    were during test flights of newly completed builds.

    It is true that the 2-cycle requires more monitoring by the owner, but the advantages in power to weight ratio is often worth the trade-off. The key to safety is to educate yourself on the characteristics of the 2-stroke engine and how to avoid the pitfalls that I see so many 4-stroke users fall into due to ignorance or complacency.

    My personal Hi-Max has a Rotax engine and, with proper care and monitoring has performed flawlessly for over 200 hrs to date. This engine was purchased used and had points ignition. Before flying this a/c, I removed the engine from the plane & checked out the compression, crankshaft seals and points. I replaced all bearings, points, and belts before reinstalling the engine for run testing. After adjusting the carb to the proper egt & cht temp ranges, the engine has been perfect. Just be aware that ambient temperature and humidity changes will require carb adjustments to maintin proper mixture settings. None of these adjustments are difficult and take only several minutes to make.

  9. #19
    bwilson4web's Avatar
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    Thanks Ed,
    Quote Originally Posted by ehawkins View Post
    2-cycle engines of today are much better than in previous years due to being designed and built for aviation use specifically. The improvements include automatic oil injection to eliminate mixing errors with fuel, dual electronic ignition, and gear-driven PSRU"s to slow the prop speed down and eliminate drive belt failures.. . .
    I'm also going with factory installed fuel injection to manage the mixture. But I have no illusions that any engine is 100% reliable plus I remember how I flew my ~320 hours.
    Bob Wilson

  10. #20
    bwilson4web's Avatar
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    Quote Originally Posted by LeTempt View Post
    Good luck to you Bob.
    Thanks Jeff,

    I also noticed my Yahoo Dragonfly list membership was pulled. Fortunately N19WT is not dependent upon the Dragonfly list.

    Too bad, I was going to share progress on my airframe and navigation light work.

    Bob Wilson

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