Planetary gear drive for corvair, Duel plug heads

Discussion in 'Corvair' started by don january, Mar 24, 2015.

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  1. Jan 29, 2016 #41

    rv7charlie

    rv7charlie

    rv7charlie

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    Bill,
    My question isn't about Corvairs with planetaries.
    You made a very generalized statement about planetary gearsets: "they can have their own issues... heavy, harmonics, lubrication...and more." So, I repeat my question: Can you provide some examples to support your contentions about planetaries? Specific engines that are 'overweight, harmonic-plagued, have lube issues, more,' due specifically to the use of planetary reduction drives?

    Thanks,

    Charlie
     
  2. Jan 29, 2016 #42

    rv6ejguy

    rv6ejguy

    rv6ejguy

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    Lubrication of the planet gears at high rpms and loadings is a big deal on Ross and GAP designs using the Ford components at hp levels over 200 or so. Russell Sherwood of SARL fame, had several of them disintegrate or wear out in a few hours on his EG33 and spent years modifying them for better oiling to no avail. He finally replaced them with a Marcotte (internal helical design) and had no further problems. You can watch one of them disintegrate in flight on YouTube, requiring a scary/hasty landing. Russell is a very smart ME BTW. He agrees with me that the Marcotte is a much more robust gearbox than the Ross or GAP planetary drives and has many design advantages over planetary boxes for most piston engines.

    The RWS planetary drive reverses the output which is a smart idea. This reduces loadings on the planet gears considerably, which is why they last much better and have a good reputation.
     
  3. Jan 29, 2016 #43

    rv7charlie

    rv7charlie

    rv7charlie

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    The only RWS box that reverses the output was the original ~2.17/1 drive. The much more common (these days) 2.85/1 drives turn the same direction as the input shaft. Either can have helical gear thrust issues, without proper thrust bearings, just like any helical gear. Neither have any issues with proper thrust bearings. There are RWS drives running on 3 rotor rotaries producing well north of 250 HP. So, if multiple examples work and one doesn't, where do you look for problems?

    Oiling is a 'systems' issue; not a component issue. How well would your Subie run without proper oil supply & pressure? The statement was a generalization about planetary gearsets; not about anecdotal problems from a particular manufacturer. Planetaries seem to work fine in turbines (fair degree of rpm there...), a/c radials, virtually every automatic transmission in a road vehicle today, etc etc, so I'm trying to understand his blanket statement in some other context than "The product I sell doesn't use it, so it's bad."
     
  4. Jan 29, 2016 #44

    TFF

    TFF

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    Robbed of the net. For a GO-480 but about operating the gearbox.
    Tips to make TBO
    "
    This information has been derived from conversations with very knowledgeable people. Freight operators, Lycoming engineers,

    Aero Commander “old-timers” and many Lycoming Shops.



    In a nutshell, the secret to long life of your GO-series Engine is to Never Ever let the air turn the prop!

    The Lycoming planetary gearbox is pretty stout, things really begin to bang and clatter if you don’t have a solid, positive power setting.

    Always keep the manifold pressure up.

    You will be able to hear the gearbox “whining” if you come down final at too low a throttle setting.

    Don’t push the prop levers forward upon arrival at the airport.

    This probably goes against everything you were ever told by your instructors, but when running a GO-series engine, you’ll be doing the gearbox a BIG favor by keeping the RPM back at 2700-2800 rpm until landing.

    If you need to go around, it is perfectly safe to advance the throttle fully before bringing the RPM up- unless you are running a supercharged engine, GSO-480, ect.

    Keep your idle speed up, below a 1500 RPM idle will “chatter” the gearbox causing rapid wear of the outer planetary ring gear, a $3500.00 part

    Move the throttle VERY SLOWLY!

    Lycoming recommends a minimum of 30 sec. from fast idle to takeoff power.

    Follow this rule when going the other way, go even slower.
    "
     
    delta likes this.
  5. Jan 29, 2016 #45

    rv6ejguy

    rv6ejguy

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    No, don't think you understand the design differences between the Ross/ GAP and RWS. I don't mean reverses prop direction. The way Tracy designed his drive is "backwards" from the other two which slows planet gear speeds. This is why they live. I never said they didn't last, I said the RWS DOES last. And no, the other drives have serious oiling issues because the oil won't stay on the planet gears due to the extreme speeds. Tracy is a smart engineer and saw that as a possible issue which is why he designed his as he did.

    Planetary drives work very well for many applications if designed properly.
     

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