Conference vmszoo::rc

    >>> Why don't they gear down the engine to get the
    >>> rpm.
    
    I wonder how long the gears would last at 25,000 rpm?
    

    Gears are heavy, expensive and consume quiet some power. There are
    gears available, but the other way round. They put it on a ZG38 and get
    the revs down to 2700 rpm. They drive props with 32 inches in diameter!
    This setup is by far the closest to reality (soundwise) that I've ever 
    seen.
    
    To the other subject, I've looked into the possibility to convert these
    chainsaw or whatever engines to airplane ones. The following problems I
    encountered :
    
    1) The carburettor in most applications won't allow inwerted operation
    2) The housing is larger with additional baffles for mounting the
       airblower for cooling. Needs to be cut away. 
    3) The exhaust often is on the wrong side 
    4) You need something to mount the prop.
    
    All in all too much effort. In US you get the ZG23 to a very reasonable
    price. Especially modified for airplane use. Why would one want go 
    through all this hassle and trashing other equipment to get the plain
    engine ?
    
    
    	Bernd
    

    I think that it should be possible to modify a weedeater engine for
    airplane use if you have access to the parts for athe prop shaft and
    engine mount.  Many weedeaters have the exact same carb that comes with
    the G-23/G-38.  As you say, the G38 has no thrust bearings.  I've seen
    complete weedeaters for around $100 which is half what you pay for a
    G38 with no muffler.   We are paying too much for Zenoah engines but
    it's because it's a specialty business compared to chain saws and weed
    eaters.
    	I've seen belt drives that I like much better than gears.  As Bernd
    said they are used to gear DOWN the prop RPM to swing bigger props.  I
    doubt that you could build a gearbox that would work in a ducted fan
    application for very long!  You also could not afford the weight and
    power lost in the gear train.  
    
    Charlie
    

    There a lot of hidden issues with using an unmodified cahin saw engine.
    Not least of which is the internal balance.
    
    I have seen people try and mofify weed whacker engines and the eventually 
    just give up and do what they should have done in the first place, 
    purchase a commercially available aero version.
    
    It might be fun to play with one but if you want to have smooth reliable
    performance buy one that is designed for the job.
    
    Regards,
    
    Eric H.

    A couple of weeks ago I went to an antique engine show here in Cedar
    Rapids.  There were all kinds of very old internal combustion engines
    running everything from small corn shuckers to washing machines.  Most
    of these engines were of the flywheel and single cylinder design where
    some real interesting mechanics have the piston firing once every two
    or three seconds.
    
    At the same show there was a fellow with about 20 modified chain saw
    engines for use on R/C airplanes.  He had done some machine work to
    make mounting a prop simple and had some home made mufflers.  I looked
    at them and a few of them had the same walbro diaphram carb that is on
    my Zenoah G38.
    
    The question is, once you have built a quarter scale plane and have
    nearly a grand invested in it, would you risk that in order to save a
    hundred bucks on the engine???  If you stuff a quarter scale plane it
    makes a bigger dent in the ground (or whatever else it may hit) than 
    a sport R/C plane.
    
    Will

    I disagree.  The Zehoah engines are not modified except for a prop
    adapter shaft and a firewall mount.  They are industrial engines.  If
    you have a good prop shaft adapter that has minimum runout and is
    strong enough to do the job then what risk is there?  I spent the extra
    $$ for the Zenoah mostly because I did not want to bother with doing
    the mods but I believe that it could be done reliably.  These engines
    are not that complicated.
    
    Charlie
    

    Some Engines I've seen do have extra walls and stuff at the housing so
    that you need to do some grinding or whatever. Without having special
    equipment it will be real difficult. At least true for some German
    brand chainsaw engines. I think to remember also true for some American
    made (or sold) ones. 
    
    
    Bernd
    

    I have a mystery substance that shows up in my filters in my YS
    engines. I have found it in my YS-45, 61 and 120. 
    
    It is a semi-fiberous material that completely blocks the fuel filter
    to the engine. It will not blow out with a pressure line and can only be 
    removed by soaking the filter element in Acetone for about an hour.
    
    The other parameters are that the fuel I use is Red MAX 2-c, 10 or 15%, 
    1/2 castor. I also exclusively use Mobil-1 as my after-run oil.
    
    I have been finding it for over two years now and I address the problem
    by changing filters every two or three months or whenever the engine
    gets hard to start.
    
    The YS's send crankcase pressure directly to the tank so any gunge from
    the crankcase can and will reach the tank. Then possibly the filter. All 
    YS's cycle the fuel through the crankcase in 2-c fashion.
    
    I double filter all my fuel. In the fuel bottle pick-up and the filler
    line.
    
    I suspect that the after-run oil is acting with the Mobil-1 or that
    vegetable or grass fibers are getting in via the carb. Fortunately the 
    YS pressure system can cope with a partially blocked filter. I now watch 
    for any bad starting. This is when the pressure in the tank is initially 
    low. I also watch for any unreasonable needle setting changes.
    
    Some of the guys were not using filters, last year, and experienced gungy 
    needle valve assemblies that often caused the engine not too start.
    This was/is the same problem, I think?!.  
    
    I have not found this gunge in the crankcase pressurised systems of my 
    OS25, 32, 46, 4-c 91 or my ST 90. The OS Hanno has a fuel pull pump so I 
    do not expect it to happen, but I will be watching. So far it is only the
    YS's that are doing it. I was unable to blow through the YS120's
    filter on the Dalotel last night. I wonder if a lot of the running
    problems I experienced in the past were attributable this filter-gunge 
    problem?.
    
    Any theories out there?.
    
    E.

    Sounds like the old "sugar in the gas tank" trick. 
    
    I had the same stuff in my YS45 check valve.  (No filter used)  I had
    to clean it out a couple of times when the engine had troube making
    tank pressure.  I don't know what the stuff is.
    
    Charlie
    

    I shall call it "Wyesterone" untill it is identified scientifically!
    :-)

I'll bet the engine just sucked in some Balsa-Slo one of the times Jim C.
pitted for you guys 8^)

>>I'll bet the engine just sucked in some Balsa-Slo one of the times Jim C.
>>pitted for you guys 8^)


  Actually it's my other formula....Glo-Slo-YS.  I'm currently working on a
Glo-Slo-OS that works on OS engines.  It's fairly safe stuff in that it only
eats away at the inside of the engine and eventually turns it into a useless
hunk of junk.

  Don't let Eric know, but I just successfully tested yet another invention
called Electro-fast!  It sucks all the power out of NiCds!  :^)




                 Jim 


  P.S.  Anyone else in the Marlboro area happen to notice a thunderstorm or
        six last night???  :^)

Right as I was dropping stuff off at UPS (just got in the door with the 
boxes) one came through. Impressive!

I heard there was an underpass on Rt20 with 3' of water under it. (I headed 
back up Rt140 to 290)


I see you've been working on Magnum carbs as well!

    
    Eric,
    
      If you run ALL your YS engines the same way that you ran the YS-45 in
    your Gremrocket, the substance is probably molten piston metal that
    found its way back to the filter! :)
    
                                       Finally waking up...........
    
                                                             DW2

    I must correct a previous entry. The only stuff that dissolves the
    Whyesterone is K&B thinners. Acetone just makes it become like gum. I
    used K&B thinners last night because the Acetone had not worked over
    night. The K&B worked its magic in minutes.
    
    
    The blockage that whyesterone creates is 100% efective. Nothing can get
    through. The filter on the pressure line to the tank, however, was clear. 
    (I had fitted an extra one as an experiment once whyesterone started 
    showing up).
    
    Once dissolved the whyesterone leaves the filter gauze as good as new. 
    This stuff occurs with metal or plastic filter elements.
    
    Still looking for answers.
    
    Regards,
               
    E.

    
    Not too long ago I bought real nitro thinner that costs a fortune. When
    washing the brush there was this strange white something that could be 
    squeezed like a sponge. Could it be that someone mixed nitro thinner 
    instead of nitromethan ?  Nah, nobody would do that !  (Have you
    cleaned your engines with something ?  Or oil-incompatibilities ?
    
    Just a thought

     I was having problems last night with my OS. After getting home and
    taking it apart I noticed how gunked up the inside of the head was.
    Gave it a good cleaning will try it again to night. This is the first
    time I have had a problem with gunk. I use to use Rem-oil (gun oil with
    teflon) as an after oil. The stuff works great but is kind of
    expensive. I switched over to trany fluid after reading about it in MA
    a couple of months ago. Since than the gunk problem started. I was
    going to use Mobil 1 but someone at the field said its risky with these
    engines because at high temperatures mobil 1 brakes down leaving a
    different kind of compound. Point is that I was wondering if the
    interaction of the fuel with the after oils like Mobil 1 or trany fluid
    at high temperature may be causing Eric's problem and my gunk problem.
    

    The other side is that Mobil-1 has prevented any damage to the silicone
    parts as well as keeping the bearings shiny.
    
    E x E.

    Does trany fluid affect non-metal parts?

    Eric's problem is in the fuel system.  How would after run oil get in
    there????  His fuel filter was gunked up.  I have been using Mobil-1
    for over two years with no problems.  It does not kill glow plugs (some
    oils do), it doesn't attack silocone fuel tubing, and the engine
    doesn't kick back like a mother the first time you start it.  I used to
    use Marvel Mystery Oil and it had two problems.  It kicked like a
    mother the first time you started it and the oil would destroy silocone
    fuel tubing in a heartbeat.  I've seen no evidence that Mobil-1 gunks
    up engines either.  I have hundreds of flights on my OS25, OS32,
    OS91Surpass, YS45.  I liberally apply Mobil-1 after every flying
    session and the only engine I've torn down was the OS91Surpass.  There
    was carbon buildup around the valve seats and the valve stem but no
    other indications of wear or bearing rust.  I'm a Happy Camper with
    Mobil-1.
    
    Transmission fluid is a good after-run for engines with no silocone
    parts but it will attack fuel tubing and the silicone parts in pumped
    engines.  It CANNOT be used in YS engines without destroying the fuel
    regulator diaphram.  You could probably get away with using it in OS
    pumped engines because it is unlikely for the oil to get into the pump.
    I'd still recommend Mobil-1 after our HTA experience with it.
    
    Charlie
    

    The tank on a YS is pressurised directly from the crankcase. After-run
    compounds can easily reach the tank and then the carb. 
    
    In my case I put a filter in the pressure line and the fuel line. The
    mystery is that the pressure line filter stays clear and only the fuel
    line filter gets blocked.
    
    Something is being filtered that is either in the raw fuel or is
    combining with it.
    
    
    EVL-2

    Good point!  That goes for the OS pumpers also.  In that case, don't
    use petrol based oils in OS pumped engines either.  Maybe the gunk is
    something from the castor oil.
    
    C.