Conference vmszoo::rc

    gee, isn't that what the hole in the hub is for???  Just tie a piece of
    string from the hub to the nose wheel and you will never lose your
    hub!!
    
    :-) :-)
    jeff
    

I had to go to Aubuchon's Hardware on sunday for this very reason. I ended up 
using a washer, lock washer, nut arrangement and didn't have anymore problems.
One thing that I've noticed is that it seems to happen after I've had a hard
start and had to really crank it with the starter. If you go the "hardware 
store" route make sure you don't get "hardened" nuts (calm down out there ;^)
since you want the nut to strip before the crankshaft. I lost a very nice
turned/threaded spinner/propnut for my Webra .20 in the swamp a few weeks ago
and now I'm stocking up on 10 cent replacement nuts for my field box. Boy, was
I glad Aubuchon's was open on this past weekend after losing the only one I
had with me on such a beautiful day.

    I would not recommend using loctite because you may get the nut
    partially loose holding the prop and then need to maul the aluminum
    backplate to get the nut all the way off.
    
    Do you balance your props?  It is amazing how bad some of them can
    be.  As a quick tip I paint clear dope on the backside of the light
    blade untilthe prop balances.  If your props are balanced then you
    might check for a loose motor mount or a cracked firewall that is
    only showing itself under vibration.
    
    Good Luck
    
    Will

    The first few weeks into this hobby I watched an experienced RC pilot
    put a screwdriver into the exhaust port to prevent the shaft from
    turning while he removed a broken prop.  I'm new to modeling, but I am
    not new to machinery; I didn't think circumstances should lead to that
    practice.  Shortly thereafter I learned that Master Airscrew plastic
    props could deform onto an OS 40 shaft enough to defy removal --- but I
    damn well wasn't going to use his screwdriver technique.  I guess those
    first few tough ones I faced I removed by grabbing the drive washer
    with pliers.  Until I solved the problem. 
    
    Remove the drive washer, set aside the collet inside, and drill a small
    hole cross-wise through the washer --- in the grove, through the axis,
    and out the other side. Then remount the washer and collet.  You have a
    washer with two grip points on opposite sides.  Take a particular
    automotive tool, the special pliers made of sheet steel that are used
    to remove the clips that retain window cranks, and grind a pair of
    points to grab these two holes in the drive washer.  The result is a
    newly specialized pair of pliers to secure the shaft from turning, a
    non-abusive way to remove the most stubborn props. 
    
    With this control of the shaft, it wouldn't matter if Locktite were
    to be used to secure the nut.  I've tried it.

    If your 2-stroke is spitting props, you are probably doing one of the
    following things wrong:
    
    1.  Not tightening the prop tight enough.  The prop should slip over
    the shaft, not thread onto the shaft.  If the hole is too small, ream
    it out.  The nut should be tightened quite tight.  The shaft threads
    are hardened and you won't strip them unless you use a very long
    wrench.
    
    2.  Flooding the engine with fuel and applying a starter.  This
    causes the nut to loosen up if you don't have a spinner.  You can also
    bend the connecting rod if you hydro-lock the engine with fuel.  This
    often happens on inverted engines.  Make sure that it will turn over by
    hand easily (glow driver removed) before using a starter.
    
    3.  Detonation may be loosening the prop.  This is caused by the fuel
    firing before the piston gets to top dead center.  Improper mixture or
    a glow plug that's too hot can cause this.  It's rare on 40 2-strokes
    but very common on 4-strokes.  Too lean a mixture is usually the cause.
    
    
    Hope this helps
    
    P. S. I've never used locktite on prop nuts, only engine mounting nuts.
    My SS40 with a Graupner 10/6 and OS40 FSR had the same prop on it all
    season and I never even tightened it.  I also never use a starter.
    
    

See Model Aviation November 1989 page 22.

"Another product which has arrived in my mail some time ago is from Performance 
Products Unlimited. It is called Disk-Lock, which is a prop washer designed to 
prevent props from being kicked off the crankshaft in the event of a 
backfire... ........ etc:   "

John

    I just read this note, and it rung a resounding chord.  I have been
    breaking in a brand new OS .40 FP, and on two occasions on the test
    stand, it threw the prop.  I had reported the first such occurance
    elsewhere in this conference, and have been discussing the problem with
    my "to be" flight instructor who has witnessed the engine actually
    running backwards.  
    
    I cannot actually say that it was running backwards when it threw the
    prop, since I was not that cognizant of exactly what was going on,
    although I am now.  However, on the chance that it was running
    correctly and threw the prop, the question in my mind is whether this
    particular engine has some kind of basic defect, either an engineering
    shortcoming or a manufacturing defect, that is at fault?  If others are
    likewise experiencing the same problem with this particular OS engine,
    let's rise up and revolt against OS to get our money back.  I don;t
    know about the rest of you, but the prospect of eating my prop while
    its doing 10K doesen't appeal to me one bit.  Not to speak of the
    potential for disaster to others who may be in the vicinity when it
    happens.
    
    This engine really scares me!
    
    -Joe

I've got an OS 40 FP, and it surely does like to start up going backwards, but
I don't have the problem of it spitting the prop. I like to torque the prop
on good and tight. 

I generally flip-start the engine, unless it absolutely won't fire, in which
case I borrow someone's electric starter. When it runs backwards, I open the
throttle wide, causing it spit fuel like a cornered panther, at which point it
usually kicks back to normal operation by itself. Maybe that's when yours 
spits the prop.

Dave

It sounds like you guys think that the function of a model
airplane engine is to get soaked with fuel.  No, believe it or
not, they're supposed to run!  I too, was deluded once.  Only I
thought that the function of an engine was to be tinkered with
and cussed at.  Surprisingly, they do turn a prop.  Only the ones
with a "B" and a "K" in their names remain to be tinkered and
cussed.

I'm breaking in my OS 40 FP now.  It had one blubbering run on a
tank.  Even in its first run it did not spit out fuel like other
engines I've broken in. In fact, I was so surprised about this I
kept shutting it down because since it wasn't spitting out fuel I
figured it was overheating.  Nope.  Yesterday I ran it on the
rich side of lean and got a good run with only minor overheating.
I'll back the valve out a quarter turn for the next run or so.

I use a starter on the .40, and I think it makes a big difference
when starting a balky engine.  Anyway, crank in on the needle a
little, I think you'll like it.

    Like John, I too, run an O.S. 40FP and have never had it run backwards.
    I always use an electric starter.  I have had a problem to get it to
    run smoothly as Al Casey can testify, but it DOES run in the right
    direction.  Since my mishap in Phoenix, I have rebuilt the PT40 (
    just finishing covering the ailerons) and pulled the engine and have
    it on a Testone test stand.  Run it several times over the weekend,
    but it still not running as consistantly as it should, so I'll not
    put it back into the plane until I'm confident of it's reliability.
    
    Chuck
    

    My brother has a OS.40FP that started up bacwards.  Only happened
    once.  My OS.40FP hasn't done it yet.  We are both finding out that
    these engines for some reason are a pain to keep running.  After
    about two minutes of flight they die!  More practice in tuning I
    guess.  But!!!!! they haven't spit any props yet.
    
    Ken

    Re: last several,
    
    Regarding comments about engines running backwards, lemme' just offer
    the fact that virtua<lly _all_ engines can and will run backwards,
    regardless of who manufactured them.  When hand starting (which I
    prefer to do), the O.S. .61FSR-ABC in my ol' B�cker will invariably
    start backwards once or twice on the first start-up (when cold).  The
    O.S. .60FSR in the MiG-3 behaves similarly.  This does _NOT_ signify
    anything wrong with your engine; it's completely normal behavior for
    almost any engine, particularly when starting it a little on the wet
    side (too much priming/choking).  Also, as John T. states, if the
    engine is being run quite rich, it's more liable to hiccup (backfire)
    and run backwards after starting and running in the proper direction.
    This is when the prop is most likely to be spit off as the _very_
    sudden change in direction puts quite a load of opposite torque on the
    pron and associated hardware.  Like John, I tighten the H*ll outa' my
    props and have had essentially no problem with throwing the prop.  If
    the wrench didn't hurt my fingers when tightening the prop (with almost
    visible compression of the wood), then I didn't get it tight enough.
    
    This problem is most likely to occur when running a plastic/nylon/carbon 
    filled prop as its inherent rigidity doesn't allow you to get this
    compressed effect which helps keep the hardware tight.  Personally, I
    shun these 'artificial' props due to this and numerous other safety
    hazards anyway.  IMHO, the ONLY reasonably safe prop to run is a wood
    one.  You might want to try one and see if it minimizes the problem.
    
    Also, as John, Chuck and Ken state, the running backwards problem can be 
    all but totally eliminated through the use of an electric starter. 
    Chuck's problem has managed to elude me on the two occasions I've had
    to see it.  The engine seems to start and adjust normally enough on the
    ground but invariably begins to sag (go lean) and eventually quit once
    airborne unless it's set gugling rich before takeoff.  This, normally,
    suggest a problem in the fuel tank, fuel delivery system (tubing,
    filters, pumps, et al) and or carburetor but, as I've said, my exposure
    to the problem has been to brief to resolve it as yet.  The fact that
    it appears to exhibit the same problem running on a test stand seems to
    point to other than the fuel tank and associated components, i.e. the
    carb seems the prime suspect at the moment.  Hang in there Chuck and be
    sure to let us know what the solution turns out to be.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

    On the OS46SF I had on the Train-air 40, which was totally broken
    in by the way, it was not unusual for it to run backwards while
    starting (hand starting). A couple of blips on the throttle 
    straightened right out. 
    
    Steve

    One trick I have learned is to start with a little more throttle
    opening if the engine tends to start backwards.  As Al said any
    2-stroke will run backwards but the timing is way off.  You can kill it
    by opening the throttle.  It usually won't run even at half throttle
    backwards.  I always hand start my engines unless it's below 40 degrees
    out and they refuse to fire by hand.  I do this for two reasons: 
    First, I feel that any properly running and adjusted engine should
    start first or second flip by hand.  I use this as an indicator as to
    whether the engine, plug, and fuel are right.  I have very few
    dead-stick landings because my engines run well.  A marginal setup will
    run if you use a starter and grind away at it.  The second reason I
    hand start is that I feel it's safer.  I expect to get arguements about
    this, but let me explain my logic.  The starter can slip off the
    spinner and hit the prop.  I saw the rubber thing clock a guy in the
    face when the starter slipped.  The starter can losen the prop nut and
    cause a prop spit.  That's right, the direction the starter turns
    losens the nut!  I've seen the whole thing come off if the engine
    backfires while trying to start.  Also, you can bend the con rod if you
    try to start with a starter and there's too much fuel in the motor. 
    This is very common on inverted engine setups.  Always turn it over by
    hand before applying the starter.
    	Most of the prop injury incidents I have seen and heard of happened
    after starting not during.  Reaching over the prop to take off the plug
    warmer is very bad. (You should walk around the plane to do this) Also,
    having the plane get away from you (usually big engines) after starting
    can cause an accident.  I have had my finger wacked while starting, but
    this is usually far less serious than getting bitten by a running
    engine, even at idle.  
    
    	I guess I sort of got off the subject.
    
    Charlie
    

Charlie, you mentioned that you use hand starting as a check to
see if the fuel, plug, and engine are OK.  You really only have
control over one of these variables, the plug, which you can
change.  What do you do about the other two?

One method I've used to control fuel flow is to adjust the needle valve by 
putting my fingers through the prop arc from the front. I've done this more 
times than I care to remember...

Seriously, if I suspect bad fuel flow I generally unscrew the needle valve 
all the way and blow it clear. I generally have extra (unused) fuel tubing in
my flight box and I use that to blow air through and clear any blockage. I might
also swap the fuel line filter if I suspect it. The fuel line filter is usually 
the culprit.

    John,
    
    	I think what Charlie is referring to is the fact that if an
    engine is set up properly, it should start easily with a hand flip.
    If he can't start his engine by hand, then he suspects a problem.
    
    An engine set too rich will be dificult to start by hand, but will
    start (apparently normally) with a starter. Likewise for an engine
    that may have the low end incorrectly set. Where you are starting
    the engine close to idle, it would be hard to start by hand, but
    you can get it running with a starter.
    
    So, one of the way's Charlie checks the condition of his engine
    is by the "degree of difficulty" in hand starting.
    
    Steve

    What I meant by fuel being ok is just that!  I've run into more people
    at the field that have bad fuel that's been sitting around unsealed. 
    In this climate,  moisture gets in and the nitro gets out and the
    result is very poor starting and running reliability.  The engine will
    quit abruptly right when you need it most three feet in the air
    clearing the runway on takeoff.  I've seen people grind away with their
    trusty starter for a minute before checking if their ni-starter and
    glowplug are working.  I have developed a starting technique that
    ususlly gets my engines running in one or two flips.  I save the hassle
    of carrying a starter and battery although I do keep one in my van just
    in case.  Cold weather is the only reason I have had to need it for my
    own engines.  I guess I developed this from my UKIE days when noone had
    an electric starter or a throttle either for that matter.  I also have
    a leather work glove in my box for starting my big 4-stroke.  I have to
    admitt that I probably should use a starter on that mother. (OS120
    Surpass)  It has a gear pump that has a nasty habit of draining the
    fuel system all the way back to the tank if it runs backwards which it
    seems to do quit frequently.  Then I have to start all over repriming
    it.  I'm not against starters, I just feel like I don't need to use one
    routinely.  Enyone that flys with me knows that I never spend much time
    fooling around with balky engines. (Unless they belong to someone
    else.)
    
    Charlie
    

RE: -.1

    I've got an OS90 4 stroke that has startup up backwards a couple of times.
    Just how in the (#$(&#($ does it keep running? Running backwards, the
    valve timing is pulling air through the muffler and blowing it out of the
    carb.  I just about couldn't believe it the first time I saw it happen.
    Does anybody know where the fuel is coming from when that happens?
    Maybe the muffler is drawing fuel through the muffler pressure line?

Glenn Schrader

    There is enough valve overlap to get the 4-strokes to run backwards
    although not well.  My OS91 Surpass will also do this.  The OS120 won't
    for long because the pump drains the carb very fast when it runs
    backwards.  Speaking of backwards, I had a friend once that somehow got
    the timing way off on his 2-stroke moterbike.  It would kick and run
    backwards.  He sure got a surprise the first time he dumped the clutch
    in first gear and shot backwards instead of forwards.  I wish I had a
    video of this.
    
    Charlie
    

    To continue on with my comments in .12 and Al's in .14 and also some
    in .20, I want to share a "revelation".  I'm sure many of you know this
    already, but what I finally figured out is:    BAD FUEL!! I have been
    keeping my fuel (10% nitro and Castor) in it's original plastic jug and
    it does NOT keep long that way.  I think I also accelerated the problem
    by being in Phoenix last summer where the fuel jug was subjected to
    very high temperatures (>115 degrees).  Well, having finally figured
    out what any intelligent RC'er would have known in 10 minutes, came the
    problem of trying to find a metal can. One solution would have been to
    buy K&B fuel (@$15.00/gal) or find another source. I checked a few
    auto body shops for an empty acrylic lacquer thinner cans, but didn't
    have any luck, as most shops get their thinner in either 55-gal drums
    or 5-gal cans.  Solution: for those in the Colorado Springs area,
    Dale's Paint Supply, 509 N. Circle Drive. It's on the East side of the
    street just 2 doors North of Platte Ave.  They have brand new EMPTY
    1-gal cans with metal caps; $2.00 + tax = $2.13.
    
    I think I'm all set now (until the next stupid blunder)
    
    Chuck