One of the problems with the GMS engines is the darn thing won't shut off.
Some have had sucess with smearing red rtv around the carb. GMS engines are
not for a newbie with little to no experience. The Thunder Tiger or Magnum
engines would be a better purchase. Evolution has a 40 something sized
engine that is guarranteed to work without problems right out of the box.
All these engines are under $100 USD. If you insist on GMS, then seek out
http://gmsengines.com for a fantastic price - $70 USD delivered to your door
for the .47.
Here's a repost of my "GMS .47 Mini-Report":
Got my GMS .47 on monday may 20. All the way from merry England.
Wednesday evening i ran three tanks through it without making much
of an attempt to tune the high and low speed needles other than to set
the top end a little rich, because i found out early on that each
adjustment affects the other.
Prop was a 10x5 zinger, fuel was my infamous "platinum break-in
formula," the result of many bottom o' the can pourings and with
enough additional sig castor added to bring the oil content to around
25% or more. My best guess is the nitro is probably 10 or 12%.
Never at any time during the short break-in, which was done on a
test stand, did the engine sag from a peak setting, but i kept peak
runs short and to a minimum until the third tank.
Sunday and monday i had the chance to fly this engine in a Modeltech
Magic. 2.5 oz. total or one additional oz. of lead were required in
the tail to balance the airplane with the GMS in place of the Fox .46;
about 1/4" behind recommended. I adjusted it to idle reliably (but it
wouldn't shut down with the carb fully closed), and adjusted the high
speed a few hundred rmps rich. Prop was APC 12.25x 3.75, fuel
Powermaster 15% synth/castor blend.
After nine flights of about eight minutes or so each i'm very
pleased with this engine. It no longer seems as though the high and
low speed adjustments interact. By setting the idle at what to me is
a wee bit lean, the engine will now shut off at no throttle. High
speed was set just a tad rich from peak. Accelleration was quick and
firm, no deadsticks were encountered. Plug was the same tower power
plug i used for break-in.
Despite my suspicions that an 11x4 APC might be the best performing
prop for this airplane/engine combo, the APC 12.25x3.75 roolz, and i
think it's because this engine has more than enough moxie to handle
it. The large diameter and heavy-ish weight may help the prop to act
as a gyroscope, possibly, who knows? All's i know is that it was
easier for me to hover and i hovered better and longer than i ever
could before (which is to say, "not very well, but best yet"). The
airplane would easily and instantly accellerate vertically from a
nose-up hover, or any other position for that matter. Yee hah.
Apololgies to the technically-oriented. I haven't tached this
engine yet so no numbers, mainly because i already know that the
Magic and the GMS .47 makes for a good combination and that's all that
ps - The engine shutdown/"lean" idle situation was corrected forever
by tightening the needle valve assembly to the carburetor body. I've
got many happy hours on this engine now and it's still clean as a
whistle. If there's a better value in the .46 size I don't know about
Thanks, Pete. That pretty much echoes my experiences with them. I replaced
one of the famous Raptors with one on my trusty Ballistick and I think I get
better performance. This is due to the fact that the GMS turns an 11X6 a
little better than the Raptor.
| not even if you cut the line in two and throw a shop rag in the prop!
Now THAT would be damn cool!
I'd take a glider with generous dihedral, trim it so it flies in a
pretty straight line, take out all the radio gear, and let it go. It
would fly forever, probably annoying people all over the place ...
| > Won't shut off? Even if you pinch the fuel line?
Seriously, pinching the fuel line kills it, as will pinching off the
exhaust, holding the spinner, making it into a lawn dart or putting
your hand/face/leg/etc. into the prop. (I don't suggest the latter
three methods of stopping it, however.)
The complaint is that you cannot kill it by putting the throttle all
the way down. I don't have any GMS engines, but I have a Tower
Hobbies engine (which I hear is just a rebadged GMS engine) and it
suffers from this problem. It's really not a big deal, at least not
to me. But some people feel it's unsafe if you can't kill your engine
at will from your transmitter.
Doug McLaren, firstname.lastname@example.org
"Life, loathe it or ignore it, you can't like it."
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