RADIO CONTROL AEROBATICS - 2003/10

THERE IS A pair of new engines aimed at
the Pattern market: the 3M Mintor 1.40 and
the Mintor 1.70. Both are rear-exhaust
engines produced by an Italian company,
and they have been designed, engineered,
and manufactured to meet the needs of
modern F3A models. The manufacturer of
the new engines states:
“Until now, very few engines on the
market have been able to meet these
demands; in fact, other than the Japanese
Yamada and O.S. models, there are no other
valid alternatives on the competitive field.
[This firm may not be familiar with the
German-made Webra 1.45, and you can
debate the word “valid.”]
“Mintor srl, a Bergamo company
specialized in precision mechanics for over
thirty years, has achieved its aim by
providing top performance at a very
attractive price. The engines were created
from an innovative structural design and
processing procedures that are not found in
large-scale standard production.
“Hours were spent working towards the
goals set the moment the project was
started; from months of bench tests and
flight tests, to adjustments and meticulous
fine-tuning, resulting in the final version.
“All the engine parts that are normally
cast (crankcase, pumps, piston, carburetor,
etc.) are machined from solid aluminum
instead of castings. Only the best
aeronautical aluminum has been used,
allowing a reduction in weight and total
absence of micro-porosity, as well as much
greater structural rigidity than even the best
castings available on the market.
“Finally, all the engine parts have been
subjected to anodizing and anti-corrosion
Eric Henderson, 303 Shady Ln., Marlton NJ 08053; E-mail: [email protected]
RADIO CONTROL AEROBATICS
Die-hard Pennsylvania Avenue Radio Control Society (PARCS) members at Frank
Granelli’s recent Pattern primer contest in Brooklyn, New York.
PARCS contest winners were happy about just beating the N.E. spring monsoon!
The 3M Mintor is installed in a Hydeout for testing. The author
uses ES O.S. 1.40 carbon-fiber pipe and 3M header.
The new 3M Mintor 1.70 fresh from Italy is shown on an engine
mount by Wayne Galligan. Photo by Wayne Galligan.
October 2003 99
100 MODEL AVIATION
treatment which protects them against the
effects of nitro-methane.”
Manufacturers’ claims are one thing. The
proof of the pudding, however, is in the
eating. The 1.70 version was fitted to my
“year 2000” Hydeout. It used to be the home
of a YS 140 L, then most recently it hosted a
YS 140 DZ.
When changing engines, the center of
gravity (CG) is often affected. A good
practice is to drill a 1⁄16-inch-diameter hole
in each side of the fuselage where it (not the
assembled airplane, but the fuselage itself)
balances. This is best done after the flight
tests. Then any subsequent changes to the
fuselage configuration can be checked on
the bench to see if they have changed the
balance. Things that can cause weight
changes are servos, batteries, pipes, mounts,
spinners, and of course, engines.
It is interesting to see how much
variance there is in the weights of our
current choice of two-meter power plants.
The following engines were weighed with
headers included, but no propeller nuts or
washers. The YSs had the steel CD
header without the Teflon connectors.
The two-stroke engines had their
aluminum headers, but no silicone
Dedicated Pattern enthusiast and NSRCA District 1 VP Frank
Granelli demonstrates maneuvers at Pattern primer.
Pattern recruitment may well lie with purpose-designed ARFs
such as the Creek Hobbies Quest .90, held by Fred Weiss.
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couplers. They all had glow plugs.
Engine: Weight
YS 120 AC: 2 pounds, 3.6 ounces
YS 140 L: 2 pounds, 1.6 ounces
YS 140 DZ: 2 pounds, 3.0 ounces
O.S. 1.60 FX: 2 pounds, 3.8 ounces
Mintor 1.70: 1 pound, 15.8 ounces
Establishing the combined header-andengine
weights is useful in determining what
needs to be done to maintain the CG’s
integrity when engine changes are made.
You can usually move the battery and/or use
a heavy (nonlightened-backplate) spinner
backplate to get the CG back when
swapping from a four-stroke to a two-stroke.
So how did the Mintor 1.70 perform?
Respectably, indeed. The latest readings at
the time of this writing are with an almostbroken-
in engine. With a 17 x 13 APC
propeller, two A5 plugs, and using
PowerMaster 15⁄16 fuel, you get a steady
7,900 rpm. The head temperature stays at
roughly 90- to 100°, and the crankcase stays
at 78° (measured using a laser temperature
gauge).
The wee beastie has a bit of power, to
say the least. On verticals you could use full
power, but you are advised to back off to
half power on the 45° up-lines, lest you run
the risk of overshooting your destination.
The Masters and Fédération
Aéronautique Internationale Diamond Loops
can be performed at the size of your choice.
At all times the engine transitioned
flawlessly and only quit when the fuel tank
was empty. This is probably because the
twin plug head does its job.
Now we have O.S. 1.40s (EFIs and
RXs), YS 140s, Webra 1.45s, O.S. 1.60s
(FXs and FIs), Mintor 1.40s and 1.70s, and
soon Webra 1.60s, etc. from which to
choose. The Pattern scene gets more and
more intriguing with all of these choices,
unless you are indecisive!
Engine Mounts: There is a time when a
two-stroke engine idles so low that it
“bounces” as much as a four-stroke at idle.
They both smooth out at 2,000-2,500 rpm.
The best setup is a non-nose-ring isolation
mount such as the Type A Hyde Mount.
All current nose rings seem to add
airframe vibration. They provide poor
isolation compared with the mounts. They
must be set with no side pressures to be isoeffective.
Nose-ring installations tend to
cause aileron “buzz” at certain in-flight rpm
settings. This kills the digital aileron servo
and drains battery power! The four-stroke is
the worst culprit by far.
The smoothest setup is a two-stroke with
no nose ring. The newer airplanes have
room for a bigger “hockey puck” rear plate.
Models with fiberglass cowls are much
easier to install without Herculean
engineering of a nose-ring support.
There is a flood of Pattern Almost Ready to
Flys (ARFs) coming into the USA, such as
the top-end Tai-Ji, low-end Tai-Ji, Swallow,
Stream 50, Zen, TT Imagine, Focus, Focus
II, Majestic, Advance, Javelin, EZ Hydeout,
etc. Then there is a whole raft of so-called 3-
D airplanes such as the U-Can-Do,
Freestyle, and Giles, and there are a bunch
of aerobatic sport models.
This influx at club fields creates a
veritable harvest that we precision
Aerobatics pundits should prepare to reap!
As a reader of this column, you are an agent;
every one of you has the power to run an
Aerobatics fun-fly.
Do a clinic in the a.m. and a simple
contest in the p.m. Contact your National
Society of Radio Controlled Aerobatics
(NSRCA) vice president. (Go to
www.nsrca.org.) Ask fellow NSRCA nuts to
help you. Give presentations at your club.
Sell (not tell) the fun and challenge of
following a schedule and doing it well, and
add the pleasure of taking a model home in
one piece after a fun-fly!
Frank Granelli, who is the NSRCA
District 1 vice president (AMA Districts I
and II), showed what can be done. He
hooked up with Vlad Camaev of the PARCS
(Pennsylvania Avenue Radio Control
Society) club, which flies at Floyd Bennett
Field in Brooklyn, New York. Frank and his
wife Ann ran a Pattern clinic in early May,
then he recruited me, Rick Wallace, and Joe
Lachowski as judges and ran a Pattern
contest at the end of the month. Frank
104 MODEL AVIATION
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