O.S. engine 49PI Setup guide

It is of vital importance, before attempting to
operate your engine, to read the general
'SAFETY INSTRUCTIONS AND WARNINGS'
section on pages 2-6 of this booklet and to strictly
adhere to the advice contained therein.
●Also, please study the entire contents of this
instruction manual, so as to familiarize yourself
with the controls and other features of the
engine.
Keep these instructions in a safe place so that
you may readily refer to them whenever
necessary.
It is suggested that any instructions supplied
with the aircraft, radio control equipment, etc.,
are accessible for checking at the same time.
●
●
ROTARY ENGINE 49PI
Due to updating and improvement, latest products may
occasionally differ from those shown in the photos.

2 ~ 6
7
8
9
10
22
19
11
~ 13
18
20
16
17
21
14
15
CONTENTS
SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR O.S. ENGINE
INTRODUCTION
BASIC ENGINE PARTS
GLOWPLUG
MOUNTING THE ENGINE
BEFORE STARTING
STARTING
RUNNING-IN("Breaking-in")
PRE-FLIGHT CHECKING
SUBSEQUENT READJUSTMENT
ENGINE CARE AND MAINTENANCE
GENUINE O.S. PARTS &ACCESSORIES
ENGINE THREE VIEW DRAWINGS
ENGINE EXPLODED VIEWS
ENGINE PARTS LIST
CARBURETOR EXPLODED VIEW
& PARTS LIST
1

Remember that your engine is not a "toy", but a highly efficient internal-
combustion machine whose power is capable of harming you, or others, if it is
misused.
As owner, you, alone, are responsible for the safe operation of your engine, so act
with discretion and care at all times.
If at some future date, your O.S. engine is acquired by another person, we would
respectfully request that these instructions are also passed on to its new owner.
SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O.S. ENGINE
The advice which follows is grouped under two headings according to the
degree of damage or danger which might arise through misuse or neglect.
WARNINGS NOTES
These cover events which
might involve serious (in
extreme circumstances, even
fatal) injury.
These cover the many other
possibilities, generally less obvious
sources of danger, but which, under
certain circumstances, may also
cause damage or injury.
2

WARNINGS
Model engine fuel is poisonous. Do not
allow it to come into contact with the eyes
or mouth.Always store it in a
clearlymarkedcontainerand
out of the reach of children.
Never operate your engine in an en-
closed space. Model engines, like auto-
mobile engines, exhaust deadly carbon-
monoxide. Run your engine only in an
open area.
Model engines generate considerable
heat. Do not touch any part of your
engine until it has cooled. Contact with
the muffler (silencer),
cylinder head or exhaust
header pipe, in particular,
may result in a serious burn.
•
•
•
•
Never touch, or allow any object to come
into contact with, the rotating
propeller and do not crouch
over the engine when it is
running.
A weakened or loose propeller may
disintegrate or be thrown off and, since
propeller tip speeds with powerful
engines may exceed 600 feet(180 metres)
per second, it will be understood that
such a failure could result in serious
injury, (see 'NOTES' section relating to
propeller safety).
•
Model engine fuel is also highly
flammable. Keep it away from open flame,
excessive heat, sources of sparks, or
anythingelsewhichmightignite
it.Donotsmokeorallowanyone
else to smoke, near to it.
•
3

NOTES
•
•
•
•
•
This engine was designed for model
aircraft. Do not attempt to use it for any
other purpose.
Mount the engine in your model securely,
following the manufacturers' recommenda-
tions, using appropriate screws and lock-
nuts.
Be sure to use the silencer (muffler)
supplied with the engine. Frequent
exposure to an open exhaust may
eventually impair your hearing.
Such noise is also likely to cause
annoyance to others over a wide area.
Install a top-quality propeller of the
diameter and pitch specified for the engine
and aircraft. Locate the propeller on the
shaft so that the curved face of the blades
faces forward-i.e. in the direction of flight.
Firmly tighten the propeller nut, using the
correct size wrench.
If you remove the glowplug from the engine
and check its condition by connecting the
battery leads to it, do not hold the plug with
bare fingers.Use an appropriate tool or a
folded piece of cloth.
4

NOTES
•
•
Always check the tightness of the propeller
nut and retighten it, if necessary, before
restarting the engine, particularly in the
case of four-stroke-cycle engines. If a
safety locknut assembly is provided with
your engine, always use it. This will prevent
the propeller from flying off in the event of a
"backfire", even if it loosens.
If you fit a spinner, make sure that it is a
precision made product and that the slots
for the propeller blades do not cut into the
blade roots and weaken them.
Preferably, use an electric starter. The
wearing of safety glasses is also strongly
recommended.
•
•Discard any propeller which has become
split, cracked, nicked or otherwise rendered
unsafe. Never attempt to repair such a
propeller: destroy it. Do not modify a propeller
inanyway,unlessyouarehighlyexperienced
in tuning propellers for specialized
competition work such as pylon-racing.
Take care that the glow plug clip or battery
leads do not come into contact with the
propeller. Also check the linkage to the
throttle arm. A disconnected linkage could
also foul the propeller.
After starting the engine, carry out any
needle-valve readjustments from a safe
position behind the rotating propeller. Stop
the engine before attempting to make other
adjustments to the carburetor.
•
•
5

NOTES
•
•
•
•
•
Adjust the throttle linkage so that the engine
stops when the throttle stick and trim lever
on the transmitter are fully retarded.
Alternatively, the engine may be stopped by
cutting off the fuel supply. Never try to stop
the engine physically.
Take care that loose clothing (ties, shirt
sleeves, scarves, etc.)do not come into
contact with the propeller.Do not carry loose
objects (such as pencils, screwdrivers, etc.)
in a shirt pocket from where they could fall
through the propeller arc.
Do not start your engine in an area
containing loose gravel or sand.
The propeller may throw such material in
your face and eyes and cause injury.
For their safety, keep all onlookers
(especially small children) well back (at
least 20 feet or 6 meters) when preparing
your model for flight. If you have to carry
the model to the take-off point with the
engine running, be especially cautious.
Keep the propeller pointed away from you
and walk well clear of spectators.
Warning! Immediately after a glowplug-
ignition engine has been run and is still
warm, conditions sometimes exist whereby
it is just possible for the engine to abruptly
restart if the propeller is casually flipped
over compression WITHOUT the glowplug
battery being reconnected. Remember this
if you wish to avoid the risk of a painfully
rapped knuckle!
6

OPERATING PRINCIPLE
In place of the piston and cylinder of a
conventional reciprocating engine, the Wankel
motor has a three-lobe rotor which moves in a
circular path, while rotating about its own axis,
THE NSU/WANKEL SYSTEM
Now available in a new and improved
PI(peripheral inlet) model, its outstanding
features remain its high specific power output,
its almost total freedom from vibration, its
relatively low noise level and its compact
shape.
This highly successful application of the
NSU/Wankel System to a power unit of
miniature proportions, was only made possible
by the expertise of O.S. research and
development engineers and by the high levels
of precision craftsmanship achieved in its
tooling and manufacture.
within a housing having an epitrochoidal bore -
i.e. a wide-waisted figure-of-eight
shape.Planetary rotation is controlled by an
eccentric shaft, an internally-toothed gear and
a fixed pinion mounted centrally on the rear
cover plate. The tips of the rotor are in
continuous contact with the housing, forming
three chambers, each of which changes in
volume, with rotation, to effect suction,
compression, expansion and exhaust phases,
as in a four-stroke reciprocating engine.
Spring-loaded tip seals on the rotor prevent
gases from passing from one chamber to the
adjoining one and the rotor uncovers ports, as
in a two-stroke engine, to control intake and
exhaust timing.
The engine is fitted with a conventional throttle
type carburettor that gives smooth and
progressive control of engine speed from idling
to full power. It is also supplied with a compact
matched muffler that very effectively
attenuates exhaust noise without causing
undue power loss.
7

Carburettor Complete
Engine Mount
Glowplug
Drive Hub
Spinner Nut
Rotor Housing
Front Housing
BASIC ENGINE PARTS Carefully insert plug, with
washer, fingertight only,
before final tightening with
the correct size plug
wrench.
Installing the glowplug
Glow plug
Washer
8

The role of the glowplug
With a glowplug engine, ignition is initiated by the
applicationofa1.5-voltpowersource.Whenthebattery
isdisconnected,theheatretainedwithinthecombustion
chamber remains sufficient to keep the plug filament
glowing,therebycontinuingtokeeptheenginerunning.
Ignition timing is 'automatic' : under reduced load,
allowing higher rpm, the plug becomes hotter and,
appropriately, fires the fuel/air charge earlier;
conversely,atreducedrpm,theplugbecomecoolerand
ignition is retarded.
Install a plug suitable for the engine.
(i.e. O.S. Type RE)
Use fuel containing a moderate percentage of
nitromethane unless more is essential for racing
events.
Do not run the engine too lean and do not leave the
battery connected while adjusting the needle.
However, plug life can be extended and engine
performance maintained by careful use, i.e.:
Apart from when actually burned out, a plug may
need to be replaced because it no longer delivers its
best performance, such as when:
When to replace the glowplug
Filament surface has roughened and turned white.
Filament coil has become distorted.
Foreign matter has adhered to filament or plug
body has corroded.
Engine tends to cut out when idling.
Starting qualities deteriorate.
•
•
•
•
•
•
•
•
Glowplug life
Particularly in the case of very high performance
engines,
glowplugs must be regarded as expendable
GLOWPLUG
A specially designed O.S. Type RE glowplug is
fitted to this engine Carefully fit plug finger-
tight, before final tightening with the correct
size plug wrench.
9

Firmly bolt the engine's radial mounting flange
to the model or to a rigid test stand, using self-
locking nuts or secondary nuts locked to the
first.
Make sure that the three cap screws securing
the mounting flange to the engine itself, are
tight and are fitted with spring washers.
The engine is normally mounted so that the
carburettor is horizontal on the right side and
the glowplug on the left ( i.e. when viewed
from astern).
The engine should receive a free flow of
cooling air. Do not obstruct airflow with an
oversized spinner.
If the engine is cowled, make sure that the air
entering at the front is able to escape easily:
the outlet area for the cooling air should not be
less than the entry area and should preferably
be larger.
MOUNTING THE ENGINE
Position the fuel tank so that when full, the fuel
level is approximately in line with the fuel jet.
Keep the fuel line short, i.e. install the tank as
close as possible to the back of the motor.
10

BEFORE STARTING
Tools, accessories, etc.
The following items are necessary for operating
the engine.
FUEL
For this engine, use top quality methanol-based mod-
el engine fuel containing approximately 25% castor-oil
and between 5% and 15% nitromethane.
REMINDER!
Model engine fuel is poisonous.
Do not allow it to come into contact with
the eyes or mouth. Always store it in a
clearly marked container and out of the
reach of children.
Model engine fuel is also highly flammable.
Keep it away from naked flame, excessive
heat, sources of sparks, or anything else
which might ignite it. Do not smoke or
allow anyone else to smoke, near to it.
The suitability of the prop depends on the size and
weight of the model and type of flying. Determine the
best size and type after the engine has been run in.
Check the balance of the propeller before fitting it to
the engine. Unbalanced propellers cause vibration
and loss of power. Wooden propellers are to be pre-
ferred. Some nylon propellers are not strong enough
to withstand the high power output of these engines
and a thrown blade can be very dangerous. As a
starting point, we recommend 9x5~6, 9.5x5 and 10x5
for general use.
Never touch, or allow any object to
come into contact with, the rotating
propeller and do not crouch over the
engine when it is running.
PROPELLER
REMINDER!
11

Battery leads
12V Battery
Starter
Battery leads
These are used to conduct current
from the battery to the glowplug.
Basically, two leads, with clips, are
required, but, for greater conve-
nience, twin leads with special glowplug connectors,
as shown on the right, are commercially available.
Fuel tank
For installation in the model, is 240cc(8.5oz.) tank, is
suggested.
Fuel bottle or pump
For filling the fuel tank, a simple,
polyethylene"squeeze"bottle,with
a suitable spout,is all that is
required. Alternatively, one of the
purpose-made manual or electric
fuelpumpsmaybeusedtotransfer
fuel directly from your fuel
container to the fuel tank.
Fuel bulb
Manual
Electric
Fuel pumps
Resistance coil
(nichrome wire)
Adjust applied voltage by changing the position of clip on
resistance coil until glowplug element is glowing bright red.
Battery leads
Raise
voltage to
increase
brightness.
Lower voltage to
reduce brightness.
Warning (Very hot)
Never touch the nichrome wire while the battery is
connected.
1.5 volt heavy-duty
dry battery or 2 volt rechargeable lead-acid cell (at least 5Ah)
If a 2-volt cell is employed,
use a resistance wire, as
shown, to reduce applied
voltage, otherwise element
will overheat and burn out.
Glowplug battery
The power source for heating the glowplug may be
either a large heavy-duty 1.5volt dry cell, or preferably,
a 2-volt rechargeable lead-acid cell (accumulator).
An electric starter is recommended
for starting.
Electric starter and starter battery
12

Fuel can filter
Fit a filter to the outlet tube of your
refuelling container to prevent entry
of foreign matter into the fuel tank.
Fuel Can Filter
Silicone tubing
This is required for the
connection between the fuel
tank and engine.
Plug wrench
Used for tightening glowplug. The
O.S. long plug wrench is available
as an optional accessory.
For tightening
glowplug
13

Fill the fuel tank and open the needle-valve 2-3
turns from the closed position.
STARTING
Prime the engine fairly liberally with fuel
through the carburettor. Turn the propeller
through one complete revolution and prime
again. Repeat this procedure once more so
that all three chambers, formed between the
rotor flanks and housing, are primed. Now
rotate the prop through several revolutions so
that any excess of fuel is blown through the
exhaust port. This will leave the chambers with
just about the correct proportion of fuel and air
for starting.
An alternative priming procedure, that some
users may find preferable when an electric
starter is being used, is to simply finger-choke
the intake (throttle fully open) while turning the
prop for six revolutions.
Now close the throttle to between one-quarter
and one-third open, connect glowplug lead and
apply electric starter.
After starting, allow the engine to warm up for
5~6 seconds, then remove the plug lead, open
the throttle fully and adjust the needle-valve.
Adjust for rich, reduced-rpm running when the
engine is new (see paragraph below on
"Running-in" ) : otherwise adjust for full power.
When re-starting the engine hot, do not prime:
simply close the throttle and apply the starter:
it will burst into life again immediately.
14

RUNNING-IN ("Breaking-in")
For running-in, fit the engine with a well-bal-
anced propeller intended for actual flight. Use
a fuel mixture as specified. Running-in proce-
dure is the same as for a conventional recipro-
cating model engine. After starting the motor,
open the throttle fully, but use a rich needle-
valve setting to reduce rpm, increase lubrica-
tion and lower running temperature. This will
produce a smoky exhaust but will ensure that
the engine does not become overheated and
damaged during this critical period.
The break-in should be split up into periods of
not more than 5 minutes, allowing the engine
to cool between spells of running. After about
30 minutes' running time have been accumula-
ted, the needle valve may be gradually closed
on each succesive run until continuous full-
power is being delivered. This is with the nee-
dle-valve set slightly rich of the setting at which
maximum speed is reached. If the engine
shows signs of slowing-up and overheating,
immediately reopen the needle-valve and con-
tinue the running-in process.
15

Prior to releasing your model for take-off, care-
fully check that the engine continues to run
steadily in all flight attitudes: this includes hold-
ing the model with the nose pointing vertically
upwards. In that attitude (assuming the model
to be equipped with a stunt type fuel-tank) the
engine must not quit: if it does, the mixture is
set too lean. Open the needle-valve until the
engine runs safely in this attitude. Adjust the
carburettor (needle-valve and throttle stop)
carefully and make sure that the R/C servo
linkage moves fully and freely between the idle
and full-throttle positions.
PRE-FLIGHT CHECKING Once the engine has been run-in and the con-
trols properly set up, it should be unnecessary
to alter the mixture settings; except to make
minor adjustments to the Needle-Valve occa-
sionally, to take account of variations in climat-
ic conditions.
The use of a different fuel, however, particular-
ly one containing more, or less, nitromethane
and/or a different type or proportion of lubricat-
ing oil, is likely to call for some readjustment of
the Needle-Valve.
Remember that, as a safety measure, it is ad-
visable to increase the Needle-Valve opening
by an extra half-turn counter-clockwise, prior to
establishing a new setting. The same applies if
the silencer type is changed. A different silen-
cer may alter the exhaust pressure applied to
the fuel feed and call for a revised Needle-
Valve setting. The use of a different glowplug
may also require compensating carburettor re-
adjustments.
SUBSEQUENT READJUSTMENT
16

ENGINE CARE AND MAINTENANCE
At the end of each operating session, drain out any
fuel that may remain in the fuel tank.
Next, energize the glowplug and try to restart the
engine to burn off any fuel that may remain inside
the engine. Repeat this procedure until the engine
fails to fire. Remove the glowplug and eject any re-
sidue by rotating the engine with an electric starter
for 4 to 5 seconds while the engine is still warm.
Finally, inject some after-run oil into the engine.
Rotate the engine a few times by hand, to make
sure that it is free, and then with an electric starter
for 4 to 5 seconds to distribute the oil to all the
working parts.
Do not inject after-run oil into the carburetor as
this may cause the O-ring inside the carburettor
to deteriorate.
These procedures will reduce the risk of starting
difficulties and of internal corrosion after a period of
storage.
Note:
1.
2.
3.
17

■(72403050)■(71531000)(71521000) 
■
■■
(23024009)
1/4"-28(L)(73101000)
■
(41651010)
O.S. GENUINE PARTS & ACCESSORIES
SPINNER NUT
EXHAUST PIPE
ASSEMBLY LONG PROPELLER NUT SETS
SUPER FI LTER NON-BUBBLE WEIGHT LONG SOCKET WRENCH
WITH PLUG GRIP
18

4.97 cc (0.303cu.in.)
2,500
~ 18,000 r.p.m.
1.27bhp / 17,000 r.p.m.
335g (11.8oz.)
■
■
■
■
■
■
THREE VIEW DRAWING
Displacement
Bore
Stroke
Practical R.P.M.
Power output
Weight
SPECIFICATIONS Dimensions(mm)
19