Os-engines 60B Carb - 27981010 Bedienungsanleitung PDF herunterladen

INSTRUCTIONS FOR THE O.S. TYPE 60B CARBURETTOR

The O.S. Type GOB is an entirely new carburettor of sophisticated design that has been developed specifically for the

O.S.MAX-61SX-H and MAX-61RX-H series helicopter engines designed for F.A.I. F3C competition use.

It incorporates a total mixture control system that enables the helicopter expert to fine-tune his engine to suit individual

requirements at different stages, i.e. at idling speeds, in the hovering mode and in high-speed flight. Once the adjustments

have been correctly set, the carburettor automatically controls the fuel/air mixture strength through the entire performance

range.

The Type 608 is also fitted with a special insulating sleeve to minimize the transfer of heat from the engine to the carburettor

body. An excessively hot carburettor preheats the fuel/air mixture and lowers the weight of the charge entering the

combustion chamber, thereby reducing power output. Also, variation in carburettor temperature can have an adverse effect

on throttle response.

Three

adjustable

mixture

controls

are

fitted

the

Type

60B.

They

are as follows.

A The High-Speed (Main) Needle-Valve

When set to produce maximum power at full throttle, this

establishes the basic fuel/air mixture strength. This is then

maintained by the carburettor's automatic mixture control

system to cover the engine's requirements at reduced throttle

settings.

B The Idle Mixture Control Screw

This provides the means of manually adjusting the 60B's mixture

control valve. -By setting the Mixture Control Screw for the best

idling performance, the mixture control valve automatically

ensures that fuel is accurately metered to maintain the correct

mixture

strength as the throttle is opened.

C The Medium Speed Needle Valve

This is an extra control that can be brought into play, if

necessary, after adjusting A and B above. It provides the means

of fine-tuning mixture strength over that all-important part of

a helicopter's throttle range where the model is flying in, or near,

the hovering mode.

Note: The Type 60B is not fitted

with an adjustable throttle stop

Hiqh Speed Needle Valve

(Main Needle)

screw. The throttle linkage to the

servo should be arranged so that

Medium Speed

the throttle trim lever on the

Needle Valve

transmitter can be used to set the

required idling speed. This also

Idle Mixture

provides the means of stopping

Control Screw

the engine from the transmitter.

Fig.

PROVISIONAL SETTINGS

Use a muffler-pressurized fuel feed and, before starting the engine

for the first time, check that the three mixture controls are set up

as follows

1. High-Speed Needle Valve: exactly two turns open from the fuily

closed position. (Note: If a different muffler is used, this setting

may require readjustment.)

2. Idle Mixture Control Screw : exactly two turns open from the

fully closed position.

3. Medium Speed Needle Valve : exactly one turn open from the

fully closed position.

ADJUSTMENT

Existing Position

Please observe the following before

beginning to make any adjustment.

a High-Speed Needle Valve. Turn

this approximately 30 (3 to 4

clicks) at a time, when making

initial adjustments; then in steps

of •approximately 15° (1 to 2

clicks) when making final adjust-

ments.

Desired Position

Richer

b Idle Mixture Control Screw. A special technique is required

here. (see Fig. 2.) If intending to make an adjustment (e.g.

) in one direction, first turn the screw an extra 90° in the

same direction, before returning it to the new setting. If this

procedure is not followed, movement of the throttle rotor may

become stiff, resulting in undue loading of the throttle servo.

c Medium-Speed Needle Valve. Turn approximately 45" (4 to 5

clicks) at a time.

The general course of adjustment procedure is shown in the

ADJUSTING CHART and is correct for a fuel containing 20%

lubricant and a nitromethane content of between 10% and 30%.

Bear in mind that fuels containing relatively large percentages of

power-boosting nitromethane operate at richer mixture settings than

are needed for mild fuels and will, therefore, require the High-

speed Needle Valve to be readjusted accordingly. The type and

percentage of lubricant used is also a factor here, as noted later in

these instructions.

ADJUSTMENT PROCEDURE

As a safety measure, first check the transmitter controls, including

the throttle stick and trim lever positions, and hold the main rotor

securely before starting the engine.

1. Warm the engine by allowing it to idle for about 30 seconds. If

the engine stops, advance the throttle trim lever slightly to

Fig.

increase the idling rpm. Then open the throttle sufficiently

to 'float' the model above the ground.

If, at this time, the engine is slow to pick up and produces an

excess of exhaust smoke, the mixture is too rich. Correct this

condition by turning the Mixture Control Screw clockwise.

If the mixture is extremely rich, engine rpm will become

unstable: opening the throttle will produce a great deal of smoke

and rpm may drop suddenly or the engine may stop. . This

condition may also be initiated by an excessively prolonged

warming-up period.

If, on the other hand, the mixture is too lean, this will be indi-

cated by a marked lack of exhaust smoke and a tendency for

the engine to cut out when the throttle is opened. In this

case, turn the Mixture Control Screw counter-clockwise to

enrich the mixture.

Needle Valve too far open

High Speed Needle Valve

Setting varies according

to the curve

Adjustment range of Idle Mixture Control Screw

Fully Closed

Throttle Opening

Fully Open

Fig. 3

Needle Valve too far closed

Adjustment range of

Medium Speed

Needle Valve

2. Having provisionally set the idle mixture, the next step is to

adjust the mixture for hovering flight.

Hover the model and actuate the throttle to observe response

over the medium speed range. If the engine smokes excessively

and throttle response is poor, the mixture is too rich: in which

case, land the model and turn the High-Speed Needle Valve

clockwise. Do not close the High-Speed Needle Valve more

than the recommended initial adjustment (3 to 4 clicks) at a

time, keeping it a little on the rich side at this stage. DO NOT

touch the Medium Speed Needle Valve.

If, on the other hand, hovering is not stable and response to the

throttle is over-sensitive, or if the engine tends to overheat,

this indicates that the mixture is too lean and should be correct-

ed by turning the High-Speed Needle Valve counter-clockwise.

When satisfactory hovering flight has been achieved, land the

model again and re-check the engine's idling qualities. After

about 10 seconds of idling, open the throttle to 'float' the

model. If the transition is smooth, the idle mixture is O.K.

If the symptoms of either rich or lean running are observed,

readjust the Idle Mixture Control Screw accordingly.

Note: With this carburettor, neither the Idle Mixture Control

Screw adjustment, nor the Medium Speed Needle Valve adjustment

has any effect on mixture strength when the throttle is fully (or

almost fully) open.

3. Now adjust the High-Speed Needle Valve to achieve the best

performance when the model is flying at full throttle. If, at full

throttle, acceleration is poor, the exhaust is unduly smoky and

the model fails to reach expected straight line speed, the mixture

is too rich and the High-Speed Needle Valve setting will need to

be reduced.

If, however, after smoothly accelerating to satisfactory high-

speed straight and level flight, power is lost when the model is

pulled up into a climb, the mixture is too lean. In this case,

land the model immediately and readjust the High-Speed Needle

Valve to a richer setting.

4. Having now found the optimum setting for the High-Speed

Needle Valve, re-check the engine's idling performance, fine-

tuning the Idle Mixture Control Screw, if necessary, to perfect

the idle.

5. Now re-check hovering performance. It may be found that

(with the High-Speed Needle Valve now set for optimum full-

throttle performance) hovering will reveal symptoms of slightly

lean running at medium speeds. DO NOT touch the High-Speed

Needle Valve.

It is at this point that the Medium Speed Needle Valve,

previously kept one turn open, may be brought into operation.

Open the Medium Speed Needle Valve 45°, or 4-5 clicks, then

fine tune until the optimum hovering performance is obtained. If

on the other hand. hovering reveals rich running, close the

Leaner

1 2

ADJUSTING CHART 2

Inhaltsverzeichnis

Seite 1

INSTRUCTIONS FOR THE O.S. TYPE 60B CARBURETTORThe O.S. Type GOB is an entirely new carburettor of sophisticated design that has been developed specifi

Seite 2 - ADJUSTING CHART

ADJUSTING CHARTHigh Speed Needle Valve—2 turns opened from fully closed position.Medium Speed Needle Valve—1 turn opened from fully closed positionIdl

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Os-engines 60B Carb - 27981010 Bedienungsanleitung

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