10
PROPELLER
Use well balanced propellers only. Unbalanced propellers
cause increased vibration and loss of power. Determine
the best size and type after the engine has been run in.
Suggested propellers are high quality wood or glass
15x14-16 or 16x13-15. Final selection should be made, of
course, after test flights.
For safety, keep your face and other parts of the body well
clear of the propeller when starting the engine or when
adjusting the needle-valve while the engine is running.
Remember that, with the bigger propellers that this engine
is capable of turning, the blades cover a much larger area.
Refer again to the Warnings and Notes on the first page of
these instructions.
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.
WARNING!
There is a risk, particularly with large capacity
engines, of the propeller flying off if the propeller nut
loosens due to detonation or "knocking", should the
engine be operated too lean or under too heavy a load.
Obviously, this can be very hazardous. To deal with
such risks, we have developed the special propeller
locknut assembly supplied with the MAX-140RX. This
prevents the propeller from flying off, even if the
propeller itself should slip or loosen.
Fit the 140RX safety locknut assembly as follows:
Fit the propeller to the engine shaft, followed by the
retaining washer and prop nut.
Tighten the nut with the 14mm wrench.
Finally, fit the locknut and tighten firmly with the 12mm
wrench, making sure that it locks into the propeller
retaining nut.
1.
2.
IMPORTANT:
With any engine, regardless of the type of propeller
attachment used, make a habit of checking prop
tightness before starting the engine. Remember that,
especially with wooden props, there is a tendency for
the material to shrink, or for it to be reduced by the
serrated face of the drive hub.
11
TUNED SILENCER
The O.S. Type T-6010 tuned silencer has been specially prepared for the MAX-140RX engine. It allows the engine to
develop high performance at lower engine r.p.m. (e.g.around 8,000r.p.m.) which enables the contest flyer to qualify for
noise reduction bonus points.
Here is an example of a combination with which maximum performance is obtainable at around 7,300-7,600r.p.m. You
may, of course, use other combinations, but it is recommended to refer to this combination as a starting point.
Propeller
Fuel
Exhaust Header Pipe
Tuned Silencer
Effective Pipe Setting
APC 16x14
Commercial good quality fuel
(10% nitromethane)
Actual length 240mm
(see sketch below)
O.S. Type T-6010
245mm (see sketch below)
Effective Header Pipe Setting ( 245mm)
Note :
Effective Header Pipe Setting means the distance from
the engine's exhaust flange to the entry to the tuned
silencer.
Header Pipe Length (245mm)
Center Line Length
5mm
Exhaust Header Pipe
Tuned Silencer
12
Adjusting effective header pipe length
Use the silicone tube sleeve supplied with the O.S. T -
6010 and connect the silencer and exhaust header
pipe together so that the effective pipe length is as long
as possible.
Start the engine, open the throttle and measure the
maximum r.p.m. at which the engine runs steadily for a
lengthy period. Then shorten the header pipe setting by
10mm and measure r.p.m. again. Repeat this
procedure, checking r.p.m. each time, until no further
increase in speed is recorded.
For other combinations or conditions, set the effective pipe
length as follows.
(Important : Make sure that the engine is adequately
run-in before operating it at full throttle for lengthy
Note: Be sure to use the same fuel and propeller while
making these checks.
r.p.m.
High
Start with this setting.
r.p.m.
Low
Long
Effective Header Pipe Length
Short
From this measured data, you will find a range of
settings through which r.p.m. do not vary significantly.
Set the header pipe length at the beginning of this range
(See diagram bottom left ) and fly the model.
If the pipe length is too short, the needle-valve
adjustment range at maximum r.p.m will be narrow, and
r.p.m. will tend to vary too much in the air, especially
when revolutions build up as load decreases. Also,
power will tend to drop off excessively against increased
load in the air. To correct this, increase the header
pipe's effective length.
Note:
Engine r.p.m. recorded on the ground are different from
those achieved in flight; not only because of increased
propeller loading when the aircraft is stationary, but also
because the cooling airflow over the engine and tuned
silencer is reduced. Therefore, optimum header pipe
adjustment should be finally set only after actual flight
tests. The power absorption of individual propellers of the
same size (dia. and pitch), even from the same
manufacturer, may differ quite markedly. This can cause
r.p.m. to vary between 300 and 500 with standard
propellers and between 100 and 200 with high quality
propellers. Therefore, it may be necessary to readjust the
header pipe length when a new propeller is fitted. Be sure
to check the r.p.m. in addition to the balance and pitch of
the propeller, before using it for flight.