What
is the RCV equivalent in power to?
The RCV engines are equivalent to any other conventional 4-stroke
in terms of power. To relate this to a 2-stroke design the
60SP is equivalent to a 40 2-stroke, the 90SP is equivalent to a
60 2-stroke and the 120SP is equivalent to a 90 2-stroke.
What model
weight would suit the engines?
This really depends on the model it is used in. i.e whether it
is fast or slow running model and we generally believe the kits
give the best sort of guideline. As a rough estimate, the
following can be applied (weights can be more or less depending
on the plane & type of flying):
|
Engine
|
Kit
Recommendation
|
Weight
(approx.) |
| 60SP |
.40
2-stroke / 60 4-stroke |
3kg
/ 7lb |
| 90SP |
.60
2-stroke / 90 4-stroke |
4kg
/ 9lb |
| 120SP |
.70
- .90 2-stroke / 120 4-stroke |
5kg
/ 11lb |
What
are the approximate fuel consumption figures?
The typical fuel consumption based on 'average' flying is approximately
60SP - >0.4 fl oz/min
90SP - >0.55 fl oz/min
120SP - >0.7 fl oz/min
Can
you suggest a typical test bench for running in the RCV?
During the 1st hour of running in, the SP engines may not run
smoothly. Test stands must be substantial to cope
with the larger than normal tortional forces (no ironing boards
please!). If you are able to start from scratch, below is
a basic drawing of a suitable test bed.
We have also kindly been sent a photo of one of
our customers test stands. Thanks to J. Carey, USA
What
is a typical noise reading?
Noise readings are completely dependent on numerous environmental
factors (ground cover, buildings, traffic noise) so specific Db
figures are hard to give by any engine manufacturer. To
give an idea the following noise levels could be achieved at 7m:
RCV60SP - 80 - 82 Db
RCV90SP - 80 - 86 Db
RCV120SP - 82 Db upwards
The RCV however is marginally noisier than conventional 4-strokes,
so in clubs with very tight noise limits (ie. 80 Db) consideration
to reducing the noise through building and installation will be
necessary. NB. We do not advise rubber mounts due to the
high tortional vibration.
Wouldn't
it be beneficial to cast the cooling fins to allow better air
flow and better cooling through the fins?
You'll be surprised how many times we are asked this question.
The design of the cooling fins is dictated by the fact the SP
series engines are cnc machined not cast. We have however
performed many tests and have found the direction of the cooling
fins does not cause any cooling problems.
What
would happen if the engine wasn't cooled properly?
The RCV design is intended
to run at a reasonably high temperature due good thermal characteristics
(see below). Therefore
insufficient cooling should not have adverse affects on the engine.
If cooling was not sufficient the worst that would happen is that
the engine would lose some power and if really hot a propeller
could melt.
Thermal Characteristics:
On the model engine
the clearance between the rotating cylinder and outer jacket is
very small (<0.1mm). The heat is transferred across this gap
by the oil film. On larger versions of the RCV oil cooling is
employed whereby oil is pumped over the outside of the rotating
cylinder to dissipate the heat from the cylinder.
The RCV design has excellent thermal characteristics with the
rotation of the cylinder relative to the piston and ports ensuring
that thermal distribution is very even throughout the engine.
This means that thermal distortion is very low. Unlike a conventional
engine there is not hot and cold side to the combustion chamber,
and not hot exhaust valve to cause detonation.
If
the engine is tightly cowled, do you have any suggestions to improve
cooling?
The cylinder jacket has been designed to dissipate heat and when
flying there is the added advantage of the engine being cooled
with the airflow on the propshaft. This does however require
airflow.. If the engine is closed in a cowl, airflow needs are
similar to other engines therefore the exit are needs to be at
least 2 x larger than the air inlet area. It is very hard
to give a precise figure for this inlet, but we would recommend
that at least 1 square inch is available for the inlet and 2 for
the outlet.
In a tightly cowled model it is essential to arrange
a deflection duct to scoop air over the engine. A schematic
of such a duct is shown below.
What
size props are recommended?
The RCV is a geared engine therefore the prop is turning at 1/2
the speed of the engine. For this reason much larger
propellers can be used. Pitches would normally be between
10 and 14 inches (in general double that of a conventional engine). We do not recommend any propeller with a pitch
less than 10.
As an example the props we use for much of our in-house testing
are:
RCV60 - 16x12 propeller;
RCV90 - 18x12 propeller
RCV120 - 20x12 propeller.
RCV Engines are able to supply propellers suitable for use with
our engines for more information of the range of propellers available
please click here
Can
wooden props be used?
We always use and recommend glass composite propellers,
however wooden propellers can be used if necessary and have been
used successfully in some RCV testing. It is important however
to use a good quality / heavier wooden propellers because generally
wooden propellers are too light and do not produce the flywheel
effect. RPM figures will be lower when using wooden propellers.
Where
can I obtain a spinner for my RCV?
If you are finding it difficult getting a spinner for
your RCV SP engine due to the large pitch propellers, Tru-Turn
are able to supply a good range of spinners which
are suitable.
Can
these engines be started from the front by spinning the prop?
Or only from the starter socket?
We ONLY recommend you use the behind the prop starting method
for safety reasons. It is possible however, to start the
engines by spinning the prop if that is your preference. You need
to remember that due to the 2:1 reduction gearing, not only is
the prop larger than on conventional engines, it is also spinning
at half the speed of the engine, so the 120 size is not as easy
to start using this method.
How
does my starting adapter fit into my starter motor?
Take off the rubber cup and
then unbolt the cup on the starter, revealing a shaft. File a small flat on the shaft at the point where the adapter
grub screw will grip to the shaft.
Fit the RCV adapter onto the shaft and tighten the grub
screw.
For full instructions see Starting
Adapter
How
does the 'behind the prop' starting work?
With the use of a hand held electric starter
(and the starting adapter) inserted directly into a socket located
on the end of the crankshaft, the engine can be started from behind
the prop. This turns the crank gear which then turns a gear formed
around the base of the cylinder.'
Would
it cause any running problems if I rotated the engine but
didn't keep the glow plug was not at the top?
No, but the fuel tank height would require adjustment to compensate
for the different carb position
How
should the engine be mounted?
The larger than normal tortional forces from
the geared prop mean the engine needs to be very securely mounted.
Fuselage construction around the engine mount must be very rigid
(bear this in mind when choosing a model) and test stands should
be substantial.
Mounting Instructions:
The engine would normally be radially mounted on the same bulkhead
that would take the nylon engine bearers for a conventional engine.
We recommend putting a reinforcing metal plate. A mounting
plate is now included f.o.c with the RCV120-SP and mounting plates
suitable for the 60 & 90-SP engines are available from RCV.
For more details please click
here NB. We do not recommend using rubber
mounts.
Troubles
with starting
RCV engines are honestly about the most instantaneous
starting of model engines providing everything is in order. Starting
difficulties can usually be put
down to the following.
1 A starter that is not powerful enough
to spin the engine over quickly OR
an electric drill
2 Starter going the WRONG way (this is
VERY common and a simple mistake to make) the starter will be
going in the reverse direction to a conventional set up due to
the gearing which reverses the direction of the crank for a given
propeller direction. To check - just ensure that your propeller
is turning ANTI clockwise ( viewed from
front ).
3 Fuel should be 10% nitro synthetic based
( M T Duraglo or similar ).
4 Power Panels - these can be worse than
useless - ESPECIALLY if the same ( small ) battery is also supplying
the glow element voltage - what happens is that the starter pulls
down the battery voltage reducing the glow - despite everything
appearing fine when you do a glow test - an OS F plug pulls around
3 amps.
To start the engine ensure that the above are all ok and then
:-
1 Open the main needle several turns from
closed ( too rich is no problem you can always close it down after
the engine fires - too lean and the engine will NOT fire at all
)
2 OPEN the throttle wide - place your
finger over the inlet and choke the engine until it is very "wet"
feeling ( fuel may even drip from exhaust under such a situation
- this is fine )
3 CLOSE the throttle to one third - energise
the glow and make sure that the clip is a good fit ( I prefer
two croc clips to any commercial clip ).
4 Apply starter - the engine will fire
immediately and should continue to run - albeit roughly until
the two needles are set.
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