Specifications

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L-OS38000 O.S. GT55 Petrol ..............................................£649.99
Displacement: 54.93cc (3.352cu.in.)
Bore: 41.2mm (1.62in.)
Stroke: 41.2mm (1.62in.)
Power Output: TBA
Practical RPM: 1500~8000 rpm
Weight: TBA
The biggest single cylinder engine made by O.S. and manufactured
specifically for R/C. The styling is unmistakably O.S. yet draws on their
extensive experience in engine design to keep weight to a
minimum and power, torque and cooling to a maximum.
The mounting lugs have been positioned to be compatible with
the pattern used by the most popular engines on the market,
making installation very easy. That front mounted, Walbro
carburettor helps to keep the mounting standoffs short and
therefore limits vibration. Throttle response is instant and
progressive - a great feature for those that want to prop
hang!
The CDI ignition system enables quick starting,
great throttle response and a steady, low idle. The
durable, magnetic sensing system is designed
for accurate understanding by the CDI unit of the
timing requirement at all throttle settings.
Inside, there is a tough rotary port crankshaft running in
precision bearings (the front is rubber sealed). The roller bearing
big end in the CNC machined conrod transfers the piston load to the
crankshaft efficiently and effortlessly. In turn, the light, CNC machined piston
(with single ring) moves inside a plated cylinder that has been optimised for
the operating RPM range and the throttling characteristics required. The propeller
driver uses a central locating shaft and four radial bolts in the same pattern
as many popular engines on the market. The same goes for the exhaust port
mounting bolt holes, making for
ready access to the various scale
and sports mufflers already on the
market.
With 55cc of O.S. power on tap,
there couldn’t be a better choice!
Since 1986, O.S. owners have enjoyed the unique
experience of owning and operating the fabulous FR5-300
Sirius 5 cylinder radial. Models have become bigger over the
years and O.S. wanted to release a new radial engine to
cater for that market. The result is the gorgeous FR7-420.
With 7 cylinders and a capacity increase to nearly 70cc, the
FR7-420 offers a dramatic increase in both torque and power.
In keeping with the scale image set by the Sirius, the new FR7-420
has been styled in the same way with front pushrods and separate
rocker boxes for the inlet and exhaust valves. These totally new cylinder
heads are not just about ‘style’, they offer a more efficient design
that contributes to the power output. That neat frontal
appearance is maintained by keeping the single, dual
needle carburettor at the back and hidden in the
centre of the engine mount. The prototype engine
shown here will have some detail
changes (cast cylinder heads etc)
made before release, but the
general style will be similar. It
would almost be a crime to
hide it away in a cowling!
Quality and style this
good is something to be
proud of owning. The wide
range of large propellers
recommended makes
choosing the right one for
your model simple. At these
sizes, they could be close to
scale!
Prototype Engine Shown
O.S. FR7 420 ..........................................................................................£TBA