Vintage RC Helicopters - Horizon
Horizon 60 (1980)
In 1981 Mr Helmut Holder started selling the Horizon 60 which had a number of features not commonly found on most 'pod and boom' types. The tail rotor was mounted inline with the main rotor disc thus requiring the use of a flexible drive, however, instead of running through the boom and into a 90 degree gearbox; it ran outside the boom and then curved round at the rear to directly drive the tail rotor shaft. The engine was also fitted with a three blade fan (similar to the German Vario system) fitted inside a shroud and thus had positive engine cooling at all times. In many respects the engine layout mirrored the original Lark / Cricket design and also utilised a belt driven primary drive. By all reports they had very good flying characteristics even in the earlier 'Flybarless' version which in 1980 Hubert Bitner won the Expert class of the US NATS.
Of note is that the control system
incorporated a rocking servo mount, not much unusual in that however, the tail
servo was also on this mount thereby giving collective / tail rotor mixing.
Another advanced feature was the counterbalance weight fitted to the tail blade
holders which tended to reduce the loading on the servo by countering the force
which tended to return the blades to neutral. Additionally there
is no overrunning clutch (bearing) in the drive train to allow for autorotation
landings even though the helicopter can do auto's. The centre of the
driving hub of the clutch is square and the shoes are held against this square
with a coil spring encircling the outer perimeter of the two, semicircular
aluminium, free-floating shoes. The spring force is set to obviously hold the
shoes away from the clutch bell's lining at idle and is also strong enough to
allow an easy release at a rather high speed. So, under load the angle of the
square causes a wedging action against the inner edge of the shoes and jambs the
shoes toward the clutch drum lining. Pull power off the engine and this
wedging action goes away allowing the bell to spin free; result autorotation....
Also, the tail rotor stays driven with the main rotor allowing direction control
on the way down.
Horizon 60 Review - Magazine review V good detail and colour shots.
Though not produced for many years there remained quite a few unsold kits and so a modern CCPM version was produced.
The above version was produced by mark Spies and Helmut's version has the horizon head with side plates which did not originally make it to production.
Test flying was carried out and all was fine though with modern radio gyro and control system it was to be expected.
Helmut has also developed an electric version.......
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