DE20006526U1 - Tail rotor drive for a model helicopter - Google Patents

Description

Tail rotor drive for a model helicopter The invention relates to a tail rotor drive for a model helicopter according to the preamble of claim 1. A model helicopter requires a gearbox to drive its main rotor, which is large in comparison to a propeller. Depending on the design, these are implemented in one or two stages. To drive the tail rotor required for torque compensation, two bevel gear pairs are generally used in the case of a shaft drive for the tail rotor or two pulleys and a spur gear pair in the case of a drive for the tail rotor using a toothed belt. The figures show an example of a two-stage gearbox with a belt drive for the tail rotor. However, the invention described below is independent of the design of the gearbox, whether single-stage/two-stage or shaft drive/toothed belt drive.

Problem:

When flying a model helicopter, the pilot has to decide whether he wants a tail rotor that rotates in autorotation, i.e. in a powerless descent, or whether he wants a tail rotor that is stationary. The tail rotor is not required in autorotation, as the stationary drive does not generate any counter torque that the tail rotor would have to compensate for. The advantage of a tail rotor that rotates in autorotation is that it can still be controlled around the vertical axis, whereas a helicopter with a stationary tail rotor turns into the wind like a wind vane. For a pure emergency landing, a stationary tail rotor is advantageous, as the kinetic energy of the rotor system is used up more slowly. However, the ability to land safely is limited.

The choice of tail rotor drive in autorotation is therefore subject to the personal preferences of each pilot. The problem here is that converting the gearbox from a stationary to a rotating tail rotor or vice versa was previously only possible by purchasing, replacing or adding various parts, or in extreme cases not at all.

The invention is based on the object of making it easy to change from one variant to the other without having to replace any parts of the gearbox.

This object is achieved according to the invention by the characterizing features of claim 1.

The invention is explained below with reference to the drawing figures, for example.

Fig. 1 a gearbox with a rear output for an in autorotation

rotating tail rotor

Fig. 2 a gearbox with a rear output for an in autorotation

standing tail rotor

The invention is based on the principle of being driven by either the upper gear 7 or the lower gear 4 by simply rotating the pinion shaft 8.

The illustrations show an example of a two-stage gearbox. The motor drives the gear 4 via a pinion 2 and a reduction gear 3. The gear is connected to the rotor shaft 6 via an autorotation freewheel 5. The gear 7 is permanently connected to the rotor shaft. The pinion shaft 8 has a pulley 9 at its upper end, which drives the tail rotor via a toothed belt 10. The position of the bearings 11 does not need to be changed for the pinion shaft 8 to rotate.

Operating state (motor 1 running): Positions 2,3,4,5,6 and 7 rotate, the angular velocities of positions 4,5,6,7 are the same, thus the position of the pinion shaft 8 is irrelevant.

Autorotation state (motor 1 stopped):

Positions 2, 3, 4 and 5 remain with motor 1. Rotor shaft 6 and gear 7 continue to rotate.

When the pinion shaft 8 is positioned as shown in Fig.1, the tail rotor is driven in autorotation.

When the pinion shaft 8 is positioned as shown in Fig.2, the tail rotor remains in autorotation.

The conversion from one drive variant to the other is done by loosening a few screws and turning the pinion shaft and can therefore also be carried out with
required on the airfield.

Claims (3)

1. Tail rotor drive for a model helicopter, characterized in that a pinion shaft 8 provided with a spur gear on the output side engages by simple rotation either in a gear 7 firmly connected to the main rotor shaft or in a gear 4 which is firmly connected to the autorotation freewheel 5 working on the main rotor shaft 6 . 2. Tail rotor drive according to claim 1, characterized in that the module and number of teeth of the gears 4 and 7 are identical. 3. Tail rotor drive according to claim 1, characterized in that the drive of the pulley 9 for the tail rotor rotating in autorotation is effected via two spur gears, the larger gear only serving to drive the tail rotor and not the main rotor and the smaller gear is located on a common shaft with the pulley 9 .