Petrol mechanics 87:21

Ord.No. 1002/22

The latest VARIO petrol mechanical system is based on many years' experience flying full-fuselage helicopters with a rotor disc diameter of 1600 - 1810 mm, and trainer helicopters with rotor diameters of 1630 / 1780 mm.
This mechanical system has been developed specifically for left-hand rotation scale models, since most full-size helicopters also employ a left-hand rotation system. In the mid-90's one renowned manufacturer announced in a circular that all future developments would favour "left-hand rotation systems": "When compared with right-hand rotation versions in full-size helicopters, this saves one additional gearbox stage; as a result production costs are reduced, together with a reduction in standard periodic maintenance and its cost".
Due to the higher stresses which a petrol engine imposes on helicopter mechanics, the construction of this system differs significantly from other mechanics in our range. This size of engine produces higher levels of vibration and heat compared to a .60 glow motor, and this is counteracted by making the mechanics baseplate and side frames of aluminium. In contrast, the transverse connecting pieces between the side frames are moulded in glass fibre reinforced plastic. This combination of disparate materials has a positive effect on the absorption of vibration. Large-area aluminium plates help to diffuse excess heat from the engine crankcase.
Since modern scale models of full-size helicopters allow no compromises, the petrol mechanical system features a GRP tail rotor housing to avoid unsightly non-scale tails.
Many models would otherwise require an unattractive tail cap for the fuselage, in order to enclose the much larger aluminium housing.
Provided that bevel gear meshing clearances are set correctly, and are adjusted regularly, rates of wear in the tail rotor system are just as low as with an aluminium housed tail rotor. Even this does not represent extra effort, as a metal housing also needs to be maintained carefully if the model is to be reliable and a pleasure to operate.
Please be sure to keep to our specifications when selecting the tail rotor blades for this system. Too large a tail rotor disc, with a corresponding rotor blade mass, can lead to overloading of the angle gearbox unless its rotational speed is reduced. Excessive rotating mass in the tail rotor can also cause unwanted oscillations in the tail rotor drive system.
As a general rule, if you are considering making any modifications of any kind, and you are not certain of the consequences of your action, in the interests of safety please ask the advice of someone who ranks without question as an expert!

• BO 105 # 6002
• Agusta # 9020
• Ecureuil # 9002
• Hughes 500 # 9006
• BK 117 # 7002
• Schweizer 300 # 6030

The mechanics is supplied in kit-form, i.e. not assembled.
Without motor and petrol components (see Ord.No. 26/100).