GMP Cricket

Tail boom & tail gearbox

The tail gearbox was the Hirobo item used on many of their machines throughout their range of helicopters in the 80’s. Interestingly enough, not only was it used here on a .25 cubic inch helicopter but also on the 1/7th scale Hirobo Bell 47 with a 1.8 metre rotor diameter. This example is the result of bringing together the best items salvaged from a number of different items bought on the Internet.

Alignment of the tail is critical for success, the tail drive wire runs up into the tail boom through a narrow aperture and should not come in contact with the sides. The geometry of the tail is dependent upon the tail supports that are mounted to the rear undercarriage legs. To aid starting a wood stand was built to prevent the starting procedure from flexing the undercarriage and hence altering the tail boom geometry. The stand for starting can be seen in a later stage.

With the addition of lubrication the tail gearbox is a very smooth unit and more than adequate for the Cricket even though it is held in position by a Jubilee clip around the tail boom!

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