First Helicopters

My RC experience started out with model aircraft but I soon became bored with them.  Then one day a friend of mine said “Why don’t we build a radio-controlled helicopter?” My initial reaction was “don’t be stupid”. This was still in the early 1970s when helicopter kits hadn’t been thought of and only one or two people had even attempted such a complex feat of engineering. I told my friend that no one else had managed to build one so what makes him think we could, and if we did, where would we start? “Well”, he said in his naive manner, “It’s very straightforward – we just copy a full size one.”

Basically neither of us had a clue – and not only that, we hadn’t even got basic machine tools such as a lathe or the experience of using one. Another major obstacle was the connection to a servo - you couldn’t buy ‘ball-links’, which today are essential to controlling the moving parts on a helicopter. But it didn’t stop us – after all it was ‘a challenge’.

We decided on building a Hughes 300, which seemed pretty straightforward as it didn’t have much of a fuselage. What it did have we made from fibreglass. To power the rotor blades we used a Merco 61 engine with two glo-plugs but as this was designed for use at the front of an airplane where there is plenty of air passing over the cylinder to keep it cool, we had to incorporate a fan in the design of the mechanics.

We used a clutch from a lawnmower driven by a chain from the engine and built a gearbox by bolting together two slabs of metal which enclosed the gears. The gears themselves came from various scrap metal yards and from the parts supplier Moffats. At that time we didn’t have any moulding capabilities so the gears where meshed together by carefully filing the sides of the gearbox as well as the gears themselves until they fitted.

The tail drive was ordinary piano wire which given its shape (oval and not round) caused all sorts of vibration problems. The main rotor blades were made from hardwood leading edge and a balsa trailing edge. This was sand-sealed and covered in Fablon – a popular self- adhesive covering for use on kitchen work surfaces. For paddles we used 5cm diameter tin cans – they looked stupid but they turned out to be highly effective.

After six months our model was ready to test fly. It was 80cm wide, 180cm long and 80cm high. It wasn’t exactly a scale model but the dimensions were in proportion to the full size model. It even had a fully collective pitch (something that very few others were trying) – purely because the full size we copied had that.

Don't try this method of trimming - particularly in your back garden!

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