Counter Rotating Flapping Helicopter

This was created some time after Frojo the flapping helicopter. It was inspired by the helicopters which don't require a tail rotor. This is done by having counter rotating blades which cancel out each others torque. Generally there are two configurations for this ie. having the blades stacked above each other or offsetting the rotors (either in line or abreast)  to prevent the platform from growing too large. In this case the rotors abreast style was chosen. The rotors need to be synchronised with each other to avoid them interfering with each other. This resulted in a frog like aircraft with rounded body. The flapping rotor bit was added to keep to the general monster theme. The body is built using similar methods to the older monsters, where a sturdy brazed or silver soldered wire frame holds most of the mechanical bits and a woven thin wire structure adds shape. Following previous themes is the sealed sewn silk covering with painted patterns. The patterns made up of simple geometric shapes and bright colours. A silk covered vertical fin is added to make the model more interesting (a bit of a frog crossed with a fish - something one may expect to find in a rock pool at the coast?)

Fat little frog body and rounded curves evident in full body shot above

Details of painted silk patterns on a rotor

The biggest challenge in building this monster was making the gears to drive the rotors. This was done by silver soldering brass teeth to a bent wire frame. The rotors are mounted at a relatively shallow angle to the main drive so commercial gears were not freely available. The final drive looked interesting but did not perform well. When making the video it was a challenge to get the monster to operate without jamming the gears. The main problem was located to the teeth of the rotors  interfering with the main drive axle. This was solved by lifting the rotors a few millimetres with a spacer bent out of wire placed between a stop soldered to the main rotor shaft and the wire bearing through which the shaft was mounted. The movement was also limited by the flapping mechanism only acting on one surface of the swash plate. This was fixed and the monster worked without jamming for the rest of the video session. 

Brass and wire gears for the synchronous counter rotating mechanism

Mechanism to act on the swash plate when going up or down

This was the first monster to introduce decorative glass beads into the wire work. This was inspired by typical African art, of which there were abundant examples around locally (especially in Boom Street in front of the National Zoological Gardens in Pretoria). In this case the neck of the monster is decorated with glass beads (the head still being the common crab claw). The main wire wheels, by adding some extra loops, have also got a slightly different design to the older models. Suspect this was supposed to make it easier to get the wheels to approximate a circle and run a little truer. Guess it is time to try a new helicopter configuration....sometime?

Monster crab claw head and glass beads