Challenger

This Challenger is based on the Quad City Challenger, a kit built ultralight aircraft. The original was a collection of aluminium tubes, nuts, bolts & pop rivets and fittings delivered in a very large plywood box. Add some fibre glass, a Rotax engine and gearbox, some dope and fabric and you have a toy you can fly in.

ZU-CPH near the Vaal, before my carrier type landing

Basic description of the Challenger.
The Challenger 3D sketch follows the same basic shape as the real deal, with 2 crew to add to the effect. The only big discrepancy is that the wings flap (something that is avoided at all cost on the big one, therefore the struts).

The frame of this monster is made up of relatively thin wire with a structure of triangular geometric shapes to add strength. This is a departure from the brazed thick wire frame structure used in earlier models. The individual wire triangles are filled with a grid of copper wire. The copper wire is a slight variation on the standard theme, and is much softer to bend. Didn't take off though as it is also comes loose easier (ie. does not hold tension as well).  In the original Challenger I covered the wings the traditional way with Superflite fabric and a large variety of dopes (nitrate, clear butrate, silver for UV and colours). For this monster silk, clear butrate and pretty paint trim in geometric patterns did the job. Oh, the original wing was glued to the frame, this one sewn. 

The wire monster has an electric motor driven from 2 batteries to spin a hand carved wooden propeller.  The electric motor happened to have a diameter which was the same as an AA dry cell, therefore the handy tubular construction. The original also had a custom made wooden propeller with red tips. The model propeller was made by laminating a number of thin plywood strips together and then carving the shape.

Details of the hand carved wooden propeller and motor.

The switch mechanism for the motor is also a custom design. The one pole of the battery connects with the electric motor. The other pole of the second battery is connected to the metal battery and motor housing, and the other side of the motor via a brass contact attached to stranded wire. The brass contact is pulled against the battery pole when the stranded wire is clipped under the "switch". 

Custom motor switch above the aircrew

The aircrew are the now familiar crab claw heads mounted to wire and tin plate necks. The mechanism to flap the wings and move the heads is a fairly straight forward crank and lever arrangement, with the pilots moving together. Thought that in this case it would work better if they pulled together as a team.

A variation in this monster from the previous monsters documented in this blog is that the wheels are cast from lead. Not recommended in this day and age, but the origins of collecting and casting lead come from my childhood in the late '60s. We used to go to the Swartkop Country Club which was close to my best friends home. Behind the clubhouse there was a large pile of old wine bottles which still had a lead foil around the neck (apparently to protect the cork from being gnawed away by rodents or infested with cork weevels - I'm sure that having a toxic foil really chased the pests away). We collected the lead from the bottles, melted it and cast sinkers or other lead weights. Well the wheels are an extension of this. The molds were hand carved from a soft engineering plastic. This only lasted long enough to get two or so wheels molded before the heat destroyed the mold. So these are fairly unique, never to be exactly repeated wheels. The lead this time was sourced at tire merchants who discarded the old weights used to balance the wheels. My only advice is that if you ever lay your hands on one of these monsters - don't suck the wheels! The axle is soldered to the wheels - another advantage of the lead is relatively easy soldering. The end result is that these wheels are centered a lot better than the wire only versions. I suppose these are similar to mag wheels on cars, where the engineer missed the brief about reducing the unsprung mass.

One last picture which, without the aid of photoshop, to show that ZU-CPH actually flew (not so the Challenger sketch --- but it is only a sketch after all)

Flutterbee

This is the next one in the numbered series that I still have (no. 3 was "borrowed" and never returned). Firstly I have to apologize for mixing languages in the you tube video (the hazard/benefit  of living in a multilingual environment). This is inspired by butterflies (wings) and bees (body). Actually if I have to be honest the "Flutterby" name came from a sketch that I did some years ago to document the elements which make up the movement of the monster, but on reflection is should be Flutterbee.

This monster uses a similar construction technique as developed for the previous examples. There is a wire frame which is covered by a weaved wire cover or painted material. In keeping with the sketch theme not everything is filled in, and the holes in the wire grid helps to display the internal mechanism. A little character is added with the crab claw head.

This monster experimented with the use of copper and silver solder to construct the abdomen of the flying insect. The shape is inspired by bee bodies. The external form is generated with brass wires threaded through the copper ribs of the body. The ribs are attached to the former using an egg-box technique, which I learnt from my father when building model aircraft. This makes it easy to keep in position while silver soldering the components (self-jigging).

This is similar to the technique used by the 3D wooden puzzles built by slotting various pieces into each other. The following image shows an example of a wooden bee which inspired the monsters abdomen's . The paint work is strongly influenced by Ndebele art patterns. A very relaxing way to spend some evenings and a good way to test patience.

The final image shows the shape and colour scheme of the wings. It is definitely more butterfly than bee, therefore the flutterbee. The movement (in the video) of the monster could be smoother, but it is only a sketch. Maybe in the future I will get around to refining the movement, but it is always a good idea to have some unplanned features.