Nautilis

This Nautilus monster is based on a Nautilus gear set which is available on thingiverse for printing with a 3D printer. The gears that I sourced were provided by MishaT. My question was whether it could be used for anything practical. The only examples on the internet seem to be based on showing how a pair of gears mesh, but nothing beyond that. These strange looking gears do not look as if they should be able to work. What they do do is provide a variable gear ratio. So the monster was designed with a forward set of wings which flap at a constant rate, and smaller rear wings which do a quick flap every cycle. Guess one could imagine that the main wings are providing lift with the rear ones providing some pitch correction each cycle.

Nautilus gear set in typical demo configuration

The general shape of the Nautilus monster was largely influenced by the size of the actual gears. This meant that a large belly, or a large monster was required. The belly option seemed more fun. 

The  body has some elements of earlier "dinosaur  riding old bicycles" monsters in the form of spines along the back of the body (also seen in the first monster).  The overall design was another attempt at a whirligig. It also failed due to excessive resistance from the mechanics, but it did get a propeller drive out of the deal. The propeller was designed to have 3 blades for variety. It was built from strips of fine grained Oregon pine roof beams that were recovered when a house was modified to stop a roof leak.

To allow enough propeller blur during videos without having frantic flapping a planetary reduction gearbox was placed between the propeller and the gears.  This was another design that was sourced on Thingiverse. The original design was for a 3D printed peristaltic pump, but I chose it because it only had 3 internal gears, so fewer gears to modify for the power take-off drive. The standard single print planetary gear designs seem to favour 5 gears. The gears (Nautilus and planetary) were printed from natural PLA which is supposed to be stronger and almost white. This was painted with acrylic paint to make it more interesting. Side effect of the silver paint is that it is less noticeable in the structure. In retrospect don't think that was the best idea.

The body profile was influenced a little by World War II fighters which had large belly intakes, such as the P51 Mustang. This belly is larger than that of the aircraft which inspired it, but it does look a little like a 3D caricature of the real thing. The cockpit precedes the typical bubble canopies of the well known WWII fighter, but suits this monster better. The construction technique for most of the body was bent wire held together with crimped ferrules (sourced from a Chinese jewelry supply store).  It was challenging to get the gears to fit without interfering with the fuselage sides, but perseverance and choice language (under my breath) got the whole lot rotating.

The filled in bits are sewn closed with parachute silk, and then varnished a lot with a water based varnish. Painting with acrylic paint and lots of spots in a vague arboreal pattern. Colour scheme a little too pink, but always game for a change.

The wheels are once again cast lead wheels, with the raw material recycled from wheel balancing weights. This is done to prevent lead waste from being indiscriminately dumped in landfill sights. A matching colour scheme is painted on the wheels to add to their appeal. They are then lightly varnished so that inadvertently touching the wheels won't lead to a heavy metal build up in the victim. A reject wheel with additional wire work was used in the video to support the tail of the monster in the correct attitude for flight (in this case demonstrating reuse rather than recycling).

The video was taken using a black background. This was done to try and control the lighting better than the lighter backgrounds used in the previous videos. It also seems to set the silver wire off a bit better than a white background. Not yet  convinced that this is the final answer, so I will still need to experiment in future videos. 

What are the chances of this fat cat surviving?