The Starting Blog

This is the first of the actual KR3DS blogs. The purpose of these sketches are to demonstrate some form of movement. This particular one hasn't got a name or originated from any great inspiration, but was purely born out of a "what if ?" moment. 

The basic movement of most of these rotary kinetic sketches is the wheel driving a crank and the crank flapping wings (via one or more push rods). After this there follows many variations of the theme. This particular one has an additional hinge on the end of each wing and an offset fixed point coupled with a push rod. This allows the tips of the wings to swivel and add a little complexity to the basic flapping motion.

Image to give the impression of flapping wings.

The basic movement of the 3D sketch is demonstrated in the following video.

This video shows the sketch (or monster) mounted on stand with a motorized drive for the wheels. The motorized drive is battery powered and drives a large reduction gearbox to provide the necessary torque to turn the mechanism. Originally the intention was to push the monsters on the ground to provide rotary motion via the wheels. Unfortunately the wings generally provide a very unbalanced load, and the wire wheels do not have sufficient grip for smooth motion over the full flap cycle. If you push with enough downward force for a convincing demonstration you end up deforming the monster (wire bends after all). Anyway the motorized drive means that one can have a video without the pusher getting face (or hand) time. There is also the added benefit of not having to be behind the camera as well as in front of the camera at the same time. I prefer it this way.

This monster shows most of the construction techniques employed in the series. 

The frame is constructed using thick wire which is brazed or silver soldered. The overall shape of the sketch is formed with thinner wire, generally woven to create a sturdy structure. Wings are covered with silk in this and the later models. This is stretched and stitched keep it taut. The silk is coated with clear coats of dope, and usually has a pattern painted on the surface.

This particular monster has a cover made of aluminium printers tray with false rivets, for an aeronautical effect. It is attached with brass plates and small pop rivets.  The surface of the wing is painted with red veins to mimic a bats wing with back-lighting from the sun. I don't know why I decided on this paint scheme, but I guess it does fit in with the general theme of "things that could possibly fly".

Here is a link to a longer video showing the basic movement of the 3D Sketch as well as a close up of the mechanism in motion (the crank bits which flap as well as the forward flung hinged wing tips). Youtube video of the starting monster