Pneumatic Drives and Paper Mechanics

Lecture during the 13. International Cardboard Modelers Convention
in Bremerhaven/Germany on 28th April 2001

Since 1989  the Deutsche Schifffahrtsmuseum  (German Maritime Museum) in Bremerhaven organizes International Cardboard Modelers Conventions every year.  There the friends of cardboard modelling can exchange their experiences, listen to interesting lectures and present their made-up models.  Peter J. Visser from Holland has made a lot of pictures for a report about the last two meetings (please click on "Pictures: Fairs and exhibitions" on his website). The theme of my lecture was "Pneumatic Drives and Paper Mechanics", you can see the manuscript and the shown transparencies below.

1. Introduction My today's contribution takes up the subject from the last year and leads it on. Last year it concerned the transformation of a rotary motion into the intended movement of the paper model. I have shown the way a crank slider, an oscillating lever with connecting rod, an oscillating lever with slot crank motion, a wobble disc, a cam, a ratchet and a friction wheel work. In the centre of my today's explanations is the pneumatic drive of paper models. I will explain it with five models.

	2. Models 2.1 Rocket In the model of the Phantasia-Verlag in Wyk/Föhr (Germany) a small rocket is launched by compressed air. The compressed air is produced by the rapid compression of a bellows. The components of this model are: bellows, launching tube and flying object. The long launching tube ensures a good guiding, and the loss of pressure is minimized. Demands of the assembly: Folding and gluing of the bellows is fiddly, leaking patches could cause a fall in pressure. Launching tube and rocket must be rounded well, otherwise there's a problem of jamming.

2.2 Dragster The pneumatic dragster designed by Fritz König of the Atelier GAG in Bremen resembles a rocket on wheels. By compressed air a  dragster will be moved. The needed large quantity of compressed air is produced by a piston air pump. The cylinder of the pneumatic pump is shaped as a starting tower with square base. There a square piston must be put in quickly. The long starting tube which juts far into the dragster ensures guiding and avoids loss of pressure. It is important that launching tube and its counterpart, a case in the dragster, are exactly in line, otherwise it will jam. An exact use and a smooth area are required for starting.

	2.3 Wedding Cake Paul Spooner's "Wedding Cake" is one of seven automata which have been published by Virgin Books, London in 1986 as "Spooner´s Moving Animals". In the same year the German edition came out as "Automatenzoo" with the subtitle "Park der Stille" by Rogner & Bernhard / 2001-Publications.
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	The Wedding Cake consists of three layers which covers are fastened movably by hinges. A pneumatic cylinder with a movable piston as push rod is located in the inside of the cake. An air channel in the base connects cylinder and mouth pipe. The compressed air is produced by a jerkey blowing into the air channel. The push rod is driven up, first of all it pushes the cover of the upper cake layer upwards. This carries away the covers of both lower layers as well, and the hinges open up. By hand the cake is folded up again. The upwards movement of the push rod is limited by a string which is glued in. So an overstretching of the hinges and the push rod slipping out of the cylinder can be avoided.
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	The hinges are shaped as skeletons, and this resulted apparently in a dispute in the publishing house. They were afraid that the sudden appearing of eighteen skeletons out of a wedding cake could offend against good taste, so that some people in the public would feel agonized. Spooner was successful with the argument that visitors who cannot think about their mortality calmly should better not come to the "Moving Animals".

2. 4 Museum of the Mind Paul Spooner's "Museum of the Mind" is a head from paper which opens by compressed air and which allows a look at the likewise pneumatic moved thought contents. The first edition was published in 1992 as "Spooner´s Museum of the Mind" by The Museum of Automata, York. The German edition was published 1992 by Rogner & Bernhard, 2. edition 1998. A horizontally lying air pump is installed in the head, the air channel snaps off right-angled upwards. Compressed air is produced by pushing in the piston ("drawer"). It lifts a vertical sleeve which is put on the vertical part of the air channel. In principle the construction is similar to that of the rocket and the pneumatic dragster. On the upper edge of the sleeve which is movable through air pressure a linkage is fastened which opens up both halves of the head. A a ratchet prevents the sleeve from sinking if the air pressure is dropping down. By pulling out a release tab a detent pawl can be removed. If the pneumatic mechanism fails the piston also can be lifted by a tab on the backside, and the head can be opened in this way. On the upper edge the cover has a square hole for inserting four different states of mind: "They are intended to transform insubstantial ideas into solid paper."

	2.4.1 The Vacuum Cleaner Man The first state of mind shows a man with a vacuum cleaner. The vacuum cleaner is fastened to a pneumatic movable piston which is moved to and fro by pressure and below atmospheric pressure. This movement is transfered to the man, who is fixed to the vacuum cleaner and provided with joints. The movement of the vacuum cleaner man is caused by pushing back and forth the big air pump. Spooner thinks that most people need a device "that can be installed in the head to suck up all the unwanted material, leaving a nice blank space in which to construct pure thoughts."

2.4.2 The Dodo

The second state of mind is represented by a Dodo, a bird which flaps its small wings. "In the dodo mechanism a piston works vertically to raise and lower the bird's body on the end of the shaft. The wings are hinged to the body and levered up and down by forked fulcrum." The Dodo is a died out or wiped out bird. The reason for its extinction is self-satisfaction: "Consider the train of events that led to his passing: an avian, possessing the power of flight, finds himself without predators on a luxury island in the Indian Ocean. He no longer needs to fly, so he doesn't bother." And therefore it falls victim to hungry sailors. "Whatever the facts are concerning dodos and their lifestyle, the metaphorical dodo that flies in the Big Head epitomizes Wishfulness and Idle Speculation about what might have been if only ..."

	2.4.3 Europe and the Bull
	The third state of mind is shown by a model of Europe and the Bull. The bull makes a gallopping movement. This is achieved when two pistons are raised and lowered alternately. Forelegs and hind legs of the bull are fastened to these pistons. The air supplies of both pistons is driven by a piston-like jumping valve: "Holes in the piston distribute air two ways - like the valves in a trumpet. As air enters from the spigot, it passes through the valve, out of its upper port into one branch of the air passage, to raise one sleeve to its limit (...). Further inpumping sends the valve up its sleeve, cutting the air from the first side and supplying the other side through the lower port." For the assembly of the Europe you can choose between a modest and a usual varaint. The ususal Europe is bare, the modest is wearing a blue swim-suit. To the meaning of this model Spooner writes: "No model of the human psyche would be complete without a treatment of sex and violence. (...) Given Zeus' track record thr sex can be taken as read; to be run off with a bull must at least amount to extremely rough handling."

2.4.4 The Headache The fourth state of mind is the Headache. The compressed air pushes up an outer sleeve with two wheels. Spooner describes the mechanism: "To work the headache, air pressure lifts the sleeve which carries a pair of ratchet wheels past two springy papers driving pawls. Another two pawls stop the wheels turning to this upstroke. On the downstroke, the driving pawls catch in the teeth of the ratchets and carry them round one step. A brightly-coloured  fork is attached  to each driving pawl whose purpose is to shudder as the pawls operate, adding to the visual irritation caused by the spiral patterns on the ratchets."  When the outer sleeve has reached the topmost point it opens a flue and the escaping stream of air acts on the vanes of a turbine which moves a thirtysix times jagged coloured wheel that is attached to the turbine shaft.

2.5 Paper Organ The paper organ was placed at my disposal for my lecture kindly by Fritz König / Atelier GAG. The patent had been registered in 1990 for Benjamin Hurdle in Great Britain. Actually it is distributed by Marcle Models in the U.K. and Scheuer & Strüver in Germany. The organ's main parts are: a double bellows, a pressure vessel, a distributor of compressed air, eight organ pipes and a transport device for a punched paper tape. The paper tape serves as a valve and regulates the air pressure supply of the organ pipes. It is pulled through a narrow opening between distributor of  compressed air and organ pipes by turning a crank. While the not punched  part of the tape is between distributor of compressed air and organ pipe nothing happens. When there is a hole the air can pass and a sound will arise. The duration of the sounds is determined by the length of the holes. Base and top of the pressure vessel are elastic and bend when activating the bellows. An elastic band that connects both components limits the bending and helps rising the compression. At the top a trapeziform indicator is fastened, it is connected to two paper strips which on the other hand are fixed in front and behind on the top. If the top bends upwards the paper strips tighten and swing the trapezium top, the states of indication are "Pump" und "Play". top