Tandem Monster Flapper

TANDEM MONSTER FLAPPER

This monster owes it's existence to this blog. While writing the initial helicopter blogs I realized that I did not have a version of a tandem helicopter, which is the dominant configuration for heavy lifters. This seemed to be a suitable mechanical challenge. So hopefully I will feel complete after this blog - maybe.

 

 

 The scene is set in an African village, sort of. I decided that hessian would create a suitable neutral background. This helps with the camera auto exposure (when compared with the white or black background). It also hints towards of a high veld grassland, which could be considered its natural environment. I felt a need to build a corrugated iron hut as part of the background and to create the mood. Unfortunately I also added a Baobab tree, which occurs to the North of country and would die in a high veld winter. But it does add an African feel. 

The overall view shows the twin rotors of the tandem flapper, which are placed one behind the other (my previous dual rotor helicopter had the rotors next to each other). The challenge was to design a mechanism which would turn the rotors in opposite directions (counter rotating), and flap them up and down twice every revolution.

 

 

The flapping mechanism consists of a rod which runs inside the rotor shaft. This is done to limit the number of mechanisms which are external the main helicopter shape (a refinement of the first 2 flapping helicopters). The up and down motion is transferred from a lever which moves up and down via 2 discs attached to the rod. Thus allows the rod to turn with the rotors, as well as move up and down.  

The up and down motion is transferred to the rotor blades with an arm attached to the top of the rod and blades via wire links. The blades are hinged around the top bearing, which allows them to flap up and down. The rod and arms need to rotate with the blades, and therefore the complicated rotating cone couple at the bottom of the rotor mast.

 

The above image shows the rear rotor drive chain coupled to the rotor shaft (brass bit).

The chain drive to the front rotor drive is shown above. The flapper mechanism can be seen at the bottom of the image.

The counter rotating chain drive for each rotor is driven by a chain from the wheels axle. It goes through a right angle drive to get the chains in the correct orientation for the rotors. A simple gearbox out of thin flat bar with silver soldered brass bushes hold the axles for the counter rotating gears. The drive chains rotate at the same speed as the main axle. The gears were sourced from a robotics shop. The chain drive gears where cast from epoxy many years ago.

To provide 2 rotor flaps per revolution, a 2:1 ratio gear box is driven from the main shaft. This drives cranks for the rotor flappers. The cranks are out of phase with each other, so that the rotors do not move together (not strictly necessary because the same can be achieved by adjusting the "timing" with the chain drives). But it does look good when its moving.

The final mechanism was built to move the head of the pilot. With all the chains and gears dedicated to the flapping mechanism, I did not feel like adding additional drives for my usual head drive, so I tried a cam instead (as seen driving numerous automatons). The cam was made out of wood (seemed liked a good idea at the time). The cam drives a copper dome on the end of a push rod to try and get the mechanism to have relatively low friction. I had to add a small spring as gravity was not enough to keep the push rod tracking the cam. The spring is not very stiff, so overall the mechanism moves relatively smoothly.

So that's about it. The blog created the inspiration for the tandem configuration, and watching other peoples automaton videos inspired the cam mechanism. The power of modern communication. Hope you enjoy the video more after this explanation.

Luzinda's Dragonfly

Luzinda's Dragonfly

This monster was a follow on to the phantom flutterer, or Monster #F (June 2018 blog). The departure was to construct a body which was self-supporting instead of the frame and grid style used for the previous dragonfly. The structure results in a dragonfly which is much lighter, and therefore more suited to flying wire insects.

The image above shows the form of the dragonfly with its lightweight body mounted on the drive used to move it for the video. This form of construction was first used on the dragonfly as an experiment, to see if  I could use crimped ferrules for most of the construction rather than the wrapped wire technique I used in the holiday special 4 person transporter (April 2019 blog). The overall effect of the silver ferrules seems to be to make the whole body look lighter (the wire wrap darkens over time, and generally has a heavier look).This was also an attempt to ease the strain on my hands by reducing the number of twisted wires in a monster. Not entirely successful as the crimping also requires effort and a lot of planning to allow for tool access.

The bulging compound eyes use the same technique as the first dragonfly, except only in red. They are basically hexagonal shapes with long beads threaded on thin copper single strand wires. The  bulging shape is achieved by wrapping the flat hexagonal sheet over a wire dome form.

The wing flapping mechanism was kept simple. The first dragonfly tried to implement a flapping mechanism which moved forward/backward as well as up down (basically X from front and top). It added a lot of complexity, and was not that dramatic. For this dragonfly the wings only move up and down in a very balanced motion (the one set of wings move against gravity, while the other set are gravity assisted, and visa versa). To achieve this the axle has 3 cranks. The center crank driving the front set of wings, and the 2 outer cranks the back set of wings. The head is driven from one of the side cranks, which slightly spoils the balance.

The last description is of the wings. These are relatively simple with my standard varnished silk covering. The coloured pattern is painted with acrylic paint with lines basically trying to create the vein and membrane wing look, and spots to provide colour elements. This is finally covered with artists varnish to increase the colour depth. 

That basically finished the dragonfly. And then I gave it away?

Running Man

This is a continuation of the whirligig theme, going towards a more traditional format. This was created while on a coastal holiday, where the weather favours whirligigs (excuse for not getting previous attempts to utilize wind power during videos). Shown below is the wire contraption in a holiday setup - surrounded by beach cottages close to the sea (sea side is into the sun, not great for photos).

 The running man theme was chosen as a simple way to test whether I could drive a machine with wind power using basically wire and pliers to construct it. This is definitely a low tech production technique which needs a very tolerant design. 

The basic design consists or a 4 bladed propeller directly driving a worm gear. The worm gear allows the running man to run at a realistic rate, as opposed to the road runner style leg motion when avoiding Wile E Coyote. It also increases the torque which is produced by the propeller, allowing for a bit more friction in the mechanism and a little less precision in the gears. The screw gear drives a 9 tooth gear at right angles, which directly drives a crank for the legs. Each leg drives an arm out of phase. The legs have pivoted knees to allow for a realistic motion, but the arms don't have working elbows. This simplifies the design, but still allows for a realistic motion (basically don't flex arms a lot when running, but pump them backwards and forwards). The whole lot is mounted on a piece of trimmed drift wood. I had to do the trimming with a mini Leatherman pocket knife, so the rustic look is preserved.

The whole contraption has a tail added to try and keep the propeller pointed into the wind. This required a little bit of adjustment. The initial design had the pivot point too far forward, so it did not weathercock. This was moved back towards the propeller. It was not quite enough so an additional tail was added below. It sort of works now, but as seen in the video is not quite steady in the breeze. Not sure whether this is entirely due to the design, or due to the wind swirling between the holiday houses. Like the effect in the video of allowing the aspect to change constantly, so have not changed it yet.

A weak point in the design is that the shaft of the propeller, connected to the screw gear is made of 1.6mm wire (the thickest that I had at the time). It hasn't bent under wind power yet, but it just feels like it should have a more substantial shaft. It does mean that the clearance between the propeller and man had to be increased to prevent the propeller colliding with the runners elbows when the wind velocity increases. The actual blades of the propeller have been constructed using aluminium sheet recovered from tin cans (beer and mixers), which are freely available during the holiday season. The aluminium sheet is bent around a wire frame. This is easier to do when the shapes have straight lines and not curves. I'm sure it will improve with practice, but it is functional. The same technique was used to give the arms and legs a little more substance. The rest of the mans shape was hinted at with wire. The head was simplified to show the outline from various angles, with no attempt to complete all the bits. I like the effect as it requires a little more imagination (something that is generally required with wire objects as it requires you to fill in the missing bits).

 The final image shows the running mans expression when trying to go forward quickly. Has a nice upright posture with open shoulders. Think he will be a good runner in a breeze.

Pull Together

The last blog for the year. This one is being written at our holiday destination. Had to drive to our destination as rowed airship did not start?

This was the first attempt at a whirligig, or a wind powered object for amusement. It did work in a gale force breeze, but not suitable for a permanent installation on the highveldt. More of a coastal variety ornament, but I don't live at the coast.

The short video shows the first attempts at testing the "whirligig" in a breeze. As can be seen it was a strong breeze that got the bits moving. This shows a 4 bladed propeller driving the gears. This was marginal, so the propeller diameter has been increased and an extra blade added. This has not yet been tested in real conditions. Overall it has not been a very successful experiment, but it has been fun and launched 3 other propeller driven monsters.

This is a black and white photo taken later during the video sessions showing the upgraded 5 bladed propeller. The propeller is turned using a custom flexible drive supported by 2 wire helpers (or basically bearings supports). The photo was taken with a Mamiya C330 twin lens reflex camera with expired Kodak film. Development time was effectively extended by not compensating for warmer developer temperature and increasing the exposure time by stop when the images were captured. In the background of the image is a tin shack, which was added to provide some context for the monsters. The shack is constructed out of aluminium foil laminated with aluminium tape, and corrugated using a tool designed for card making. The frame of the shack uses bamboo skewers and ice cream sticks. The intention is to expand on the background buildings as time goes on.



The monster is basically an airship powered by 4 rowers. The propeller goes through 2 reduction gear boxes and chain drive to reduce the torque requirement. This allows the propeller to turn in the wind, but unfortunately means that the rowers cannot be accused of an over energetic display. The video is taken with the motor drive going at full pace, but the movement is still slow. During the short demo with the wind providing the power, the propeller turns somewhat faster and the rowers are closer to the speed I would have liked. So if this were to be powered by external motor the whole time I should reduce the gear ratios. I think I will rather wait until I move to a windier place and mount it outside. In the meantime it can collect dust.

This image shows the detail in the propeller hub and five bladed propeller. The brass plate is attached with miniature brass panel pins, to add some typical aeronautic detail, as well as keep the plate in place. The plate holds a brass tube, which fits over the propeller shaft and is secured with a steel pin (actually bent piece of wire). This allows the propeller to be removed for repairs as required, as well as allowing the power to be transferred to the mechanism efficiently. In the back ground the first of the reduction gear boxes can be seen. This serves 2 purposes. The first to reduce the torque required from the propeller shaft, and the second to move the drive shaft to the bottom of the airship. This was required to allow for sufficient offset for the rather large chain gear, and still keep the drive mechanism close to the center of the airship. Just looks more balanced to have the drive at the center of the shape, otherwise it would feel as if the airship would pull up or down as the propeller speed is changed.

The final reduction drive can be seen above, where a bevel gear is used to change the direction of rotation through 90 degrees for the rowers mechanism. The drive arm uses a triangular trussed beam to transfer the power to the four rowers, as a simple linkage would not have been stiff enough.

The four rowers are linked to each other with simple wire links driven from the back of the airship. The bodies of the rowers are constructed from wire twisted in a random pattern to form narrow waisted, broad shouldered rowers. They have obviously doing this for awhile. The heads of the rowers are once again crab claws, which basically defines the monsters.

The paddles are hinged on vertical wire shafts attached to the air-frame, and attached on one side to where the hand of the rower would be. The linkages between the rowers are attached to the hands. The bodies of the rowers are hinged at the hips and the shoulders with the arms attached to each other with a shaft through the shoulders. This allows the heads of the rowers to move forward and backwards as the oars are moved.

The oar blades are painted with a pattern of crosses which vaguely hints at a union jack like origin, whereas the tail of the airship has dark Germanic like crosses. This is allowed as I have ancestors in both camps and I like the effect.

So this is the last of the whirligig inspired monsters, which was made first, and the only one to briefly demonstrate the concept of wind powered objects with bits that whirl.

Bi-Flapper : a Kinetic Rotating 3D Sketch

Another one of the attempted whirligigs. In this case there was a 4 bladed propeller which came off the first whirligig attempt (still to be video'd). The machine almost worked in windy conditions, but needed slightly more power, so I made a 5 bladed propeller with a slightly larger diameter. Therefore the spare prop. The previous attempts using the 3-bladed and 6-bladed propellers didn't even seem close to working due to the unbalanced weight of mainly the wings. The obvious solution seemed to be select a design which had balanced wings, which in this case resulted in a biplane configuration.

View of the 4-bladed propeller and almost balanced wings.

The biplane layout deviates a little from the classical formats in that the upper wings are supported by what looks a little like the base of an inverted Vought Corsair wing, which adds a classical fighter but not biplane look to the aircraft (not realized during construction, but only during blogging). Construction of the wing supports was difficult, as it was narrow, and I didn't want to do a square woven mesh as used in the older monsters. To overcome this it is covered with a 0.9mm wire diamond mesh connected with jewelry sourced crimp ferrules. 

The pilot has been given a classic cockpit windscreen and headrest fairing to improve the looks. To keep the structure rigid the cockpit supports were joined with ferrules which were crimped and soldered. The technique works well enough to use whenever a structure is not firm enough using crimped wires only. The pilots neck was meshed using the old weaving technique ... still has its place. And the standard crab claw head had to make it's appearance.

To enable the propeller to turn quickly while still having a reasonable wing flapping rate a planetary gear set was printed for the front-end. This is the same thingiverse sourced, print in one go, herring bone, planetary gearbox as used in my previous whirligig attempts. To mount the gear set a tin ring was constructed with silver soldered attachment points for wire supports. The wire supports were twisted to represent cylinder heads similar to what would be found in a radial engine. These are attached to the fuselage. The springs (cylinders) can easily be adjusted to allow the 'radial engine' to be centered. The propeller is attached to the gearbox via a universal joint. This was required to allow for some de-centering as would be expected with a wire construction. 

The back of the planetary gearbox has a bent wire with two cranks to flap the wings and pilots head when the propeller is turned. The mechanism is relatively simple with the wings flapping in the opposite direction. This is done so that when gravity acts on the top wing, it assists the bottom wing to fight gravity, and visa versa. The pilot head has a lead weight added to try and achieve a neutral balance. This was done in an attempt to get the mechanism smooth enough to be wind powered. 

Unfortunately friction, inertia and the difficulty to get the wire bits well centered seems to result in too great demands in the power department. That combined with living in an area where wind is not all that plentiful means that I cannot confirm that it is a whirligig. This is why all the video shots show it turning with external power.

To complete the monster it was covered in silk and varnished until it looks like old skin. The acrylic detailing in a predominantly blue colour scheme was added and varnished with a hard glossy artist varnish to protect the finish. Cast lead wheels were added to match those of the other whirligigs so that it could look like a series. The normal warnings about sucking the wheels apply, even though there is the acrylic detailing and varnish finish. 

The birds eye view of the monster is added to show the swept back effect of the wings and the overall rounded bat like curves.  Real planes don't generally have wings which are as swept back as these monsters, but it does look more like one would expect from a natural flying object. Wonder if there was ever a bird with four wings? Guess not.

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?

THE HOLIDAY SPECIAL

This monster was born during the December holidays 2018, and completed early 2019. Holiday monsters generally require a simpler approach to construction than when at home with all my toys and therefore have their own challenges. This one started by searching the beaches for inspiration, which in this case came in the form of some bones. The bones dictated the general shape of the monster, resulting in a big bellied flapper. This lent itself to having space for lots of passengers. So then the family trip idea was generated.

Monster birthplace taken during first moments of 2019

Leading up to the holiday I had been searching for some group of people that would have something in common with moving models. During this search I came across  whirligigs, which are generally simple models powered by wind driven propellers, and which would find a home on top of a post box, if there were still post boxes. As this seemed to originate in America in the depression era, I guess they could have ended up on post boxes. Anyway I thought it should have a propeller and not be driven by the wheels, as I have generally done in the past. So the idea ended up having a long central shaft with many cranks. The were to drive the flapping wings and small family. In this case the pilot (representing driver), and 3 passengers. Only one focused on the road ahead. The rest having animated discussions in different directions. During the holiday I managed to get the wire work completed, with the motion basically established.

The post holiday construction took advantage of the home advantage. The wings are covered with parachute silk and sealed with water based varnish to give a semi-translucent finish. Details are added with craft paint and lots of colours. The final finish is covered with gloss artists varnish to bring the colours out. 

The casting process in the back yard

For this monster I carved molds for the wheels out of .engineering plastic which came from some rapid prototypes which were machined decades ago. Using these molds I cast the wheels using lead recovered from wheel balancing weights. The molds generally allow 6 to 8 items to be cast before they are damaged too much from the heat. The final wheels have unique characteristics due to the gradual degradation of the molds. The closest two were selected and had bearings soldered in. These were made from sections of a small diameter copper tube. The wheels were then painted as a variation to my normal plain finish.

The propeller was the fun bit. It is made from wood ripped from some old Oregon pine beams. This seems to have proper scale grain. Six blades were chosen in an attempt to make it wind powered, but the resistance was too great. At least it looks interesting. The paint job is done to increase the blades visibility when turning. The propeller drives a reduction planetary gear box to get a realistic propeller speed without having frantic passengers in the back. The planetary gearbox was printed from PLA using a low cost 3D printer. The planetary gearbox design was found on thingiverse and is printed as a single unit. With a little bit of effort and some grinding paste it ends up moving smoothly. The overall result is very surprising. The planetary gear is mounted within a steel ring with copper tubes silver soldered onto the ring for the wire interface. The gears are self supporting (using a herringbone gear), so that the propeller can be mounted directly to the center gear without additional hardware.

A final view from the top shows a rather plumb monster with low center of gravity. The spreading waist line may touch a sensitive point?

Santa in an upgraded sleigh.

This monster started off during a December holiday at the coast. Therefore the Christmas theme, as it was the season to be jolly. The framework was constructed on holiday, as well as the bead work. At the same time the flying surfaces were covered using a recycled cold drink can, chosen for its colours which matched the seasonal themes. The last holiday contributions were the rather large bird (gull?) feathers and a crab claw for Santa's head.

The monster was completed with a few technical aids which were not available on holiday. This involved casting lead wheels, a hub for the feather based rotors and a hub for the pusher propeller. The rotors also required some brass work and silver soldering. The original propeller was constructed with the outside of some large seed pods and aluminium tape. Problem was they disintegrated over the 10 or so years it took to get to this blog.

Last Christmas there was an attempt to do a video. For the video a rotor motor was added. This was a motor and pulley from an old CD, which was specified to run from 5 Volts. An old single cell Lithium Ion from a cell phone provided the energy and a rubber band transferred the power to the lead rotor hub. The pulley ratio (and band slip) combined with the mass of the rotor worked out well (by fluke), and provides a realistic slow rate of rotor rotation as expected of a large twin blade rotor. Nothing too frantic. 

Next a lot of Christmas stuff was raided from the Christmas tree decorations. This included a miniature Christmas hat, small presents, socks, teddy bear and candy sticks with red and white stripes. Basically most of the colourful bits.

The last Christmas video didn't get published. Something to do with ignoring guests and getting too absorbed in my own projects. I modified my behaviour and enjoyed the holiday much more. The photo below shows the last year version of the monster with static pusher prop.

The new attempt at a Christmas video was initiated by upgrading the Santa sled with more movement. The first upgrade was to redo the 3 bladed propeller using a more durable material. Like all classic props, it was now wooden. The wood was stripped from old Oregon wood beams which were replaced when a flat roof became a tunnel. Fixed the leak. Next it had to have a classic prop paint job, therefore the mostly red tips. Easier to see if the prop is spinning quickly, thus reducing the number of elves which may be decapitated? (See video to see the effect)

The next phase involved a long prop shaft and another ex-CD motor. This time the prop had a direct drive, and therefore spun much faster. Again realistic for a small pusher prop. The motor got a bright almost Gypsy paint job, which adds some interest to the tail. Unfortunately it also added some paint to the motor bearing and resulted in a cleaning job being required before the prop would spin again. Not everything goes smoothly during development. Typical result when the marketing department overrides the engineering department and wants to add unnecessary features to make it look better.

The final enhancement was to add the flashing navigation light in the front. The red-nose of the sleigh. This was activated by a 3D printed plastic cam driving a re-purposed micro switch from an old printer. The cam was glued to the wheel axle, which also had a crank to drive Santa's head.  The flashing light proved to be challenging as it had to be bright enough to overcome the lighting required for the video. The holder was again printed on a 3D printer from PLA. Initially a small red LED was used in the white plastic holder. This was when the lighting situation became obvious. Take 2 involved using a high power LED (1 Watt) from a down-light which had an expired power supply (the preferred failure mode for LED lights). The plastic holder required a paint job to get the red-nose effect. This reduced the light output a bit, but it is visible in the video when the switch works.

The final video was enhanced by selecting music which was not one of the traditional Christmas carols. This was mainly due to copyright issues with music. The end result was much better than I anticipated. The details of the music are available in the comments section of the Youtube video. It takes a lot more effort to find music which one may use without paying royalties, but it does expose one to music which may otherwise stay obscure.