Duckie learning to fly whirligig (100% 3D-printable).

Preview model in action:

Video presentation and instructions:

This is a working model of a whirligig that shows the wind direction and helps the duckie to make the first attempts in the flying craft. Initially I made it more as a proof of concept that a working whirligig can be made of printed plastic parts only without using metal parts such as wires, bearings and screws, but the model turned out to be strong and reliable and survived a hot summer with strong gusts of wind and a cold winter with lots of snow, so now I can recommend it as an attractive element of the garden for anyone who loves cute yellow rubber duckies :)  I know a lot of ways to improve it and to increase its performance, but I tried to make this model as simple as possible. The main disadvantage of the direct transmission is that a weak wind which is typical for my area can only raise a very fragile and lightweight 20-30 grams duck. I wanted to make a more advanced and complicated version with a reduction gear, but after lubricating the moving parts with a silicone spray I'm quite satisfied with the performance of this model. It is easy to print and assemble, and it works pretty well, this is why I don't want to change it anymore. I publish it as a workable model that should be treated with some love :) It can be used as a garden toy or a weather vane for a roof ridge.

I printed all the parts with PETG because the model was intended to be used outdoors and PLA parts will most likely deform under the Summer sun. So all the tolerances were made for PETG and tested with Ender3V2 and 0.4 mm nozzle. ABS is even better because it withstands higher temperatures and weights less than PETG, but I rarely use ABS now because it is toxic during printing.

The performance of this model very much depends on the quality of the printed parts, so before printing anything I recommend to tune the printer and get at least basic understanding of the print settings. You should understand by the shape of the object when it's better to print from outside to inside and when to print from inside to outside and how it affects the inner and outer dimensions, especially the dimensions of the holes.

REQUIRED STUFF.

You only need glue and a knife to assemble this model. An engraver/dremel and a 2mm drill bit will also help if your printer has difficulties in precise printing (haha, most of them have!). Wire cutters are usually bundled with a 3D printer, at least I’ve got one with Ender3V2, but if you don’t have it, you may use a knife to cut the filament.

Optionally, you may need freeware openscad (https://openscad.org/) to generate some custom parts such as adapters for various axis diameters. You don’t have to learn openscad because I already wrote the code for you. You only need to set your value in the first line of the code, render (F6) and export the rendered model to stl (F7). Some models of bearings can also be tweaked in openscad to get the best bearings that your printer can print.

PARTS TO PRINT.

All the parts are pre-rotated for 3D-printing.

duck.stl

The original model was designed by willie (https://www.thingiverse.com/thing:139894, Creative Commons - Public Domain Dedication license), and I modified it to add movable wings. As this is the most simple whirligig model that uses a direct transmission without a reduction gear, the performance of the device very much depends on the weight of the duck. The best results were shown by a 22-grams duck printed with 1 wall and 20% lightning infill. 2 walls were used in the adapter hole and in the places where the wings are attached to the body with the help of “modify settings for overlays” feature in Cura because these parts of the duck suffer from the most loads and 1 wall would be too thin there. This duck can fly fast with a help of a 40W home fan using 3 small 15x3 cm turbine blades. Another 29-grams duck printed completely with 2 walls and 21% lightning infill doesn't start flying with these blades and the same fan. It needs at least 4 bigger 18x4 cm blades. It may seem that this 7 grams difference is nothing to worry about but as I could see it really drastically changes the situation! I recommend to keep the weight of the duck as little as possible - don't use weighty patterns of infill like grid or cube or whatever to get an immortal 100-grams duck - it will not fly unless you print really huge blades for it. However, 1-wall duck is very fragile and can be broken by a strong wind, so it can only be recommended for careful home use only. 2 walls and lightning infill seem to be the best choice for this duck. Support is not needed to print it.

duck-wing-left.stl
duck-wing-right.stl

The wings for the duck. They are the same, just mirrored. Print without support.

base.stl

This one is easy to print. Use enough infill to prevent bending, especially if you use heavy turbine blades. I printed with 50% grid infill and it seems to be fine.

hub*.stl (hub*.scad)

I used modified openscad files originally made by schuetzi99 to generate turbine parts for this model (https://www.printables.com/model/34046-wind-turbine-experiment, Creative Commons-Attribution-NonCommercial-ShareAlike license). The author provides openscad files to generate a hub for different number of blades and also blades of different sizes and shapes. I tried hubs for 3 and 4 blades and I came to the conclusion that more blades allow the duck to start from a weaker wind but then rotation speed will be not too fast. And the hub with 3 blades will need stronger wind to start the rotation, but then it will rotate faster. As far as the blades angle is concerned (specified as "anstellwinkel" in hub*.scad), I found that 35 degrees work better than 45 degrees. I didn't try lower values though, maybe they are even better. Or not. You try it and tell me. Anyway, a lower value is more preferable because if you print a hub with 30 degrees, you will be able to use 0-60 degrees angle, but if you print 45 degrees, it will only rotate from 0 to 45 degrees. Lower values give higher range to test various angles and find the best one, and finally you can just glue the blades in the position that you found optimal or print a new hub for that position (in this case it will work fine without glue).

blades*.stl (blades.scad)

The generated stl is for large blades (180x40mm with 50% scale to the tip and 15 degrees twist). Use blades.scad to generate the blades that you need:

scale([0.4,0.4,1])linear_extrude(height = 180, twist = 15 , scale = 0.5)

0.4 is width, means 40mm. Change to 0.3 to make 30mm or to 0.5 to make 50mm. If you increase the width, you also need to make a longer hub axis.

180 is the length.

15 is twist in degrees. I feel that no twist (0) will perform better, but I did not test it.

0.5 is scale to tip. I feel that no scale (1) will perform better but I did not test it.

You can generate and try different sizes and shapes of blades to find the one that works better with your duck. Then tell me which ones showed better results :) It’s not that I don’t want to try it myself but I already spent a lot of plastic on this project, so now it’s your turn :)

The blade twist and scaling to the tip seem to do more harm than good. From what I saw I expect that 3 huge blades without scaling to the tip will perform better than 4 smaller blades with scaling because their total weight will be lower, but the area that deals with the wind will be basically the same.

Blades are printed with 3 walls horizontally without infill and support, but I recommend to add 50% infill to the place where the blade meets the mounting cylinder because it is very fragile without infill (I broke one zero-infilled blade in that place when I tried to attach it to the hub).

For further information on the turbine please refer to the info page of the original author and special literature. I'm not a turbine engineer so I don't claim that the blades that I printed are really perfect for this model (most likely they are not!).

Warning: Cura 5.2.2 has a kind of bug that slices the blades in the most horrible way you can imagine (parts of it are printed “in the air” for some unknown reason). I tried to change various settings but nothing helped. PrusaSlicer slices the blades well, but I finally sliced them from Cura 4.13.1 and it sliced perfectly. Cura allows to add custom infill only in the places that you specify, maybe PrusaSlicer also can do it, but I don’t know it because I rarely use it.

hub-axis*.stl

This is a 5x5mm axis for a hub that should be printed with 100% infill because it should be strong.

hub-axis-83mm.stl - for 3 cm blades and a hub with anstellwinkel>=35.
hub-axis-88mm.stl - for 4 cm blades and a hub with anstellwinkel>=35.
hub-axis-93mm.stl - for 5 cm blades and a hub with anstellwinkel>=35 (not tested).

Try to make the length of the axis as little as possible to reduce vibrations. For example, a 83 cm axis should be enough for 4cm blades attached to a hub with anstellwinkel=45. There should be at least 5 mm between the blades and the base for safety.

bearings*.stl

There's no doubt that metal bearings work better than 3d-printed ones. You can use any metal 608 bearings with this model, just glue bearings-adapter.stl inside. But as this is a 100% printable model, it can work fine with plastic bearings as well. I tried something like 10 different models of bearings and selected 2 models that showed the best performance with this whirligig. If these bearings don't work well for you, you can use any other 608 bearing models, just add a 5.2x5.2mm rectangle at the center (in blender, freecad, openscad or whatever software you use). Recommended layer height for printing is 0.12 mm or less and very slow speed (15-20mm/s).

bearings-maxstupo*.stl 

This is a classic ball bearing that should be printed with support. It was generated with the Bearing Generator by Maxstupo (https://www.printables.com/model/230892-bearing-generator, https://www.thingiverse.com/thing:1729699, Creative Commons – Attribution license). The bearing works well but may get stuck sometimes if the surfaces of the balls that were printed on the support are not round enough. It will continue rotation when a stronger wind appears. The only solution to avoid it is to make the balls as spherical as possible with any tools that you have at hand (sharp knife, engraver). Openscad files are also available to play with the number of balls, tolerances, etc to get the best bearing that your printer can print. After many tries I'm quite happy with bearings-maxstupo-7balls-lowtolerance.stl. It has low tolerance but it can be printed on Ender3V2 fine with 0.12 layer height and 0.12-0.2 mm distance from the support. bearings-maxstupo-7balls.stl has higher tolerance and works louder and less stable. Of course you can tweak tolerance for your printer in the scad file. These bearings work really well but you need to spend some time with a sharp knife and an engraver to remove the support carefully and make all the balls perfectly round.

bearings-guppyk*.stl

More complicated bearings that don't need support to print. Designed by guppyk (https://www.thingiverse.com/thing:4821342, Creative Commons - Attribution – Non-Commercial license). They work more quiet and smooth than most no-support bearings that I tried, but only if you manage to print them perfectly. I've got one perfect print that works just great and 3 failed prints that rotate worse than many other models of bearings and I have no idea why because the settings were the same. Most likely leakable PETG makes a drop somewhere in a wrong place and the surface inside the bearing becomes not so smooth. As this is a closed bearing, there's no way to clean it inside, so I got tired of reprinting it and finally switched to the ball bearings by Maxstupo that show better results after some handwork. Anyway, if you hate to remove support from the ball bearings, I think this model by guppyk is worth trying - if you are lucky to print it successfully, it will work just a little worse than the ball bearings without the need to remove support - just separate all the movable parts with a sharp knife (especially in the first layer) and these bearings are ready to use.

bearings-clip*.stl
bearings-clip-caps.stl

They are used to fix the bearings in their position. Although after you test the bearings and find their quality acceptable, I recommend to use hot-glue gun without any clips and caps, it is more reliable and it's easy to remove it in case you need to change the bearings later. Warning: bearings-clip-stronger.stl pushes hard on plastic bearings and bends them, thus reducing their performance, so it is only recommended for metal bearings. bearings-clip-weaker.stl has just little pressure on the bearings and works well with plastic bearings, but you may need glue to fix them reliably if you are going to use the device in strong wind conditions.

circle.stl

This circle transforms rotation movements into up-down movements. Print it with any infill.

lever.stl

This lever is used to connect the circle and the duck post. It is rather thin, so 100% infill is recommended to prevent bending.

duck-post.stl

This post lifts the duck and also suffers from wind blows. It should be strong, so 100% infill is recommended. It looks better when printed with a transparent PETG: when you look from afar, it seems like the duck is flying without any support.

duck-adapter.stl

Universal adapter to join the duck post with any duck. As the center of mass will be different for all the ducks printed with different settings, you will have to find the center of mass of your personal duck and glue the adapter into that position. But I recommend to generate a custom adapter instead of using this one. The adapter installed in the correct center of mass point noticeably reduces the friction and increases the overall performance of the device.

duck-adapter-custom.scad

It allows you to generate a custom duck adapter for your personal duck (much stronger than the universal adapter). You need openscad for it. Just specify the length from the front of the duck hole to the center of mass in millimeters on the first line of the scad file, render (F6), export (F7), print. Default length is 21mm (center of mass for my duck).

wing-support.stl

Connects the base with wings. You need to print 2 things. Recommended color is transparent to make them less noticeable from the distance. Infill 100%.

filament-cap*.stl

These are used as caps for filament axes. You need ~12 of them but I recommend to print more because they are small and can be lost easily. I made the axes and caps in transparent color but the color is only depends on your taste.

axis-adapter-custom.scad

This is used to generate an axis adapter that joins the base with the central axis that you are going to use. You can use any axis 1-8 mm in diameter. You can print an axis or use a metal one (recommended). I prefer to use a 4 mm nail (or a welding rod) and made an adapter for it, but you can generate an adapter for your diameter. Just open the scad file in openscad and enter the diameter on the first line, for example "axis_diameter=5" if you have a 5 mm axis, then F6 (render), F7 (export to stl) and print.

axis-custom.scad

Since this is a 100% printable model, I provide a way to make a plastic axis. It will work but there is no guaranty that it will not break under strong wind of course. To prolong its life it should be printed horizontally with supports, and I recommend to use the maximum diameter that is 8 mm. Clean the support well after printing for easy rotation.

arrow-balancing-tool.stl (optional)

Allows to find precise weight of the arrow that you need to print to get the whole device balanced on the axis. It can be printed lightweight (10% infill) as it is only needed once.

The thing is that you have no idea what weight is needed to balance the system when you change the number and the shape of blades all the time - of course the center of mass changes every time you add or remove a blade. So the final balancing is made when you assembled the model and you are satisfied with the way it works. You should first balance the model with some other things. Use a bag with coins (bolts and nuts, nails or whatever you can find) hanging on the balancing tool. Add/remove coins from the bag to reach the balance. Then use required amount of infill to print the arrow with the balancing weight that you have found using the coins. The weight of the arrow = the weight of this balancing tool + the weight of the coins.

Although this device can work even totally unbalanced, I recommend to balance it so that it could "find" even slow wind and show its direction more accurately.

arrow.stl

This one shows the direction of the wind and also balances the turbine. This is the last element to print because it plays important role in balancing. This arrow model can weight from 29 grams (3 top, 3 bottom, 10% grid infill) to 58 grams (with 100% infill) when printed with PETG. If it's not enough, you can add even more weight. This is why the arrow has additional holes - they may be used to attach more weight if the weight of the 100%-infilled arrow is not enough to balance the construction and a little bit more weight is required. What can it be - whatever weighty useless stuff you can find :)

arrow-fat*.stl

Alternative version of the arrow with increased weight for weighty blades. Its weight ranges from 32*2=64 grams to 90*2=180 grams (PETG) depending on the infill, so you have a possibility to try even huge blades! After finding the balancing weight with the balancing tool as described above, use Cura to reach the required weight divided by 2 by changing the amount of the infill. I recommend printing slightly lower weight because you will additionally use some glue that also has weight, besides, you can still use holes in the arrow to attach even more weight. Note that Cura can also make mistakes. For example, the prediction for my half of the arrow was 34 grams and the resulting arrow was 28 grams. But this difference doesn't have tremendous effect on performance. I just added more infill for the second part for compensation! So print both sides and use 7-8 mm length pieces of filament to insert into 3 holes on one side of the arrow. They are used for fast and precise alignment of both parts. They are very useful if you use instant glue and have little time for alignment. Then use glue to join both parts together.

I'm not sure that the shape of the arrow is really good for the whirligig because it is rather slow to catch the wind that changes its direction often, but I made it that huge to allow wide range of possible weight to balance different turbines. If you have tons of free plastic you can try different shapes and sizes and then tell me which one works better (or upload your arrow as a remix if it really works much better than mine).

HOW TO ASSEMBLE.

Assemble as shown in the tutorial video to avoid many mistakes!

I recommend to assemble the first try without glue to make sure that everything was printed fine and works. When you are sure that everything works well and satisfied with the performance, you can assemble it with glue (where needed) to let the bird free into the wild nature :)

All the possible defects of 3D-printing such as “elephant foot” should be removed right after printing, otherwise they will make a lot of problems for you later. All the 2.1 mm holes should be cleaned with a 2 mm drill bit and the 1.75 mm filament should pass easily through them. Do not use thicker drill bits to clean the holes! Larger holes lead to parasite movements of parts that increase vibrations and reduce the overall performance. Use only straight (not bent) pieces of 1.75mm unused filament as axes. The caps are attached to the filament with a touch of a hot knife or solderer. There should be approximately 0.5 mm distance between the cap and the moving parts for easy movement.

Wings are attached to the wings-support with a U-shaped piece of filament. It should have 5 mm between the tips and the length of every U-side should be 9 mm. Bend the filament when it is slightly heated with a gas lighter so that not to break its structure - when it cools down it will save its new shape without cracks. The tips of the U-sides should be slightly and gradually sharpened with a knife or an engraver for approximately 4.5 mm length.

If everything is made accurately, they can be attached to the corresponding holes of the wings without glue by pressing on them hard. There is not much load on the wings so glueless connection works fine here (but you can use glue if you sharpened them too much and they fall off). Update: I printed another set of wings with different settings and the holes were rather loose for the filament. In this case I just heated the filament a bit and pressed on in with fingers to make it elliptical, it holds well inside the holes. Personally I don't want to use glue here because it will be difficult to disassemble the glued model and reuse the wings if I decide to change anything later, but if you are sure that you will not change anything later, you can use glue without doing anything with the filament.

Connect everything except the lever and the circle and fix them with caps. Connect the lever and the most outer hole of the circle but do not fix the cap from the back side of the filament now. Attach the turbine.

Now find the wind (or use a 35-40W fan instead) and test the system. If the duck doesn't want to fly at the required wind force, the possible reasons and solutions are:

- poor quality of the printed bearings (most likely) / try other models of bearings that you can print well.

- the duck is too fat and the blades are too small for it / print a low-weight duck or bigger blades).

- 2.1 mm holes were not cleaned somewhere and make a lot of friction / clean the holes with a 2-mm drill bit.

If nothing helps, you can reduce the duck lifting height by attaching the lever to another hole in the circle. The closer the hole to the center, the lower will be the lifting height and the easier it will be for the wind to raise the duck. Try all the holes and find the one that works at the desired wind force. There are holes for 34 mm, 30 mm, 26 mm and 22 mm lifting height. Of course the duck that raises higher will look more interesting, so start trying with 34 and end with 22. When you are satisfied with the performance, you can close the cap on the filament axis from the circle side, attach the arrow, balance it, and your whirligig is ready to use.

MOUNTING.

In the garden:

Use something like 2.5 m x 32 mm polypropylene tube or a wooden stick. Attach the axis to the top side of the tube (use hot glue gun or print a custom adapter). Dig the bottom side of the tube into the ground somewhere in an open windy area at least 0.5 meters deep.

On the roof top:

The same as the for the garden version, but a short 0.5 m tube can be used. You will have to make a custom adapter to fix the tube on your roof.

PAINTING.

The duck was originally printed with white PETG. The yellow duck was painted with a yellow spray paint that was originally bought to paint gas pipes a few years ago :)  It paints PETG fine. The eyes were covered with a sticking tape before painting to keep them white. The beak and the eyes were painted with permanent markers. I don't have red paint and I'm not going to buy it just to paint a beak, so a red maker is better than nothing anyway,

FINAL WISHES.

Take your time to assemble your duck with love and attention and it will surely learn to fly someday :) Don't let it fly to your neighbor's garden by making a reliable mount!

I know this model is not for everyone because it may disattract many people by the amount of the handwork required to make it work, but still if you are a real duckie fan and completed the assembly, I will be happy to see your whirligig photo in the “makes” section or post a link to a youtube video showing your model in action. 

LICENSE.

This model is free and it is for non-commercial use only! Please note that the turbine used in this model is also licensed for non-commercial use by its respected author.

You may use these model files to print this model for personal needs. You may print this model as a free gift to your friends. You may make and share remixes of improved separate parts of this model without sharing the complete set of model files (please provide a link to this page instead). You may not sell these model files or remixes based on these model files or the items printed using these model files.

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UPDATES:

1. I found that shifting the duck adapter slightly to the front of the duck's center of mass reduces tension and increases performance. Most likely this is because the wind and the rotating circle slightly pushes the duck to the front. So, my recommendation is to skip initial finding the center of mass as I showed in the video but assemble the device completely and find the best position of the duck adapter by rotating the turbine and shifting the duck adapter to different positions to find the place where the tension of the duck post is the weakest (the duck post should be comparatively loose inside the hole but not fall to the front or to the back side of the hole. Then generate a custom duck adapter and install it.
2. Spray a little bit of Silicone Lubricant on all moving parts of the model, especially the bearings and the duck post. This gives an incredible increase in performance and the duck starts flying even with a weak wind!
3. The model was tested in the temperature range from -30 to +40 degrees Celsius for almost a year, even under snow! There are no damages to the construction and it still works perfectly (printed with PETG). However, the mechanism may freeze when the temperature varies around 0 degrees Celsius, especially after rains or wet snow. This does not damage the construction but the duck will not fly until the temperature gets above 0 degrees. If you want to make it fly earlier, you will have to take it at home for an hour to let the ice melt, and then you can let it free to the nature again. It will fly fine and will not freeze again if the temperature keeps lower than -5 degrees. The snow is not a problem most of the time as it is cleaned by the wind, but wet snow may sometimes glue to the model and the duck will need your help. Due to this reason I move the duck from the house top to a 2 meters high post for the winter time to make the maintenance easier, as we often have temperatures around 0 degrees during Winter time.