Hi,
I am back to present you an optimized version of the so-called "weather merry-go-round" :
- size of the Sun figure is reduced (which is more coherent with current weather in Paris area…)
- I carved 2 windows in the cover housing, so that people can view inside mechanism
- I dug hollows in the cover housing to avoid wasting material
- I added a washer underneath the cover, which should prevent from removing the cover (that could lead to piston disengagement…)
Up-to-date pictures and CAD model are bellow. Note : the modifications have generated a 22% cost saving according to Sculpteo automated 3D printing quote !
For new comer on this post, please read general description of the project hereafter.
Reminder : like button is still available at the end of this post ! :)
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Hi all,
I recently discovered 3D printing technology and got very excited about the possibilities offered by this kind of manufacturing process. Indeed, long time ago I used to create CAD products as a hobby, but having no chance of making them real was somehow frustrating ! In the mean time I heard about the MoveIn3D contest and found it quite challenging.
First of all, I thought of presenting a complex design made of gears, bearings, rack mesh or ball nut… But having a new baby at home inspired me a more poetical object, which could also help with my WAF (Wife Acceptance Factor) when spending time on CAD system !
Actually my project is an original miniature merry-go-round, a kind of small toy, similar to these animated mechanisms that can hypnotize young children for hours. And as a personal touch I replaced the merry-go-round horses by weather symbols : a sun, a snow-man and a rainy cloud (looks a bit like a Zeppelin though…). Here is the result :
When rotating the cover housing, the 3 characters follow the motion and, at the same time, they also have an upward and downward movement. This allegorizes in a certain way the alternating weather, reminding French popular saying : after the rain shines the sun (“Après la pluie le beau temps”). Maybe should we call this a “weather merry-go-round” ?
If you do have some difficulties to figure this out, surely due to my confusing explanations, please take a look at the following videos showing it through short animations :
But enough with poetry, let’s talk now about 3D design and technics ! The mechanism is composed of an inclined rotating plate that acts on 3 tie-rods linked to 3 pistons. Each piston support a weather character. The rotating plate is driven by the cover housing through a ball joint contact.
When the cover housing carries along the inclined bearing, the tie-rod lower ball joints get the same rotating movement around the base. The tie-rods vertical altitude is also modified (going through a maximum and a minimum height during a complete revolution), due to the bearing inclination. This upward and downward motion is transmitted through the tie-rods to the pistons (the pistons travel a vertical stroke of about 12mm). Meanwhile, the contact ball between inclined bearing and cover housing travels along a vertical curve.
This mechanism is derived from an automotive HVAC rotating compressor (with some difference because in the case of a compressor, the cover housing is fixed and the base is rotating). In real full-size merry-go-round, the upward movement is probably created by a cam device, while the downward motion results from gravity effect. In the “weather merry-go-round”, the tie-rods push and pull and always manage the piston altitude, which means it should also work even if the toy is up-side-down !
The mechanical constraints that drive the kinematics are the following :
Note : in the simulation you may viewed in the above video, I had to change the tie-rod / piston ball joint to a hinge joint, otherwise the tie-rods DoF (Degree of Freedom) are insufficiently constrained : tie-rods and piston can freely spin around their own axis because it’s a pure kinematic study (in real world, friction helps solving this issue, but simulation gets much complex and would request FEM or ADAMS type studies).
Speaking of friction effect, let me share a worrying question : are the necessary plays between the components compatible with the plastics frictions ? I’m afraid that big play combined with high friction might block the whole mechanism… For sure 3D printing and real trials will give us the answer !
Last but not least, let’s emphasize 3D printing superiority for this application, compared to traditional manufacturing process. The whole merry-go-round can be printed at one time, w/o any assembly operation, which is impossible otherwise. In fact, ball joints and bearing would need press-fitting or crimping operation. In the same manner, if the pistons and their corresponding characters are not 3D printed, traditional process would require an additional fastening operation between 2 subcomponents (piston + character). And 3D printing is also an open door for creative customization of the characters of the merry-go-round : you could imagine it with animals, cars, planes, whatever you want...
As a conclusion, I hope this study raised your interest and that you like it (in this case, please, do not forget to click the corresponding button !!!). Do not hesitate if you have questions, I’ll do my best to answer. Further developments could be the following one : integrating a motion source (spring based or electric one) with a nice or funny music accompanying the motions… But let’s hope first going through the 3D printing step !
