Physically powered spinner that whistles when in motionToys
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A device that makes a noise without the use on batteries, that's small light and portable.
This device makes use of resonance in a cavity.
As its an acoustic device we need to provide it with air.
But rather than applying the air by blowing into it we will propel the device at high speed to force the air.
Propulsion at high speed is provided by a wound string.
By pulling the ends of the wound string in opposing directions it causes the string to unwind and propel the spinner.
Once the string has unwound the rotational energy causes the spinner to wind the string in the other direction.
Unless energy is fed back into the system by again pulling the string the process would eventually stop.
Before use and periodically during use check that the spinner has no issues and that the string is not fraying.
If any issue are found better to reprint a new spinner and to re-thread with a new string.
As a precaution wear eye protection in case there is a failure of the spinner or the string should snap.
Stretch out the string loop to form two parallel lines with index and middle fingers of each hand looped through the turns at the extremes
Clasp the string in closed fingers.
Stretch out the string loop to form two parallel lines clasp the handles in closed fingers.
The rest of the process is applicable to either method.
Centre the spinner along the string so as to be positioned equidistant between your hands by sliding along the string loop.
Hold the string loosely with forearms parallel such that the spinner and string form a "V" shape with the spinner at the bottom of the "V".
The string is tensioned by rotating both hands in unison (creating small arcs), maintaining the "V" shape (as far as possible); as the string tightens it should shorten as it is wound.
Once the string starts to produce kinks, it is would sufficiently.
At this stage maintaining parallel forearms pull your hands outward away from each other.
The spinner will start to spin unwinding the twist previously applied whilst simultaneously whistling.
Once unwound the momentum will cause the string to wind its self in the opposite direction but at the same time losing momentum and slowing down.
During this stage relax the opposing pull between your hand and pull them apart again causing the spinner to rotate in the opposite direction picking up speed in the process.
Repeating the process with a smooth co-ordinated action will keep the spinner rotating and whistling.
It may take a little practice the get the spinner to rotate.
It's also a good exercise for your arms.
Further details can be found here:
Materials and methods
Layer Height - 0.15 mm
Infill - Tri-Hexagon
Infill Density - 50%
Base Adhesion - Brim
Filament - PLA
Weight - 9 grams
Print Time - 1 hour 22 mins
Once printed remove the Brim.
Remove any blemishes or strings from the surface by filing, sanding or cutting.
Sand the flat side of the spinners to remove any roughness as this will help ensure the surfaces fit together evenly and prevent gaps in the spheres that will affect the sound due to air leakage.
Regarding leaks, the 3D printing process is known to produce small gaps between and in layers as a result these will require filling in.
The gaps are filled in with lacquer, enamel paint or epoxy resin this is applied both internally and externally and left to dry.
If necessary clear out the holes in the spheres with a 2 mm drill bit.
Clear out or widen the holes for the strings as required.
Following this a suitable plastic glue is applied to the flat surfaces of the two halves and these are bonded together.
The spinner is complete.
Measure approximately 1 metre (39 inches), of string/twine.
Thread the cord through both string holes to form a loop and tie the ends together with a suitable knot, I used a square (reef) knot.
Subject to the string diameter and finish you may wish to add handles or use gloves to prevent the string rubbing your fingers.
Handles may be created from the following:
Two large body felt tip pens (loop the cord around the body), dowels (looped with cord or through holes), or circular disc cut from wood (loop cord through hole and body). Other options may be considered such as 3d printed handles.
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