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R-theta Etch-a-Sketch

Polar coordinates Etch-a-Sketch
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It looks and acts similar to an X-Y Etch-a-Sketch, but the screen is round, and instead of controlling the X and Y position of the etcher, the knobs control the radial (R) and angular (theta) coordinates.
AO, Jun 18 2003

How an Etch-A-Sketch works http://entertainmen...com/question317.htm
[DrCurry, Oct 05 2004, last modified Oct 17 2004]

Polar Coordinates http://www.bartleby...pages/A4pocoor.html
[AO, Oct 05 2004, last modified Oct 17 2004]

One possible approach . . . http://bz.pair.com/fun/rTheta.html
[~55Kb image] [bristolz, Oct 05 2004, last modified Oct 17 2004]

Another possibly possible approach http://www.geocitie...chdesign/rTheta.htm
[AO, Oct 05 2004, last modified Oct 17 2004]

Can you stand one more? http://half_crazy.tripod.com/hb/rtheta/
A bad drawing of the core mechanics that I think could make it work. (Might take a bit of imagination, I'm no bristolz either) [half, Oct 05 2004, last modified Aug 15 2006]

Worm gears http://www.howstuffworks.com/gear5.htm
"the worm can easily turn the gear, but the gear cannot turn the worm" Still would cause a bit of extra drag, but minimal interference between the 2 axes. [half, Oct 05 2004, last modified Oct 17 2004]

Elliptical gears http://www.cunningham-ind.com/ellipt.htm
To elaborate on my earlier tangential annotation. [half, Oct 05 2004, last modified Oct 17 2004]

Escher Sketch http://www.ebaynham...ops&Product_Count=9
[kevindimie, Oct 05 2004, last modified Oct 17 2004]

(?) Etch-a-Sketch Doodle Dome http://cgi.ebay.com...5572&category=19019
How about a Rho-Theta-Phi Etch-a-Sketch? [spiraliii, Oct 05 2004, last modified Oct 17 2004]

Computerized sphere etch-a-sketch http://www-personal...nterm/ddd/#pictures
This guy did some pretty cool stuff with his toy [NotTheSharpestSpoon, Sep 10 2006]

Polar Coordinate Etch-a-Sketch simulation http://mitxela.com/...inate_etch-a-sketch
[mitxela, Nov 20 2015]

bristolz's illustration on archive.org https://web.archive...com/fun/rTheta.html
[mitxela, Nov 20 2015]

[link]






       The thing about regular x-y etch-a-sketch is that its internal mechanics are quite simple. How would you propose to get it to do this?
(+ for the idea anyway)
Jinbish, Jun 18 2003
  

       Good for building mazes.
bristolz, Jun 18 2003
  

       nice idea
hazel, Jun 18 2003
  

       jinbish: the mechanism is easy enough to picture - one knob rotates a dial, while the other moves the pointer out along a groove in the dial and back. All wires routed via the middle.
bris: why mazes?
DrCurry, Jun 18 2003
  

       Because I can't think of much else I'd be able to draw with it. That's not a criticism, though.
bristolz, Jun 18 2003
  

       [DrC]: no, no, no - I mean the inside (internal!) mechanics. X and Y can be done with simple wire set. But I can't picture a simple way of pulling a pen that could be facing any direction. I think this will take a clever bit of manipulation.   

       On saying that, there are two interpretations. One has an adjustable radial arm. The other has a pen that can go forward or back in a straight line and can be turned to face different directions. I was thinking the latter - when quite clearly [AO] means the former, sorry.
Jinbish, Jun 18 2003
  

       HB is going Etch-A-Sketch crazy...
-alx, Jun 18 2003
  

       bris: I'd've thought the other idea, a regular Etch-A-Sketch with a pen-down option, would have been better for mazes...? Doh! Just twigged - you mean circular mazes - I was thinking of square ones.
jinbish, um, yeah, so did I.
DrCurry, Jun 18 2003
  

       Wedge-a-Skedge.
jutta, Jun 18 2003
  

       shmegma-wretch
nratzan, Jun 18 2003
  

       I read it as "Retch-a-Sketch", and that made me sick.
blissmiss, Jun 18 2003
  

       And they deleted my Halfbakery Buzzwords idea, it would be going crazy on Etch-a-sketch!!
PiledHigherandDeeper, Jun 19 2003
  

       Ooooh Your mechinism is much more simple than what I had in mind - it deserves a bun in and of itself.
Worldgineer, Jun 19 2003
  

       That is brilliant, Mr. DeGroof. It would be more fun to play with if each knob directly controlled one disk, especially if you did not initially know how it worked.
AO, Jun 19 2003
  

       I thought about this last night and decided that the easiest way, in my opinion, is to run the stylus on a trammel across the glass to draw along the theta and rotate the glass itself to draw along the radial (do I have my axes names mixed up here?).   

       With this method the stylus can draw all the way to the center and, even, through the center.   

       I did an illustration of my shot at it. (link)
bristolz, Jun 19 2003
  

       I can envision a fairly simple mechanical solution that would permit the trammel to be rotated to control theta by one knob while still being able to cause the stylus to traverse its length, controlling r, via a separate knob.   

       I think this could work, +
half, Jun 19 2003
  

       The thing I coudn't get around was how to prevent the rotation from interfering with the other axis. Having the stylus drift from unwanted influence from the other axis would be very annoying and probably hard to manually compensate for while drawing. There seemed no reliable way to separate the two until I realized that the glass itself could be the vehicle for the other axis and that the two would be completely isolated.   

       In the drawing I "gear up" the drawing surface glass rotation so that the rate of line drawing is about the same for either axis.
bristolz, Jun 19 2003
  

       [bz] I wish I could give your illustration a bun.   

       So a bluetooth controlled stylus controlled by piezoelectric knobs would be considered more complex, right?
Worldgineer, Jun 19 2003
  

       That’s a very nice illustration, bris.   

       I was thinking that the scraper would be pulled along the radial arm by a string that ran up through the central axis, then over a pulley and along the arm. There would be a pivot at the attachment point to let it untwist. The string would pull the scraper toward the center and a rubber band would maintain tension and pull it away from the center. At the pivot point the arm would be hook-shaped to allow the scraper to slide all the way to the center.   

       See my lame-o illustration.
AO, Jun 19 2003
  

       Thank you for the compliments.   

       Nice, [AO]. I see how you sidestep axis control cross contamination but think that relying on elastic to draw the stylus back is not as good as positively controlling both directions. For one thing, you'd have to build a lot of drag into the system to prevent stylus (scraper) creep and, also, the control knob would rotate more easily one direction that the other.
bristolz, Jun 19 2003
  

       The elastic could be replaced by a string that is also routed through the axis and to the drive wheel. (Not really a second string, but part of a loop.) But, I’m not sure that there would be a way to prevent the two strings from getting twisted around each other.
AO, Jun 19 2003
  

       Lets re-invent the wheel, here, more or less literally. Instead of adding the addtional pulleys and control knobs for the R-theta movement, The etch-a-ray, or whatever you would most like to call it, could sit in housing which allows the screen to be rotated clockwise and counterclockwise. Better yet, is to have the frame stationary along with a slip-free base and to have a thumb dial located in the frame's center front edge for rotating the mechanical unit within the frame itself for the same result. I believe this will produce the perfect ray at any location everytime while keeping the overall design simple, unless I have overlooked a fundamental element. An Etch-a-sketch version like this would best be featured with a circular screen and housing alike. By rotating the mechanicla unit via a thumb dial, you will also retain the ability to synchronize your dialing and turning functions, if you feel so inclined to do so; something I'm sure we all recall with nostalgia these days despite our frustration with it as children.   

       [bristolz], your illustrations, and this one in particular, are indeed fascinating. What software do you use?
Tiger Lily, Jun 19 2003
  

       3dsMax5 for 3D and markers on paper for the other stuff.
bristolz, Jun 19 2003
  

       Kids all over the world have been trying to dra circles on an etch a sketch. with the Spiro-Sketch, they will be trying not to draw circles!   

       Brilliant...
dbsousa, Jun 20 2003
  

       As a related idea, how about designing a "turtle graphics" etch-a-sketch, where one knob sets the angle at which the other knob will move the pointer (so if I turn the first knob to 3 o'clock, the other knob will move the pointer left and right; if I turn the first knob to 1:30, the other knob will move the pointer at a 45-degree angle, etc. I'd expect the mechanics to be a little tricky, but not totally unreasonable.
supercat, Jun 20 2003
  

       If you're going to allow the display surface to turn, why not simply have a third knob to turn a circular display on a (slightly modified) regular X-Y etch-a-sketch. Then you can draw in polar or rectangular coordinates.   

       Ideally you'd like to manipulate the center coordinate of the polar axes so you could draw circles anywhere, but I can't think of a straightforward way to do that.
dweeb, Jun 20 2003
  

       I think I got it (or somone already said it that I didnt catch),. How about a circular etch a scetch with the machanics of a regular etch a scetch, so you can still draw boxes, and a third nob for rotaiting the screen, for making circles? That way you can make circles and boxes.
DarkRanger, Jun 21 2003
  

       That's what [dweeb] suggested, above, and I think it's the best idea of the bunch unless, of course, someone can figure out how to draw circles anywhere on the screen, too.
bristolz, Jun 21 2003
  

       That would complicate things quite a bit.   

       Tangentially, that makes me wonder about an arrangement that would allow interconnection of the 2 knobs of a traditional Etch-A-Sketch by a series of changeable gears, cams, elliptical gears, connecting rods, etc. to permit drawing patterns by turning just one knob. Rather like a very complicated spirograph. I'd play with it.
half, Jun 21 2003
  

       Back to the idea: here's a rough approximation of what I was thinking when I said I thought it could work. (link)   

       In this design, the drag of the stylus moving in the r axis would try to translate to the theta axis. The use of worm gears would minimize that interference. ('nother link)
half, Jun 21 2003
  

       [half]: your design makes a lot of sense. [Steve]: I'm having some trouble "seeing" your design.
bristolz, Jun 21 2003
  

       I think SD is thinking along the same lines that I was when considering your challenge. I was thinking that you could somehow mount my r-theta mechanism with it's own stylus in place of the stylus on the traditional x-y version. Then drive the r-theta mechanism with flexible shafts. Messy, but I think it would actually have a chance of working.   

       Having the stylus offset from the intersection of the x,y mechanisms (by distance r) would be problematic though. You could easily run the stylus off the glass or not be able to reach edge of the glass.   

       I think I'll stick with the r-theta.
half, Jun 21 2003
  

       I think I got it again (I think somebody already said this idea??). The real problem is trying to find a way to make circles anywhere of any size on the screen. It would be 4 nobs, 2 like the regular etch a sketch for the x and y axis, 1 for rotating the screen, and the 4th for extending and arm attached to the pin (the writting thing). The x and y axis nobs would move the base of the pin, the point at which the pin will spin on for creating circles. Now, we got movement anywhere for the circles, now we need any size. For this, the 4th nob will extend the extractable arm for the size of the circle, now just rotate the screen and you have your circle, anywhere of anysize, with the ability to draw boxes as well. (Yes I know nob is spelled knob)
DarkRanger, Jun 22 2003
  

       Now that we’ve solved the problem of drawing perfect circles, I think we need to tackle the perfect ellipse. Hence, I propose the following: six knobs – four for the X and Y coordinates of both foci, one for the aspect ratio, and one for the angle.   

       Also, there should be a gear-shift lever to switch into modes for drawing ellipses, parabolas and hyperbolas. It would be called the conic-sec-a-sketch.
AO, Jun 23 2003
  

       You going for a purely mechanical version of AutoCAD next?   

       (link) non-circular gears: to elaborate a little on my earlier tangential annotation which may now be a bit less tangential.
half, Jun 23 2003
  

       CADaBabbage
bristolz, Jun 23 2003
  

       An engineous name if I've ever heard one.
half, Jun 23 2003
  

       I keep reading that as “BAD Cabbage”, which makes me want to retch-a-sketch.
AO, Jun 23 2003
  

       "CADaBabbage"
And when the inevitable service releases are issued, they would be delivered cheaply by using child labor which would result in said children becoming known as CadABabbage Patch Kids.
  

       Or not.
half, Jun 23 2003
  

       it seems that this idea will remain gloriously unbaked for a while, a croissant from me if that's some consolation..   

       Dear Neil:   

       Thank you for inquiring. At this time the Ohio Art Company does not have any plans to pursue the R-Theta etch-a-sketch device.   

       Kind Regards, Victoria Spencer, Executive Secretary, R&D
neilp, Jun 28 2003
  

       Oh, halfbakery... for the umpteenth time, I have an idea, google it, and find myself taken straight back to the bakery. However, I already went and made an interactive illustration for it, so I'll link to it here. I wonder if [AO] will ever see it.
mitxela, Nov 20 2015
  

       How about an Etch-a-Sketch with three knobs, two of which control the coordinates, and the third of which lets you choose between Cartesian, polar, hyperbolic, etc coordinates?   

       Thinking further - how about an Etch-a-Sketch in a more abstract coordinate system? Let's say twelve knobs - four of them control the coordinates and the other eight define a matrix via which the coordinates are mapped into two-dimensional space.
Wrongfellow, Nov 21 2015
  
      
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