Hi, this is Wayne again with a topic “MAKE : Inventions “The Etch A Sketch””.
This january andre cassagne passed away. He was a french inventor kite designer and toy maker. His name isn’t a household word, but one of his creations is known around the world and is as popular today as it was when it was invented more than 50 years ago. In the 1950s, cassania was replacing a light switch in a factory that used fine powdered metals. The story goes that he used a pencil to write on a translucent decal covered in aluminum powder. He noticed that the pencil displaced the powder and revealed the writing on the back of the decal intrigued with the idea he worked in his spare time to come up with the lecran magic or magic screen. It was a pad you could draw in forever, never running out of ink or paper and in 1959 he took it to the nuremberg toy fair, where it was greeted with little immediate interest, but all was not lost. Eventually, his invention came to the attention of the ohio art company. They called it the etch-a-sketch and revealed it to the world the summer of 1960., while other drawing toys have come and gone.
The etch-a-sketch has remained popular for more than 50 years. Here is the original patent drawing for the tracing device, which looks nearly identical to today’s iconic red box. Turning a knob moves, a cable through a series of pulleys, so that two parallel cables move in the same direction. When you attach a crossbar to these cables, it will move back and forth in one dimension mounting two sets of pulleys at right angles to each other, creates an area where the crossbars can intersect anywhere by adding a stylus that slides on both crossbars. You can draw by moving the cables. This is a pretty standard way to move things in two dimensions and you can find similar arrangements in some plotters.
Cnc mills and 3d printers the real magic comes from what covers the inside of the screen. According to the patent aluminum powder or other pole, virulent material is added along with glass beads. These help spread the powder evenly when you turn it upside down and shake it with that in mind, let’s try to make one first, i sketch a design to rough in the position of all the parts. Patents really list dimensions, so i’m basing it around a salvaged piece of glass. Then i build a rough frame to hold the pulleys and i add a couple of wings to the bottom corners to hold the control knobs after the glue is dried. I drill axle holes for all the pulleys.
The eight central pulleys float spinning freely on their axles, while the control pulleys are connected to their axles, which will be turned by knobs. For these i use a bit of copper tubing as a bushing to reinforce the wood with the axles in place. It’S time to string it up. I use fine stranded, steel, beading wire as the cabling, because it’s strong, flexible and won’t stretch to help transmit the power from the knobs.
I wrap it around the control pulley several times to keep it from slipping. Now we add the stylus. It has two holes big enough to slide freely over the crossbars they’re right angles to each other, but don’t intersect. Next, we need a point that touches the glass to scrape off the aluminum powder, but won’t wear down or damage the glass.
I adapt a nylon screw that i sharpened to a point. I thread two brass tubes through the stylus and attach them to the wires with the mechanical parts done it’s time to make the case. The top of the case mostly holds a pane of glass and encloses. The mechanism to recreate this, i essentially make a deep picture frame from custom routed molding the patent calls for a fluid tight case.
This is important because the aluminum powder we’re using is incredibly fine. It can escape from the smallest hole after sealing the wood with polyurethane sealant. I cut a gasket to keep the powder from escaping around the back panel. I drill holes for the control knobs and then attach bushings and more custom gaskets around the holes.
After playing around with aluminum powder, i bought from a chemistry supply house. I realized it doesn’t stick to glass very well. Looking back to the patent, it merely says the pulverian material is adapted to adhere to the glass. It doesn’t say how so i experimented trying different materials, combinations amounts and techniques. I looked at other patents for inside and examined aluminum grains under a microscope. It looks like the commercial powders i bought were completely oxidized, essentially aluminum rust, and it takes an industrial process to turn them back into real aluminum.
The best alternative i found is from handmade aluminum filings about a quarter millimeter in size. It doesn’t stick near as well as the original toy, but at this point i’ll take what i can get after epoxying the glass in place. I added my powder, then it’s time to seal, it up, add the knobs and see if it works and now the moment of truth.
It doesn’t cover the glass as well as i would have hoped, but you can draw on it and when you turn it upside down and shake it, it does erase andre cassane’s magic screen. Will mechanically simple does have magic in it? He followed his curiosity and created something that is not only truly unique but has stood the test of time and created treasured memories for generations. I’M steve hoefer for make inventions .