The mechanical movement I chose, which can be found here, uses the constant rotation of the input gear to drive the output gear at variable speeds. Through one rotation of the input gear, the output gear turns at 3 different speeds.
This happens because the radius of the gear is different, so the gear ratio (and thus the speed) is different at the 3 different points.
To model it in Adobe Illustrator (AI), I first took a screenshot of the gears from the 507 Mechanical Movements website. After opening the photo in AI, the first step was to perform an Image Trace. Simply using the default trace settings produced a strange result:
So I played around with the different settings, finally settling on using the “3 Colors” option. I then Expanded and Ungrouped the photo. This enabled me to do more complex edits.
Because I want to laser cut only the outside profiles of the gears, I decided it would be simplest to remove the inner divisions. To do this, I used the Shape Builder Tool to make all of the parts of the gear into a single shape profile.
I was careful not to include the innermost circle, because I will need that.
Next, I selected both circles and copied them down lower on the art board by holding the Alt key as I dragged them down. This maintained their spacing from each other, which will be important later.
My subsequent task was separating the two gears from one another. The first time I did this, the lines got messed up a bit where the gears had been touching in the photo, so I spent a while with the Pen and Curvature Tools fixing them up. As I am writing this I am going through the steps all over again, and this time the two gears separated perfectly. I am not sure why they had problems the first time, but the bright side is that I got some practice editing lines.
At this point the gears are pretty much done, but for them to work after they are cut out they will need to be properly spaced from each other and held in place. The two circles that I copied lower on the art board earlier are for this purpose. I drew a large rectangle around them to use as a base plate. I also drew a new circle in the center of all the existing circles using the Alt and Shift keys.
These new circles have a diameter of 1/4 inch, instead of the random original measurement. I then deleted the original circles. The purpose of changing the diameter of the circles is to ensure that I can find an appropriately sized rod to hold the gears and allow their rotation.
The final step was to select everything and change the stroke size to 0.001 inches, and make sure that the objects were all nested appropriately in order to minimize waste. The only thing left to do is cut them out using this file: Harpole HW 2-1efj7x3
In addition to the laser cutter and some material to cut, I will also need 2 short lengths of 1/4″ rod to hold the gears. This could be wooden dowel rod or metal rod, or anything else cylindrical and of the appropriate diameter.
Not having done that yet, my main concerns are as follows:
- The size of the holes might not be correct. I am not sure how wide the kerf of the laser is, or exactly how wide a quarter inch dowel rod is, so minor corrections to the hole diameter might be necessary in order to get the gears to turn freely but securely.
- The screenshot or the Image Trace might not be accurate enough to ensure that the gears interact properly without binding. I might need to adjust the spacing between the two holes in the base plate.
