A functioning model of the internal mechanism of a classic railroad safety light
Skills: CAD, Waterjet, Mill, Lathe, Drill Press, Resin 3D Printing, FDM 3D Printing, Press Fitting, Circuitry
The second project in Mechanical Prototyping was to create some form of "automata" which took input motion and put it through at least one mechanism of our choice. Apart from having a "clock cage" or some form of structure, the only other significant requirement was to use at least one 3D printed part. Eucaboard/wood was provided for this project, although I wasn't especially excited by these materials and thought I would learn more if I fabricated it out of metal. I had just been waterjet trained, so I wanted to gain more experience and practice on the tool as well as the other machine shop tools.
I started the project by making several very crude geometric models in CAD to gain a better understanding of how Gyralights work. I based these on videos I found online, the original patents, and educated guesses. Once I understood how it needed to move, I created a new CAD project for my final design. I spent a lot of time in the software optimizing the geometry to find the lengths and offsets needed to give the light the correct circular motion.
I designed my main components to be cut on the waterjet out of 1/4 inch aluminum plate. All holes were undersized and then drilled and tapped to size. This was done to avoid the waterjet's V shaped kerf on important mounting surfaces. I found a couple of bushing and bearing blocks which I decided to use for this project. All of my ball joints and my U-joint were resin 3D printed. I connected the two primary plates forming the chassis of the Gyralight using a threaded rod with aluminum standoffs that I made on the lathe. AEM-7 reverser for scale as I was powdercoating trained the same day.
I decided to press-fit the gears into place while milling a set screw into the top cam. This was done so that I would be able to adjust the offset between the upper and lower cams (the lower one is fixed to the gear). Below is an image of my test fitting the joint after reaming the hole.
One of the challenges in this project was figuring out how to make the correct geometry. There wasn't a ton of information online, so I had to spend a lot of time in CAD testing different motions. In the end this worked out and I was able to fabricate it successfully. Another challenge that I had was the V shaped kerf on the waterjet. I solved this by under sizing all of my holes and then drilling and tapping them out afterwards. A third challenge that I had during this project was how to attach the gears and cams to the shaft. I solved this by press fitting the gear and using a set screw on the cam, which held both in place firmly but allowed for adjustability.
I'm very happy with the end product of this project. I learned a lot through making it all out of aluminum and gained more experience on a lot of machines in the shop. I even learned to use to autofeed and knurling tool to make the knob on the hand crank. I also decided to add a motor as an afternoon project over the weekend. I think that I certainly met my requirements for the project.