The model for this concept will consist of both a U-Joint, or universal joint, and a Double Cardan joint. Both shafts will be geared together so that as one is turned via a hand-crank, the other turns at the same speed. The output of both shafts will have indicators to make it clearly visible that they are not always going the same speed. The Double Cardan joint output shaft will be rotating at the same speed as the input speed while the U-Joint output shaft will be moving at a varying speed.

The double-cardan joint is located at the top of the assembly. The input shaft of the Double Cardan joint is geared to the U-Joint input shaft via an idler gear. The output shafts have arrow pin indicators much like the initial design to display that the output and input shafts of the Double Cardan joint have the same angular velocities while the U-Joint shafts have varying velocity with respect to one another.

The different components of the device are provided in the BOM table

The Lesson Plan for the Double Cardan Joint is attached to this page for the Instructors who wish to teach students about this device.

Post Processing note: If you are printing with an FDM printer you should expect small ridges on parts where the extruder last touches the piece. Carefully inspect each piece after they are printed for these small imperfections as they will hinder the operation of your device.

Step 1: Print CV Joint Parts

Download the 15 .stl files and upload them to your 3D printer's system. The quality of each part will increase depending on the orientation of the part on the print tray. Print each respective part based on the orientations shown in the images provided.

Step 2: Post Process Individual Parts

Based on the brand and quality of your 3D printer, the tolerances of your parts will vary so your parts may not need any refinements, or they may need a lot. The steps we have provided are the techniques we found were useful for making the device run as smoothly as possible. The following tools were used to refine the parts; file (varying sizes), fine sandpaper, Dental picks.

For CV Joint:
Ensure to sand down any shafts that will be rotating within the assembly this includes sanding down the shafts of the Double Cardan shaft, U Joint Shaft, Double Cardan gear shaft, Pivot Pins and U Joint push pins.
Ensure to bore/file out any thru holes on the device to ensure smooth rotation for any components.

Step 3: Assembling the Device

Now that all the parts are refined they are ready to be assembled to create the operational CV Joint.

Insert the U Joint Shaft-Gear into the Main base
Insert the Arrow Pin into the U Joint Shaft-Gear
Insert the 1.25 pitch gear onto the embedded shaft in the main base
Insert the Arrow Pin into the embedded shaft
Insert the Double Cardan Shaft Input into the Main base
Insert the Arrow Pin into the Double Cardan Shaft Input
Insert the Crank handle over the Double Cardan Shaft Input
Insert the U Joint Into the U Joint Shaft
Insert the two U Joint push pins securing the U Joint in the 1st axis
Insert the gear-less U Joint Shaft over the U Joint
Insert the two U Joint push pins securing the U Joint in the second axis
Insert the U Joint into the Double Cardan Shaft
Insert the two U Joint push pins securing the U Joint in the 1st axis
Insert the Double Cardan Joint over the U Joint
Insert the two U Joint push pins securing the Double Cardan Joint to the U Joint
Repeat steps 10-11 to secure the Double Cardan shaft
Insert the Pivot Base over the shafts of the U Joint shaft and the Double Cardan shaft simultaneously
Insert the Arrow Pins into the U Joint and Double Cardan shafts
Insert the Pivot Pin into the Pivot Base
Insert the Angle Locator pin into the Pivot Base