Robotics Education & Competition Foundation
Online Challenges

Getting the Shaft


Entry ID #: 4591
Created: Sun, Jan 7, 2018 9:07 PM

Last year, my robot used a reinforced shaft to drive its lift. If I had used a normal shaft, it would have bent under the immense torque produced. However, it is currently impossible to legally connect a reinforced shaft to a potentiometer. My custom VEX part would solve this problem, allowing reinforced shafts to link into normal shafts in an extremely compact and efficient way.

My part would be used to transfer torque between different types of shafts through c-channels. It is shaped similarly to a bearing flat, and functions similarly to one as well. It consists of 3 pieces:


  1. A brace is screwed down to secure the part in place.

  2. A specially-sized nylon spacer is used to alleviate friction and wear between components.

  3. A shaft size transfer piece is inserted into the brace with the nylon spacer between the other 2 parts.


The part would be attached to a c-channel or some other piece of metal. A reinforced shaft would be inserted into the exposed end of the shaft size transfer piece, and a normal shaft would be inserted into the other side. This could be used to link reinforced shafts to potentiometers. Because the distance between a motor and the metal that it's mounted on is so small, motors may even be able to turn reinforced shafts using this piece because short normal shafts have a lower risk of bending.

To design my new part, I used Autodesk Inventor 2018.


  • First, I made the shaft size transfer piece. I sketched a circle with a diameter of 0.5”, which I then extruded to form the cylinder that I would shape into the final piece. Next, I took measurements from both sizes of shafts and made sketches of both types of shaft dimensions. I then extruded both sketches inward slightly less than halfway to form the shaft receptors. I also decreased the diameter of the “normal shaft” side of the piece.

  • Secondly, I designed the brace. I took measurements from a c-channel and used the recorded spacing to sketch a 3x1 plate (including holes). I then removed the center hole and extruded it to the thickness of a c-channel. Next, I sketched a 0.5” (diameter) circle where the center hole used to be and extruded it outward. Then, I measured the diameter of the small end of the shaft size transfer piece and used that measurement to make a hole in the center of the extruded cylinder.

  • Finally, I designed the special spacer. I sketched two holes: one with a diameter of 0.5”, and a smaller one with the same diameter as the small end of the shaft size transfer piece. I then extruded the space between the two circles to form a spacer.


In conclusion, I learned a lot in the process of designing and modeling my custom VEX part. I realized how useful and effective CAD software is when it comes to conceiving ideas. Inventor is extremely useful in the field of competitive robotics because it allows us to try out new ideas without having to spend money on wasted materials. I will also probably consider using it in the future to design models for technological projects such as Virtual Reality helmets and music hardware. For example, I want to be an electronic music composer when I grow up, so I will likely use Inventor to design electronic stage elements and special electronic helmets for performing. Inventor is a very powerful tool that could and should be used by everyone because it makes designing things so much easier.

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