Author: dnilles71

Barbell Collars

After finalizing my P-I-P hinge program in Grasshopper 3D, I had been looking for good projects to use it on. There never seem to be enough good barbell collars in the gym so I began wondering if I were able to prototype one.

The design for my 3D printed barbell collar is nothing revolutionary. It is essentially the same as other cheap collars.

Generic Barbell Collar
My 3D Printed Collar
Latch View of Generic Collar

Similar to other projects of mine, I aim to capitalize on the advantages of additive manufacturing. Using the same principles as my PIP hinge design, I am able to make the whole assembly from one print; a part count of one. From a manufacturing perspective, minimizing part count is a great way to cut costs of finished goods. My design requires no assembly, just a bit of support removal. 

Getting to this first working prototype wasn’t as simple as it should have been. To start, I wanted to be sure my hinge design on the back of the collar would work. My PIP hinge generator worked very well first try.

From there I had to design the latching mechanism. I using the same tolerances as the hinge for my first print. I ended up with a single complex piece, an offset shaft that kind of reminds me of a crankshaft. The tolerances worked well, but I did the latch incorrectly. It didn’t open fully or easily.

Closed Latch
Open Latch

I put the latch clip on the short piece of the mechanism. I should have put it on the large piece for better mechanical advantage. The latch action is incorrect and will not work.

After fixing I had a working prototype:

Möbius Strip

One of my favorite theoretical shapes is the möbius strip. Named after August Ferdinand Möbius who, concurrently with Johann Benedict Listing, discovered the shape.

A continuous closed surface with only one side; formed from a rectangular strip by rotating one end 180 degrees and joining it with the other end.

Princeton University

I really like mobius strips due to their simplicity. The geometry can be pretty quickly created in Grasshopper, within Rhino 3D. I wrote a script that allows me to get a slicable .stl file in minutes.

I have 3D printed a couple of mobius strips. Below is the largest.

For college I made a mobius fidget spinner, as an exercise to use the 3D printers. We had to create a spinner using the three nuts seen inset below.

There is an unintended feature of this fidget spinner. The geometry naturally causes a really cool optical illusion. The edge rolls over in only one direction.

Grasshopper Definition

I created a Grasshopper 3D definition to produce 3D models of mobius strips. I can control by the selections below, outer radius, inner radius, thickness, and rotations. There are a few more variables that are buried in the code.

This seems to me like a great introduction to Grasshopper. My script works as follows:

Step 1

The first step is to define the overall size of the calculated Mobius strip. Here we define 3 circles, all directly on the XZ plane.

Step 2

Here is where we can set the number of rotations the strip will do.

University of Virginia Architecture

Finding interesting Grasshopper definitions is always a treat. The University of Virginia Architecture program has an awesome website sharing many definitions.

Other Examples

This guide is far easier than mine.