Thursday, May 24, 2012

The Venerable Hair Clip

How much engineering goes into a design like this?
The purpose of this post is to rebut my video interview that Dora was so nice to post on the Siemens PLM blog.  It will either justify my position, or just show the world how crazy engineers can be.  And I'm a mechanical engineer, not electrical.  We all know their brains are wired wrong.

This image is a representation of the hair clip I was referencing in the video.  I used this as an example because of a funny story I experienced in the presence of my wife.  Engineers, be honest, raise your hands if you ever found yourself in a similar situation.  Comment if you are man enough to share.

My young daughter had left her hair ties on the kitchen counter.  Not overly familiar with female beauty accessories, I picked up one of the hair ties and actuated it, stopping short of actually trying it out myself.  (You can see in the video that I have fairly short hair. The hair ties wouldn't work anyway.  No reason to test my theory to get objective evidence as proof.  Guys, take note.  Putting hair ties in your hair when playing dress up with your daughter is OK.  Putting hair ties in your hair to prove an engineering theory is not.)  Immediately, my mind went to
  • fatigue,
  • strength of the materials,
  • Goodman diagrams,
and it blew up from there:
  • yield strength,
  • material compatibility with hair products like shampoo, conditioner, spray, gel, etc. -- you wouldn't want your hair turning green;
  • raw sheet stock,
  • progressive die design,
  • heat treat,
  • finish treatments, and on and on. 
Organic or non-organic finish?  What if the paint chips off?  Will the metal rust?  Do I need to pre-treat for painted finish?  Spot weld the tip or cold-press a rivet?  How much hand assembly or do I tool up to automate the assembly?  Where are the contact points for painting?  Do I do hand touch-up afterward?  What type of adhesive to use to glue the flower on?  Will the petals break off on first use?  What environments do kids actually get into?  Playground? Classroom?  Nap with the clips on? I think you get the picture.
Imagine the situation. I'm there, standing in the kitchen, frozen in the moment, staring at this hair clip as I flip it open and closed.  How do the forces equalize in two positions to keep it open and closed?  What does the free body diagram for the load conditions look like?   Then my wife walks in. "What are you doing?!"

She looked at me like I was some alien entity.  "It's just a hair clip," she said.  To a "normal" person that may be true, but to an engineer, this is a marvel.  There are so many small nuances that had to be considered in the design, yet to still be able to make them so inexpensively.  This is the world we live in.

To an engineer, the world is not something that is just interacted with and expected to work.  It is something designed, thought of, created, and developed.  Someone had to think of this before it even existed.  There is an existential connection to everything we contact.  Non-engineers can't see it and look at us like we're crazy.  Engineers look at them and wonder how they can't be fascinated by it.

Why should you become an engineer?
Because the world is a beautiful place.  Learn how to shape it, not just use it.


  1. If I had to put on the hair tie to correlate the FEA data, I'd do it. 

  2. This post rings a bit too close to home for me...  It reminds me of a conversation long ago between myself, an old girlfriend, and her daughter, that eventually degraded into them debating whether I should be classified as a 'Dorky Geek' or a 'Geeky Dork'