Saturday, December 27, 2014

Analysis Is In

One more (final) look at the failed bearing in my Honda Helix transmission and then from now on, we'll just ride the darn thing. 

Of course I shared my aborted ride story with as many of my friends as possible, hoping that someone might shed more light on what happened or why.  Jenny took a special interest since she's spent many years learning about and understanding metallurgy though she was quick to admit that she's no real specific experience with the study of bearings.  What she did know, explored and came to learn will be more than sufficient for my needs.

I sent my broken down pieces along with her a few weeks ago; she very curious to learn more about what might show up upon taking a closer look at the evidence.  Today the package arrived and with it, an explanation of what she found.

"There's good news and bad news" she shared.  "The good news is that there wasn't a lack of lubrication, something you already knew."

That part I was very confident of.

"Bad news is that it looks like overloading may have been the main culprit......though maybe..." 

This was something I was more than willing to accept since my yellow scooter has seen a fair number of miles with a pillion passenger or loaded with camping gear and even when it wasn't carrying an additional passenger, it hasn't been babied.  While it's possible that the hard jolt that daughter Lauren and I felt that ill-fated day had something to do with this major failure, the widespread and relatively deep spalling would lead me to believe that something was going wrong long before that day back in July.

Jenny first sectioned the inner race and then potted the 2 samples, facing the top surface with a fine grinding process to make the exposed metal surface uniform and very consistently flat.

A closeup of the spalling......any resulting chunks flying off of this surface would need far more than good lubrication to prevent damage.

Where the thermoset plastic potting meets the bearing material in the curved part of the inner bearing race.  Fragments flaking and ready to flake off.

Higher magnification.....

Jenny attempted to find out more about the actual material composition of the bearing material but found it difficult to learn very much since the various bearing manufacturers appear to keep that information proprietary.

Something that really surprised her and me as well with my very limited experience of looking at samples much like these is that the granular material of the steel itself has more voids and what appear to be foreign materials than what we've seen before.  A very uniform granular structure is what we'd have expected.  You can see clearly see the 'other' specs above and in the higher mag images below.

So, my scooter's problem may have resulted from both a batch of bearing steel that was less than ideal as well as too many miles with too big of load.  I'm betting that the next 25K miles with more or less equivalent use will not have the same result on the new round part.

Many thanks to Jenny for pursuing this, her time and effort it in explaining this to me so that I could understand what she discovered.


  1. Interesting… Makes you wonder if it's a fluke or just poor quality material...

  2. It would be interesting to compare the new bearing once it has 25K or thereabouts on it with these results.

    1. It really would be interesting to see. Almost but not quite curious enough to open up another new bearing and see how it might compare right now. Hopefully there won't be any more first hand experience with bearing failure.

      P.S. We finally had a chance for some driveway snow removal yesterday, first time in weeks! Two more intervals like that and we'll be worried more about the daffodils!

  3. Wow, how very cool to be able to put it under that kind of magnification.

    1. As you can imagine, there are some amazing tools for failure analysis. The high mag can identify all sorts of things and that's just one tool.

  4. Wow Coop - does it make it any better knowing why? I think I might begin to worry obsessively about inferior materials and products (yikes, like we don't already have enough to worry about while riding!) Then on the other hand the science of it all is really interesting - is that the satisfaction that brought the cat back?

  5. Karen, I was pretty satisfied just getting the scooter back together for more 'trouble-free' miles. Still, I was curious enough to show the shrapnel to the coffee drinkers, wondering what sorts of input I'd get. The group is varied with years and years of skills/experience in all sorts of things. I had my notions but was open to anything anyone else could add. When Jenny said..."let me see" I knew that she was very capable of bird-dogging the problem and never expected her to take off with it. I was looking forward to whatever it might be that she'd come back with.

    In the end, this was a component on one of mine that I never would have guessed would fail. I'm going to bet that I'll never see anything like this ever again. :)