Recently I was riding my 2005 Harley Davidson Screaming Eagle V-Rod when I heard a rattling that sounded like some part that was loose. I looked, but I couldn't find the culprit. The handle bars, little windshield, highway bars, and fenders all seemed good and tight. I decided it was probably some of the stones that suck into the radiator cowl and rattle around in the sheet metal. I vowed to suck them out with my shop vacuum.
A few days later, I was riding home on my 13-mile commute. I neared my exit on Interstate 83 at rush-hour, and traffic slowed to a stop in my exit lane. When traffic started up, the bike wouldn't move, even though the engine was running fine. The rear wheel was locked up! It didn't take long to see the problem. The lower belt guard had fallen down onto the belt, and it wedged between the main drive belt and the pulley.
Be careful of the tiny screw that holds the lower belt guard on the 2005 Harley Davidson Screaming Eagle V-Rod.
I pulled the bike back a couple of feet and reached down to pull the guard out of its errant location. I walked the bike to the shoulder, strapped the twisted chrome guard onto the seat, and rode the rest of the way home.
This was not a terrible outcome. However, the more I thought about this, the more I was shaken. Moments before my rear wheel locked up, I had been riding almost 60 miles per hour. It would not have been easy to keep the bike from spilling at highway speeds with a locked-up wheel. Furthermore, the following traffic may not have been alert to keep from hitting me during the extreme stop in the middle of rush-hour traffic. If I did spill, I could have easily become a speed bump for an 18 wheeler! This was potentially a very bad situation.
That's why bikes used to use chains. Seriously, though, this column points to a common design flaw found in many products, where there's a single point of failure. And when I say point, I mean it literally, in that it often comes down to a single screw or fastener. Further, when that fastener comes loose (and usually not in the way it was intended; i.e., it comes out violently), you often get a stripped, ripped, or otherwise broken mounting point, which makes repair difficult.
Wow, that's one scary possible outcome from one very small design flaw. Just goes to show how important every component can be and why design for failure mode and effects analysis needs to be a critical part of the development workflow.
From Dell / Intel® New Paradigms in Design Work Scott Hamilton, vertical market strategist for Dell Precision workstations, 5/2/2013 5
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