Swish, swish, swish
Evan Zabawski | TLT From the Editor September 2013
Another example of how proper lubrication leads to better performance.
There exists one lubricant that even ardent lubrication engineers overlook when maintaining their vehicle.
NEARLY ALL DRIVERS remember to change their engine oil, especially when many of today’s vehicles are equipped with dashboard reminders. Fewer drivers pay attention to their transmission fluid and power steering fluid, unless they notice a performance issue. Many drivers who prefer manual transmissions neglect the clutch fluid. However, in my humble opinion, there exists one lubricant that even ardent lubrication engineers overlook when maintaining their vehicle.
I speak of windshield wiper lubricant. No, I am serious. This isn’t among those bogus products like muffler bearings or headlight fluid that form shopping lists for naïve new hires in parts departments. This product truly exists and is even factory-applied on OEM and aftermarket wiper blades to overcome significant friction.
The coefficient of friction between dry rubber and glass is actually higher than that of dry rubber on asphalt. Appreciating the horrible noise and ugly skid marks a sliding tire produces, it’s a wonder wipers even work when they’re dry. Luckily for the wiper blade, it is mostly employed when the glass is wet, but in doing its job it is removing water, a form of lubrication. To supplement this loss, many blades are coated with solid lubricants like graphite, silicone or Teflon®.
It seems the latter lubricant is mostly utilized in aftermarket products, and I suspect that has more to do with the marketability of the brand name. Would you be as drawn to a blade marked “graphite infused to promote quiet, smooth operation and longer life”?
Silicone blades are touted as being superior to regular blades, but given their higher cost, increased labor at installation (windshield must be pre-treated), and shorter life, most drivers pass on them. Graphite is sufficient and can be found on the least expensive replacement blades and most OEM blades.
Graphite is ideally suited for wiper blades. It has a chemical structure made up of planes of polycyclic carbon atoms oriented hexagonally. The distance between carbon atoms is longer between planes which lends itself to a weaker bond. Contact with water vapor weakens this bond to a lower level of energy than the adhesion energy between the graphite and the blade, causing it to slip and thus reduce friction.
Higher carbon content coupled with higher graphitization increases the lubricity. My November 2011 column spoke of another automotive lubricant application for graphite, however graphite’s lubricity was known thousands of years earlier and is partly evidenced from its name which was given by Abraham Gottlob Werner in 1789. Graphite comes from the Ancient Greek graph—meaning “to draw/write” for its use in pencils.
Graphite is soft enough to prevent scratching glass, metal and even paper, yet self-lubricates to glide smoothly; when wipers moves smoothly they clear the windshield effectively. Graphite’s one major drawback is witnessed when using a graphite pencil — it rubs off easily and therefore wears out. Often enough, the blade’s rubber substrate also has degraded and necessitates replacement, thereby negating a need for relubrication.
The next time you turn on your wipers and they chatter across the windshield, you will know it is due to insufficient lubrication and you may want to consider replacement. Remember that according to the children’s song
The Wheels on the Bus, it’s the people on the bus who go chatter, chatter, chatter. The wipers are supposed to go swish, swish, swish.
Evan Zabawski, CLS, is a reliability specialist in Calgary, Alberta, Canada. You can reach him at evan.zabawski@gmail.com.