Precision timepieces operate much like the inner workings for automotive machines. Underneath the back cover lies a series of gears and springs designed to measure the passage of time. We are told how these inner workings are created with such precision that they are able to measure the time accurately over whatever time period that the name brand manufacturer wants to advertise.
Think about these “precision components” within the watch necessary to create this “machine” whose fastest rotational output is one rotation per minute, compared to an automatic transmission that has components that rotate more than seven thousand RPM!
35 years ago, the world of automotive transmissions moved from three speed boxes to four speed transmissions. In the late 90’s, six speed transmissions were introduced into the market offering improvements in fuel economy and shift quality. In the past five years, many automotive OEM’s launched several eight speed designs. Today, nearly every OEM is either launching or developing nine and ten speed transmissions, with patents being applied for eleven speeds.
Drivers of change
The drivers for this progression in development of automotive transmissions is:
drivability, or shift quality
The goal is to make sure the vehicle is in the most optimum gear ratio for whatever speed and acceleration combination the vehicle may be in from zero to whatever the legal speed limit may be in your area. This provides the best fuel economy. The more gear ratios you have available to you; the better chance you have of being in an optimal condition which improves overall efficiency.
From a shift quality point of view, think of it like a staircase. A typical staircase has 11-13 steps in order for a person to comfortably climb. Imagine if you reduced that to six or four steps, each step would be a struggle to walk up making the climb slow and cumbersome. Perhaps you have heard concerns regarding the vehicle “constantly shifting” or driven some of these vehicles with the higher number of speeds. The experience is actually positive in that the shifts are so smooth; you don’t actually feel them.
Competing for space
It is important to note that the vehicles are not becoming any smaller. If anything, the trend is for smaller vehicles for better fuel economy. Obviously, a ten speed transmission had many more components than that of a four or six speed, but all of these parts need to fit within the same size transmission case.
All of the different component groups are therefore fighting for real estate. A typical rear wheel drive transmission is roughly a meter long. In design meetings an entire room full of people may be negotiating over a tenth of a millimeter. This is the average diameter of a human hair. Many of the component tolerances are in the range of a hundredth of a millimeter. We are not only talking about splitting hairs, but we are talking about splitting hairs into ten layers!
It is inspiring to me to think about these new transmissions and what it takes to put together these precision components and rotate them at more than seven thousand times per minute with enough balance that it doesn’t vibrate the driver out of the vehicle. These machines are just as much a piece of art as the “Precision Timepieces” and Parker is proud to be part of this process.
For more information from the Engineered Materials Group, please visit the Parker Engineered Materials Group Landing page.
pplications engineering manager, Automotive.