Thetruthaboutcars.com Celebrates Spring Equinox
March 20, 2010. Spring Equinox. Spring has sprung. How could Thetruthaboutcars.com celebrate the first day of spring 2010 better than with a concise pictorial history of springs?
Apart from tires and seats (which typically have their own springs, the seats, not the tires) the car’s suspension is what protects your (personal) rear end and spine from the rigors of the road. Apart from shock absorbers (which we’ll celebrate the minute we’ll find an appropriate season for shock absorbers), springs are an essential ingredient of your suspension. Springs come in three basic flavors.
The common leaf spring has been in use in cars and trucks into the mid eighties. From then on, they became an object of derision, except on heavy duty trucks, which use them to this day. The leaf spring was also called “carriage spring,” because it is as old as the horse-drawn carriage. Hence its humorous effect.
To the untrained, a coil spring seems to be the most logical choice. It’s inbred: Most of us have been created with some type of coil spring involved. (See picture left.) To remove or to install a coil spring, you need to be able to operate a coil spring compressor tool. If you don’t know how to operate it, this can have similar effects as a coiled snake. The coil spring is sometimes used in combination with the leaf spring. Or with a shock absorber inside. We’ll get to that later. There are many other coil springs in your car, from valve springs to the spring that pulls your accelerator back – or not.
Then there’s the torsion spring, that strange contraption I learned to hate when I was a young copywriter and they threw me on the Volkswagen account. Die Drehstabfeder or Der Torsionsstab is (so it has been drummed into me) basically a rod that twists along its length. It was popular in the VW Beetle, in the Porsche 356, in the early Barockengel BMW 501/502, in early Porsche 911s, and several Chrysler and GM cars. To this day, I don’t understand why one would twist a poor old rod if there are springs. To this day, they use torsion bars.
From here on, we get into more complex matters, such as coil-over-oil, (or possibly coil-over-gas, but it doesn’t rhyme). It is a combination of a shock absorber and a spring, also known as a McPherson strut. When I was a young copywriter in 1973, this was a big deal. Later, they confused me completely by combining a McPherson strut with a double wishbone suspension. At that point, I turned into a Creative Director and was above such minutiae.
This concludes our TTACesque celebration of the Spring Equinox. May the sun shine bright on you, don’t forget to change the winter tires, and give your car a good rinse to get the salt out.
Bertel Schmitt comes back to journalism after taking a 35 year break in advertising and marketing. He ran and owned advertising agencies in Duesseldorf, Germany, and New York City. Volkswagen A.G. was Bertel's most important corporate account. Schmitt's advertising and marketing career touched many corners of the industry with a special focus on automotive products and services. Since 2004, he lives in Japan and China with his wife <a href="http://www.tomokoandbertel.com"> Tomoko </a>. Bertel Schmitt is a founding board member of the <a href="http://www.offshoresuperseries.com"> Offshore Super Series </a>, an American offshore powerboat racing organization. He is co-owner of the racing team Typhoon.
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Chryslers had torsion quiet ride: http://wheels.blogs.nytimes.com/2010/03/20/classic-ad-chrysler-new-yorker/?ref=automobiles which gave them superior handling from 1957 on until they were dropped. I remember my 1965 New Yorker could have its front raised or lowered by adjusting them. Chrysler later came up with "transverse" torsion bars, which were supposed to retain the torsion bar handling advantage while providing a softer ride. I don't think that worked out so well. My 1984 Honda CR-X had torsion bars up front. None of its competition handled as well.
The other benefit of torsion bars that enables softer ride and superior handling is that the entire mass of the spring (the bar) is sprung mass (at least as executed by Chrysler in the 60s and more recently in their IFS 4x4 pickups pre-2006). In both leaf and coil springs a portion, typically ~half, of the spring's mass must be considered unsprung. Belleville springs (or Belleville washers) are also used in F1 racing per Wiki. The Wiki page has a good technical writeup about how they're useful. I've also seen them used as Wiki describes in an anti-sway bar's end links to tune the spring rate along with urethane isolators. Elastomeric bumpers or snubbers are also springs. They're often used to soften the blow of a bottoming suspension or to prevent catastropic crash at the end of a shock absorber's travel, or just to prevent structural transmission of vibration (tuned as a sort of spring-mass damper with additional visco-elastic damping). A coil-over shock isn't necessarily a "strut." Struts typically replace both the upright/knuckle and the upper control arm in an independent suspension. A coil-over shock merely runs the coil spring and shock absorber concentrically, often in conjunction with the typical members of SLA suspension (double wishbone), or even with leaf springs.