LEATHER FETISH PART2:SHOCKS

New Straits Times - - Cars Bikes & Trucks -

EV­ERY time we en­joy our favourite back roads in our favourite car, we have to thank one of the key tech­nolo­gies that made high-speed mod­ern-day mo­tor­ing pos­si­ble and safe - the dampers or more com­monly known as shock ab­sorbers.

As the name sug­gests, this part puts a damper on the os­cil­la­tion of the springs, oth­er­wise cars would not stop bounc­ing from de­par­ture to ar­rival.

To­day’s dampers are tubu­lar types. They usu­ally con­sist of a shaft that slides in­side an oil-filled tube. In most cars, the dampers sit in­side the coil spring or next to the leaf spring.

Within that damper is a se­ries of me­tal wash­ers with holes in them.

The num­ber of holes, their sizes and po­si­tions are de­ter­mined by the spec­i­fi­ca­tions set by the man­u­fac­turer, and are selected to achieve cer­tain char­ac­ter­is­tics.

A damper that acts quickly on com­pres­sion will have a dif­fer­ent set of wash­ers com­pared to one that is de­signed to work more on the re­bound.

There are dampers that re­act dif­fer­ently to wheel move­ment, de­pend­ing on the speed of move­ment, while oth­ers may main­tain a con­stant re­sis­tance level ei­ther way.

At the end of the day, the damper has to rein in the spring os­cil­la­tion so that the car ab­sorbs road im­per­fec­tions while main­tain­ing com­po­sure and con­sis­tent tyre con­tact with the tar­mac.

When the car was be­ing born, there were those who be­lieved that high­speed may be detri­men­tal to health, not in the sense that it could re­sult in FailArmy videos on Youtube, but rather that speed it­self could in­duce blind­ness or cause men­tal dis­rup­tion.

In the be­gin­ning, cars were not al­lowed to ex­ceed 15km per hour and had to have a flag bearer run­ning in front of it.

As you can imag­ine, Messrs Sachs or Bil­stein were not par­tic­u­larly wor­ried about the per­for­mance of their dampers. In fact, the top damper brands at that time were Hart­fords, Lu­vax, Gir­ling and Armstrong.

Shock ab­sorbers or dampers that were used in the early days of mo­tor­ing had no re­sem­blance to the slid­ing tubu­lar vari­ant that has be­come ubiq­ui­tous to­day.

While the rest of the car may be do­ing its best to over­come en­ergy wastage or re­sis­tance, the damper re­lies on en­tropy, fric­tion and dis­si­pa­tion of en­ergy to rob the spring some of its po­ten­tial en­ergy.

If the damper doesn’t rob the spring of po­ten­tial en­ergy, then the spring will os­cil­late a few hun­dred times be­fore dis­si­pat­ing the en­ergy.

An­dre Hart­ford came up with the idea of us­ing fric­tion plates that could be com­pressed to ad­just the damp­ing force. In the be­gin­ning, they used treated leather as the fric­tion plate and later, wood.

The main prob­lem with leather was a phe­nom­e­non called stic­tion, where it took a con­sid­er­able amount of force to ‘un­stick’ the leather, which meant that the dampers would be very stiff in the ini­tial move­ment un­til the stic­tion is over­come.

Wood has a more con­trol­lable fric­tion qual­ity but, as you can imag­ine, they were about as durable as wooden den­tures.

Most cars used this type of dampers un­til World War 2. A few com­pa­nies, like Bu­gatti, de­signed their own dampers or they used Ge­orges de Ram’s de­sign which in­volved fric­tion plates. But this time, the de­sign used more than one and they were ar­ranged in­side a cylin­der.

The de­sign was usu­ally quite heavy and the en­tire as­sem­bly was mounted on the chas­sis and acted on by the wheels through a lever sys­tem.

Since WW2, sin­gle tube and dual tube dampers have dom­i­nated the mar­ket with their sim­plic­ity and gen­eral abil­ity to con­trol sus­pen­sion move­ment at low and medium speed. It was also suitable for use with coil springs.

Only cars that use air sus­pen­sion or elec­tron­i­cally-con­trolled sus­pen­sion sys­tems do not need dampers.

While fric­tion plate dampers seem crude, they have the ben­e­fit of be­ing easy to fix. If you have worn-out fric­tion pads, all you have to do is loosen a few nuts and bolts, find some leather and, voila!, you have a new set of dampers.

I like the look of those fric­tion dampers. They are def­i­nitely more hip­ster and steam­punk than our cur­rent tubu­lar shock ab­sorbers.

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