Helical Steel Springs

To illustrate how traditional materials such as metals limit the design process, consider a spring. The manufacturing process in metals limits the options available in producing a variety of shapes in this material. As a result, steel springs are produced in basically only three shapes the torsion bar, the helical coil, and the flat-shaped leaf spring. By comparison, TPs and TSs can be easily fabricated into... 

Garter spring a helically coiled spring, typically made of carbon steel or stainless steel wire, formed into a ring, and used in a shaft seal to help maintain contact between the sealing lip and the shaft. 

Many isolators, notably helical coil springs of steel, have straight-line force-deflection curves in their rated load range. For such isolators the slope of the force-deflection curve is equal to the stiffness and the stiffness is simply related to the static deflection s that the isolator experiences due to the load it supports. The static deflection needed to obtain a given transmissibihty may be estimated from... 

Fig. 16.3. Left Schematic picture of the damping system of MimiGRAIL. The suspension consists of seven stages, the upper four made of CuAl followed by three copper masses. The upper CuAl mass is suspended from the top flange of the cryostat by stainless steel cables hanging from helical springs. Mass number 5, the first copper mass, will be cooled by the dilution refrigerator. Right Picture of the four CuAl masses hanging from the top flange (courtesy of Leiden Cryogenics).

The glass helices may be purchased from the Scientific Glass Apparatus Company, Bloomfield, N. J., or the American Instrument Company, Silver Spring, Md. Wire helices are readily made from No. 18 B. and S. gauge copper or Nichrome wire, by simultaneously winding two strands side by side on a j-in. steel mandrel. The spirals are cut into single helices by means of a thin emery wheel and then removed from the mandrel. 

A helical spring of Fig. 5.54 with diameter D — 50 mm and circular section diameter d — 16 mm is made of high strength steel heat treated to 1,400 MPa ultimate strength and fatigue limit oy = 700 MPa. It is subjected to a cyclic load F variable from 500 to 6,000 N. Verify whether it can sustain at least 10 cycles. The generic section is subjected to a torque M, and a transverse component of force F the result in a maximum and minimum shear stress given by... 

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