Pitch length

The pitch length of a belt is its circumferential length at the pitch width of the belt. The pitch width of a belt is shown in Figure 8.12, and is provided by manufacturers as standard data. It can be calculated by... 

We show the nominal inside length for various standard sections of belts in Table 8.9. According to the table the nearest standard belt available has a pitch length of 3330 or 3736 mm. For a more closer length of belt, either change the pulley size or select another make of belt or have it made to order. But a length of 3330 seems reasonable, hence it is accepted. 

Note To avoid uneven distribution of load on the belts when more than one belt is used the pitch length of the belts must be identical, subject to permissible tolerances. For this purpose, it is advisable to use all belts of one make only. As standard practice all belts are marked on their surfaces with their length and permissible tolerance for easy identification. 

Table 8.6 Correction factors for belt pitch length...

Transmission of load and suitability of bearings 8/213 Table 8.9 Nominal inside lengths, pitch lengths L for all standard sizes of multiple V-belts... 

The diameters of the inside and outside circles, the pitch length, and the cohesive energy per atom for helices are given in Table 2. The number of pentagons. 

Structure / (nm) r, (nm) Pitch length (nm) Cohesive energy (eV/atom) Spring constant (meV/nni)... 

Because of the versatility of roller chain drives, certain standards have been established. With these standards, interchangeability of chains is possible between one manufacturer and another. As long as chains are identifiable, they can be cross-referenced easily without any serious operational problems arising. Table 58.7 shows the standard roller chain American Standards Association (ASA) number by pitch length for single, double, and triple strand chains. 

The unit cell is orthorhombic, with a = 11.4 A (1.14 nm), b = 9.8 A (980 pm), and c — 33.7 A (3.37 nm). A double helix was proposed in which two identical, left-handed strands are antiparallel to one another. Each strand has four disaccharide residues per pitch length. 

Figure 7.4 Simplified macroscopic model for cholesteric (a) lateral and (b) top view of left-handed superhehx (photographs display a half-pitch length) composed of left-handed helical screws with pitch-to-diameter ratio much smaller than Jt. (Reprinted with permission of John Wiley Sons from Circular Dichroism—Principles and Applications, 2nd ed., N. Berova, K. Nakanishi, R. W. Woody, Eds., Copyright 2000.)...

In particular most of the early studies on CPL were based on the incorporation of a luminescent achiral chromophore in a chiral nematic or cholesteric liquid crystal. Chiral nematic liquid crystals (CNLC) are intrinsically birefringent and exhibit a helical supramo-lecular architecture, which is characterized by the pitch length p (Figure 5.11). 

FIGURE 5.11 Supramolecular, helical architecture and definition of pitch length p of chiral nematic liquid crystals. 

Films of pure CNLCs have a unique transmission behavior as CP light with the same sense of circular polarization as the CNLC is filtered out by reflection, while CP light of the opposite handedness as the CNLC film is transmitted. This selective optical transmission characteristic is referred to as a one-dimensional photonic stop-band or a selective reflection band. The stop-band is centered at a certain wavelength Ac, which is dependent on the pitch length p and the average refractive index n of the CNLC ... 

The thermochromic behaviour of cholesteric LCs results from the fact that the pitch length, and hence the wavelength of the reflected light, is dependent on the temperature. 

Pitch length (or pitch). The number of base pairs per turn of a duplex helix. 

Fig. 3. The structure of the 33-residue region of yeast transcription factor GCN4 is a two-stranded coiled coil, and is viewed here perpendicular to its long axis. The chains each have a heptad substructure and an a-helical conformation. Because GCN4 contains leucine residues in each d position, except for the most C-terminal one, the structure is commonly referred to as a leucine zipper (PDB coordinate reference number 2ZTA). The pitch length of the left-handed coiled coil has an average value of about 20.4 nm (Harbury et al, 1993 Kuhnel et al, 2004).

Fig. 4. The structure of human vasodilator-stimulated phosphoprotein (VASP) is that of a parallel chain, four-stranded coiled-coil (Kuhnel et al., 2004). The sequence contains a pair of 15-residue repeats, resulting in the formation of a right-handed coiled coil with a pitch length of 18.5 nm, a value directly comparable to that seen in left-handed two-stranded coiled coils. Figure courtesy of Sergei Strelkov.

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