Sheaf

If it is desired to observe the crystalline form of the osazone, draw up in a glass tube a few drops of the cold filtrate containing the fine crystals, and transfer to a microscope slide. Cover the drops with a slip and examine under the microscope unless the filtrate has been cooled very slowly and thus given moderately-sized crystals, the high power of the microscope will probably be required. Note the fine yellow needles aggregated in the form of sheaves. Compare with Fig. 63(A). 

Osazone formation. Forms an osazone, m.p. 206 (see however footnote, p. 140) this osazone, unlike glucosazone, is soluble in hot water. See p. 139 for preparation. Examine the crystals under the microscope and note the sheaves of plates, not needles (Fig. 63(B),... 

Since it is good practice to maintain a selected inventory of spare parts for drives, economy can be achieved by standardizing conveyor drives throughout the plant. For example, intermediate speed reduction by means of V belts, sheaves or chains, and sprockets can frequently permit using the same speed-reducer size for several drives. Thus, it may be necessary to keep only one repair-stock speed reducer for a number of conveyors. 

The silicon-controlled rectifier with a dc motor has become predominant in adjustable-speed drives for almost all commonly used conveyors when speed adjustment to process conditions is necessary. The low cost of this control device has influenced its use when speed synchronization among conveyors is required. This can also be done, of course, by changing sheave or sprocket ratios. 

Wirbel, m. whirl, vortex, eddy whirlwind whorl spiral vertebra Tech.) spigot, button, collar, swivel, sheave, etc. vertigo intoxication crown (of the head) warbling. Wirbel-. whirl-, vortical vertebral, vertebrate, -bein, n. vertebra, -bewegung, /. vortex motion, eddying. 

A V-belt greatly increases the deliverable torque, since the wedging of the belt in the sheave groove increases the force of contact between the surfaces (N) far above the tension force (P). The driving... 

A fan handling 85°F air is installed hut has insufficient capacity. The unit is v-helt driven, and the available on hand sheaves to place on the unitwill run the speed to 1,108 rpm. Use the same fan wheel. 

This is too hot an installation for V-belt drives. However, they may be used if ventilation is good and perhaps an insulated hot wall is interposed between the sheaves and fan housing. Allowance must be made for belt losses from manufacturers tables and also any other mechanical losses of the driver. If a motor is used, the shaft output should be 5 hp to cover losses and allow for nonoverload. The 0.2 overload at peak conditions does not justify a 7.5 hp motor because expected operations will be at 3.0, and a 5 hp motor can usually be overloaded 10% without difficulty. 

Specify type direct (specify type and make of coupling, keyed or screwed, and whether or not manufacturer is to supply), and single or double-ended spiral threads, supplying details V-belt or flat-belt sheave. 

In addition to the standard types of V belts (see Figure 3-19), many manufacturers make V belts that arc specifically designed to have a higher horsepower capacity. 4 hese V belts are shown and compared to standard V-belt cross-sections. These superpower V belts allow shorter center distances and narrow er sheaves without imposing any extra total bearing stresses. Such belts are able to reduce the drive by 30-. )0% and less for horsepow er capacity. In addition, speeds can be increased up to 6000 ft/ min without dynamic balancing of the sheaves because the sheaves arc smaller. 

Formed-steet, light-duty sheave with integral hub... 

For V-bell applications D and d are sheave pilch diameters. From the geometry ol Figure 3-22, 6 is always less than or equal to 180° or n radians. The lower guideline for 6 is approximately 150°. Below this value there will be increasing tension and slip, which will result in decretised life of the V belts. This limit on 6 imposes a lower limit on the center distance and thus a practical limit on the speed ratio attainable is a given V-belt design. 

Shorter center distance is a very practical design objective. Such a design uses space economically and allows for a stable operation. In general, center distances are limited by the physical dimensions of the sheaves, or the minimum angle of 6, i.e.. 150". Maximum drive centers are limited only by available V-belt stocked lengths. 

For V-belt drives with more than two sheaves, belt length is calculated from sheave coordinates and drive dimensions in layout drawings. 

This can also be expressed in terms of sheave pitch diameter. This is... 

The total friction force, F, (lb) acting tangent to the sheave is fF ... 

Figure 3-23 shows the constant speed forces in the V belts with drive sheave transferring power via the V belt to the large driven sheave [11]. If centrifugal forces and slippage are neglected, then taut side tension force Fj (lb) is... 

The power P(hp) transmitted by the drive sheave to the driven sheave is... 

Find the V-belt speed using Equation 3-16 using pitch diameters of sheaves. Speed must be below 600 ft/min (or 100 ft/s). 

Knowing the speed (in rpm) of the smallest sheave and its pitch diameter, find the horsepower capability per V bell using the appropriate table for the V-belt type to be used (see Tables 3-9-3-16). 

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