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Tawas, atau dalam bahasa Inggrisnya disebut "Alum" adalah suatu kristal sulfat dari logam-logam seperti lithium, potassium, calcium, alumunium, dan logam-logam lainnya. Kristal tawas ini cukup muda...
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Descripción: Velocidades V
Mecanismos 3
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Descripción: Economía
Hukum V
Design of V-belt transmission
T. Cicone
DESIGN OF V-BELT TRANSMISSION (STAS 1163 – 71 & ISO R 155). Design Data • input power (at the driving sheave), P1 • input rotational speed (of the driving sheave), n1 (rot/min), • transmission ratio, iBD. • center distance, A. • application (service) factor c f (Ks).
γ/2
β1
F0
F0
β2
A
Fig. 1. Geometry of belt drives
Fig. 2. Power rating chart for V-Belt selection Select the V-belt (cross-section) size function of the power and rotation speed at the input, using the diagram from Figure 2. If the point is close to a demarcation line, it is recommended to select the belt size under this line (with greater load capacity). Table 1 gives data for all dimensions of the belt cross-section. Machine Design 2003-2004
1
Design of V-belt transmission
T. Cicone
Select the working diameter of the driving sheave, Dp1. It is recommended to select a normalized value (STAS 1162-67). The range of normalized diameters is in accordance with the size of the belt (see Table 2). Sheave diameters below minimum values recommended for the belt size in question should not be used because the higher bending stress materially reduces the belt life. Calculate the working diameter of the driven sheave:
D p2 = iBD ⋅ D p1
(1)
If there are no restrictions for the transmission ratio, the diameter can be normalized to the closest value (see Table 4 STAS 1162 – 67) Included angle:
γ = 2 arcsin
D p 2 − D p1
(2)
2A
where normally D p2 ≤ A ≤ 3( D p1 + D p 2 ) Shaft distances that are too short (short belts) result in higher frequencies, causing excessive heating and thus premature failure of the belt. Shaft center distances that are too long (long belts) may result in belt vibrations, especially of the slack side, also causing higher belt stress. Angle of wrap (arc of contact): on driving sheave β1 = 180o − γ , on driven sheave β 2 = 180o + γ Working length:
L p = 2 A cos
γ 2
+
π 360
( β1 ⋅ D p1 + β 2 ⋅ D p 2 ) ≈ 2 A +
π ( D p1 + D p 2 ) 2
+
( D p 2 − D p1 ) 2 4A
(3)
A normalized value of the working length should be selected from vendors catalogues (usually the closest value is selected). Standard values are given in Table 3. Peripheral velocity:
v=
πD p1 ⋅ n1 60000
[m / s]
(4)
It is recommended a maximum peripheral velocity vmax=40 m/s. Preliminary number of belts: z0 =
Table 2. - Normalized values for working length Lp [mm]
Working length Lp [mm]
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6200
8000
10000
12500
Example of notation: SPA 2000; STAS 7192-83 (V-Belt size SPA, with working length Lp=2000 mm) Table 3. - Normalized values for working diameters, Dp [mm]
where
63
71
80
90
112
125
140
160
180
200
224
250
280
315
450
500
560
630
710
800
900
1120
1250
1400
1600
1800
2000
2500
400
cL - length correction factor (Table 4) function of the working length L p .
cβ - wrapping factor: c β = 1 − 0.003(180 − β1 )
(6)
P0- nominal power transmitted by one belt is given by vendors Tables 6...9 give values from STAS 1163-71. Linear interpolation should be used for intermediary values. z0- may should not be rounded off. Final number of belts:
z=
z0 cz
(6)
where c z is belt load repartition factor (see Table 5). The result should be rounded to the upper integer. It is recommended that z ≤ 8 . Bending frequency:
f = 103 ⋅ x ⋅
v [m/s] [ Hz ] Lp
where: x – number of sheaves.
Machine Design 2003-2004
3
(7)
Design of V-belt transmission
T. Cicone
Bending frequency should not be greater than 40 Hz . Peripheral force:
P1[kW ] [N ] v[m / s ]
(8)
F0 = (1,5.....2) Fu [ N ]
(9)
Fu = 10 3 ⋅ Belt tensioning (Preload) force:
Note that the belt tensioning force is the radial force loading the shaft (supported by the bearings). Adjustment of shaft center distance (Minimum take-up allowance): X>0.03 Lp Y>0.015 Lp The dimensions of the grooves for V-belts are standardized (STAS 1162–84) see Figure 5 and Table 10. Table 4. Length correction factor cL
