= 900 / 235
= 3.83
- By referring table 4 sprockets of 88 and 23 teeth give a ratio of 3.83:1
- The power ratings of 3/4 pitch chain, 13.2kW is required for step 2. For a 23 tooth sprocket running at 900 rpm single chain is rated at 13.39 kW.
- The range of C: 30 * pitch < C < 50 * pitch
30 * 19 < C < 50 * 19
570 < C < 950
Therefore, C = 750mm is selected.
Chain length, L = 2C/P + (T + t) / 2 + KP/C
= 2 * 750 / 19 + (88+23) / 2 + 107 * 19 / 750
= 137 pitches
where
L = Length of chain in pitches
C = Center distance in mm
P = Pitch of chain in mm
T = Number of teeth in large sprocket
t = Number of teeth in small sprocket
K = Factor from table 3
Drive specification:
- Sprocket of single chain with 23 teeth fitted to gasoline engine shaft.
- Sprocket of single chain with 88 teeth fitted to loaded conveyor shaft.
- Chain of pitch 3/4 (19mm) and length 137 pitches.
B. Requirement for V-belt drive:
- It is used for a 55kW diesel engine.
- It is run at 1200rpm that driving a piston compressor runs at 760rpm.
- The center distance is 1600mm.
- The duty is 20hrs/day.
- The diameter of engine shaft and compressor shaft are 70mm and 85mm respectively.
V-belt transmission:
- Service factor = 1.4
- Design power rating = piston compressor rating * service factor
= 55 * 1.4 = 77kW
- Belt section indicated is V-belt-C
- Speed ratio = driving rotating speed / driven rotating speed = 1200 / 760 = 1.6
- Standard pulleys of 250mm and 400mm pitch diameters given the required speed ratio.
-
Belt pitch length, L = 2C + 1.57(D+d) + [(D-d) 2/4C]
= 2*1600 + 1.57(250 + 400) + [(400-250) 2 /4C]
= 4224mm
where
L is the pitch length of belt;
D is the pitch diameter of larger pulley;
d is the pitch diameter of smaller pulley; and
C is the center distance of drive
- The nearest standard pitch length = 4060mm
-
Center distance, C = A + (A2 - B)1/2
= 1600
where
A = L/4 – π(D+d)/8 = 4224/4 – π(400+250)/8 = 800.7
B = (D-d) 2 / 8 = (400-250) 2 / 8 =2812.5
C is the center distance of drive;
D is the pitch diameter of larger pulley;
d is the pitch diameter of smaller pulley; and
L is the pitch length of belt
- Power rating per belt is 9.85kW with additional power for the speed ratio of 0.94kW, i.e. a total of 10.79kW
-
Arc of contact correction factor is decided by value of (D-d)/C corresponding to the value of proportion of 180˚ rating.
(D-d)/C = 0.094 <=> 0.99
Arc of contact correction factor = 0.99
- Belt length correction factor = 1.02
- Number of belts = W/XYZ = 77 / 10.79*0.99*1.02 = 7.06
i.e. 7 belts.
where
W = design power rating
X = power rating per belt
Y = Arc of contact correction factor
Z = length correction factor
- Summary of pulley requirements:
- Smaller pulley fitted to diesel engine shaft 250mm pitch diameter with 4 grooves C section.
- Larger pulley fitted to piston compressor shaft 400mm pitch diameter with 4 grooves C section.
- V-belt required, C section belts, 4060mm pitch length.
