Page 424 - Marks Calculation for Machine Design

P1: Naresh
January 4, 2005
Brown˙C09
Brown.cls
406
U.S. Customary 15:28 APPLICATION TO MACHINES SI/Metric
Note that the mass moments of inertia of the Note that the mass moments of inertia of the
hub and spokes are very small. hub and spokes are very small.
Step 7. Using the mass moment of inertia Step 7. Using the mass moment of inertia
needed from the rim of the composite flywheel needed from the rim of the composite flywheel
found in step 6 and Eq. (9.77), determine the found in step 6 and Eq. (9.77), determine the
required mass of the rim (m rim ) as required mass of the rim (m rim ) as
1 1
I rim = m rim d o 2 I rim = m rim d o 2
4 4
1 1
2 2 2 2
29.3 slug · ft = m rim d o 39.1kg · m = m rim d o
4 4
Solve for (m rim ) Solve for (m rim )
2
2
4 (29.3 slug · ft ) 4 (39.1kg · m )
m rim = m rim =
d 2 o d o 2
2
2
4 (29.3 slug · ft ) 4 (39.1kg · m )
= =
(3ft) 2 (0.9m) 2
117.2 slug · ft 2 156.4kg · m 2
= =
9ft 2 0.81 m 2
= 13 slug = 193 kg
Step 8. Using the mass of the rim found in Step 8. Using the mass of the rim found in
step 7, determine the required width of the rim step 7, determine the required width of the rim
from Eq. (9.78) as from Eq. (9.78) as
m rim = ρπd o tw rim m rim = ρπd o tw rim

slug kg
13 slug = 15.2 π(3ft) 193 kg = 7,850 π(0.9m)
ft 3 m 3
×(0.25 ft) w rim ×(0.07 m) w rim

slug kg
= 35.8 w rim = 1,554 w rim
ft m
13 slug 193 kg
= 0.363 ft = 4.36 in = 0.124 m = 12.4cm
w rim = w rim =
slug kg
35.8 1,554
ft m
Step 9. Using the mass of the rim found in Step 9. Using the mass of the rim found in
step 7, determine the weight of the rim as step 7, determine the weight of the rim as
W rim = m rim g W rim = m rim g

ft m
= (13 slug) 32.2 = (193 kg) 9.8
s 2 s 2
= 419 lb = 1,891 N
Step 10. Calculate the total weight of the com- Step 10. Calculate the total weight of the com-
posite flywheel using the weights of the hub, posite flywheel using the weights of the hub,
spokes, and rim found in steps 2, 4, and 9, spokes, and rim found in steps 2, 4, and 9,
respectively. respectively.
W W
composite = W hub + W spokes + W rim composite = W hub + W spokes + W rim
flywheel flywheel
= (18) + (24) + (419) lb = (93) + (116) + (1,891) N
= 461 lb = 2,100 N