Page 302 - Analysis and Design of Machine Elements

Analysis and Design of Machine Elements
280
Steps Computation Results Units
(4) Circumfer- According to d VI and Table 4.1, the dimension of a key is Key for gear
entially selected as b × h × l = 20 × 12 × 40 mm. Meanwhile, to ensure 20 × 12 × 40
locating better concentricity between the gear hub and shaft, the fit H7/n6
elements on between the gear hub and the shaft is selected as H7/n6. Key for
the shaft Similarly, a parallel key used to connect the half coupling and coupling
the shaft is selected as 14 × 9 × 70 mm, and the fit is H7/k6.
14 × 9 × 70
A light interference fit is selected between the bearing and H7/k6
shafts. The tolerance of shaft diameter is selected as m6.
(5) Determine Select the shaft chamfer as 2 mm. The fillet radii of shaft
the shaft fillets shouldersare showninFigureE10.2.
and chamfers
The initially designed shaft structure is shown in
Figure E10.2.

4. Force analysis
(1) Determine Since the reference diameter of the low-speed stage gear is F = 4558 N
t
the forces d = m z = 3 × 108 = 331.739mm F = 1699 N
n
acting on the 2 cos cos 12.4 ∘ r N
gear 2T 2 × 7.56 × 10 5 F = 1002
a
F = = = 4558N
t d 331.739
2
Therefore
F tan 4558 × tan 20 ∘
F = t n = ∘ = 1699N
r
cos cos 12.4
∘
F = F tan = 4558 × tan 12.4 = 1002N
t
a
The directions of tangential force F , radial force F and axial
t
r
force F are shown in Figure E10.3.
a
(2) Forces on Forces acting on the gear are assumed to act at the midpoint R H1 = 1461 N
the shaft of the face width. Select the value for the effective reaction R = 3097 N
point as a = 27.4 mm from the bearing catalogues for bearing H2 N
7313C [12]. According to the previous structural design, R V1 = 1539 N
decide the spans of L = 118.4 mm, L = 113.6 mm, R V2 = 160
1
2
L = 53.6 mm.
3
Resolve the forces in two perpendicular planes, usually
horizontal plane and vertical plane. Perform free body
diagram analysis for the reaction forces at all supporting
bearings in each plane. Therefore,
Reaction forces in horizontal plane are
R = 1461 N, R = 3097 N
H1 H2
Reaction forces in horizontal plane are
R V1 = 1539 N, R V2 = 160 N
(continued)