4 - SHAFT DESIGN ME 411
TOPIC NO. 4
SHAFT DESIGN
SHAFT UNDER PURE TORSION
This topic includes the following:
4.1 Pure Bending
4.2 Pure Torsion
4.3 Combined Loads(Torsion: Bending/
Axial) Maximum torsional stress
4.4 Shaft design using codes
- PSME Code 16T
Ss S sd (for a solid shaft)
- ASME Code
D3
16TD
Ss S sd (for a hollow shaft)
SHAFTING D4 d 4
Shaft – a rotating member, usually of circular
Or
section, used to transmit power or motion.
Its primary load is torsion.
16T 1 d
Axle – a non-rotating member which carries Ss 3 4
S sd : B
D 1 B D
no torque and is used to support wheels,
pulleys, and the like. Its primary load is
Angle of twist (torsional deformation)
bending.
TL
Spindle – a short shaft or axle. ; in radians
JG
Terms such as line shaft, head shaft,
Where: J D 4 for solid shaft
transmission shaft, machinery shaft, 32
countershaft, and flexible shaft are names
associated with special usage. J
32
D 4
d 4 for hollow shafts
Most machine design books generally
used the term shaft to mean all of the above
terms.
MACHINE DESIGN 1 Page 32
, 4 - SHAFT DESIGN ME 411
SHAFT UNDER PURE BENDING *Case c) Shaft has fixed supports with load P
at midspan
Maximum Flexural Stress
32M Csc 192
Sf Sd (for a solid shaft)
D3
32MD Two General Classifications of Shafts
Sf Sd (for a hollow shaft)
D4 d 4
Transmission Shaft – shaft that connects a
Or
prime mover to a machine.
32M 1 d
Sf 4
Sd ; B
D3 1 B D Machinery Shaft – shaft that is an integral
part of a machine
Shaft Deflection Shaft Design Stresses (Only Sy and Su are
3
PL known)
y ;(For special cases only)*
C xc EI Shear design stress:
S sd 0.3S Whichever is smaller:
*Case a) Shaft acts as a cantilever with load If shaft has a keyway,
S sd 0.18Su
P at free end Consider a strength
Reduction factor of 0.75
Normal design stress:
S d 0.6 S Whichever is smaller:
Csc 3 If shaft has a keyway,
S d 0.36 Su
Consider a strength
Reduction factor of 0.75
*Case b) Shaft is simply supported with load
P at midspan
Allowable deformations
Angle of Twist
Machinery shaft:
allow 0.08 to 1 per foot of
length
Csc 48
MACHINE DESIGN 1 Page 33
TOPIC NO. 4
SHAFT DESIGN
SHAFT UNDER PURE TORSION
This topic includes the following:
4.1 Pure Bending
4.2 Pure Torsion
4.3 Combined Loads(Torsion: Bending/
Axial) Maximum torsional stress
4.4 Shaft design using codes
- PSME Code 16T
Ss S sd (for a solid shaft)
- ASME Code
D3
16TD
Ss S sd (for a hollow shaft)
SHAFTING D4 d 4
Shaft – a rotating member, usually of circular
Or
section, used to transmit power or motion.
Its primary load is torsion.
16T 1 d
Axle – a non-rotating member which carries Ss 3 4
S sd : B
D 1 B D
no torque and is used to support wheels,
pulleys, and the like. Its primary load is
Angle of twist (torsional deformation)
bending.
TL
Spindle – a short shaft or axle. ; in radians
JG
Terms such as line shaft, head shaft,
Where: J D 4 for solid shaft
transmission shaft, machinery shaft, 32
countershaft, and flexible shaft are names
associated with special usage. J
32
D 4
d 4 for hollow shafts
Most machine design books generally
used the term shaft to mean all of the above
terms.
MACHINE DESIGN 1 Page 32
, 4 - SHAFT DESIGN ME 411
SHAFT UNDER PURE BENDING *Case c) Shaft has fixed supports with load P
at midspan
Maximum Flexural Stress
32M Csc 192
Sf Sd (for a solid shaft)
D3
32MD Two General Classifications of Shafts
Sf Sd (for a hollow shaft)
D4 d 4
Transmission Shaft – shaft that connects a
Or
prime mover to a machine.
32M 1 d
Sf 4
Sd ; B
D3 1 B D Machinery Shaft – shaft that is an integral
part of a machine
Shaft Deflection Shaft Design Stresses (Only Sy and Su are
3
PL known)
y ;(For special cases only)*
C xc EI Shear design stress:
S sd 0.3S Whichever is smaller:
*Case a) Shaft acts as a cantilever with load If shaft has a keyway,
S sd 0.18Su
P at free end Consider a strength
Reduction factor of 0.75
Normal design stress:
S d 0.6 S Whichever is smaller:
Csc 3 If shaft has a keyway,
S d 0.36 Su
Consider a strength
Reduction factor of 0.75
*Case b) Shaft is simply supported with load
P at midspan
Allowable deformations
Angle of Twist
Machinery shaft:
allow 0.08 to 1 per foot of
length
Csc 48
MACHINE DESIGN 1 Page 33
