07 Shaft Diameter

7/28/2019 07 Shaft Diameter

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Shaft Design: Diameter

determination

Design 1

Mechanical Engineering FacultyEngineering Division

Universidad Santo Tomás



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What is a shaft ?

It is a rotating machine element thattransmits power or motion.

It is usually a slender element of roundcross section (hollow or solid).

It usually carries power-transmittingcomponents (gears, belt sheaves, chainsprockets)



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What is a shaft ?

Keys, pins, snap rings, clamp collars, shoulders,interference fits, are used to secure power-transmitting components.

A shaft is usually supported by bearings (rolling-contact or journal).

Most shafts are under fluctuating loads of combined bending and torsion with variousdegrees of stress concentrations.



4

Common shaft topologies

Constant

Diameter

Stepped

Crankshaft

From Convertech Website

From HUP YIK Website

From Tianrun Website



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Stepped Shaft example

From Norton, p. 506.



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Others Shaft examples



Other definitions

Axle: nonrotating element that carries no torque

and it is used to support rotating members

(pulleys, wheels). It is a “round beam”

Spindle: short shaft.

Flexible shaft : transmits motion between two

points where the rotational axes are at an angle

with respect to one another.



Other Definitions

AxleSpindle

Flexible Shaft

From Melrose Wheel Chairs Website

From 4WD Factory Website

From Flexishaft Website



Materials for Shafts

Steels

Cold-drawn or machined from hot-rolled, plain carbon steels

Alloy steels

Carburizing grade steels

Stainless steels

Nodular High Strength Cast Iron

Bronze



Shaft Design process

1. Design based on strength

2. Deflection Verification (stiffness design)

3. Critical Speed Verification



1. Design based on Strength

1.1 Determine rotational speed and power to be

transmitted by the shaft.

1.2 Determine the power-transmitting

components that will be mounted on the shaft.

1.3 Specify the location of bearings.

1.4 Propose the general topology of the shaft,

considering the attachment method for each

power-transmitting component.



1.5 Produce a complete static analysis of theshaft (free-body diagram, determination of the

radial and axial forces exerted on the shaft,

Solving for the reactions on all bearings).




1.6 Produce the complete torque, shearing force

and bending moment diagrams to determine the

distribution of bending moments and torque inthe shaft.

Once you finish these six steps, you can identify

critical locations on the shaft, i.e., sections withhigh torsion-bending magnitudes and presence

of notches.




1.7 Select the material and specify its condition.

1.8 Choose the appropriate minimum acceptable

diameter equation, according to the type of loading.

1.9 Determine the minimum acceptable diameter

for each critical location.

1.10 Specify diameters for each step, considering

tolerances and fits, preferred sizes, mounting

parts, etc. ITERATIVE PROCESS




ASME Design Equation

SAFE

ZONE

N f > 1

FAILURE

ZONE

N f < 1

3

32

d

M K a

f a

3

16

d

T mm

Fully reversed bending:

Steady torsion:

von Mises relationship:3

y

ys

S S



General Equation (Goodman

Criterion)3

32

d

M K a

f a

Fluctuating bending:

Fluctuating torsion:

3

32

d

M K m

fmm

3

16

d

T

K m

fsmm

3

16

d

T

K m

fsa

von Mises Stresses: 2/122'3 aaa 2/122'

3 mmm

f ut

m

f

a

N S S

1''



Preliminary K t values

Bending Torsion Axial

Shoulder-sharp fillet 2.7 2.2 3.0

Shoulder – Well rounded fillet 1.7 1.5 1.9

End Mill Keyseat 2.2 3.0 -

Sled runner keyseat 1.7 - -

Retaining ring groove 5.0 3.0 5.0




Shoulders:

Well rounded filletSharp fillet

Adapted from Mott, p.542.




Keyseats:

Adapted from Norton, p.528-529.

End-Mill (profile) Sled runner



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Keyseats:

Adapted from Norton, p.529.



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Retaining Ring Grooves:

from Seeger-Orbis website.

Tipical radius at the bottom of the groove: 10% of the ring thickness ≈ m/10



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References

Norton, R.L. Machine Design: an integratedapproach. 3rd ed, 2006.

Budynas and Nisbett. Shigley’s MechanicalEngineering Design. 8th ed, 2006.

Mott, R.L. Machine Elements in MechanicalDesign. 4th ed, 2004.

Deutschman et al. Diseño de Máquinas. 1987.



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References

Convertech Website

http://www.convertech.com/small-diameter-

expanding-air-shafts.php

HUP YIK Website

http://hupyik.com/products/productList.aspx?cate

gory=Water%20Pump%20Part&pageIndex=1

Tianrun Crankshaft Co Website.

http://tianrun.en.gasgoo.com/auto-

products/17399.html

http://www.convertech.com/small-diameter-expanding-air-shafts.php


http://hupyik.com/products/productList.aspx?category=Water%20Pump%20Part&pageIndex=1


http://tianrun.en.gasgoo.com/auto-products/17399.html


















































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References

Melrose Wheel Chairs Website

http://www.melrosewheelchairs.com/index.php?m

ain_page=product_info&cPath=8_4&products_id

=124

4WD Factory Website

https://www.4wdfactory.com/store/products.php?

product=Dana-44%2C-GM-10-bolt-Front-

Spindle%2C-6-Hole-Flange%2C-Big-Bearing-

Journals

http://www.melrosewheelchairs.com/index.php?main_page=product_info&cPath=8_4&products_id=124



https://www.4wdfactory.com/store/products.php?product=Dana-44%2C-GM-10-bolt-Front-Spindle%2C-6-Hole-Flange%2C-Big-Bearing-Journals


































































References

Flexishaft Website.

http://www.flexishaft.com/powertransmission.htm

Seeger-Orbis Website

http://www.seeger-orbis.com/en/design-details























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