Abu-Dhabi University College of Engineering &Computer Science Department of Mechanical Engineering MEC43 Machine Design Mini !ro"ect # !ro"ect $itle% Shaft Design
Stuent name
Stuent 'D
Abdul Ahad Iqbal
1000536
Bilal Ahmad
1029653
Ibrahim Ramzi Awad
1006869
Signature
Table of Contents Table Table of Contents........................... Contents............................................... ........................................ ........................................ .................................. .............. 2 Abstract...................................... .......................................................... ........................................ ................................................... ............................... ........ 3 Introduction....................................... .......................................................... ....................................... .................................... .............................. .................. .... 3
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Preliminary Design.................................. Design...................................................... ......................................................... ..................................... ....... 4 Function Function Decomposition Analysis............................................ Analysis.......................................................................... .............................. ..4 .. 4 Sub-Function Sub-Function Decomposition Analysis................................................. Analysis................................................................. .................... .... Conceptual Design an! "eneration of Alternati#es$................................................ Alternati#es$................................................ Assessment of Alternati#es........................................... Alternati#es..................................................................................... .......................................... % Preliminary Analysis for Si&ing 'ain Components$............................................... Components$............................................... .1( 'ain Design Calculations......................................................................................14 S)aft Design................................. Design..................................................... ........................................ ..................................................... ................................. 14 "ear Forces..................... Forces........................................ ....................................... ........................................ .................................. ........................... ............. 1* Diameter of +olts.............................. +olts.................................................. .......................................................... ...................................... .......... 1% Selection of a Clutc).................... Clutc)....................................... ................................................................ ............................................. ......... 2( Appen!i,............................ Appen!i,................................................ ........................................ ....................................... ................................. ........................ .......... 22 CAD Draings$................................. Draings$..................................................... ............................................................ ........................................ ......... 22 Reerences..................................... ......................................................... ....................................... ....................................................... .................................... 24
Abstract !his desi"n #ro$ect aims at the desi"n o dierent com#onents o a "ear bo% or an industrial saw& !he main desi"n com#onent or this #ro$ect is the shat alon" with the 'e(wa(s) illet radius) bearin" seats and s#lines& !he desi"n has to be done throu"h a #reliminar( anal(sis ollowed b( the detailed calculations o the orces and stresses&
2
'ntrouction A "ear bo% can be deined as a set o "ears that are #resent in an enclosed s(stem and are used to deli*er mechanical ener"( rom a #rime mo*er to an out#ut de*ice& +!oolin", -./) 2013 !he tas' "i*en to the "rou# deals with desi"nin" a s#eed reducer or a saw that is used to cut tubin" or *ehicle e%haust s(stems& !he s#eciications o its o#eration ha*e been deined alon" with the diameter o the shat that is used in the motor& !he /.A rame 28! motor will be required to ha*e a shat which can accommodate 12%12 inch 'e(& !he machine has a band t(#e saw and the selection o a desired clutch mechanism with a suitable en"a"ementdisen"a"ement unction is also one o the ob$ecti*es o the #ro$ect& -econdl() the housin" in the shat is assumed to be i%ed b( our bolts& !he sizes and the orces on them are to be calculated ater the detailed anal(sis o the shat& !he requirements o the #ro$ect also state that cost o #roduction is a 'e( as#ect in terms o all the calculations done as the owner wants the cost to be #ut ahead in terms o an( decision re"ardin" the desi"n o the reducer& !hirdl() the #ro$ect *eriies the o#eratin" durations o the machine alon" with the en*ironmental actors in which it will be #laced& !he desi"n has to be done in such a manner that the lie o the shat is e%#ected to be at least i*e (ears& !he additional requirements o the #ro$ect are based on the sizin" o com#onents li'e #ulle(s) s#roc'ets and lastl( ollowed b( an assembl( drawin" o the shat with all the com#onents&
3
Figure 1: Assembly of a shaft (Shafts and Bearings)
Preliminary Design Function Decomposition Analysis Speed Reducer for Saw
Poer supply Coupling on motor si!e Spee! re!ucer
4
Clutc) engagement mec)anism Clutc)
Sub-
Function +earing attac)ment
Decomposition Analysis
Frame attac)ment
Conceptual Design and Generation of Alternatives
T)e conceptual !esign an! generation of alternati#es p)ases are normally prece!e! by intensi#e searc)es in all possible c)annels. Some of t)ese oul! be$
iterature searc) /eb searc) 'ar0et searc) Patent searc) nternal company searc)
T)e folloing alternati#es )a#e been arri#e! at by !oing eb searc). n ot)er proects some of t)e abo#e searc)es oul! be important an! critical especially patents searc). Alternative ! Spur Gear Reducer
Alternative-" #evel Gear Reducer
*
Alternative-$ %orm Gear Reducer
5
Assessment of Alternatives
Assessment of alternati#es may !epen! on t)e no#elty in eac) alternati#e t)e si&e of t)e proect an! criticality of t)e c)oice. T)ese met)o!s may range from subecti#e tec)ni6ues simple analysis more !etaile! analysis simulation met)o!s an! e,perimental met)o!s. Some of t)e met)o!s t)at may be use! are liste! belo$
Decision matri, Decision tree Simple analysis Detaile! analysis Simulation an! numerical met)o!s 7,perimental met)o!s
For t)e abo#e alternati#es e use t)e folloing c)oice matri,$
Decision &atri' for Gear #o' Alternatives Alternative Criteria
%eig (t
Spur Gear Type
%
#evel Gear Type
%orm Gear Type
Score
Score ) %eig(t
Score
Score ) %eig(t
Score
Score ) %eig(t
*+ciency,!
(.2
1(.(
2.(
1(.(
2.(
.(
1.(
Simplicity
(.2
1(.(
2.(
5.(
1.
%.(
1.5
Cost
(.1
1(.(
1.
5.(
1.2
%.(
1.3
(.1
1(.(
1.
1(.(
1.
2.(
(.3
(.2
5.(
1.
%.(
1.5
1(.(
2
(.1
1(.(
1.(
%.(
(.%
%.(
(.%
Reduction ratio," Space re.uiremen t *ase of maintenanc e ( )eight * score
!/0
1/2
1/0
3/$4
(1) Spur and bevel gears have much higher eciency (>!") than #orm gears (may be as lo# as $!") because the rolling friction (in spur and bevel) versus sliding friction (in #orm gears)% (&) 'e may achieve much higher reduction ratio in #orm gears but the speed ration is integer%
Preliminary Analysis for Si5ing &ain Components A/ PR*67&78AR9 S7:78G ;F S
/e nee! to )a#e an initial si&e for t)e main components to start t)e !esign process. /e 8n! an appro,imate si&e for t)e s)aft an! from t)at si&e e 8n! ot)er component si&es by proportions. T)e !ri#e s)aft recei#es poer of 3 )p. T)e spee! of t)e s)aft is (( rpm. /e use t)e folloing relations$
d = 2π ⋅ n ⋅ d = π ⋅ d ⋅ n 60 2 60 2 lb ⋅ ft π ⋅ d ⋅ n d V = ) T = F t ⋅ ) hp = 550 12 sec 2 F ⋅V T ω T n hp = t ) hp = = v = ω ⋅
33000
6600
63000
1(
)ere$
d: pitc) !iameter (inch)
n: gear rotational spee!
(rpm)
/e use t)e folloing e6uation for t)e tor6ue on t)e motor s)aft$ 63000 hp
T +lb&in
=
n
=
63000 35+ hp 1450 + rpm
=
1)260 lb&in
An! e ma0e sure t)at t)e tor6ue on t)e sa s)aft is e6ual or more t)an t)e re6uire!$ 63000 hp
T +lb&in
=
n
=
63000 35+ hp 500+ rpm
=
)10 lb&in
)ic) is more t)an t)e minimum re6uire! tor6ue of 3*( lb-in. /e c)ose a s)aft material$ AS 1(3( CD it) t)e folloing$ S y !* psi* Su +*, psi* -&%+.1$ psi* /11%$.1$ psi* and 0B1+ To obtain an initial estimate for t)e s)aft !iameter e assume an initial factor of safety of 4.( an! e use (9 more tor6ue to account for ot)er loa!s :ben!ing moment s)ear an! a,ial force; as ell as stress concentration an! fatigue stress concentration t)en$ ib .∈¿
¿ 16∗(1.5∗4410 )¿ τ =
Tc J
T (
= π (
d 2
d
)
4
32
)
= 16 T =¿ πd
3
/)ic) gi#es
11
d =1.75 ∈¿
T)is is 6uite in agreement it) t)e gi#en !ata for t)e motor s)aft )ic) )as a !iameter of 1.5* in. T)erefore e ill use d =1.875 ∈¿
#/ PR*67&78AR9 S7:78G ;F G*ARS
T)e 8gures s)o t)e !imensional parameters of t)e gear an! t)e toot) an! t)e 8rst table gi#es t)e A"'A Stan!ar! "ear Speci8cations )ereas t)e secon! table s)os stan!ar! selection #alues for !iameter pitc)es. t s)oul! be note! t)at all !imensions are function of t)e circular pitc) p or t)e !iameter pitc) pd an! e )a#e t)ese relations$ 2ircular pitch:
p=
πd π N = , p d= ,d : diameter of the pitch ¿˚ N Pd d
/e start by t)e pinion gear an! e try to minimi&e space re6uirements an! t)erefore e use a small pinion it) no eb as s)on in 8gure$
From t)e abo#e 8gure e assume t)e pitc) !iameter of t)e pinion to be$ d pinion =d p= 2.0 d shaft =2.0∗1.875 ∈¿ 3.75 ∈¿
From t)e table of stan!ar! !iameter pitc)es e c)ose$ 3.75 ∈¿∧ N = 30 tooth
pd =8
tooth
¿
, whichgives p d= 8=
N N = d p ¿
12
=
ωg ω p
=
ng n p
=
500 rpm 1,750 rpm
whichgives : d g=d p
1,750 rpm 500 rpm
=13.125 ∈¿
=nce again using t)e table it) t)e proportional !imensions e obtain all geometrical !imensions of t)e gear.
13
C/
PR*67&78AR9 *ST7&AT*S ;F F;RC*S
G*AR
T)e folloing relations may be use! to calculate gear forces noting t)at t)e stan!ar! pressure angle φ is e6ual to 2(o.
d = 2π ⋅ n ⋅ d = π ⋅ d ⋅ n 60 2 60 2 π ⋅ d ⋅ n lb ⋅ ft d ) T = F t ⋅ ) hp = 550 V = 12 sec 2 F ⋅V T ω T n = ) hp = hp = t v = ω ⋅
33000
6600
)ere$ d: pitc) !iameter (inch) rotational spee! (rpm)
n: gear
63000
F t F r
=
=
F n cos φ F n s in φ
F t$ Toot) tangential force F r$ Toot) ra!ial force F n$ Toot) normal force D/ PR*67&78AR9 S7:78G ;F = *9S A8D S
=ne of t)e most common ays of transmitting tor6ues beteen t)e s)afts an! t)e gears is by use of t)e 0eys. T)e 0eys or0 in a ay in )ic) a longitu!inal groo#e is mac)ine! on t)e s)aft calle! a 0eyay an! a correspon!ing gro#e is ma!e into t)e bore of t)e )ub. T)e 0ey is t)en able to 8t simultaneously in bot) groo#es. T)e folloing 8gure gi#es appro,imate
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proportional !imensions for s6uare an! >at 0eys. /e c)ose a s6uare 0ey :most common; an! use t)e folloing relations$ Ls=
4 T f s
S yt D
∧ Lb =
4 T f b
! S yc D"
)ere$
Ls : !ey #engthbased on shear strength ( factor of safety : f s ) Lb : !ey#engthbased onbearing strength ( f actor of safety : f b ) D : Shaft diameter , : !ey width , L : !ey #ength " : ha#f !ey height , S yt : $ie#d strength∈ tension,S yt : $ie#d strength ∈ compression ! : Tria%ia# stress factor , 1.0 &! & 1.5
&ain Design Calculations S(aft Design Assumptions$
engt) of s)aft is * in an! ra!ius of 8llet r ? (.1 in Forces are Ft ? 4*(4 lb an! F r ?
−¿ 1*12 lb :Foun! using #alues from
preliminary analysis; T)ese forces are applie! at t)e center of t)e gear )ic) is 4.2 in from t)e center of bearing 1. T)e reaction forces are applie! at t)e center of t)e bearings. Assuming a reliability of %%9 reliability Ta ? 'm ? ( an! factor of safety ? 2
1
@'& ? ( ? : −¿ 1*12;:4.2; B : y2;:; ? ( y2 ? 13(2 lb @Fy ? y1 B 13(1.5 ' 1*12 ? ( y1 ? 41( lb @'y ? ( ? : −¿ 4*(4;:4.2; B :&2;:; ? ( &2 ?
−¿ 3** lb
@F& ? &1 −¿ 3** B 4*(4 ? ( &1 ?
−¿ 112* lb Figure &: Shear and Bending 3oment 4iagrams
Total moment at beginning of 0eyay ?
√ (−4198 ) +(1527 ) ? 44* lb.in 2
2
'aterial c)osen for s)aft$ AS 1(3( Steel as rolle! Se ? (. :Sut; ? (. :*%5((; ? 3%%(( psi 0a ? a :Sut;b ? 3%%(( :*%5((; -(.%% ? (.2% 0b ? (5*% :!; -(.1(* ? (5*% :1.5*; -(.1(* ? (.52 0c ? 1 1
0! ? 1.((5 0e ? (.514 6 ? (.*5 E t ? 1.% E f ? 1 B 6 :E t −¿ 1; ? 1.4 6s ? (.53 E ts ? 1. E fs ? 1 B 6s :E ts
−¿ 1; ? 1.42
Se ? :(.2%;:(.52;:1;:1.((5;:(.514;: 3%%((; ? 142(1 psi
E ts ? 1.2 E f ? 1.*24 E fs ? 1.14 Se ? 14132 psi
A s6uare 0ey is c)osen :12 , 12 in; f s ? f b ? 2
0 :tria,ial stress factor; ? 1 'aterial c)osen ? AS 1(1 Steel col! !ran Tensile Strengt)
15
s)oul! brea0 8rst before t)e s)aft in case of o#erloa!ing. Assuming t)at t)e tensile strengt) is t)e same as compressi#e strengt)G 4 ( 4410 )( 2 )
4 T f s
5s ?
( 47100 )( 2.75 )( 0.5 )
S yt D ? 4T
5b ?
? (.4 in
4 ( 4410)( 2 )
f b
! S yc D" ?
(1 )( 47100 )( 2.75 )( 0.25 )
? 1.1 in
et t)e lengt) of t)e 0ey in t)is case 1. in as t)is ill ensure ample strengt) to resist bot) failure by s)earing an! failure by crus)ing. Gear Forces Assumptions$
T)e tangential force on t)e s)aft is t)e same as t)at on t)e gear. φ ? 2(o
Factor of safety ? 2.(
() d
T ? Ft
2
(
2 T
F t ?
d
2 4410
?
)
2.75
? 32(* lb
F t ? F n cos φ 3207
( t
F n ?
cos ❑
?
cos ( 20 )
? 3413 lb
F r ? F n sin φ ? 3413 sin :2(; ? 11* lb F t ? 32(* lb F r ?
−¿ 11* lb 1%
Assuming t)e face i!t) :F; to be 1. in 1.571
Circular toot) t)ic0ness :t; ?
p d
1.571
?
? (.1% intoot)
8
At ? t , Face i!t) ? (.1% , 1. ? (.2%4 in 2 1.25
De!en!um ?
Mg ?
? (.12 intoot)
p d
−¿ 32(* lb
'pg :'oment !ue to tangential force at base of toot); ? : −¿ 32(*; :(.12; ?
−¿ (1 lb.intoot) −(−501 )
− )c Ima, ?
?
*
(
( ( t )
0.196 2 3
)
−(−735 ) ?
(
( )( ) + 2 t
Jma, ?
12
−¿ 132 psi
?
I1 ?
B
2
-
I2 ?
2
−¿
√( ) -
2
+ τ 2
2
√( ) + - 2
? *%552 psi
2
2
τ
?
2
1.5 0.196
12
3
(
0.196
−¿ 331 psi
I3 ? (
2(
)
3
) ? *31 psi
2 I ? √ 79882 −( 79882 ) (−3351 )+ (−3351 ) ? 51(% psi 2
Sy ? 2 :51(%; ? 13215 psi 'aterial c)osen for gears$ AS 4(3 Steel :
Ia ? E f , Ia ? 3** psi Im ? :3 :E fs , Jm;2;12 ? 2533 psi Ima, ? Ia B Im ? (5 psi Assuming t)at t)e loa! on t)e bolts is I ma, an! increasing t)is by 1((9 to account for any un0non loa!s an! using a factor of safety 4G Sy ? 4 , 2 , (5 ? 254 psi et t)e bolt material be SA7 gra!e 2 it) bolt !iameter of (.* in since t)ese )a#e minimum yiel! strengt) of *((( psi 254 psi. T)e application of pulleys sproc0ets are not applicable in our !esign of s)aft.
Selection of a Clutc( T)e group !eci!e! to implement a centric centrifugal clutc) base! upon t)e operation of t)e sa an! t)e ease of its engagement an! !isengagement mec)anism. A centrifugal clutc) )as a great !eal of a!#antages in !iOerent applications t)at are motor !ri#en. T)e use of centrifugal clutc) allos t)e selection of a normal tor6ue motor for running loa!s rat)er t)an t)e c)oice of )ig) tor6ue motors for starting loa!s. :Prof.
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Nitinc)an!ra . Patel April 2(13; T)is type of clutc) is base! upon t)e principle of utili&ing to forces )ic) are t)e centrifugal an! t)e friction force. T)e reasons be)in! our c)oice of t)e centric centrifugal clutc)es ere base! upon t)e !elaye! engagement along it) t)e automatic engagement an! !isengagement. T)ere are no slippages )en t)e operation is at full spee! an! it also pro#i!es acceleration )ic) can be consi!ere! as controlle!. T)is type of clutc) mec)anism also pro#i!es resistance to s)oc0 loa!s !uring t)e process of start up. T)ey can be customi&e! as to meet t)e speci8c re6uirements of t)e system. T)e c)oice of t)is clutc) enables ecient protection from t)e s)oc0 loa!s )ic) can cause catastrop)ic !amages to t)e components of t)e !ri#e. Secon!ly it also era!icates t)e nee! of implementing )ig) factors of safety in or!er to protect t)ese components against t)ese s)oc0s. =ur c)oice as also base! on t)e fact t)at centrifugal clutc)es are able to re!uce t)e re6uirements nee!e! for t)e start up )ile 0eeping t)e )eat losses to a minimal )en t)ere is a !irect start of a !ri#e. :C7NTC C7NTF<"A C
22
Figure 6: 2entrifugal 2lutch (7rof% itinchandra 8% 7atel* April &16)
Figure 9: 2entrifugal S#itch (2-8;2 2-8;F
23
Appendi' CAD Drawings
24
2
+eferences 2-8;2 2-8;F
Prof. Nitinc)an!ra . Patel S. D. :April 2(13;. Design of Centrifugal Clutc) by Alternati#e Approac)es use! in DiOerent Applications. ;nternational =ournal of ;nnovative 8esearch in Science* -ngineering and echnology %. Shafts and Bearings% :n.!.;. etrie#e! 2(14 from )ttps$.engineersaustralia.org.ausites!efault8less)a!oearne! 92("roupsNational92(Committees92(an!92(Panels7ngineering 92(DesignPart92(.p!f ooling< S3-% :2(13;. etrie#e! from Tooling
ouie A. :2(12 Kuly 1;. Spur gear tooth Stress* Strain* and 4eection for Static 5oading. etrie#e! 'ay 2 2(14 from PSAS$ )ttp$psas.p!,.e!ul#2cgui!ancespurRgearRtoot)RstressRR44RRRstrainRR44RR Ran!R!e>ectionRforRstaticRloa!ing
2
