Helical Gears Project

7/23/2019 Helical Gears Project

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CONTENTS

Abstract i

List of Figures ii

List of Tables ii

Nomenclature iii

1. INTRODUCTION 1

. LITERATURE SUR!E" #

.1Intro$uction to %&T #

.Establis'ment of Com(an)*s +ranc'es #

.#Com(an)*s &ilestones ,

.,About -raga Diision /

#. -o0er transmission

#.1T)(es of $ries

#.A$antage of gear $ries

#.#Disa$antages of gear $ries 2

,. INTRODUCTION TO 3EAR DRI!ES 4

,.1Intro$uction 4

,.3eneral classification of gears 15

,.#3ear terminolog) 1,

,.,S(ur gear 1

,./C'aracteristics of 'elical gears 12

/. -RO+LE& DEFINITION

/.1Design (roce$ure for 'elical gears #

/.calculations /

6. FINITE ELE&ENT &ET%OD. ANAL"SIS

2. RESULTS AND CONCLUTION /,

4. REFERENCES /6


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ABSTRACT


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This project involves the design of a set of helical gears for gearbox of a thread rolling

machine at HMT. Thread rolling is a cold forming process in which different types of threads

are formed by rolling action.

In this project problems posed by spur gears like noise, lack of free movement

during power transmission and high impact stresses at the time of engagement of gears

are eliminated by replacing them with helical gears.

The design constraints in this project work are centre distance between the gears,

tranmission ratio and the gearbox dimensions.

irst, set of helical gears to be designed theoretically using !"#I$ "%&'TI().

$tresses induced in those gears are to be evaluated and they should be within the safe limits.

!ater, inite element package ')$*$ will be used for analysis. 'im of the analysis is to

determine the maximum deflection and stresses induced in the helical gear. Tangential, radial

and axial loads are analy+ed using ')$*$ software. The stresses produced in the gears

should be with in the limits, if not the process would be repeated accordingly and the stress

produced in the gear which is within the limits should be achived.

i

LIST OF FIGURES

Figure 1 : Thread rolling machine


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Figure 2 : $pur gear

Figure 3 : Helical gear

Figure 4 : Herring bone gear

Figure 5 : $traight bevel gear

Figure 6 : Hypoid gear

Figure 7 : rossed gear

Figure 8 : #orm gear

Figure 9 : -ear terminology

Figure 10 : Meshed gear

Figure 11 : ompressive stress diagram

Figure 12 : eformed shape of helical gear

LIST OF TABLES

Ta!e 1: $pur gear results

Ta!e 2 : Helical gear results

ii


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"O#E"CLATURE

$ % /ressure angle, degrees

$& % )ormalpressure angle, degrees

' 0 Helix angle, degrees

a( 0 esign stress, )1mm2

)e 0 "ndurance limit stress, )1mm2

)e* 0 $urface endurance limit of a gear pair, )1mm2

a 0 enter distance, mm

0 ace width, mm

C 0 ynamic factor depending upon machining errors

C* 0 $ervice factor

C+ 0 #ear and lubrication factor

C, 0 3elocity factor

- 0 /itch circle diameter, mm

Fa 0 'xial thrust, )

F( 0 ynamic load on gear tooth, )

F. 0 Tangential load at pitch line, )

F* 0 ynamic strength of the gear, )

F+ 0 !imiting load for wear, )

/ 0 !oad stress factor

0 Module, mm

& 0 )ormal module, mm

" 0 $peed, rpm

0 ircular pitch

( 0 iametral pitch

0 ircular pitch, mm

iii


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& 0 )ormal circular pitch, mm

0 4atio factor

0 /itch line velocity, m1s

0 orm factor

0 !ewis form factor

0 )o. (f teeth on gear

e 0 "5uivalent no. of teeth

iv


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CATER 1

I"TRO-UCTIO"

The thread rolling is a cold forming process in which different types of threads are

formed by means of rolling action. The thread rolling machine can produce threads, worms,

knurls, serrations, annular forms, roll finishing and straightening. There are different types of

thred rolling machines like6

axial rolling,

radial rolling,

tangential rolling.

In the thread rolling machine rolls are pressed into the component,stressing the

material beyond its yield point. This causes the component material to be deformed

plastically, and thus, permanently. &nike thread cutting, the grain structure of the material is

displaced not removed. 's the material will be plastically deformed by pressure, it should

have a minimum elongation of 78 and a maximum tensile strength of 29:,;;; /$I. Materials

that have less than 78 elongation or a significant hardness greater than 9; H4c, such as cast

iron, hard brass alloys and other hardened materials are not suitable candidates for thread

rolling process. The only re5uirement for the rolling process is that either the component or

the rolling head, or both, are rotating towards one another. Thread rolling tools can be used

on a wide variety of standard and special machine tools.

Threads are produced in second and in only one pass, whereas ) single pointthread cutting re5uires numerous passes and a much longer cycle time. !ong roll


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ig = Thread rolling machine and thread rolling process

Ca.er 2

Li.era.ure *ur,e

2;1 I&.r


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company diversified into #atches, Tractors, /rinting Machinery, Metal orming /resses, ie

asting D /lastic /rocessing Machinery, ) $ystems D Aearings. In =B:;s, the company

set up new units at /injore, Ealamassery and Hyderabad. In =BF;s, they set up HMT

International !td as a subsidiary company to channel HMT>s products and technical services

abroad.

2;2 E*.a!i*e&.


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Machine Tools !td and HMT #atches !td have been incorporated and these subsidiaries will

take over the business of Machine Tools and #atches of the company.

In the year 2;;9, the company signed agreement with &E


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pace with the ever changing technology. In addition, the company also manufactures a wide

range of industrial forgings for railway, automotive and ordnance applications.

/4'-'$ wisest investment has been in it excellent collaboration with cutter and tool

grinders, gambian of france for milling machines, escofier of france for thread rolling

machines, george fisher of swit+erland for copying lathes,mitsubishi heavy industries of

japan for machining centres and keiyo seiki of japan for ) lathes. The collaborations have

culminated in /raga producing machine tools of the highest 5uality conforming to

international standards. Ay virtue of their dependability, precision engineering and proven

performance , praga machine tools are penetrating larger segments of foreign markets

including &E, I$, anada, Aulgaria,Indonesia, -ermany, apan, etc., praga is even more

proud of the fact that it has contributed to the development of the machine tool industry in the

country and the creation of a vast band of skilled technicians. Thus, /raga today, is a nam to

reckon within the machine tool industry.

HMT !imited has =G manufacturing units.The constituent subsidiaries are given

below while the holding company retains the tractors business group.HMTs tractor business

commenced its operations in =BF= in technical collaboration with

M(T(E(3, +echoslovakia. HMT started the operation with the manufacture of

27 H/ tractor at the manufacturing plant in /injore, Haryana state. (ver the years, it has

developed tractors ranging from 27 H/ to F7 H/.

HMT !imited took over /raga Tools !imited as one of its subsidiaries =BGG. /raga

Tools !imited was established in May, =B9C as /raga Tools orporation !imited to

manufacture machine tools with its head 5uarters at $ecunderabad. It was renamed as /raga

Tools !imited in =B:C. It is mainly involved in manufacture of machine tools including )

machines.


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CATER 3

O?ER TRA"S#ISSIO"

/ower transmission is transfer of rotary motion and power from one shaft to another. The

transmission of power can be done in different ways like belt drives, rope drives, chain drives

and gear drives.

3;1 Te*


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-ears offer positive power transmission.

-ear drives are compact in construction due to relatively small centre distance.

-ears provide power transmission with high angular or linear accuracy.

-ear drives can avail a wide range of power transmission beyond the range of belt

drives or chain drives.

-ears can change the rate of rotation of a machinery shaft.

-ears can change the direction of the axis of rotation.

-ears can change rotary motion to linear motion.

-ear drives have a provision for gear shifting thus changed the transmission ratio over

a wide range.

3;3 -i*a(,a&.age*


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CATER 4

I"TRO-UCTIO" TO GEARS

-ears are most common means of transmitting power in modern mechanical world.

They vary from a tiny si+e used in watches to the larger gears used in marine speed reducers,

bridge lifting mechanisms and rail road turn table drives. They form vital elements of main

and auxilary machanisms in many machines such as automobiles, tractors, metal cutting

machine tools, rolling mills, hoisting and transmitting machinery, marine engines etc.

Toothed are used to change the speed or power ratio as well as direction between input and

output.

4;1 -e=i&i.i


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Manufacturing of gears is complex, since special tools and e5uipment are necessary to

manufacture.

ue to errors and inaccuracy in their manufacture, the drive may become noisy

accompained by vibration and high speed.

They are not suitable for large center distances because the drive becomes bulky.

4;2 GE"ERAL CLASSIFICATIO" OF GEARS:

epending upon the relation between the axes, shape of the solid on which the teeth

are developed, curvature of the tooth trace and any other special features, gears are

categori+ed into the following types.

4;2;1 Sur gear*:

In a pair of mating spur gears the axes of the component gears are parallel, that is they

are mounted on shafts which are parallel to each other. The gear teeth are straight along the

length and parallel to the axes.

ig 2

4;2;2 e!ia! gear*:


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In these gears also the axes are parallel and the pitch solid is cylindrical. The traces or

the elements of teeth are helices and these may be left handed or right handed.

ig C

4;2;3 erri&g


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ig 7

4;2;5


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ig F

4;2;7 ?


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ig B

a@ i. ir!e:

/itch circle is an imaginary circle, which by pure rolling motions would give same

motion as the actual gear.

@ i. ir!e (iae.er:

It is the diameter of the pitch circle. The si+e of gear usually specified by the pitch

circle diameter. It is also called pitch diameter.

@ i.


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g@ -e((e&(u:

It is a radial distance of a tooth from pitch circle to the bottom of tooth.

@ A((e&(u ir!e:

It is the circle drawn through the top of tooth and is concentric with the pitch circle.

i@ -e(e&(u ir!e:

It is the circle drawn through the bottom of tooth and is concentric with the pitch

circle.

@ Ciru!ar i. :

It is the distance measured to the circumference of the pitch circle from a point of one

tooth the corresponding point on next tooth. It is denoted by /c .

/cKL)

#here /cK circular pitch

K diameter of pitch circle

)K no. (f teeth on wheel

@ -iae.ra! i. :it is the ratio of no. (f teeth to the pitch circle diameter in mm, it is

denoted by /d.

/dK )L K /c

!@ #


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It is the radial distance from addendum and the dedendum circle of a gear. It is e5ual

to the sum of addendum to the dedendum.


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It is the radius that connects the circle to the profile of the teeth.

@ a.


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proportional to the magnitude of the pitch error. This can be some what alleviated by

providing tip relief of teeth and lapping the teeth to have a crowning.

!onger duration of meshing period generally reduces noise level. Helical gears are

better than spur gears in this respect, because the engagement of teeth is gradual and more

teeth are mesh simultaneously which helps to cancel out the bad effects of tooth error

resulting in smoother operation.

-ears may become more prone to vibration due to resonance. Therefore, natural

fre5uency of the system must lie away from the critical +one or the inclination towards co

vibration should be corrected by providing appropriate shape and providing vibration

damping methods.

-ear box housing should be so designed that the resonance effect is avoided by

damping. #ebs and ribs should be appropriate placed to attain this objective.

4;5 CARACTERISTICS OF ELICAL GEARS :

Helical gears are analogous to a set of stepped gears which consist of a number of

identical spur gears so arranged that the teeth of each individual member are slightly out of

phase relative to each other. In such an arrangement there is an mesh at the pitch line, other

mating pairs of teeth are in different phases of contact including approach and recess

contacts. ' helical gear construction is approximated if a composite body is made up of an

infinite number of such stepped gears, each of which is a lamination of infinitesimal

thickness, placed side by side successively with a slight phase difference.

4;5;1 Tru*. ara.eri*.i*


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rotation of individual gears. $ince the axial force or thrust is created due to the helical

orientation of the teeth, there by altering the direction of main tooth force ?normal force@.

The helix angle should be chosen carefully. or single helical gear running on parallel

shafts it is prudent to confine the helix angle within 2; degrees.

4;5;2 F


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*oungs modulus K 2L "7 )1mm2.

/oissons ratio K ;.C

Maximum bending stress K 9;; )1mm2

Maximum design compressive stress K ==;; )1mm2

ensity K F.GBL"


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CATER 5

ROBLE# -EFI"ITIO"

The objective of this project is to give a design of helical gear drive, which has

interchangability with the existing spur gear drive. There are constraints to be taken care of

i.e, centre distance and transmission ratios. The existing gear box has a single gear drive,

which restricts its user to have variable speeds at a time, so a gear train is to be designed for a

minimum of 9 speeds.

The given data of the existing gear drive is as follows6

/ower ?/@ K CF2G.7 #

$peed ?)@ K =9C; rpm

entre distance ?a@ K ==; mm

ace width ?b@ K27 mm


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air* 21@ 7634 7139 6545 5852 3476 3971 4565 5258

Tra&*i**i

5;1 a@ -e.eri&a.i


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MnK O?tLw@1?PdLvLEL*@Q=12

#here

tK /Ls13

wK =.=7

PdK 7:.9 )1mm2

vK :.=1?:.=R3@

3 K SLpL)p

pK ?pLmn1cos@

a K O?pRg@Lmn12 osQ

E K b1mn

bK O?=.=7LSLmn@1sinQ

* K SLy

yK ;.=22

5;1 @ -e*ig&


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bK =.=7LSLmn1$in

eK 1osC

5;1 @ S.re&g.


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)2K :9; rpm

mnK O?tLw@1?$dLvLEL*@Q=12

tK /L=;;;13

sK =

3 K SLpL)p

K ?SLpLmnL)p@1?:;;;;Los@

pK O2aLosQ1OmnL?iR=@Q

K ?2L==;L;.B:@1C.2C7Lmn@

K :7.CF1mn

3 K ?C.=9L:7.CFL=9C;@1?;.B:L:;;;;@

K 7.;B m1s

K CF2G.7L=17.;B

K FC2.7 )

Pd K 7:.9 )1mm2

vK :.=1?:.=R3@

K :.=1?:.=R7.;B@

K ;.797

E K b1mn

b K O?=.=7LSLmn@1$inQ

K O?=.=7LC.=9Lmn@1;.2GQ

K =C.==

* K SLy

K S?;.=79< ;.B=21Te@


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y K ;.=22

K C.=9L;.=22

K ;.CGC;G

mn K O?FC2.7L=.=7@1?7:.9L;.797L=C.==L;.CGC@Q=12

K2.C9

m K mn1cos

K 2.C91;.B:

K 2.9C K 2.7 ?approx@

2.7 mm is selected as the standard module for all the gears as it is calculated for the highest

transmission ratio.

$ince standard modules are 2 , 2.7 , C , C.7 ......

1*. air :

a K O?=R2@Lmn12cosQ

==; K ?C.2C7L=L2.9@1?2L;.B:@ since 2K 2.2C7 =

There for =K GG1C.2C7

= K 2F

= K 2F, 2K :=

K Lm

pK 2FL2.7 K :F.7 mm

gK :=L2.7 K =72.7 mm

/ K 1 p

K 2F1:F.7

K ;.9


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/nK /1os

K ;.91;.B:

K ;.92

4oot diameter ?r@K osNn

rpK :F.7L;.B99 K :C.FC X :9 mm ? for pinion@

rgK =72.7L;.B99 K =9C.BB X =99 ? for gear @

(uter diameter ?o @K R2mn

op K :7.7R9.G K F2.C X F2 mm

og K =72.7R9.G K =7F.C X =7F mm

aK tL Tan

tK /Ls13

3 K SL pL)p

K ?C.=9L:7.7L=9C;@1?:;;;;@

K 7.;7 m1s

tK CF2G.7L=17.;B

K FCG.CG )

aK FCG.CGL;.2GF

K 2==.F )

rK tLtanN1cos

K FCG.CGLtan2;1cos=:

K 2FB.7G )

b K =.=7LSLmn1sin

K =C.==Lmn


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K C=.7 mm

eK 1cosC

epK C=

eg K :B

d K tRVOEC3?bos2Rt@osQ1OEC3R?bos

2 R t@=12QW

K 2G:.C7

KFCG.CGR

VO2;.:FL7.;7?2G:.C7LC=.7L;.B29RFCG.CG@QL;.B:12;.:FL7.;7R?2G:.C7LC=.7L;.B29RFCG.CG@=12

QW

K 7;=2.2 )

s K PeLbL*Lmn

Pe K A.H.)L=.F7 K 2;;L=.F7 KCG7 )1mm2

sK CG7LC=.7L;.C7GL2.9

sK =;929.= )

w K pLbL%Lk1cos2

% K 221?=R2@

K =.CB

E K OPes 2LsinN1=.9QLO?"=R"2@1"="2Q

K =.G:9

K:F.7LC=.7L=.CBL=.G:91;.B29

K 7B:2 )

2&(air :

a K O?=R2@Lmn12cosQ


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==; K ?2.G2=L=L2.9@1?2L;.B:@ since i K =.G2=

There for =K GG12.G2=

= K C=

= K C=, 2K 7F

K Lm

pK C=L2.7 K FF.7 mm

gK 7FL2.7 K =92.7 mm

/ K 1 p

K C=1FF.7

K ;.9

/nK /1os

K ;.91;.B:

K ;.92

rK osNn

rpK FF.7L;.B99 K FC.=: X FC mm

rgK =92.7L;.B99 K =C9.72X =C7 mm

o K R2mn

op K FF.7R9.G K G2.C X G2 mm

og K =92.7R9.G K =9F.C X =9F mm

aK tL Tan

tK /Ls13

3 K SL pL)p

K ?C.=9LFF.7L=9C;@1?:;;;;@


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K 7.G m1s

tK CF2G.7L=17.G

K :92.G7 )

a K :92.G7L;.2GF

K =G9.7 )

r K tLtanN1cos

K :92.G7Ltan2;1cos=:

K 29C.9; )

b K =.=7LSLmn1sin

K =C.==Lmn

K C=.7 mm

e K 1cosC

epK C7

eg K :9


2 R t@=12QW

K C9C.:

K :92.G7R

VO2;.:FL7.G?C9C.:LC=.7L;.B29R:92.G7@QL;.B:12;.:FL7.GR?C9C.:LC=.7L;.B29R:92.G7@=12

QW

K :=9=.B7 )

s K PeLbL*Lmn


sK CG7LC=.7L;.CF=L2.9

sK =;FBG.CC )


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w K pLbL%Lk1cos2

% K 221?=R2@

K =.2B


K =.G:9

KFF.7LC=.7L=.2BL=.G:91;.B29

K :C72.G )

3r(

air :

a K O?=R2@Lmn12cosQ

K ?2.99L=L2.9@1?2L;.B:@ since 2K =.99=

There for =K GG12.99

= K C:

= K C:, 2K 72

K Lm

pK C:L2.7 K B; mm

gK 72L2.7 K =C; mm

/ K 1 p

K C:1B;

K ;.9

/nK /1os

K ;.91;.B:

K ;.92

rK osNn


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rpK B;L;.B99 K G9.B: X G7 mm

rgK =C;L;.B99 K =22.F2X =2C mm

o K R2mn

op K B;R9.G K B9.G X B7 mm

og K =C;R9.G K =C9.G X =C7 mm

aK tL Tan

tK /Ls13

3 K SL pL)p

K ?C.=9LB;L=9C;@1?:;;;;@

K :.F9m1s

tK CF2G.7L=1:.F9

K 7CC.=B )

aK 7CC.=BL;.2GF

K =7C.= )

rK tLtanN1cos

K 7CC.=BLtan2;1cos=:

K 2;=.GG )

b K =.=7LSLmn1sin

K =C.==Lmn

K C=.7 mm

eK 1cosC

epK 9=

eg K 7B


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2 R t@=12QW

K C9C.:

K 7CC.=BR

VO2;.:FL:.F9?C9C.:LC=.7L;.B29R7CC.=B@QL;.B:12;.:FL:.F9R?C9C.:LC=.7L;.B29R7CC.=B@=12QW

K :C:C.F2 )

s K PeLbL*Lmn


sK CG7LC=.7L;.CB:L2.9

sK ==727.BF )

w K pLbL%Lk1cos2

% K 221?=R2@

K =.=G


K =.G:9

KB;LC=.7L=.=GL=.G:91;.B29

K :F9G.72 )

4.air :

a K O?=R2@Lmn12cosQ

K ?2.=2L=L2.9@1?2L;.B:@ since 2K =.=2=

There for =K GG12.=2

= K 92

= K 92, 2K 9:

K Lm


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pK 92L2.7 K =;7 mm

gK 9:L2.7 K ==7 mm

/ K 1 p

K 921=;7

K ;.9

/nK /1os

K ;.91;.B:

K ;.92

rK osNn

rpK =;7L;.B99 K BB mm

rgK ==7L;.B99 K =;B mm

o K R2mn

op K =;7R9.G K ==; mm

og K ==7R9.G K =2; mm

aK tL Tan

tK /Ls13

3 K SL pL)p

K ?C.=9L=;7L=9C;@1?:;;;;@

K F.G:m1s

tK CF2G.7L=1F.G:

K 9F9.C: )

aK 9F9.C:L;.2GF

K =C: )


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rK tLtanN1cos

K 9F9.C:Ltan2;1cos=:

K =FB.:= )

b K =.=7LSLmn1sin

K =C.==Lmn

K C=.7 mm

eK 1cosC

epK 9G

eg K 72


2 R t@=12QW

K 2G:.C7

K 9F9.C:R

VO2;.:FLF.G:?2G:.C:LC=.7L;.B29R9F9.C:@QL;.B:12;.:FLF.G:R?2G:.C:LC=.7L;.B29R9F9.C:@=12

QW

K 7GC9.77 )

s K PeLbL*Lmn


sK CG7LC=.7L;.9;GL2.9

sK ==GF7.27 )

w K pLbL%Lk1cos2

% K 221?=R2@

K =.;7


K =.G:9

K=;7LC=.7L=.;7L=.G:91;.B29

K F;;7.GG )

F


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/ower K CF2G.7 #

$peed ?)=@ K =9C; rpm

enter distance ?a@ K ==; mm

ace width ?b@ K C=.7 mm

"<

See("1@ =9C; =9C; =9C; =9C; =9C; =9C; =9C; =9C;

See("2@ :CC FFG BB; =C;: C22G 2:2B 2;:F =7::

T

Helical Gears Project

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