Roda Gigi (Gear)

Perencanaan

Gear Box

Geometri(jumlah gigi,

involute teeth)

Kecepatan

MaterialDaya yang

ditransmisikan

Efisiensi

Perencanaanporos

Friction WheelsGerak dan daya yang ditransmisikan oleh gigi adalah setara dengan yang dikirimkan oleh roda. untuk memahami bagaimana gerakan dapat ditularkan oleh dua roda bergigi, mempertimbangkan dua roda melingkar polos A dan B dipasang pada poros.

Velocity Ratio

2

1

2

1

1

2

1

2

T

T

d

d

N

N

Gear DrivesAdvantages

1. Dapat mentransmisikan rasio kecepatan yang tepat.

2. Dapat digunakan untuk mengirimkan daya yang besar.

3. Memiliki efisiensi tinggi.

4. Memiliki tata letak yang kompak.

Disadvantages

1. Karena pembuatan gigi memerlukan peralatan dan perlengkapan

khusus , oleh karena itu lebih mahal dari drive lainnya.

2. Kesalahan dalam pemotongan gigi dapat menyebabkan getaran dan

kebisingan selama operasi.

3. Hal ini membutuhkan pelumas yang sesuai dan metode yang dapat

diandalkan untuk menerapkannya, untuk operasi yang tepat dari drive.

Klasifikasi Kecepatan Roda Gigi1. Low velocity ( < 3 m/s )

2. Medium velocity ( 3 - 15 m/s )

3. High velocity ( > 15 m/s )

Bentuk GigiCYCLOIDAL INVOLUTE

Bentuk GigiCYCLOIDAL

1. Lebih kuat pada pitch yang sama dengan involute

2. Tidak terjadi interference (lebih smooth)

INVOLUTE

1. Pressure angle konstan

2. Velocity ratio tidak berubahdengan berubahnya ukuran gigi

Sistem Gigi1. 14 1/2 ° Composite

2. 14 1/2 ° Full depth involute

3. 20 ° Full depth involute

4. 20 ° Stub involute

Sistem Gigi

Interference Gigi Involute

Interference Gigi Involute

Interference Gigi Involute

Material Roda GigiPertimbangan dalam pemilihan material roda gigi

1. Kekuatan ijin

2. Noise

3. Keausan

4. Dan lain-lain

Material roda gigi

1. Metallic

2. Non-Metallic

Table 28.3. Properties of commonly used gear materials

Pertimbangan Desain Roda Gigi1. Kekuatan yang ditransmisikan,

2. Kecepatan dari roda gigi penggerak,

3. Kecepatan dari roda gigi yang digerakkan atau rasio kecepatan, dan

4. Jarak titik pusat.

Syarat yang harus dipenuhi :

1. Gigi pada roda gigi harus memiliki kekuatan yang cukup sehingga tidakrusak dibawah beban statis dan beban dinamis.

2. Gigi pada roda gigi harus memiliki karateristik keausan yang tinggi.

3. Penggunaan ruang dan material harus ekonomis.

4. Penyelerasan gigi dan defleksi pada poros harus diperhatikan karenaberpengaruh pada kinerja pada roda gigi.

5. Pelumasan roda gigi harus cukup.

28.17 Kekuatan Batang Gigi pada Roda Gigi – Lewis Equation

Tegangan kerja yang diizinkan ( σw) dalam persamaan Lewis tergantung pada bahan yang tegangan statis yang diijinkan ( σo) dapat ditentukan. Tegangan statis yang diijinkan adalah tegaangan pada batas elastis bahan. Hal ini juga disebut tegangan dasar.

28.18 Tengangan Izin yang bekerja untuk roda gigi pada Persamaan Lewis

Mekanisme gigi sepeda mengganti rantai antara sprocket

ukuran yang berbeda di pedal dan roda belakang. Naik

bukit, depan kecil dan sproket belakang yang besar yang

dipilih untuk mengurangi tekanan diperlukan untuk

pengendara. Pada tingkat, depan dan belakang besar

kecil. sproket digunakan untuk mencegah Pembalap

harus mengayuh terlalu cepat

Faktor kecepatan digunakan untuk membuat perkiraan koreksi untuk efek pembebanan dinamis. Beban dinamis disebabkan berikut :

1. Ketidakakuratan dari jarak gigi,

2. Penyimpangan dalam profil gigi, dan

3. Lendutan gigi bawah beban.

28.19 Beban Dinamis pada Gigi

28.20 Beban Statis pada Gigi

Beban statis gigi (disebut juga kekuatan batang atau kekuatan daya tahan pada gigi) diperoleh dari rumus lewis dengan mengganti batas ketahanan lentur dan batas tegangan elastis (σe) pada tegangan izin (σw) yang bekerja.

Untuk keamanan, terhadap kerusakan gigi, beban statis (WS) harus lebih besar dibandingkan beban dinamis (WD). Buckingham menyarankan mengikuti hubungan antara WS dan WD

Untuk steady loads, WS ≥ 1,25 WD

Untuk pulsating loads, WS ≥ 1,35 WD

Untuk shock loads, WS ≥ 1,5 WD

Note :

Untuk baja, batas ketahanan lentur (σe) dapat diperoleh dengan menggunakan hubungan berikut :

Causes of Gear Tooth Failure1. Bending Failure

Every gear tooth acts as a cantilever. If the total repetitive dynamic load acting on the gear tooth is greater than the beam strength of the gear tooth, then the gear tooth will fail in bending, i.e. the gear tooth will break.

The module and face width of the gear is adjusted so that the beam strength is greater than the dynamic load.

2. Pitting

The failure occurs when the surface contact stresses are higher than the endurance limit of the material.

The dynamic load between the gear tooth should be less than the wear strength of the gear tooth.

Causes of Gear Tooth Failure3. Scoring

The excessive heat is generated when there is an excessive surface pressure, high speed or supply of lubricant fails.

By properly designing the parameters such as speed, pressure and proper flow of the lubricant, so that the temperature at the rubbing faces is within the permissible limits.

4. Abrasive Wear

The foreign particles in the lubricants such as dirt, dust or burr enter between the tooth and damage the form of tooth.

By providing filters for the lubricating oil or by using high viscosity lubricant oil which enables the formation of thicker oil film.

Causes of Gear Tooth Failure5. Corrosive Wear

The corrosion of the tooth surfaces is mainly caused due to the presence of corrosive elements such as additives present in the lubricating oils.

Proper anti-corrosive additives should be used.

Spur Gear Constructiona. The dedendum circle diameter is slightly greater than the shaft

diameter, then the pinion teeth are cut integral with the shaft

Spur Gear Constructiona. If the pitch circle diameter of the

pinion is less than or equal to 14.75 m + 60 mm (where m is the module in mm), then the pinion is made solid with uniform thickness equal to the face width

b. Small gears up to 250 mm pitch circle diameter are built with a web, which joins the hub and the rim. The web thickness is generally equal to half the circular pitch or it may be taken as 1.6 m to 1.9 m, where m is the module. The web may be made solid.

Gear with Arms

Gear with Arms

Gear with Arms

The hub diameter:

1. 1.8 times the shaft diameter for steel gears

2. Twice the shaft diameter for cast iron gears

3. 1.65 times the shaft diameter for forged steel gears used for light service.

The length of the hub is kept as 1.25 times the shaft diameter for light service and should not be less than the face width of the gear.

Gear with Arms

Design of Shaft for Spur Gears

Design of Shaft for Spur Gears

Design of Arms for Spur Gears1. The cross-section of the arms is calculated by assuming

them as a cantilever beam fixed at the hub and loaded at the pitch circle.

2. It is also assumed that the load is equally distributed to all the arms.

3. It may be noted that the arms are designed for the stalling load.

4. The stalling load is a load that will develop the maximum stress in the arms and in the teeth. This happens at zero velocity, when the drive just starts operating.

Design of Arms for Spur GearsStalling load

Design of Arms for Spur GearsMaximum bending moment on each arm

Design of Arms for Spur GearsSection modulus of arms for elliptical cross-section

Helical Gear

Definisi1. A helical gear has teeth in form of helix around the gear.

2. The helixes may be right handed on one gear and left handed on the other.

3. Helical gears give smooth drive with a high efficiency of transmission.

Helical Gear Type1. Single helical gear menghasilkan gaya aksial pada gigi

2. Double helical gear terjadi keseimbangan gaya aksial

Nomenclature1. Helix angle. It is a constant angle made by

the helices with the axis of rotation.

2. Axial pitch. It is the distance, parallel to the axis, between similar faces of adjacent teeth. The axial pitch may also be defined as the circular pitch in the plane of rotation or the diametral plane.

3. Normal pitch. It is the distance between similar faces of adjacent teeth along a helix on the pitch cylinders normal to the teeth. It is denoted

Face Width of Helical Gears

Face Width of Helical Gears

Formative or Equivalent Number of Teeth for Helical Gears

Proportions for Helical GearsAmerican Gear Manufacturer's Association (AGMA)

Strength of Helical Gears

Strength of Helical Gears

Strength of Helical Gears

Contoh

Contoh

Contoh

Contoh

Contoh

Bevel Gears

Introduction Used for transmitting power at a constant velocity ratio

between two shafts whose axes intersect at a certain angle.

The pitch surfaces for the bevel gear are frustums of cones.

The elements of bevel gear pitch cones and shaft axes must intersect at the same point.

Classification of Bevel Gears Mitre gears

Angular bevel gears

Crown bevel gears

Internal bevel gears

Nomenclature

Nomenclature

Nomenclature

Determination of Pitch Angle for Bevel Gears

Proportions for Bevel Gear

Formative or Equivalent Number of Teeth for Bevel Gears

Formative or Equivalent Number of Teeth for Bevel Gears

Formative or Equivalent Number of Teeth for Bevel Gears

Strength of Bevel Gears

Strength of Bevel Gears

Forces Acting on a Bevel Gear

Design of a Shaft for Bevel Gears

Design of a Shaft for Bevel Gears

Diketahui:2 buah bevel gear 200 full depth steel denganN1 = 40 gigiN2 = 60 gigiPd = 4 pada diameter luarb = 2,5 inb’ = 1,5 inBHN = 300AGMA quality No.8

Contoh Soal 1:

Ditanyakan:

1. Kecepatan ( Vb )?

2. Daya transmisi ( hp ) ?

Apabila gear beroperasi dalam kapasitas maksimum

Keterangan :

N = Number of teeth

Pd = diameter pitch

b = face width of tooth

b’ = thickness thickness bevel gears

BHN = Brinell Hardness Number

AGMA = American Gear Manufacturers Association

Flowchart :

2 buah bevel gear 200

full depth steel

N1 = 40 ; N2 = 60 ; Pd = 4

b = 2,5 in ; b’ = 1,5 ;

BHN = 300

AGMA quality no.8

A

Mulai

Outside radius of pitch cone

ro1 dan ro2

A

Pitch cone angle of

bevel gears

α

Pitch radius

r1

Pitch diameter

d1

Factor in wear

equation

Q’

B

B

Pitch radius, formative

gear

r’1

Konstanta

( dari grafik )

K

C

C

Limit Load for wear

Fw

Dynamic tooth load

Fd

Perbandingan jml gigi

C

D

D

Massa ekuivalen dari

2 gear

me

Typical error in tooth

outline

e

Spring konstans

k

E

E

Speed of rotation

n

F

F

Kecepatan ( Vb )

Daya transmisi ( hp )

Selesai

Penyelesaian:

Keterangan :

ro = outside radius of pitch cone (in)

α = pitch cone angle (o)

r1 = pitch radius (in)

d1 = diameter pitch (in)

BHN = 300 maka K= 136 ( dari Grafik/tabel)

Dengan interpolasi

Keterangan:

Q’ = factor in wear equation of bevel gears

r’1 = pitch radius formative gears (in)

Fw = limit load of wear (lb)

Jika power maksimum maka:

Keterangan:

Fd = dynamic tooth load (lb)

Fp = horsepower force

C = perbandingan jml gigi

me = massa ekuivalen dari 2 gear

( lb sec2 / in)γ = weight per unit volume ( 0,283 lb/in3 )

e = 0,0035 + 0,0036 = 0,0071 ( dari tabel )

k = 1.667.000 x 2,5 = 4.167.000 lb/in

Contoh Soal 2:

Bevel gear pada soal pertama

mentransmisikan 100 horsepower pada saat

beroperasi pada kapasitas maksimum.

Carilah BHN dan kecepan maupun kecepatan

putaran gear tersebut harus dioperasikan.

Ditanya :

BHN = ?

Vb = ?

n1 = ?

Flowchart :

hp = 100e = 0,0071

N1 = 40 gigik = 4.167.000 lb/in

me = 304 ( lb sec2 / in)d1 = 8,612 inφ= 20 derajat

A

Mulai

Dynamic force

Fd

A

Wear Capacity of

tooth

Fw

Konstanta

K

B

B

BHN

Kecepatan ( Vb )

Kecepatan putaran (n1 )

Selesai

Penyelesaian:

Subtitusi persamaan 1 dan 2

Jika power maksimum :

= 153

BHN = 318 ( dari grafik / tabel ) dengan cara interpolasi

Worm Gears

Introduction Transmit power at high velocity ratios up to 300:1 Lower efficiency

The worm gearing is mostly used as a speed reducer

The worm (which is the driving member) is usually of a cylindrical form having threads of the same shape as that of an involute rack

Type of Worms

Type of Worm Gears

Nomenclature Axial Pitch (Pa)

Nomenclature Lead and lead angle

Nomenclature Tooth Pressure Angle

High Efficiency

Nomenclature Normal Pitch

Nomenclature Helix Angle

Velocity Ratio

Nomenclature

Nomenclature

Proportion of Worms

Proportion of Worms

Proportion of Worm Gears

Efficiency of Worm Gearing

Efficiency of Worm Gearing

Efficiency of Worm Gearing

Strength of Worm Gear Teeth

Strength of Worm Gear Teeth

Wear Tooth Load for Worm Gear

Wear Tooth Load for Worm Gear

Thermal Rating of Worm Gearing

Thermal Rating of Worm Gearing

Forces Acting on Worm Gears

Forces Acting on Worm Gears

Design of Worm GearingGiven Power Transmitted, Speed, Velocity, Ratio and The Centre Distance Between The Shafts

Determined Lead Angle, Lead and Number of Threads on The Worm

Design of Worm Gearing

Design of Worm Gearing

Contoh Soal 1

Contoh Soal 1

Contoh Soal 2

Contoh Soal 2