KLASIFIKASI PEGAS Pegas dapat digolongkan atas dasar jenis beban yang dapat diterimanya yaitu :• Pegas Tekan• Pegas Tarik• Pegas PuntirSedangkan jika dipandang dari segi bentuk, maka pegas dapat dibedakan menjadi lima bagian, yaitu :o Pegas Voluto Pegas Dauno Pegas Piringo Pegas Cincino Pegas Batang Puntiro Pegas Spiral atau Pegas jam
Types of springs • Helical springs • Conical and volute springs • Torsion springs • Laminated or leaf springs • Disc or bellevile springs
1. Helical Spring A helical spring is made up of a wire coiled in the form a helix • Circular • Square • Rectangular -Compression helical springs -Tension helical spring Closely Coiled HS Helical Springs Open Coiled HS
1. Helical Spring Compression Spring (Pegas Tekan) 1.Fungsi : a. Menyimpan gaya yang selanjutnya dikonversikan menjadi energi b. Peredam 2. Penggunaan : a. Persenjataan b. Sistem suspensi c. Pembatasan Gaya (pada pengepresan)
1. Helical Spring Pegas Tarik (Tensile Spring) 1.Fungsi : a. Penyiman gaya b. Penyimbang 2. Penggunaan : a. Timbangan b. Standrt c. Tromol
2. PegasKerucut (Volute Spring & Conical spring) 1.Fungsi : a. Memberi reaksi dan mengatur tekanan 2. Penggunaan : a. Penutup cup mobile b. Pembersi kaca di mobil
2. PegasKerucut (Volute Spring & Conical spring) Conical Spring Volute Spring
2. PegasKerucut (Volute Spring & Conical spring) The characteristic of volute / conical spring is sometimes utilised in vibration problems where springs are used to support a body that has a varying mass.
3. Torsion Springs 1.Fungsi : a. Menerima beban dan memberi reaksi puntiran b. Penyeimbang c. Suspensi 2. Penggunaan : a. Handle mobil b. Penjepit • Helical Torsion Spring • Spiral torsion spring
3. Torsion Springs Helical Torsion Spring Spiral Torsion Spring
The Analysis of Compression Springs • Solid Length When the coils contact with each other • Free Length The normal condition of compression springs • Spring Index Ratio of mean diameter of the coil & the diameter of the wire • Spring Rate The load required per unit deflection of the spring • Pitch the axial distance between adjacent coils in uncompressed state. (P) Equilibrium under the action of two forces (W) and the Twisting moment (T)
The Analysis of Compression Springs D = Mean diameter of the spring coil d = Diameter of the spring wire n = Number of active coils G = Modulus of rigidity for the spring material W = Axial load on the spring fs = Shear stress induced in the wire due to the twisting moment C = Spring index = D/d p = Pitch of the coils δ = Deflection of the spring, as a result of an axial load. • Ot only shear stress induced in the wire, the following stresses also act on the wire : • Direct shear stress due to the load W • Stress due to curvature of wire.
The Analysis of Compression Springs The direct stress due to the load W = Load / Cross-sctional area of the wire • Direct Shear • Curvature of the wire The maximum shear stress The effect Substituting D/d=C A shear stress factor (K) / Wahl Stress factor Dimana K yaitu :
The Analysis of Compression Springs The values of K for a given index C Wahl’s stress factor oncreases very rapidly as the spring index decreases. In machinery the mostly used spring index above 3.
The Analysis of Compression Springs The standard size of the spring wire may be selected from the following table
The Type of End Connections for Helical Springs Plain ends Squared ends Ground ends Squared & Ground ends
The Characteristic of End Connections for Helical Springs • Inactive Coils The part of the coil which is in contact with the seat does not contribute to spring action. • Active Turns The part of the springs that action.
The Connections of Tensile for Helical Springs • Large stress concentration is produced at this point. • Attaching device of tension spring
The Connections of Tensile for Helical Springs A Compression Spring Tensile Spring
Deflection of helical springs of circular wire Axial deflection of spring Spring Rate / Stiffness of the Spring Constant
Energy stored in helical springs of circular wire Asumtion load is applied gradually V = Volume of the spring wire If : P = load h = height
Helical Torsion Springs • The ends are shaped to transmiit torque. • Bending stress • The radius of curvature of the coils changes when the twisting moment is applied Bending Stress Total Angle of Twist / Angular Deflection Deflection
Flat SpiralSprings • Long thin strip of elastic material wound like a spiral. • Watches • Gramaphone • Since the radius of curvature of every spiral decreases when the spring is wound up, therefore the material of the spring is in a state of pure bending.
Flat SpiralSprings Bending Moment B at max distance from the application of P Bending Moment Max Maximum bending stress Deflection (angular) Asumtion : both ends of the spring are clamped Strain energy stored in the spring Deflection
4. PegasDaun/ Leaf Spring (laminated or carriage spring) Application : For heavy vehicles, they have the advantage of spreading the load more widely over the vehicle's chassis, whereas coil springs transfer it to a single point. Thereby saving cost and weight in a simple live axle rear suspension.
4. PegasDaun/ Leaf Spring (laminated or carriage spring ) Flat spring Deflection :
4. PegasDaun/ Leaf Spring (laminated or carriage spring ) Bending Stress Full length graduated Nipping Equalised Stress Stress in full length = 50% Stress in graduated Should be equal The Steps : 1. Making full length smaller thickness than the graduated leaves. 2. Given greater radius of curvature to the full length than graduated.
4. PegasDaun/ Leaf Spring (laminated or carriage spring ) The Value of initial Gap (Nip C) Nipping The Load on the clip bolt Wb 1. The final stress equal to graduated due to applied load plus initial stress. 2. The deflection due to applied load is same as without initial stress Final Stress = Stress in the full length due to applied load minus the initial stress
4. PegasDaun/ Leaf Spring (laminated or carriage spring ) The lenght of the leaf spring leaves Band is used The effective U-Bolts is Used The length of leaves Smallest leaf Next leaf Length of (n-1)th leaf
4. PegasDaun/ Leaf Spring (laminated or carriage spring ) d = diameter of eye t = thickness of master leaf Length of master leaf Standart sizes of automobile suspension springs • Standart nominal widths : 32, 40*, 45, 50*, 55, 60*, 65, 70, 80, 90*, 100 & 125mm. • Standart nominal thickness : 3,2; 4,5; 5; 6; 6,5; 7; 7,5; 8; 9; 10; 11; 12; 14; & 16mm • The recommended eye bore diametrs : 19, 20, 22, 23, 25, 27, 28, 30, 32, 35, 38, 50, & 55mm. • The diameter of centre bolts:
4. PegasDaun/ Leaf Spring (laminated or carriage spring ) 5. Clip section and sizes of rivets & bolts
4. PegasDaun/ Leaf Spring (laminated or carriage spring ) Materials for leaf springs • Automobiles : 50Crl, 50Crl V23,55Si2 Mn90 (Hardened & Tempered) • Rail road C 55 (water – Hardened), C 75 (oil – Hardened), 40 Si2 Mn 90 (Water – Hardened), 55Si2 Mn90 (oil – Hardened) • All values are for oil quenched condition and for single heat only.
B. BahanPegas (Material) • Depends on what they are used • Severe service • Average service • Light service • Severe service • Rapid continous loading • Ratio of minimum to maximum load is one half • Automotive valve springs • Average service • Intermittent operation loading • Ratio of minimum to maximum load is one half • Engine - Governor springs • Light service • Very infrequently varied Load • Safety valve springs
B. BahanPegas (Material) -The material treatment of helical springs both Cold Formed or Hot Formed. -The material treatment depends on the size of the wire. -Wires : < 10 mm Cold > 10 mm Hot - The Srength size - Small size have greath strength & less ductility cold working
Sumber http://www.masterspring.com/spring-wire-form-products/custom-springs/torsion-springs/ http://www.enginehistory.org/Propellers/Governors/hydgov.shtml http://www.automotiveillustrations.com/tutorials/how-to-draw-a-car.html http://www.islandnet.com/~westisle/History/steam2.html http://www.tanhov.com/ProductShow/Pressure-Safety-Valve/Balance-Bellows-Safety-Valve-With-Jacket.html springsandthings.com alibaba.com
A semi-elliptical laminated vehicle spring to carry a load....kg is to consist of seven leaves .....cm wide, two of the leaves extending the full length of the spring. The spring is to be 110 cm in length and attached to the axle by two U-bolts .... Cm apart. These bolt hold the central portion of the spring so rigidly that they may be considered equivalent to a band having a width equal to the distance between bolts. The leaves are to be silico-manganese steel. Assuming an allowable stress of 3500 kg/cm2, determine : • Thickness of the leaves • Deflection of the spring • Diameter of the eye • Length of the leaves • Radius to which leaves should be initially bent • Assume modulus of elasticity as 2,1x10^6 kg/cm2