L.D. college of engineering• Subject: Machine Design and Industrial Drafting

• Topic: Design of toggle jack• Year:2014-15

Sr.No. Name Enroll No. Roll No

1 Kuralkar Hemant Yogeshbhai 140283119009 419245

2 Shinde Kunal Bharatbhai 140283119024 419259

3 Sabalpara Nilesh 140283119023 419258

4 Rathod Jaydipsinh 140283119022 419257

5 Patel Sagar 140283119019 419254

6 Vaghela Kanu 140283119025 419260

7 Jadav Vipul 140283119007 419243

Content:

• Mechanism of toggle jack• Design of the screw• Design of the Nut• Design of the Pin• Design of spanner• Design of the Link

Design of toggle jack

Design of toggle jack- Assumed data

• Lifting load = 4KN • Number of Link = 8• Length of the link = 110 mm• Materials for the screw, Nut and pins = M.S.• for M.S. = 100 MPa• 𝞽 for M.S. = 50 MPa• Limited bearing pressure = 20 MPa• Pitch of the screw thread = 6 mm• Co-efficient of the friction = 0.20

Toggle Jack

Design of screw

Design of Square threaded screw

• Maximum load on screw occurs when the jack is in the bottom position.• From figure = → Ѳ = 35.1°

Design of Square threaded screw

• Each nut carries half the total load on the jack• Link CD is subjected to tension

while the square threaded screw is under pull.• F = = = 2846N• This similar pull acts on other

nut,therefore total tensile load on square threaded rod

→= 2F =5692N

Design of Square threaded screw

• Now considering tensile failure of the screw

→= * *→5692= * *100→ = 8.5 mm say 10 mmSince the screw is also subjected to shear stress, therefore let→ = 14 mm

Design of Square threaded screw

• Outer Diameter of screw → = + P = 14+6→= 20 mm.Mean Diameter of screw→d = - = 20 – 3→d = 17 mm

Checking of the screw for principal stress• = = = 0.1123• Effort required to rotate the

screwP = *) P = () = 5692()P = 1822N

Checking of the screw for stress

• Torque required to rotate the screw

→T = P* = 1822*17/2 →T = 15487 N.mmShear stress due to torque→𝞽 = 16х = →𝞽 = 28.7 N/

• Direct Tensile stresses in the screw

→ = = → = 37 N/

Checking for maximum principal stress• Maximum Principal stress→ = + + 4→=+→= 52.6 N/

• Maximum shear stress→ = + 4→ =→ = 34.1 N/

Since the maximum stresses are within limit, therefore design of square threaded screw is safe.

Design of Nut

Number of threads

• Let n is the number of the threads, which can be find by considering bearing failure of nut.

=20= =→ n = 1.776Inorder to have good stability and to prevent rocking of the screw let n = 4

Dimensions of the Nut

• Thickness of nut→t = n*p = 4*6 →t = 24 mm.• Width of the nut→b = 1.5*=1.5*20→b = 30 mm

Length of the screw

• To control the movements of the nuts beyond 210mm , rings of 8mm thickness are fitted on the screw with the help of set screw.

→length of screwed portion = 210 + 24 + 2*8 = 250 mm• Since screw is operated by spanner, therefore

extra 15 mm length both sides are provided.

→Total length = 250 + (2*15) = 280 mm

Length of spanner

• Assuming that a force of 150 N is applied by each person at each end of the rod,

→T = 150*2*Length of spanner→15487 = 150*2*L→ Length of spanner = 51.62 mmWe shall take length of spanner as 200 mm in order to facilitate the operation

Design of the pins in the Nuts

• Let is diameter of the pin.• Considering double shear of the

pin.→ F = 2**𝞽→2846 = 2**50→ = 6.02 mm ≈ 8mm

Design of the Links

Load acting on Link

• Load on the link = F/2 = →2846/2 = 1423 NAssuming factor of safety = 5→ = 5*1423 = 7115 N

Dimensions of the link• Let = thickness of the link• Let = width of the link• Assuming .• cross sectional area of the link ,A→A = * = • Moment of inertia of the cross

section ,I→I = ** = 2.25• Radius of gyration k→K = = 0.866

Buckling of the link in vertical plane• In buckling in vertical plane link

is considered as hinged.Therefore, L = l = 110 mmRankine’s constant a = According to Rankines formula for column,

=

Buckling of the link in vertical plane

• 7115 = • = = 25.7• = 5.07 mm≈ 6mm and• = 3*6 = 18 mm

Buckling of the link in plane perpendicular to vertical plane

• I = *3* = 0.25 • A = * = • K = = 0.29 • Since the buckling of the link in

plane perpendicular to the vertical plane, the ends are considered as the fixed.

→ L = l/2 = 110/2 = 55mm

Buckling of the link in plane perpendicular to vertical plane

• According to Rankine's formula = = Taking = 6 mm = 9532 N.Since buckling load is more then the calculated value,

link is safe in design.

So dimension of the link• = 6mm and• = 18 mm