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1.ESTABLISHING THE LOADS THAT STRESS THE ELEMENTS

OF THE TELESCOPIC LIFTING JACK

Fig 1.1

2. MAIN SCREW CALCULUS

2.1 Choosing the materialIt is choosen OL 37 STAS 300

2.2 Design calculus

Load calculation cQ , Npo

][17820162001.1max NQQc === 1.1..05.1= NQ 16200max =

Inner diameter of the thread 3d , mm

][30.2150

17820443 mm

Qd

ac

c=

=

=

][80....60 MPaac =

1

8/2/2019 Cric Telescopic - Costy - Final- EnG!

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Choosing the standard thread

It is choosen trapezoidal thread Tr 28x5 SR ISO 2904, with the main

dimmensions as shown in Fig 2.1 and Table 2.1

Fig 2.1

Tabelul 2.1

Nominal

Diameter

Pitch Medium

Diameter

Exterior

Diameter

Interior Diameter Angle

mmd, mmp, mmDd ,22 = mmD ,4 mmd ,3 mmD ,1,

28 5 25.5 28.5 22.5 23 30

2.3 Checking the self-locking condition

The threads pitching angle

=

=

= 57.35.25

5

2

2

arctgd

Parctg

Apparent friction angle

=== 53.6

2

30cos

11,0

2cos

' arctgarctg

12,0...11,0= for steel

Self-locking condition'

2