01-02ChapGere.0010 - T allow 5 1800lb t allow 5 4000psi W 5...

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SECTION 1.7 Allowable Stresses and Allowable Loads 41 Problem 1.7-7 A lifeboat hangs from two ship’s davits, as shown in the figure. A pin of diameter d 5 0.80 in. passes through each davit and supports two pulleys, one on each side of the davit. Cables attached to the lifeboat pass over the pulleys and wind around winches that raise and lower the lifeboat. The lower parts of the cables are vertical and the upper parts make an angle a 5 15° with the horizontal. The allowable tensile force in each cable is 1800 lb, and the allowable shear stress in the pins is 4000 psi. If the lifeboat weighs 1500 lb, what is the maximum weight that should be carried in the lifeboat? T T Davit Pulley Pin Cable = 15 ° a Solution 1.7-7 Lifeboat supported by four cables F REE - BODY DIAGRAM OF ONE PULLEY Pin diameter d 5 0.80in. T 5 tensile force in one cable
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Unformatted text preview: T allow 5 1800lb t allow 5 4000psi W 5 weight of lifeboat 5 1500lb S F horiz 5 R H 5 T cos 15 8 5 0.9659 T S F vert 5 R V 5 T 2 T sin 15 8 5 0.7412 T V 5 shear force in pin V 5 Ï ( R H ) 2 1 ( R V ) 2 5 1.2175 T Pin Pulley T 15 ° R V R H A LLOWABLE TENSILE FORCE IN ONE CABLE BASED UPON SHEAR IN THE PINS A LLOWABLE FORCE IN ONE CABLE BASED UPON TENSION IN THE CABLE T 2 5 T allow 5 1800lb M AXIMUM WEIGHT Shear in the pins governs. T max 5 T 1 5 1652lb Total tensile force in four cables 5 4 T max 5 6608lb W max 5 4 T max 2 W 5 6608lb 2 1500lb 5 5110lb V 5 1.2175 T Ê T 1 5 V allow 1.2175 5 1652 lb 5 2011 lb V allow 5 t allow A pin 5 (4000 psi) ¢ p 4 ≤ (0.80 in.) 2 A-PDF Split DEMO : Purchase from www.A-PDF.com to remove the watermark...
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This note was uploaded on 09/20/2009 for the course COE 3001 taught by Professor Armanios during the Spring '08 term at Georgia Institute of Technology.

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