Lecture Notes

Design Example - Hay Wagon

source
source

Physical Setup

Each 1250-lb bale is supported by two 4-ft cylindrical beams, which are welded to the wagon's frame.

Statics

FBD of cantilever with distributed
loading and fixed support

w = W / 2L IDE 50

internal-loading diagrams

V_max = W / 2
M_max= WL / 4 IDE 50

Mechanics-of-Materials

bending stress

s = 2WLr_o / 2p(r_o⁴ - r_i⁴) IDE 110 test 2

moment of inertia

IDE 50

shear stress

t = 2W(r_o³ - r_i³) / 3pt(r_o⁴ - r_i⁴) IDE 110 test 2

deflection

y_max = WL³ / 4pE(r_o⁴ - r_i⁴) IDE 110 test 4

Design

factor of safety

IDE 110 test 1

cost, weight, availability, etc.

prototype testing

IDE 120

FBD of cantilever with distributed loading and fixed support	w = W / 2L	IDE 50
internal-loading diagrams	V_max = W / 2 M_max= WL / 4	IDE 50
Mechanics-of-Materials
bending stress	s = 2WLr_o / 2p(r_o⁴ - r_i⁴)	IDE 110 test 2
moment of inertia		IDE 50
shear stress	t = 2W(r_o³ - r_i³) / 3pt(r_o⁴ - r_i⁴)	IDE 110 test 2
deflection	y_max = WL³ / 4pE(r_o⁴ - r_i⁴)	IDE 110 test 4
Design
factor of safety		IDE 110 test 1
cost, weight, availability, etc.
prototype testing		IDE 120