2. The principal load bearing structure for a proposed bariatric hoist is shown in figure Q2-1, and consists of a pin-jo

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2. The principal load bearing structure for a proposed bariatric
hoist is shown in figure Q2-1, and consists of a pin-jointed truss
attached to an upright beam.
a) Consider the pin-jointed truss shown with pins at A, B, C, D
and E and with a load mass of Mg as shown. Calculate the
reaction forces at A and C as well as the force in the link BE.
(6 marks)
b) Using the results from part (a) draw a shear force and
bending moment diagram of beam. You can ignore the compressive
force along the principal axis of the beam, but show clearly the
dimensions h and s.
c) The following design constraints have already been specified,
so that the hoist can support weights up to 80 cm away from the
base of the support.
Choose either steel or aluminium as the material for the
vertical beam and decide on an appropriate cross-sectional profile.
Hence estimate or calculate the following information so that it
can be used to make subsequent design decisions. In all cases
justify your decisions.
i) Calculate the rotation of the frame ABCDE in response
to the endpoint deflection at E. You can assume that the frame does
not distort in any way and rotates around point C.
ii) Calculate the internal moment (torque) in the vertical
beam at C.
iii) Give the formula for the endpoint deflection of a
beam with a single Moment (torque) loading. Hence find a value for
the EI value needed to not exceed the 3 cm movement of
the winch point E.
iv) Given that the beam will be made of a hollow circular
section and it will be made of a metal such as aluminium or steel,
estimate a value for the second moment of area and hence for the
inner and outer radii of the vertical beam. Justify your
decisions.
You may choose additional design parameters as needed but these
choices should be justified in your answer.