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How to Calculate Moment in Fuselage Frame

How to Calculate Moment in Fuselage Frame

How to Calculate Moment in Fuselage Frame

(OP)
How can a moment in a circular frame be derived due to an external couple?  I am trying to evaluate mc/i of  a frame that has a couple on two external lugs attached to the frame.  It is a symmetrical frame.

    Thanks,
      Aflick

RE: How to Calculate Moment in Fuselage Frame

cut the circular frame in two places and establish equilibrium.

Cheers

Greg Locock

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RE: How to Calculate Moment in Fuselage Frame

not quite greg ...
i think the problem is singly redundant, the usual solution is to cut the frame (releasing the internal moment) and apply a moment to remove the dispalcement between the two ends of the frame ... the unit load method.

easier is to refer to books (possibly Roark, but i know it is the Boeing static stress manual) as this is a standard problem.

RE: How to Calculate Moment in Fuselage Frame

form boeing, they've used NACA references, TN-929 and -1310, and NASA D-402.

all the NACA reports are available on-line, some NASA ones are available (for free).

assuming your applied moment is reacted by a shear flow in shell (presumable the ring frame is attached to a tube (like a fuselage), from boeing the maximum moment inside the frame 1/2 the applied moment (sort of makes sense ... at the point of application the frame reacts the moment 1/2 going one way round the frame, and the other 1/2 going the other).  But this isn't the full story, there are internal shear forces that the frame is reacting.

RE: How to Calculate Moment in Fuselage Frame

Exactly Rb,

Roark has good ring analysis.  Nasa is a great source also.  But don't forget that there is already load in the frame.  Your lugs will just add load to the frame.

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