Christopher Tidy wrote:
Bill Schwab wrote:

Chris,

Imagine the front forks of a bicycle. Now imagine two sets of forks,
one slightly smaller than the other so that it fits snugly inside.
Now make the column slightly narrower than the smaller set of forks
and drill a hole through it. Attach one set of forks to the tension
member, the other set to the roller support I described, then pass a
pin through both pairs of forks and the column. This joint would
behave as I explained, and does not in itself make the structure
statically indeterminate. Instead it makes it easier to analyse.



By its very complexity, what are describing is far more trouble than a
conventional pinned frame, which BTW is not difficult to analyze.


It is a conventional pinned frame. Furthermore the idealisation I
proposed simplifies analysis.

In fact, it can probably be done in less time than it would take to
correctly draw your proposed system.


I believe it was a correctly drawn idealisation. The two members and
support all connect to the pin, not to each other.

In the words of Professor Hoover, "take it to pieces". If I
understand you correctly, the beam is not horizonally supported at the
top, and is therefore not in equilibrium.


It is connected to the roller support via the pin. Please see the diagram.

You mean C:\docs\davit_calc2.jpg? If so, isn't that the pin you said
doesn't act on the beam? If that's the case, then we're back to the
missing horizontal force.

Otherwise, you should draw the diagrams, write the equations, and either
count the unknowns and equations, or check the moment balance on the beam.