"Anyway am I correct to assume that A is pinned and B is vertical roll?" ... yes, good assumption.
but the method has (or had) applicability and is very applicable if you want to quickly check some results.
I think the point is knowing how (and why) to construct the diagram, the idea that...
"I am asking about the rotations of elements used to evaluate the shear strains of solid elements."
Ok, you'll need to deconstruct this logic for us (well, for me at least).
1) why do you think that rotation of the elements causes shear strains ? (I've "cue bid" the answer to this by saying...
there's a forest and some trees, and you've gotten hung up on a tree.
replicating an example of a method is one thing, IMHO a very minor thing, in learning a method.
for one thing, instead of measuring an angle, you could have digitised the image, imported it into some CAD program...
yes accurately copying the structure is the problem with graphical methods like this.
ok, you say you can follow directions; the directions in your post and in my posts have been pretty clear. I think the problem is in carefully measuring the angle of the structure. Ok, why not make life easy...
ok, you used the member lengths to determine the position of the joints. so now the joints have a position in space, and so co-ordinates. So you could ask the FEM where the nodes are. But this doesn't matter.
Having drawn the last bay as you have, then you know the answer (to the lengths of...
what is the starting height ? or is this the "initial hill" (the marble starts at the top of the hill) ??
For a track I'd have 3 narrow pieces to constrain the position of the marble ... marble would ride on one and the other two would contact near the "horizontal" diameter (yes?)
it is inclined as it is in fig 8 ... the direction of the member in fig 8 is the direction of the load in fig 9 ...
this is what the method shows ... detail views of the joints show the directions of the individual loads which combine together to make a closed shape (or a force polygon).
...line representing member 1-2 in fig 8, so that it crosses the horizontal line.
the horizontal line represents the load in 1-3, and the load in 1-3 is this length divided by the length of your 70 lbs line (* 70 lbs)
and the inclined line is 1-2, and the load from the length a per above.
and...
one thought for the loop ... does the track need to be continuous ? could you launch the marble, and have it land on the other side of the loop (with less friction) ?
do you realise that fig 9 even though it looks like fig 8, is the reverse of fig 8 ?
follow the text description, you start fig 9 with a vertical line representing the load, and know the direction of the other loads (horizontal and inclined) and you draw lines to represent these in a manner to...
so really you're asking for any service experience with this construction ? So you want to talk to people you have them installed (clients) and people who installed them (erectors).
how did you make your FEM without dimensions ? (how do you make the structure without dimensions ??)
to my mind, this is a much more difficult way yo solve the truss, relying on accurate drafting (not my wheelhouse)
but each joint is solvable, starting at 5 you know the three directions and...
