You have 44 equations in 41 variables and Maple would tell you, that in
your case it is inconsistent.

Denote M you matrix matcosdir and v = Fexternas+Rvinculo.

Then you use LinearAlgebra[LinearSolve] to solve the linear equations 
M . x = - v, your 'Normales' then is that x (if there is some, there
may be none and there may be lower-dimensional spaces as solution and
there may be exactly 1).

  with(LinearAlgebra);
  LinearSolve(M,-v);

    Error, (in LinearAlgebra:-LA_Main:-LinearSolve) inconsistent system

Actually you can check it (theoretical):

  interface(rtablesize=50);      # displays larger matrices
  ReducedRowEchelonForm(<M|-v>): # cf. help + Math books (help is vague)
  map(fnormal,%,3):              # you only have 3 Digits
  simplify(%,zero): identify(%);

or 

  GaussianElimination(M);

Your matrix then is zero in the last lines, while your v is not:
it is like solving 0*x=1 for x.


PS: your sheet is another example of the incredible uglyness of
the 'standard' worksheets, it does not even allow to save in a
reasonable format as *.wms ... what a shame for Maple.

This is why I usually refuse too look at *.mw (which unfortunately is
used by beginners).

Problem SOlved :D 

Thanks a lot for your help!!