We don't have synonyms for hammer beams yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are hammer beam, hammer-beam and hammerbeam.
(n) :
(architecture) A (short) member of a kind of roof truss (a hammer-beam truss), so framed as not to have a tiebeam at the top of the wall. Each principal has two hammer beams, which occupy the situation, and to some extent serve the purpose, of a tiebeam.
(n) :
(architecture) A (short) member of a kind of roof truss (a hammer-beam truss), so framed as not to have a tiebeam at the top of the wall. Each principal has two hammer beams, which occupy the situation, and to some extent serve the purpose, of a tiebeam.