  Our main result is that many triangles of Baumslag-Solitar groups collapse to
finite groups, generalizing a famous example of Hirsch. A triangle of
Baumslag-Solitar groups means a group with three generators, cyclically
ordered, with each generator conjugating some power of the previous one to
another power. There are six parameters, occurring in pairs, and we show that
the triangle fails to be developable whenever one of the parameters divides its
partner, except for a few special cases. Furthermore, under fairly general
conditions, the group turns out to be finite and solvable of class<4. We obtain
a lot of information about finite quotients, even when we cannot determine
developability.
