Bill Quackenbush tutored him as a rookie though he partnered with Leo Boivin for most of this career. Both Armstrong and Boivin were noted hard hitters, making for an intimidating Boston back line. But Armstrong was clean, not picking up a lot of unnecessary penalties, unless of course he somehow lost his gloves and stick. Armstrong was not much of an offensive threat. He never rushed the puck and his odd goal would usually come from a blast at the point.
After 9 solid seasons in a Bruin uniform, Bob was released to the Montreal organization to coach one of their minor league teams in Hull-Ottawa of the Eastern Professional Hockey League. It was in Hull-Ottawa that Bob had a run-in with Don Cherry that merits mention in Don's book, Grapes. What Don failed to mention is that Don broke his stick over Bob's head, giving Bob a concussion.
While Bob was playing for the Bruins, he continued his schooling, eventually earning a degree from the University of Western Ontario. After being traded from the Montreal organization to Toronto, a teaching opportunity opened up at Lakefield College in Peterborough, Ontario and Bob began his second career. Along with teaching history and economics, Bob coached the hockey team.
Bob's son, Ian, played at the school, and later with the Peterborough Petes of the OHA, and in 1983 Ian was drafted by the Bruins, 142nd overall.
Bob passed away in the summer of 1995.