Many of the old powers still have tools and fittingslying around. The rusted remains of an old stove is a common sight. So are bed springs and a dented coffee pot. That shape is probably as near to a typical profile as you can get. Most of them are shorter.
Trouble is, parts of the old power buildings have collapsed, totally modifying the original profile.
The dumbbell has become a figure of speech rather than an actuality. The long belt house was no longer necessary because a short, coupled, chain drive was all that was needed. However, some installations simply had the electric motor placed on the old engine and the motor drove the belt. In those cases the original building arrangement continued to serve. Electric motors became common in new powers in the mid-1930's.