Roundhouses such as our John St. CPR Roundhouse were served by turntables which were used to line up steam locomotives with their berths in the roundhouses. On rural branch lines, turntables sometimes existed without an associated roundhouse or engine house. Our fully restored and operational 120-foot long locomotive turntable serves that function even today as we use it often to move rolling stock and engines into and out of our restoration stalls and to different parts of Roundhouse Park as needed.
Diesel locomotives used on Canadian Pacific’s premier transcontinental train being spun on the turntable of the John Street Roundhouse in 1956. Courtesy of the Toronto Public Library Archives. 
The turntable being installed after its restoration in 2007. 
A similar view of the turntable years later, after much improvement to the surrounding area. 
In 2015, CNR 6213 was moved around the park using the turntable.
History
The Canadian Bridge Company constructed the John Street Roundhouse’s turntable while the roundhouse was being constructed in 1929. In its lifetime, this turntable would have rotated many locomotives, old and new. It is a twin-span, three-point turntable that pivots on a central axis. The weight of the locomotive is supported in the centre and at both ends on trucks that ride on a circular rail extending the circumference of the reinforced concrete pit. An air motor at each end propels the turntable by compressed air pumped up from an underground generator. At 120 feet, it is easily one of the longest built in Canada. It was fully restored by Western Mechanical in Barrie in 2007 and is now completely operational.
For more information on the history of turntables, visit http://en.wikipedia.org/wiki/Railway_turntable