B&O Railroad Museum TV Network: The Turntable (January 2015)


Hi, I’m Michael Gross, host of the B&O Railroad Museum
Television Network. I’m standing on the turntable in the
center of the B&O Railroad Museum’s National Historic Landmark
1884 Roundhouse. When this sixty-foot wooden
turntable was properly balanced, one person can turn a locomotive or
railroad car weighing up to 75 tons all by hand without any assistance. The B&O Railroad Museum’s
Roundhouse was built in 1884. Designed as a passenger car repair shop, it houses 22 bays and covers
almost an acre of land. The most important functional feature in
the Roundhouse is the turntable. Originally used to turn
and position passenger cars into any one of the 22 bays in the
building for necessary repair work. Today the turntable is used for placing the
museum’s historic collection on display and on special occasions,
demonstrations are scheduled teaching visitors how a turntable works. The museum’s turntable is
60 feet in diameter and located in the centre the Roundhouse. The width was dictated by the size
of the B&O’s passenger cars when the roundhouse was built, which≈ere approximately sixty feet in length. The turntable is actually a bridge made of two wrought iron girders that support
a pair of rails and wooden decking. The entire bridge rotates freely
on a central pivot mechanism located below the Roundhouse
floor in a circular pit. This pivot mechanism is eight inches wide and sits in the cylinder lined with bronze. It supports the entire turntable
including the bridge, decking, and track structure and allows the turntable to rotate 360 degrees. The pit consists of a stone
and brick lined outer wall and a dirt floor that slopes
from the outer wall down to the central pivot mechanism. At the base of the outer wall is an
approximately two foot by one foot stone sill that supports a single rail running the
circumference of the circular pit. The purpose at the turntable’s ring rail is to support the turntable when rail cars are brought onto and off of the turntable. The support is provided by
two pairs of wheels located at opposite ends of the bridge. The wheels make contact with the rail as weight is placed on the turntable bridge. This is different from modern turntables where the guide wheels rest on
the ring rail when not in use and the entire time the railcar is rotated. In fact, the only way the museum’s
turntable will function is if the turntable bridge is free-floating with the guide wheels off of the ring rail. Stay tuned for more of the B&O Railroad
Museum Television Network. As built, the turntable bridge sat in an open pit without the wooden decking. The decking, known as an apron, was added because management determined
that it was not very efficient for the Roundhouse workers to
navigate around the open pit. The wooden decking has been
replaced several times, the most recent occurred in 2004 as part of the Roundhouse reconstruction
project to repair the building after the 2003 President’s Day snowstorm
which caused the roof to collapse. The decking is made of six inch wide
tongue and groove oak wood, and there’s an opening in the decking
that allows access to the pit. There are two methods to keep the turntable
stabilized and safe to walk on. When not being used the turntable is secured by lowering a series of jacks onto the ring rail. The jacks are accessed through
small wooden holes in the decking and screwed into place. When the turntable is being used it must
be secured or locked in place when moving rail cars on and off the bridge. This is accomplished through the
use of wrought iron sliding bars located on either end of the bridge. The bars slide into slots on the
outer edge of the turntable and keep it from moving sideways during
loading and unloading. Both methods are used to secure the
turntable when not in use. Operating the turntable is relatively simple
if the turntable is balanced properly. The weight of a rail car must be equally
distributed on the bridge and perfectly balanced to allow the turntable
bridge to float and function properly. When properly balanced, one person can
turn a rail car weighing up to 75 tons by pushing the table in the
direction they want to go. Being off by as little as an inch can make it impossible to turn. Early images show the use of a pulley system that allowed a worker to pull a
passenger car onto the turntable. today the museum staff uses a specially
modified tractor to move heavier equipment and smaller pieces are moved
on and off the table my hand. Rail Operations staff at the
B&O Railroad Museum demonstrate this example of history in
motion on special occasions. Check the museum’s website
for dates and times. I’m Michael Gross, and thanks for watching
the B&O Railroad Museum Television Network. Interested in learning more about the
B&O Railroad Museum and Ellicott City Station? Follow us on Facebook and Twitter! With daily updates on upcoming events, coupons, photographs, history, and things to do in Baltimore, you’ll never be off track.

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