Four vertical side rollers mounted on either side of the launch frame ensure that the
beam is guided centrally through the launch frame.
A roller assembly mounted on the top of the launch frame ensures that the correct
winch cable fleet angle is maintained.
A drum winch is installed on the upper and lower surfaces of the launch frame.
Attached to the winches are the wire cables used to control and operate the home
The lower winch tensioner (Figure 2. 7) is the simpler of the two tensioners fitted to
the launch frame. It is of a purely mechanical design. It consists of a spring loaded
roller which spans the full width of the winch drum and maintains a positive force on to
the cable to reduce the possibility of the rope becoming slack on the drum when too
much cable is paid off, a primary cause of winch cable nesting.
The tensioner does however have its limits and will not stop the cable from nesting; it
only allows more cable to be paid off before the cable starts to nest. The tensioner is
only a backstop; it should not be used to compensate for poor control of the winch by
the chest pack operator.
The lower tensioner is primarily used when the bridge is being lowered or picked up.
During this process slack cable is paid off the winch to allow the carriages to be
lowered, allowing the slings to be attached to the bridge.