Saturday, 14 March 2015

HMCS IROQUOIS: propeller shaft & running gear

Following on from my earlier post with a tour of IROQUOIS' engine room, this post will trace the path of the propeller shaft after it leaves the gearbox. After departing the gearboxes, each propeller shaft passes through a thrust block (which transfers the thrust of the propeller to the hull) and several plummer blocks (which support the shaft along its length).

Looking down into the AMR. A yellow and black propeller shaft runs down the left side of the photo.
  Immediately aft of the main engine room, where the propulsion machinery is located, is the Auxiliary Machinery Room (AMR). The AMR houses three Solar Saturn 750 kW gas turbine generators plus one 1000 kW diesel generator, as well as numerous other pieces of smaller equipment. The port and starboard propeller shafts also pass through the AMR.

A propeller shaft (painted yellow & black) runs through the AMR heading aft (e.g. to the right).

Plummer blocks support the propeller shaft at the aft end of the AMR.
Due to the shape of the hull and there being two of them, the shafts must pass through not only the AMR, but also a DFO service tank, and finally the Gland Compartment before passing through the hull.

Starboard propeller shaft running through the Gland Compartment. I believe the blue hose is a hydraulic hose from the hydraulic pump for the CP props.
CP prop hydraulic pump unit.
Modern warships, including the IROQUOIS and HALIFAX classes, often use variable-pitch or controllable-pitch (CP) propellers, where the blades of the propeller can be rotated to different pitches. This is necessary because gas turbines can not be run backwards, and otherwise it might be necessary to include an extra "reverse" turbine on each shaft as was done with steam powerplants in the previous generation of warships. The CP prop allows the gas turbines to run in the same direction at all times, and the transition between forward and astern power is handled by the pitch of the propeller blades. The hydraulic pump that controls the pitch of the propeller blades is located in the Gland Compartment, two compartments aft of the AMR.

The starboard shaft passes through seals and exits the hull in the Gland Compartment.
The other side - the port shaft exits the hull.
Port propeller shaft intermediate support strut.

Port variable (or controllable) pitch propeller. A V-shaped strut supports the shaft just ahead of the propeller.

Starboard "running gear": the propeller shaft showing both intermediate and V-shaped support struts.
The original variable pitch propellers fitted to IROQUOIS and her sisters were only four bladed and were shaped differently (as I recall), and new propellers (presumably quieter and more efficient) were retrofitted at some point, possibly during her TRUMP refit in the early 1990s.

Update: The port variable pitch propeller, removed from HURON before she was sunk, is on display at the Naval Museum of Alberta in Calgary.

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