Medway Queen - Rebuild of a Dunkirk Veteran Part 3

Update on Progress at the Albion Dockyard, Bristol.
(Words G Stewart - Pics Dave Elms)

Almost 12 months have passed since our last article on this historic project and work has been continuing apace at Albion Dry Dock, Bristol.

Time to catch up then!!

On Thursday 15th October this project reached a major milestone when the first hull block was removed from the fabrication shed and placed onto the keel blocks in the drydock. More on this story can be found on the Medway Queen Website

Fabrication has continued in the dry dock with more blocks being added.

Click on an image to view a larger version.

Jan 2010

A rivetted hull requires a frame onto which the plating is rivetted. This frame consists of vertical sections (which are formed into the correct profile to give the hull the correct shape) and transverse frames which run port to starboard and are fixed to the vertical items. The vertical frames are in turned rivetted to keel.
The shot below shows frames for the forward section of the hull ready to be erected.


The next photo below shows the hull in dry dock from the framed bow back to midships - with a section still to be framed. Note the smooth curve in the transverse frames - this is called camber and adds strength to the structure. In the case of open decks this also assists with drainage to the scuppers during inclement weather.

Another view of the hull looking from the after end. The two large bulkheads in the foreground of the shot divide the engine and boiler compartments. Note the opening for an access door.

A close up shot of the forementioned bulkheads. The one being positioned in the foreground is the screen bulkhead which will support the transverse heavy beam onto which the main engine entablatures will attach - the exact part is labelled 'B' in Part 2 of this series.

Back into the workshop for the next shot - here we see the top half of the "fore peak" bulkhead. The fore peak is the very front of the ship which terminates with the stem. This bulkhead incorporates a watertight access door. This piece will fit between the Main & Promenade decks and is situated on top of the bulkhead which forms the back of the anchor chain locker.

The "enclosure" in the right of the shot will be the Spirits Locker.

Feb 2010

Moving on this next shot from the dock floor shows most of the frames from the stem to midships have been erected to Main Deck Level.

This next shot shows the two heavy frames which will provide support the main engine entablatures and in turn the crankshaft and paddle shafts. As well as the forementioned support function this section of the ship must be heavier built as it has to withstand the thrust generated by the propulsion system which will drive the hull through the water - too light and the frames may distort causing misalignment or in an extreme situation structural failure.

As hull fabrication continues focus is slowly but surely turning to the machinery. Large items such as the Main Engine Block and Condenser must be installed in the hull before fabrication reaches a stage which precludes the easy installation of these pieces but before this can be carried out the pieces must be inspected and remedial / replacement works effected as required.

This next shot shows the Main Engine Cylinder Block in the workshop ready to be assessed for refurbishment. The steam enters the HP cylinder via the HP Valve. The pressure at which it is admitted is regulated by the Main Steam Inlet Valve which is in turn connected to the throttle lever. Controlling this determines how fast the engine will operate. The spent steam from the HP travels to the LP via the route shown by the blue arrow. It is then used by the LP cylinder and
finally condensed back into water and returned to the Boiler Feedwater Recovery System for re-use.

The equipment shown below is part of the Boiler Feedwater Recovery System. This is the air pump and it takes the output from the condenser, de-aerates it and passes it onto the hot well, which is the holding tank for recovery boiler feedwater. As with most ancillary equipment the air pump can be driven either by its own little steam engine or via a linkage from the Main Engine. This usually depended on the engine builder or the spare steam capacity available from the boiler to drive the ancillary equipment.

Finally we look at a boiler feedwater pump which, as the name suggests, pumped water into the boilers to be converted to steam to drive the ship. Medway Queen appears to have had only one of these but some ships (eg Waverley) had two which operate on a rota basis. It is these pumps which make the familiar whooping noise on Waverley.

So the works proceed apace - thanks once again to Dave Elms for providing the shots. If you want more information why not visit the Medway Queen Shipyard Blog or look in on the Albion Drydock Webcam

Gavin Stewart

Medway Queen - Rebuild of a Dunkirk Veteran Part 2

Focus On Main Engine Equipment
(Words G Stewart – Pics Dave Elms / G Stewart)

This is the second of a series of articles charting the progress of the rebuild of Clydebuilt paddler ps Medway Queen – Dunkirk Veteran.

The previous article focused on the the various engine parts arriving at Abel’s Albion Dockyard in Bristol prior to Christmas. Since this time a number of additional parts have arrived on site and the fabrication of the sections of riveted hull has commenced – this article will focus on these various pieces of Main Engine.

This first shot shows the Main Engine “entablatures” which provide a housing for the crankshaft main bearings as well as locating the crankshaft on the correct centerline to mate with the paddle shafts. There are three entablatures in total – the slightly wider one you can see in the background of the photo would be in the centre – it is wider as it has to withstand the force of both the Low Pressure (LP) and High Pressure (HP) cylinder connecting rods. As a result the bearing housing is also twice the width of the other two. The shots of Loch Lomond’s Maid of The Loch which has a similar machinery configuration makes a good comparison.

The part arrowed “A” would attach to corresponding mounting pads in the hull of the vessel’s engine room. The transverse hull frame onto which these pads would be fixed would be slightly heavier steel than the others to accommodate the increased weight it would have to bear. Part “B” also attaches to the ship’s hull but instead of a transverse hull frame it would more than likely be the bulkhead between the engine and boiler spaces – a piece of this bulkhead can be seen to be still attached in the photo. Part “C” is the bearing housing which contains a main bearing shell made of white metal. A corresponding shell bolts onto this via the two large studs that can be seen just below the arrow. Finally part “D” is the piston rod slide – the piston rod cross head and slippers slide up and down this part which would be lubricated with either grease or oil.

Moving on we have a photo of the LP cylinder cross head with part of a slipper still attached.

This part of the engine connected the piston rod to the crankshaft connecting rod thus converting the in / out (linear) motion of the piston rod to a rotating motion in order to drive the crankshaft round. The piston rod bolts through the cross head (Part “A”) while a u shaped link would connect either side of this area via small bearings. Part “B” shows the white metal slippers which permit the cross head to move up and down the slide on a bed of grease or oil.

The photo below shows the same equipment in position on Maid of The Loch.

Finally – for this report anyway – we look at the condenser. This unit turns the exhaust steam from the LP cylinder back into water so it can be returned to the boilers and re-used. This is achieved by circulating water (in this case it would be sea water) through a bank of tubes (Part “A”) inside a drum or casing. The forementioned exhaust steam is admitted to this drum from the LP cylinder (Part “B”) and is condensed back into water through the subsequent contact with the cold tubes.

Medway Queen’s condenser (shown below) will require a new casing and a re-tube but it is hoped to retain the end caps (Part “C”) and the steam inlet (Part “B”).

Well that’s all for now – apologies if the content is a bit overly “techy” but I don’t see the point in showing you all these pics unless I explain what they’re for and where they go!!

If you want to track the overall progress on Medway Queen why not visit the Medway Queen Preservation Society’s Ship Yard Blog.

Thanks as always to Dave Elms for providing the photos!!

Gavin Stewart

ps Please feel free to comment on these articles using the facility below!

Medway Queen - Rebuild of a Dunkirk Veteran Part 1

Part 1 - Machinery arrives in Bristol
(words by G Stewart, Photos by Dave Elms)

Back in September it was announced by the Medway Queen Preservation Society that a contract had been placed with David Abels (Boatbuilders) in Bristol to manufacture a new rivetted hull for the 1924 Clydebuilt paddler Medway Queen.

Machinery has now started to arrive at the Albion Dockyard in Bristol and thanks to good friend and Abels engineer Dave Elms the moment on Sat 6th December was captured on camera.

The following shots show the main engine cylinder block arriving and being offloaded. Medway Queen has a compound diagonal steam engine which was manufactured by her builders Ailsa.

In this shot of the Main Engine the Andrews Cameron low pressure (LP) slide valve can be seen. This valve facilitated the transfer of exhaust steam from the LP cylinder to the condenser and also admitted steam to the LP cylinder from the high pressure (HP) cylinder.

This valve would be driven via rods and linkages from the Main Engine Crankshaft.

Another view shows the engine control levers on top of the engine block. There are 5 levers in all - the throttle which regulates the admission of high pressure steam from the boiler to the HP cylinder, ahead /astern direction control lever, 2 x cylinder drain control levers which open the cylinder drains to allow any condensate which may have collected in the cylinders whilst the engine was stopped to be evacuated by the live steam entering the cylinder and finally the impulse valve lever. This lever permits the
entry of HP steam into the LP cylinder

which, due to the vastly greater surface area of the LP piston, gives the engine a "kick" of HP steam. This was used to start the engine if it stopped in a position which did not permit steam to be admitted to the HP cylinder or if a short burst of speed was suddenly required.

On the right of the photo the LP psiton rod can be seen which still has its crosshead complete with "slippers" attached. The crosshead permitted connection of the piston rod to the crankshaft connecting rod. The slippers would normally be making contact with slides which ensured that the piston rod remained supported and also was allowed to slide in and out of the engine block - the slippers are usually lubricated via grease or oil. The crosshead permitted connection of the piston rod to the crankshaft connecting rod. This connection pivots which allows the crankshaft connecting rod to rotate the crankshaft.

A shot of the Main Engine Crankshaft complete valve gear eccentrics attached. These operate the HP & LP valves which control the admission and exhaust of steam from each cylinder. In the case of the Medway Queen the rotating motion of these eccentrics was converted to a sliding motion via a rocking link. Another smaller crosshead connection is used to attach the valve rod which slides in and out of the engine block. This type of valve actuation is called Stephenson Valve Motion and was widely used in steam locomotives as well as reciprocating steam engines. Waverley's Rankin and Blackmore main engine also utilises Stephenson Valve Motion. Another method of actuating the valvegear on paddlesteamers was called Brock Valve Motion and was invented by the Chief Engine Designer at Denny Bros of Dumbarton. This type of valve motion was used for the engines of the famous Clyde paddler Caledonia and her sister Mercury.

In this final shot we can see what looks like a steam operated boiler feed pump in the foreground - perhaps built by the famous company Weirs of Cathcart. The red coloured equipment behind this could possibly be the air pump - which permits the transfer of condensate from the condenser back to the hotwell to be pre-heated prior to transfer back to the boiler via the forementioned boiler feed pump - but I am open to suggestions via the comments facility below!!

I am hopeful that Dave will continue to provide us with fascinating photos such as these as it is not every day a new paddler hull is commissioned!

Thanks Dave!

Gavin Stewart