66 Stokers and Trimmers, 10 Engineers and 2 Chief Engineers provided the manpower to operate Warrior's machinery. Working down in the Boiler Space and Engine Room, they physically manhandled 850 tons of coal from the bunkers to the furnaces - and then shovelled the ash and clinker residue away from the furnace grates. This was a filthy job in appalling conditions - men were shovelling and carrying coal on a moving deck - heaving, rolling and plunging, in temperatures of around 45 C (112°F).

It is no surprise that Stokers and Trimmers were paid 50% more than Able Seamen, working on the upper decks of the ship. And more surprising that the Stoker's uniform was white - white cotton duck!

Boilers
Boilers, port side: Photo - Peter Milford
Warrior carried ten boilers, each heated by four furnaces. Coal was stored in bunkers at the rear end of the boilers and when full, the bunkers held 850 tons of coal - all of which had to be loaded by hand, brought on board in sacks and emptied down chutes to the bunkers where the stokers were waiting. Coaling ship was a task for all crew, seamen and officers as well as stokers and engineers - lifting 850 tons onboard would take 2 days of strenous effort. The coal produced large amounts of black gritty dust which would find its way into every space. Cleaning the ship after coaling might take another week!

The stokers would shovel the coal from the bunkers and place it into steel buckets suspended from an overhead gantry. The full buckets could be pushed along, rolling along the metal girders, to carry the coal to the furnace where it would be shovelled in by hand from piles on the deck.

The fire required a continous supply of air which would be drawn down from the upper deck - the draught developed by the roaring furnaces would keep the fires going and also provide some ventilation. Heat from the furnace boiled water in the boilers, creating the steam required to turn the engines. Warrior's boilers were only able to generate steam at relatively low pressures which drove the large twin cylinder steam engine at a maximum speed of 56 rpm - pushing Warrior through the water at about 14 knots. Although this is not fast by modern speeds, it would be faster than any ship of a comparable size would manage under sail alone.

 

Warrior's boilers and engine had a low thermal efficiency - the 850 ton coal fuel load would not give a great range so steam power was intended as a sprint addition to the sails.
screw animation Up funnel, down screw

The hot exhaust gases were vented through the funnels. These were telescopic and were raised when the furnaces were fired up. The heat from the funnels, and their position when raised, meant that the lowest sails (the Courses) could not be be set when the ship was in steam.

The engine drove the single screw (propeller) by means of a long propeller shaft, running beneath the lower deck and aft magazine to the stern. The twin-blade propeller was large and when the ship was under sail, it provided a lot of drag and would slow the ship down. To overcome this problem, a complicated mechanism was invented that allowed the propeller to be lifted out of the water and up into the stern.

When the ship went over to steam propulsion, the propeller had to be lowered into position and locked to the drive shaft. At the same time the funnels were raised to carry away the furnace exhaust. Transferring from sail to steam required the Captain to give the order, "Up funnel, down screw" .

Steam power gave Warrior an immediate advantage over any similar sized sailing warship. She was not dependent on the wind and could sail at will and where she wanted. With her engines at maximum speed she could overhaul any sailing battleship - although it is likely that maximum speed could only be maintained for a relatively short time.

Boiler space - looking aft
The starboard side furnaces - looking aft with the coal bucket on its rail support - Photo: Peter Milford

Visiting the boiler room today does not give a real impression of its real working life - noisy, intensely hot, dark, the smell of burning coal, oil and steam and sweating men shovelling coal and ash. The white-hot ash and clinker had to be removed from the bottom of the furnace grate using a long (10 feet) steel rod. The ash was pulled out onto the iron plate deck and cooled with water (generating clouds of hot steam). The ash was shovelled into buckets and lifted to the deck by an auxiliary (small) engine at the after end of the boiler room. From the deck, the ash was tipped overboard.

Horizontal trunk engine
Horizontal trunk engine - forward cylinder: Photos - Peter Milford
 
Horizontal trunk engine
 
The horizontal engine took up less space than the vertical type - and placed low down in the ship gave some degree of protection as well as adding to the ship's stability.

The engines and boilers for Warrior were built by Penn's Engineering Works at Greenwich - just a little further down the Thames from the Blackwall yard of Thames Ironworks where the hull was constructed. The two pistons drive the shaft through massive cranks - with each piston moving backwards and forwards a distance of some 2 feet. The cylinders are very large - and had to be because of the low steam pressure delivered by the boilers. The low pressure and the large size of the cylinders made the engines very inefficient. Today the reproduction engine only revolves at about 2 rpm, much slower than the real engine at a maximum of 56 rpm. You can imagine the scene in the engine room though - with the massive cranks flashing round once every second.

Crank and starter gear
Trunk engine: After cylinder and starter ring and worm gear - Photo: Peter Milford
 
Working in the boiler and engine rooms was a filthy job - and recognised as such. Stokers were better paid than seamen - and were provided with baths to wash when coming off watch. The contrast between firing a boiler below decks, where temperatures reached 43 C, and then coming up to the upper deck where freezing water might be sluicing across the deck with spray flying in the teeth of a gale and temperatures in low single C is difficult to imagine today.

Warrior was fitted with screw propulsion - as had been all ships of the Royal Navy since the conclusive trials carried out in 1845. At that time there was considerable question as to which means of propulsion was most effective - screw or paddle. In 1845 the Admiralty decided to settle the question by carrying out a series of trials. Two ships were chosen, both of similar size and power, one HMS Rattler was screw propelled and the other HMS Alecto was paddle driven.

Both ships steamed around an 80 mile course in calm weather. Rattler defeated Alecto by 23.5 minutes. In another race, this time against a head sea, Rattler finished 40 minutes ahead of Alecto.

The final conclusive test came when both ships were attached, stern to stern. Both went full ahead and Rattler made away, towing Alecto astern at a speed of 2.5 knots. After 1845, all ships were designed with screw propulsion.

In 1998, there remains just one seagoing steam paddleship in operation around the UK - the Paddleship Waverley.

The Upper Deck - Under sail - The Maindeck - Armament - The engines and boiler room
The Captain's cabin - The Wardroom and Officer's cabins - Food on Warrior
Raising the anchor - HMS Warrior - facts and figures - Warrior - a short history
Return to Warrior tour home page

Page creation: July 1998
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Prepared by staff and students at St Vincent College for HMS Warrior (1860)