HMS Iron Duke was the last of four central battery ironclads built for the Royal Navy in the late 1860s. Completed in 1871, the ship was briefly assigned to the Reserve Fleet as a guardship in Ireland, before she was sent out to the China Station as its flagship. Iron Duke returned four years later and resumed her duties as a guardship. She accidentally rammed and sank her sister ship, , in a heavy fog in mid-1875 and returned to the Far East in 1878. The ship ran aground twice during this deployment and returned home in 1883. After a lengthy refit, Iron Duke was assigned to the Channel Fleet in 1885 and remained there until she again became a guardship in 1890. The ship was converted into a coal hulk a decade later and continued in that role until 1906 when she was sold for scrap and broken up.
Design and description
The Audacious class was designed as a second-class ironclad intended for overseas service. They were long between perpendiculars and had a beam of . Iron Duke had a draught of forward and aft. The Audacious-class ships displaced and had a tonnage of 3,774 tons burthen. They had a complement of 450 officers and ratings. using steam provided by six rectangular boilers. The engines were designed to give the ships a speed of ; Iron Duke reached a speed of from during her sea trials on 2 November 1870. She carried a maximum of of coal.
The Audacious class was ship-rigged with three masts and had a sail area of . Around 1871 they were re-rigged as barques with their sail area reduced to To reduce drag, the funnel was telescopic and could be lowered. Under sail alone, they could reach .
thumb|left|A [[Muzzle-loading rifle|rifled muzzle-loading gun aboard Iron Duke in the 1870s]]
The main armament of the Audacious-class ships consisted of 10 RML rifled muzzle-loading guns. Six of these were positioned on the main deck, three on each broadside, and the other four guns were mounted on the corners of the upper deck battery. The battery protruded over the sides of the ships to give the guns a certain amount of end-on fire. The shell of the nine-inch gun weighed while the gun itself weighed . It had a muzzle velocity of and was rated with the ability to penetrate of wrought-iron armour at the muzzle.
The ships were equipped with four RML 6 in (152 mm) 71 cwt guns as chase guns, two in the bow and another pair in the stern.
Construction and career
Iron Duke, named after the nickname for Arthur Wellesley, 1st Duke of Wellington, was the first ship of her name to serve in the Royal Navy. The ship was laid down at Pembroke Dockyard on 23 August 1868, launched on 1 March 1870 and was completed on 1 January 1871, at a cost of £208,763.
Iron Duke recommissioned two months later and was assigned as the guardship at Hull. During the First Reserve Squadron's summer cruise on 1 September, she was en route with three other ironclads between Dublin and Queenstown (now Cobh). In a thick fog, the ship accidentally rammed her sister, Vanguard, off Kish Bank, in Dublin Bay. Iron Duke had her bowsprit wrecked, but was otherwise little damaged. Her ram, however, had torn a hole in Vanguards side. The ram also damaged the watertight bulkhead between Vanguards engine and boiler rooms which flooded both compartments and prevented her crew from using her steam-powered pumps. The ship sank in a little over an hour after all of the crew had abandoned ship. Following the collision, Iron Duke was overhauled at Plymouth Dockyard, with attention being given to the watertight doors on board. At 10:00 on 20 November 1877, Iron Duke departed from Plymouth for sea trials. She was out when it was found that the main sluice valve had been left open and she was sinking. Her crew closed the watertight doors and manned the pumps. An order was given to fire the distress signal, but it was found that there was no powder on board. The flag signal for "sinking" was made, but it was not noticed by for fifteen minutes. Black Prince repeated the signal to Mount Wise, which repeated the signal to Plymouth. In the meantime, a crewman had managed to close the valve. He was waist deep in water and had he been a few minutes later a diver would have been required. With the valve closed, the pumps were able to clear the water, and the ship was dry at 15:00. She put back to Plymouth, the trial being cancelled. It was subsequently revealed that four condenser valves, each diameter were involved. Difficulty in closing them was caused by excessive stiffness in the springs. This was alleviated by the fact that the valve handles had been lengthened during the refit, giving greater leverage. It was reported that efforts were made by those responsible for the refit to obstruct the Admiralty enquiry into the event.
Following the loss, Iron Duke replaced Vanguard as the guardship at Kingstown, County Dublin, where she received the latter's crew and remained until July 1877 when the ship began a lengthy refit that lasted until August 1878. en route, she pulled the P&O steamship off a reef in the Red Sea Iron Duke ran aground on a sandbar entering the Huangpu River in May 1880, after five days, she was pulled free by the American paddlewheel river gunboat with little damage. Iron Duke returned home in January 1883 and began a lengthy refit that included the replacement of her boilers.
On 16 April 1885, the ship became a member of Admiral Geoffrey Hornby's Particular Service Squadron until August, when she joined the Channel Squadron. The following year, Iron Duke participated in Queen Victoria's Golden Jubilee Fleet review on 1 July 1887 at Spithead. She was reduced to reserve in 1890 and was converted to a coal hulk in 1900, serving at Kyles of Bute. The ship was transferred from Fleet Reserve to Dockyard Reserve at Portsmouth in April 1902, and eventually sold for scrap on 15 May 1906 to Galbraith of Glasgow.