In Appendix 3 of The Grand Canal of Ireland [David & Charles, Newton Abbot 1973], Ruth Delany lists three steamers built by Grendons of Drogheda for the Grand Canal Company:
- Dublin, built in 1862 and sold in 1910
- Limerick, also built in 1862; no date of sale shown
- Athlone, built in 1863 and sold in 1917.
Amongst the several canal companies who have introduced steam power on their canals is the Grand Canal Company of Ireland, who have now at work three steamboats of the class shown by the illustration[s] on [this] page. A model of these vessels, together with a photograph of their machinery, was exhibited at the recent conversazione of the Institution of Civil Engineers by Mr Samuel Healy, the secretary to the company, the boats themselves having been designed under him and Mr Wm Fairbairn, by Messrs Hudswell and Clarke, of Leeds, who supplied the models, from which the boats were constructed, to the builders, Messrs Grendon and Co, of Drogheda.
The boats, which are named respectively the Limerick, Dublin and Athlone, are each 71′ 6″ in extreme length and 13′ 6″ in breadth, and have a gross tonnage of 65 tons. The length of the hold is 35′, and the depth 6′, while the length of the engine-room is 17′ 6″. The boats carry 50 tons of cargo, and their draught when loaded is 5′ 1″; they are made of iron, the plates being ¼” and 3/16” thick.
In our engravings, Figs 1 and 2, which are respectively a longitudinal section and plan, show the general arrangement of the boats and machinery, while Figs 3 and 4 are an enlarged section and plan of the machinery, and Fig 5 a corresponding cross section. The machinery was constructed by Messrs Hudswell and Clarke, and its arrangement is shown by the figures just mentioned.
It will be seen that it consists of a pair of inclined high-pressure engines, coupled direct to the screw-shaft, which is inclined upwards from the engines towards the stern end. The cylinders are 7½” in diameter, with a stroke of 12″, and are each fixed to a pair of inclined wrought-iron frames, which are in their turn firmly connected with the sides and bottom of the vessel, by plate stays or gussets, as shown in Figs 4 and 5. A pair of wrought-iron beams are also carried across the vessel above the boiler, to which they are attached, these beams connecting the upper parts of the engine-frames, and also supporting the reversing handle brackets. The engines are fitted with “shifting link” reversing gear arranged as shown in Fig 5; the valve gear for both engines being driven from one pair of eccentrics.
The screw shaft is, as we have already stated, inclined upwards towards the stern end, where it passes through a stuffing-box, as shown in Fig 3. The screw, which is four-bladed, is of wrought iron, and is 4′ in diameter. It is made in two parts, which are put on the shaft one behind the other, the two blades on the fore part having a pitch of 6′, and those on the after part a pitch of 6′ 6″. This arrangement is said to give good results in shallow water.
The boiler is tubular, and of the form shown in the illustrations. It consists of a barrel about 5′ long, and 3′ 6″ in diameter, joined to a cylindrical firebox casing 4′ 3″ long by 4′ 6″ in diameter. The front plate of the firebox casing is flanged forward to join the barrel, and backward to meet the plates of firebox casing; the backplate is also flanged to join the casing-plates and the plates of the inside firebox. The smokebox is formed by an extension of the barrel, and the tube-plate at that end is placed within the barrel and flanged forward to join it.
The inside firebox is of wrought iron, and is cylindrical. It is 2′ 9″ in diameter by 4′ long, and is formed of two rings of plates united by one of Adamson’s flanged joints. At the inner end also the firebox-plate is flanged outwards to join the tubeplate. The firebars are placed slightly below the centre line of the firebox, as shown in Fig 3, the heating surface above them being 19½ square feet. From the firebox 77 brass tubes, each 2″ in diameter, lead to the smokebox, these giving a heating surface of 212½ square feet, making, with the firebox surface, the total heating surface of 232 square feet.
A large steam dome, 2′ in diameter and 2′ high, is placed on the top of the firebox casing, and from it the steam is taken to the cylinders, as shown in Fig 3. The dome is made of a flanged plate, and is fitted with a cast-iron cover carrying a pair of safety-valves. The chimney is carried up for a height of 7′ above the top of the boiler, and is 7′ in diameter. The boiler is carried by plate stays attached to the undersides of the firebox casing and smokebox, as shown in Fig 3, and is also steadied by stays extending to the engine-frames, and by the transverse beams over the top before mentioned. The coals are contained in a pair of coal bunkers, situated at the sides of the vessel in the fore corners of the engine-room, as shown in the plan; they afford accommodation for 5 tons of coal.
The boats which we have been describing are trading between Shannon Harbour, King’s County, and Limerick, a distance of 52 Irish miles [officially abolished in 1824]. Of this distance 40 miles are on the River Shannon and 12 miles on the Grand Canal [recte Limerick Navigation], there being twelve locks on this latter length.
When they were first set to work the boilers were pressed at 120 lb per square inch, but this pressure has been now reduced to 75 lb. Under the higher pressure the engines worked at from 180 to 185 revolutions, giving a speed, with the loaded boat alone, of 10 English miles per hour on the Shannon, and from 3 to 3½ miles per hour on the canal. The quantity of coal consumed per hour averaged 5 cwt. Under the reduced pressure of 75 lb per square inch, the number of revolutions per minute made by the engines is from 135 to 140, and the consumption of coal has been reduced to an average of 3½ cwt per hour.
The speed under these new circumstances is, with the loaded steamer alone, 8 miles per hour on the Shannon, and from 2¾ to 3 miles per hour on the canal. With one 40 ton boat in tow the speed on the Shannon is 6 miles per hour, and with two 40 ton boats in tow it is reduced to from 4½ to 5 miles per hour. We understand that the boats are performing their duties well, and that by their use a considerable saving has been effected in the working of the canal.
We are indebted to Messrs Hudswell and Clarke for the tracings from which our illustrations have been prepared, whilst the particulars of their working have been kindly furnished by Mr Samuel Healy, the secretary, and Mr W H Crowther, the engineer to the Grand Canal Company.