The advent of steam saw many changes in the design of ships. For the first time ships were able to control where they sailed and could sail headfirst into weather they would normally have to sit out. With this great leap came propulsion systems – in all shapes and flavors which attempted to put down the power and drive the vessels. The first viable form of propulsion was undoubtedly the paddle wheel. This blog post looks into the development of this surprisingly efficient form of propulsion.
The origin of the paddle wheel is shrouded in the mists of antiquity, but there is some evidence to suggest that the Chinese and Egyptians had knowledge of the use of a paddle wheel for ship propulsion. The Roman Engineer Vitruvius described multi-geared paddle wheels working as a ship odometer but the first mention of paddle wheels as a means of propulsion was in the 4th–5th century military treatise De Rebus Bellicis where an ox-driven paddle-wheel warship is described.
In 1472 there is the evidence from R. Valturius that the paddle wheel was in use instead of oars, inasmuch as he shows a view of two galleys having five pairs of wheels on each side, each pair running on one common axle with a crank in the middle and the cranks connected together. As early as 1543 Blasco de Garay, a Spaniard resident at Barcelona, propelled a ship by an engine “consisting of a large cauldron or vessel of boiling water and a moveable wheel attached to each side of the ship”. This is the earliest record of a steam ship and it is possible that the engine was a simple form of steam turbine. Nearly two hundred years later in 1736 Jonathan Hulls took out a patent for a paddle wheel, which he fitted into a framework at the stern of a vessel. The circular motion of the wheel was achieved by using ratchet wheels operated by ropes (shown below), one of which was connected to the piston of a condensing engine and the other to a falling weight; the weight being raised by the excess power of the steam piston.
In 1788 the trial of the first practicable steam ship the Dalswinton Steamboat (shown below), of which there is a surviving record and accurate data was run. The steam engine was designed by William Symington and fitted into a double-hulled pleasure boat, 25 ft. x 7 ft. beam. The compound engine had cylinder diameters of only 4 inches, but was sufficiently powerful to drive the ship, by means of a paddle wheel between the twin hulls at a speed of 5 mph.
William Symington was again advancing the state of the art in 1802 when he built the tugboat “Charlotte Dundas” for service on the Clyde Canal, and was the first steam ship to be built for actual service as well as a source of experimentation. The vessel (shown in the first image of the post) was capable of towing two barges, each of 70 tons displacement, 19.5 miles in 6 hours in adverse weather conditions. The paddle wheel was placed at the aft of the vessel and was driven by a horizontal, single cylinder, double acting steam engine (22 inch diameter and 48 inch stroke). One of the most famous paddle steamers was Robert Fulton’s “Clermont” (below left) which was built in 1807. The ship was 130 ft. by 16.5 ft. x 7 ft. deep and had a displacement of approximately 160 tons. She was propelled by two 15 ft. diameter side-wheels, which were driven by a single cylinder engine with a 24 inch bore and 48 inch stroke. On trials she averaged about 4.5 mph over a distance of 110 miles. The largest paddle steamer built by Fulton was the “Paragon” of 331 tons displacement which was completed in 1811 (below right).
A year later in 1812 the “Comet;” was built by John Wood and Co. for Henry Bell. This vessel was 40 ft. long x 10.5ft. wide, had a displacement of 30 tons and is shown in both images below. She was fitted with a side lever engine having a single cylinder 11 ins. diameter and 16 inch stroke, her crank shaft was geared to two shafts, one forward and one aft the engine; each had a paddle wheel at each end. She attained a speed of 5 knots and traded between Greenock and Glasgow in Scotland. Later she was lengthened by 20 ft. and fitted with one pair of complete paddle wheels and a new cylinder 12.5 ins. diameter This increased her speed to approximately 6.75 knots. In 1822 the Admiralty had a small tug built at Deptford, which also bore the name “Comet”. Ten years later their Lordships commissioned the building of the paddle steamship “Salamander”, which was fitted with guns as a warship.
Over the next two decades many patents were taken out for improvements and modifications to existing paddlewheels, but by far the most important of these patents was awarded to Elijah Galloway, in 1829, for what is now known as the feathering wheel. Up to this time the floats on the wheels were fixed in a radial position and thus entered the water at a fixed angle. It should be mentioned, however, that Robert Hooke foresaw the possibility of feathering wheels as early as 1683.
Paddle wheels continued to hold their own for many years and although the “Great Eastern” built in 1858 (below left), was fitted with a screw propeller she did, however, also have two paddle wheels. In 1862 the Cunard Company launched the “Scotia” (http://en.wikipedia.org/wiki/RMS_Scotia ),which was to be the last large paddle steamer for the Atlantic trade (below right). Later this vessel was converted to a cable laying ship and fitted with twin screws.
Although the days of the Large paddle steamer are passed there are still certain cases where the paddle wheel has distinct advantages, for example, the propulsion of pleasure steamers, certain tugs and shallow draft vessels on large rivers.
In 1956 the Admiralty had four diesel-electric paddle tugs built for the purpose of moving aircraft-carriers and other large warships through dock entrances and in the confined waters of dockyard basins. It has been found by experience that paddle driven tugs perform these tasks admirably. The dimensions of these tugs were: – length B.P. 145′ breadth mld. 30’ breadth overall 60’ loaded draft 10′ giving a displacement of 710 tons. The tugs have a bollard pull of 15 tons and free running speed of 13 knots. The paddle wheels are of the feathering type, with the star-center arranged inboard and on the paddle back.
As mentioned previously there are essentially two types of paddle wheel, the first is the radial wheel having fixed floats arranged around its circumference and is analogous to the waterwheel. The second is the feathering wheel shown below, having hinged floats acted on by rods, which are controlled by an eccentric. This ensures that the floats enter and leave the water without shock. A corollary of this is that the diameter of the wheel can be reduced compared with a radial wheel fulfilling the same condition of entry to the water. From the previous work it is seen that the radial wheel has the advantage of simplicity, lightness and cheapness, whereas the feathering wheel allows for smaller diameter wheel which means higher engine revolutions and hence smaller and lighter engines.
The main advantages of the paddle wheel are:
- It allows for the smallest possible draft.
- It gives a high degree of maneuverability when used in a side-wheeler, because the two wheels can be worked independently
- The ability to be easily handled when tying up at Wharves and piers.
- It is more robust and much easier to repair than a screw propeller.
Against these advantages have to be set several disadvantages:
- The immersion of the wheel versus according to the loading condition of the vessel.
- The vessel tends to steer an erratic course when rolling in bad weather.
- When side-wheels are fitted the beam of the vessel is greater than that of a similar conventional ship. If a radial wheel is fitted the machinery tends to be rather heavy due to the low rotational speed.
So to wrap this blog post up on the fascinating world of paddle vessels it is fitting to bring it up to present day. Paddle vessels gave a simple method to convert sail ships into steamers and saw a great boom as propulsion of ships evolved. The variability in ship’s draught with different cargos and also the immersion of the wheels during a seaway were the key limits of the system. However, for river vessels that don’t change draught that drastically during a transit it is a great option. So vessels like the Spirit of Peoria shown below are still being designed and built, this one in 1988. The Spirit of Peoria is not a steam vessel; adopting a diesel electric system similar to trains making it comparatively fast (15 kts) and fuel efficient (15 gph). Paddle wheels may have slipped out of commercial use but people can still enjoy this efficient form of propulsion even today!