102 REPORT — 1841. 



of a fan, by means of a peculiar arrangement of the clutch box at the centre of the 

 wheel. 



On a Plan of Disengaging and Reconnecting the Paddle- Wlieels of Steam- 

 Engines. By J. Grantham. 



There are four cases in which it may be desirable to disconnect the paddle-wheels 

 from the steam-engine in steam vessels, viz. when the vessel is on a long voyage, 

 and the fuel must be economized as much as possible by using the sails on every fa- 

 vourable opportunity ; when the engines are damaged, and, the vessel being close to 

 a lee shore, it is necessary to disengage the engines quickly, to allow the vessel to 

 make sail ; when some derangement has taken place, and the engines are allowed to 

 continue to work imperfectly to the end of the voyage, rather than detain the vessel 

 by causing the paddles to drag through the water while the engines are stopped ; 

 when, the vessel being at anchor, the action of the swell and tide on the paddle-floats, 

 while stationary, causes a great additional strain on the cables, which would be ob- 

 viated could the wheels play freely. The Admiralty had called attention to the subject, 

 by inviting plans for effecting it. Several had been proposed for disconnecting the pad- 

 dles, but Mr. Grantham is not aware of any plan having been proposed by which the 

 wheels could be readily reconnected in a heavy sea. The crank pins are usually fixed 

 in the cranks of the intermediate shaft, a little play being allowed in the eye of the 

 crank of the paddle shaft, to prevent the crank pins from breaking when the centres 

 of the three shafts vary from a straight line by the yielding of the vessel. For the 

 purpose of disengaging and reconnecting, a brass box of a rectangular form is inserted 

 in the eye of the crank of the paddle shaft, which can be moved several inches by means 

 of a screw at the back of the crank. The eye of the crank is so made that two of its 

 sides may be cut away, and through these openings the crank pin can pass when the 

 box is drawn back, or the disengaging effected. The brass box has one of its sides, 

 which restrain the crank pin when in gear, cut away one or two inches to assist in 

 reconnecting the engine, which is effected by screwing the box out one or two inches, 

 or just so far that the crank pin can pass the side which has been cut away, and come 

 in contact with the higher side. This is the correct position for reconnecting, which 

 is accomplished by a single turn of the screw. 



On Captain Couch's Chock Channels. 



Mr. Snow Harris explained and illustrated, by a model and drawings, the safety 

 chock channel, for allowing the masts and rigging of vessels to be easily disengaged 

 when the masts are carried away. Many cases have occurred in which, with the 

 rigging and ordinary channels, the greatest danger has been incurred, in consequence 

 of not being able to get clear of wreck. The ordinary channels may be blown up by 

 the sea ; whereas, if made solid, on Capt. Couch's plan, all danger from this source 

 will be avoided, and the sailors would be at once able to clear the vessel of any wreck. 



On a System of Trussing for the Roadways of Suspension Bridges. 

 By J. M. Rendel. 



Mr. Rendel placed before the Section a model of the Montrose Suspension Bridge, 

 the roadway of which had been recently restored, and a peculiar system of trussing 

 adopted. Suspension bridges were peculiarly subject to undulatory motions, which 

 proved extremely destructive to them. These undulatory motions arise from the 

 action of the wind, and the circumstances are such that the wind may tend to raise 

 the roadway at one end, and depress it at the other; and various means had been de- 

 vised to prevent these motions. In 1838 a considerable portion of the roadway of 

 the Montrose Bridge was destroyed, and Mr. Rendel being employed to restore it, it 

 struck him that if great stiffness were given to the roadway by a system of longitu- 

 dinal trussing, the desired object would be attained. He adopted, therefore, a system 

 of vertical and longitudinal trussing, extending above and below the line of the road- 

 way, so that the neutral axis of the truss is in the roadway. This had succeeded 

 most completely. In an ordinary gale of wind, the original roadway would be sub- 

 ject to a wave of from three to five feet in height, but he was satisfied that the present 



