PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 435 



Mr. Brewster, — "Would that remedy the jfluttering of the pad- 

 dles? 



Mr. Rowell. — No sir. 



Mr. Brewsrer. — Would it not make them flutter Avorse ? I 

 contend it would, because you take the whole power from only 

 two points, instead of & greater power at those two points, and 

 a less power for the remainder of the revolution. I think, too, 

 that there will be a loss from the adjusting piston. It takes some 

 time for the steam to enter the cylinder, and by the time it has 

 entered in sufficient quantity to become effective, the dead point 

 has been passed for some distance, and the steam begins to act 

 to good advantage. Besides, this new piston l>as three frictions 

 instead of one ; for each of the false piston ends must be made 

 steam tight, and will cause friction. 



Mr. Tillman. — I consider this arrangement very ingenious, 

 although I think there is an increase of friction in it. 



Mr. W. H. Bartlett. — There may be a certain distance from the 

 dead point where the increased friction upon the journal of the 

 main shaft, from the pressure of the piston-rod against the crank 

 will counterbalance the pressure of the steam. 



Mr. Dibben. — I think it could not increase the friction so much 

 that you could not gain from the added power. 



Mr. Stetson. — This depends somewhat upon the size of the 

 engine, and the size of the shaft and crank relative to the length 

 of the stroke. Exactly at the dead center, no amount of force 

 will aid the engine at all ; but from the friction upon the crank-pin, 

 the force would tend to prevent the engine from moving. The 

 angle at which the friction will counterbalance the pressure 

 would be different in a propeller engine, with a short crank and 

 thick crank-pins, from what it would be in an engine like that in 

 the " New World," with a 15 foot stroke. 



Mr. Dibben. ---I did not take into the account what power it 

 takes to start the engine. The engine friction is frequently con- 

 sidered a large proportion of the whole power. 



Mr. Stetson. — To take an extreme supposable case, the crank- 

 pin may be thickened until it becomes an eccentric, and you may 

 make it so large that even at the half-centre the steam could not 

 start it. Enlarging the crank-pin you increase the angle of non- 

 effectiveness. 



Mr. Churchill. — That is in consequence of the enormous surface 

 subject to friction acting with a greater leverage than the con- 



