AMERICAN INSTITUTE. " 577 



It is further supposed " that the piston, acting by its weight, 

 sometimes on one side of the cylinder, sometimes on tlie other, 

 will produce unequal wear. 



Eut the most weighty objection which affects nearly all oscil- 

 lating engines, is the great friction of the trunnions upon which 

 the cylinder swings. This friction is much greater than is gen- 

 erally supposed, on account of the high temperature to which the 

 trunnions are subject from the steam passing through them; with 

 high-pressure steam, the temperature reaches a point at whicli 

 metals move upon each other with difficulty, and are subject to 

 great, attrition. As an example, a brass cock, which may be 

 turned in its seat when cold, with ease, under eight atmospheres 

 of steam, will stick so fast as to be scarcely movable. 



When the distance from the trunnion axis to the crank shaft is 

 too small, the rotations are unequal, as is also the force trans- 

 mitted to the machine. 



These are some of the objections. Now for the advantages. 

 The oscillating cylinder simplifies the steam engine, particularly 

 the high pressure, against unnumbered scientific apparatus ; the 

 massive beam, the colossal connecting rod, the parallelogram 

 with its twenty joints, the oscillating cylinder lays nothing in 

 the scale, except two trunnions, with their bearings, and a single 

 connecting piece between the j)iston rod and the crank pin, not 

 the thirtieth part of the former. An oscillating steam engine 

 consists properly of nothing further than the cylinder, the crank, 

 and the fly wheel, between which parts the beam engine, the 

 most elaborate, complicated and expensive organs of the whole 

 machine, lie. Instead of a costly array of apparatus to convert 

 the rectilinear into the circular motion, the crank is worked di- 

 rectly by the piston rod. 



Oscillating engines thus being more simple, require less trouble, 

 labor and time, in their manufacture, and are consequently less 

 expensive. It has a compact and compendious form, is more 

 compressed, and requires but little space, and is much lighter 

 than ordinary engines. A tliree horse power, without the boiler 

 and fly wheel, can be carried by two men. An oscillating loco- 

 motive engine would be simple in management, require but little 

 care and knowledge on the part of tlie engine attendant. Its ap- 

 paratus is simple. Its construction is founded on no scientific 

 calculations unknown to the attendant. The connection and 

 action of its parts, the combination of theii' motions, and their 



[Am. Inst.] 37 



