358 SEC. 12. APPLIED MECHANICS. 



2136, Stationary Direct-acting Steam Engine (model), 

 Royal Geological Institute and Mining Academy (Director, 

 Prof. Ifauchecorne), Berlin. 



The cylinder and valve chest are opened so as to show the various parts. 

 The eccentric is displaceable with reference to throw and lead ; accordingly 

 the valve rod and valve are changeable. 



This model shows the general arrangement and essential details of a 

 stationary direct-acting engine, and is arranged specially to demonstrate the 

 relative motions and positions of the piston and the slide valve, and the 

 mechanisms connected with them. 



It shows : 



1. The dead points of the machine; 



2. The necessary relative positions of eccentric and crank ; 



3. The way in which a steam engine is compelled to move in one direction. 



4. The lead of the valve and the eccentric, and their influence upon the 



steam admission ; 



5. The lap of the valve and its connexion with the angular advance of the 



eccentric and the expansion of the steam ; 



6. The irregularities in steam distribution and in the transmission of 



motion to the fly-wheel, caused by the obliquity of the connecting-rod ; 

 and 



7. The effects upon the steam distribution of an eccentric rod of wrong 



length or an eccentric put in a wrong position. 



1944a. Working Model of latest improved horizontal high- 

 pressure coupled winding engines for coal, copper, iron, salt, and 

 other mines. Messrs. Robert Daglish and Co., Lancashire. 



2141. Model of a Horizontal Steam Engine, with re- 

 versing gear (Gooch's link). 



Royal Geological Institute and Mining Academy (Director, 

 Prof. Hauchecorne), Berlin. 



This model is intended to illustrate the action of the link motion generally, 

 and especially that with adjustable block. 



The link can be worked in two ways. Either its centre can be suspended 

 and an eccentric rod connected with each of its ends, or its centre can be 

 fixed, and one eccentric rod only used ; an arrangement often employed, for 

 example, in hoisting engines. 



It shows very distinctly that with two eccentric rods with their eccentrics 

 placed 180 apart, the centre of the link moves to and fro, and that this 

 error can be almost entirely prevented by giving the eccentric a little 

 advance. 



2143. Horizontal Steam Engine, with reversing gear 

 (Stephenson's link). 



Royal Geological Institute and Mining Academy (Director, 

 Prof. Hauchecorne\ Berlin. 



Along with the above model this shows the two chief systems of link re- 

 versing gear, their differences, and their comparative advantages and defects. 

 The link has here a different form to that employed in the last case, partly 

 simply for the sake of variety, and partly to show the influence of the position 

 of the point of suspension upon the motions of the link. 



Models of mechanisms : 



The eccentric is here also adjustable for variations of lead. 



