VI. MACHINERY. 415 



2142. Kinematic Pillar Vice, with triangular link-motion. 

 Royal Geological Institute and Mining Academy (Director, 



Prof. Hauchecorne), Berlin. 



This stand is so arranged that any link of the kinematic chains can be 

 fastened in it easily and securely, so that they can be shown in every possible 

 position. 



WHEEL GEARING. 



2143a. Model of a Machine for Cutting the Teeth of Bevel 

 Wheels. F. Engel, Hamburg. 



In the usual cutting and planing machines for conical toothed wheels, 

 each interstice between the teeth is produced by at least two operations ; first 

 one side of a tooth is shaped and planed, then the opposite side of the next 

 tooth. The present machine cuts both profiles simultaneously with the same 

 cutter. A lateral motion is communicated to the cutter, the axis of the tool 

 oscillating about the cutting point of the conical surface, and working alter- 

 nately the one and the other side of the tooth profile. The machine is more 

 accurate than previous ones, and other kinds of wheel can be shaped with it. 



2143b. Samples of Wheels which have been cut by the 

 Machine. F. Engel, Hamburg. 



2143c. Drawing of the Machine. F. Engel, Hamburg. 



2144. Bevel- Wheel Gearing. 



Royal Geological Institute and Mining Academy (Director, 

 Prof, ffauchecorne), Berlin. 



The models exhibited are a small portion of the collection used for 

 machine-instruction in the Koniglichen Berg-Akademie (Royal School of 

 Mines). They have been made specially for this purpose by Herr Maiss, in 

 the workshops of he Academy, upon the designs of Prof. Hermann. The 

 models of separate mechanisms have been constructed upon the principles 

 laid down in. Prof. Keuleaux's " Theoretische Kinematik " ; they are all 

 arranged for " inversion," that is, so that either of their links may be fixed in 

 the screw stand exhibited with them, and the various properties and applica- 

 tions of the inversions easily shown. 



The models are all made with the special view of illustrating in the most 

 complete, clear, and simple manner the principles of the machines and 

 mechanisms which they represent. All details not required in this relation 

 are omitted or made subordinate, the parts which it is important for the 

 students to observe are polished, the other parts, in order not to attract 

 attention unnecessarily, are made a dead black, so that all disturbing 

 reflections of the light are prevented. Care has been taken also to arrange 

 them so that all essential parts and their combinations may be visible at a 

 glance in all parts of the class-room, so that the alterations which it is 

 necessary to make during the lectures may occupy a minimum of time, and 

 altogether that teachers may find their use in demonstrations very convenient. 

 In the steam-engine models it has also been endeavoured to make the relative 

 dimensions and arrangements as far as possible to resemble those of actual 

 practice. 



2144a. A Pair of Worm Wheels, with parallel axes. 



Royal Geological Institute and Mining Academy (Director, 

 Prof. Hauchecorne), Berlin. 



