27S 



SCIENCE-GOSSIP. 



SOME NEW PHYSICAL APPARATUS. 



By James Quick. 

 (Continued from page 232.) 



TN the two last numbers of Science-Gossip have 

 A been described and illustrated some new and 

 interesting pieces of apparatus in physics. Further 



new forms, not 

 only in physics 

 but in allied 

 subjects, having 

 come under my 

 notice, I am 

 bringing for- 

 ward the follow- 

 ing as being perhaps 

 the more interesting 

 of them. 



Vertical Hot- 

 Air Motor. 



The numerous oc- 

 casions upon which 

 one wishes to have 

 at one's disposal a 

 small convenient 

 source of power in 



Fig. 1.— Vertical Hot-Air Motor. 



the laboratory or workshop, and a 

 source that can be obtained quite 

 quickly and easily, calls for special 

 consideration. It can, of course, be 

 accomplished by electric or water 

 motors, but either of these are not 

 at all times convenient. 



The motor illustrated in fig. 1 and 

 also in section in fig. 2, should be a very 

 useful addition to a laboratory where 

 limited power is needed. It is a hot- 

 air motor of vertical form, and its 

 efficiency in working is not dependent 

 upon any supply of gas, as it will 

 work equally well with a small spirit- 

 lamp. The motor is fixed upon a 

 raised hollow base, in which is 

 screwed the fire-pot B, as seen in 

 section in fig. 2. The piston consists 

 of a hollow cylinder, A, working in 

 B and connected to the crank and 

 flywheels above. A is made shorter 

 than B to allow the necessary volume 

 of air at the base of B for heating 

 and expansion. 



Upon lighting either a small Bunsen 

 gas burner or a spirit-lamp beneath 



B, the air contained expands and starts A upon its 

 upward stroke. In doing this the air is cooled 

 again. The cooling is due to the work done, 

 and also to radiation. The pressure is therefore 

 decreased, resulting in the downward stroke of the 

 piston. Speed is thus got up in a remarkably short 

 time. In fact, in tests I have made upon one of 

 these, the maximum speed and power were obtained 

 in five minutes from starting the burner. 



Different sizes of these motors are made, 

 varying from one-eightieth horse-power to one- 

 eighth horse-power. In the larger sizes water 

 jackets are made for sending a stream of cold 

 water round the cylinder to assist in cooling the 

 air ; but very little water is required. When a 

 water supply from the mains is not convenient, 

 then by fixing a small water-tank over the motor 

 and connecting on pipes from the bottom and top 

 of the tank to the bottom and top of the cylinder 

 respectively, sufficient circulation can be obtained 

 by convection currents. 



These motors work quite noiselessly and can be 

 set up in any room. Moreover, as the same air 



Fig. 2.— Vertical Hot-Air Motor in Section. 



