822 BEPORT— 1 886. 



one after the other. A barrel is thus rolled in about half a minute, which gives a 

 great saving in time and cost of production, and the material is not harmed by 

 re-heating, as was often the case in the old system. 



When the rolled barrel has become cold it is passed through a straightening- 

 machine, which takes out any short bends, or ' kinjjs,' and is thus made ready for 

 drilling. 



Before going to the drilling machine the barrel goes to a machine which ' faces ' 

 or squares up the ends, and prepares a bearing at each end of it upon which it will 

 rotate in the barrel-drilling machine. 



The barrel-drilling machine has been specially designed to drill a perfectly true 

 hole through the ban-el, and to avoid straightening by means of external hammer- 

 ing, which is extremely harmful to the barrel. Three barrels are operated upon 

 at one time and drilled simultaneously from both ends. The machine is horizontal, 

 alid the barrels rotate at from 700 to 900 revolutions per minute. 



The drills are of the form technically known as D, or half-round bits, and are 

 fed up automatically, a heavy pressure of water being injected up the barrels so as 

 efl'ectually to wash out the cuttings or ' swarth,' and thus ensure the free action of 

 the drills. 



About thirty barrels can thus he drilled in the working day by one attendant. 



This system reduces the cost of drilling to Uttle more than an eighth of the 

 former system employed at Enfield, the results as regards excellence of work being 

 at least equally good. The barrels are then rough or ' draw ' bored, and then ' spilled 

 up ' or fine bored in horizontal machines by means of square bits : this system is 

 well known and has undergone little change during recent years. 



The exterior of the barrel is next turned, and ingenious arrangements have been 

 made to secure the exterior being turned true or concentric with the bore. 



The system at present at work at Enfield eflects this with admirable precision, 

 a ' bush,' or temporary bearing, being fixed to the barrel concentric with the 

 bore. 



This bush revolves in a stay, and steadies the barrel until ' spots ' or bearings 

 have been turned upon it, and from these spots the barrel is rough turned. It is 

 afterwards finished m a copy turning lathe to the desired form, the result being a 

 barrel with its exterior practically concentric with its bore, which is absolutely 

 necessary for good shooting. In rifling, Uttle change has been made in the system, 

 but much attention has lately been given to reduce the cost of this delicate opera- 

 tion. The automatic rifling machine is coming generally into use, and now, with 

 the automatic machine which rotates the barrel after each cut, gives the feed to 

 the cutters, and finally rings a bell to summon the attendant when the barrel is 

 completed, one man can attend to a number of machines producing as many as 

 sixty or seventy barrels per working day, whereas on the old system one attendant 

 was required for each machine producing on an average twenty barrels per day. 



3. The Birmingliam Compressed-air Power Scheme.^ By J. Stukgeon. 



After pointing out the objects of the scheme, and showing that the large num- 

 ber of engines of moderate size used in Birmingham, often intermittently, renders 

 some such system peculiarly applicable to the town, the author points out that, 

 although each 1 ,000 horse-power at the Central Station may only produce 500 effec- 

 tive horse-power at the users' engines, it will displace considerably more than 

 1,000 horse-power of small boiler plant, furnaces, chimneys, &c., and the same 

 engines can be used with compressed-air as with steam. The centralisation principle 

 enables engines and boilers to be used of large power, with all the modern improve- 

 ments, such as high-pressure triple expansion, gas firing, &c. At the pressure 

 proposed (45 lbs.) the air-driven engines will indicate from 32 to 84 per cent, of 

 the power developed at the main engines, according to the mode of using the 

 compressed air. According to the investigations of Sir F. Bramwell and Mr. 

 Piercy, on behalf of the Birmingham Corporation, the present consumption of fuel 



' Published in extenso by the Birmingham Compressed-air Power Company. 



