TRANSACTIONS OF SECTION G. 881 



ripping of the threads will be caused. Much depends, also, on the material to 

 be operated upon. In mild steel the elongation is more than in hard steel • 

 in brass and gun metal rather more than in mild steel; and in cast iron it is' 

 considerably leas than in either of the other metals mentioned. Further in 

 threads with a small angle of the sides it is considerably more than in those havino- 

 a large angle. ° 



The screws used in cycle construction are subject to even more continuous 

 vibration than gun screws, but owing also to the low margin of safety in cycle 

 •work, it has been found necessary to use shallow threads, so as to give the 

 greatest possible strength to the core, and to obtain a large angle of the sides 

 of thread, which especially is important, as a large number of parts are har- 

 dened, and therefore the greatest possible strength of thread is necessary. 

 While a few firms use the Whitworth thread exclusively, others use a shallow 

 thread, as before described, in a portion of their component parts, with Whitworth 

 threads in the remainder. With the exception of two instances, as will be seen 

 from the attached list, the shallow thread is adopted throughout for B.S.A. 

 cycle components. Time, however, will not permit me to give the reasons why a 

 different thread is used in the two exceptions, but they illustrate the necessity 

 ■which sometimes arises for the adoption of a different thread to suit altered 

 conditions. 



The ' B.S.A.' thread is now extensively adopted as a standard in the cycle 

 trade, and although the B.S.A. Company make all their own screws, the screw 

 manufacturers to the trade have found it necessary to make the ' B.S.A.' standard 

 a staple article of their trade, and tool makers have also now a marketable article 

 in taps, dies, and chasers for the * B.S.A.' thread. 



The illustration which was exhibited gave the section of the ' B.S.A.' thread, and 

 for comparison also sections of the British Association, the Whitworth, and the Seller 

 threads. A list of the diameters, pitches, &c., of the screws used in the ' B.S.A.' 

 cycle components was also given. It is to be noted that the angle of the ' B.S A.' 

 thread_is_60°, with tops and bottoms rounded to a radius of one-sixth of the pitch, 

 and this is practically the shape of the thread used for the screws of the Lee-Enfield 

 Magazine Rifle, which is manufactured for Her Majesty's Government by the B.S. 1. 

 Company. 



3. The Photographic Method of jyreparing Textile Designs. 

 By Professor Roberts Beaumont, M.I.Mech.E., Yorkshire Collecje, Leeds. 



The preparation of designs for the loom has, throughout the history of 

 weaving, been regarded as a purely manual process controlled by the intellio-ence, 

 ingenuity, and skill of the craftsman. It is only natural, therefore, that the 

 invention of apparatus for this specific purpose should have created much interest 

 amongst both British and foreign textile experts. Photography, as understood 

 and practised, appeared as incapable of aiding the artist in the actual paintintr of 

 his picture as the designer in the transference and execution of the plain sketch of 

 the pattern on to the ' scale ' paper for the loom. Within the wide range of 

 technical and scientific data ia the construction and embellishment of woven 

 fabrics there is, perhaps, no phase of the work more difiicult to assail, by 

 mechanical devices, than the application and adjustment of the manifold 'weave' 

 units which compose all figured textiks. 



Design acquired in the loom is a distinct tvpe of ornamentation involved in 

 varied technicalities. It is not the result of one but of a number of processes, over- 

 lapping eaoh other, and yet uniting to construct and perfect the same woven efl'ect 

 Fabric and design have to be simultaneously obtained. These can only be 

 divorced by resorting: to the arts of printinjr, embroidery, and painting. Obviouslv 

 in the preparation of the ' design ' sketch f .r weaving, numerous hmirations have to 

 be encountered, which, on a first consideration se^m liible to be increased rather 

 than di'uinished by a photographic i)rocess of design-development. Much ino-enuity 

 has been exercised by Szczepanik in his solution of these 'weave' problems 

 bzcrepaniks apparatus is not for the origination of designs either in the 



1900- - - 3l 



