May, 1940 AIRCRAFT ENGINEERING Workshop and Production Section Details of Selected Equipment for Various Duties A Dynamic Balancing Machine BRITISH STANDARDS SPECIFICATION NEW type of dynamic balancing machine Copies of the following specification may be capable of handling small test bodies up to obtained, at the price indicated, from The British a maximum weight of 6½ lb. has recently A Standards Institution, 28 Victoria Street, London, been introduced to the British market. S.W.1. As may be seen from Fig. 2, this machine consists B.S.S. No. 881.—Nomenclature of Hardwoods. of a cast-iron base to which a cradle, supported by For some time past the confusion of names given two vertical helical springs, is fastened. The body t o various timbers has been a serious matter for to be balanced is accommodated in the cradle by man y people engaged with the marketing and two bearing traverses. These are adjustable along purchasing material for th e woodworking industries. the cradle t o suit the length of th e test body. An This confusion had increased considerably of later electric motor is arranged in the housing to the year s with the introduction on th e marke t of many left of the machine and this rotates the specimen more species of timber as an outcome of the through an clastic coupling. promotion of forest resources of th e Empir e overseas. A compensating system (also provided in the Th e need for a standard nomenclature of species housing) is driven a t the sam e speed as th e specimen. of timber was felt, and in 1935 th e British Standards This compensating device, consisting of an adjust Institutio n published a Standard Nomenclature of able disc with an out-of-balance weight of known Softwoods comprising 74 species. This has now magnitude, produces a centrifugal effect which been followed by this similar Nomenclature of counteracts the disturbing forces caused by the Hardwood s in which 240 species are catalogued. out-of-balance weight of the test body. The com The list includes all the hardwoods of actual or A New Type of Lighting pensating weight, being adjustable as to amount potentia l commercial importance in this country and angle, will neutralize the oscillations produced an d has been compiled by representative s of govern The new 80-watt, 200/250-volt, Mazda Fluorescent by the unbalanced weight of the test body after ment departments and scientific and industrial Lamp , developed by the B.T.H. Company intro being adjusted to th e righ t position. This is indicated organizations, thus assuring that its application duces possibilities which, it is claimed, may change by an optical and a mechanical measuring device will be general. th e whole aspect of industrial, commercial and fitted to the machine. The guiding principle upon which the nomen decorative lighting. A chart is provided on to p of the housing which clature has been based was to establish a single The lamp is a slender 5 ft. glass tube which pro indicates both the actual out-of-balance weight in standar d name for an y one timber, and to restrict vides a light of daylight quality from its entire ounces, and the balancing moment in inch/ounces. tha t name to one timbe r only. surface. Coloured objects can be seen in their full These values are read off the chart by means of a I n putting this principle into effect two main outdoor appearance. The ligh t is produce d through pointer which can be set t o th e diameter and position problems have had to be faced. These may be th e agency of invisible radiation acting on the of the compensation planes chosen for correction summarized as follows: fluorescent powder which coats th e inside of th e tube. of the out-of-balance weights of the test body. (1) In many cases one timber has been known This powder is a highly effective converter of invisible A disc arranged below the measuring chart by a number of different names. This has energy into visible light. indicates the angular position of the out-of-balance led to much confusion, particularly where th e The light from the lamp is a close approximation weight as determined along the radius of the test timbe r is one in common use. to north sky daylight. It has a low surface bright body. (2) In a number of instances the names of well ness—about six candles per square inch. Perfect Fig. 1 illustrates the working principle of the known woods such as oak, walnut , mahogany diffusion is therefore readily obtained and com machine, incorporating the special feature that or teak, have been applied to timbers which plicated shielding of the light source is thus un unbalance is measured by unbalance, i.e., b y a force hav e no botanical relationship with those necessary from the point of view of glare pre of the same nature. Spring or other mechanical vention. properl y so named. Names coming within elements ar e eliminated from the measuring device, thi s category are distinguished throughout Th e lamp has a n efficiency of 35 lumen s per watt, thus ensuring the greatest reliability and accuracy. th e nomenclature by quotation marks. which is approximately three times that of the Actual balancing takes place a t the resonance or Wheneve r a suitable synonym for a timber with gasfilled lamp, and five times tha t of a gasfilled lamp critical speed which can easily be found for an y a "borrowed" name could be found in common with daylight bulb. particular body by means of a variable resistance use this has been adopted as the standard name, The industrial reflector shown in Fig. 3 has been provided in the machine housing and by simply bu t in several instances this could not be done specially designed for use with the 80-watt adjusting the supporting springs. If the body is withou t causing some serious dislocation in the fluorescent lamp. The reflector is constructed from found to be in dynamic equilibrium at the critical industries concerned. sheet steel and is supplied complete with fixing clips speed it will also be in balance a t any othe r working for the lamp and with suspension fitments. The A trade practice which has somewha t complicated speed, provided the body is rigid and does no t show th e nomenclature is tha t of adopting a name for a control unit and the power factor correction con any deflexion in itself. This machine is marketed variet y of timber produced from a certain mode denser are enclosed within the box mounte d on th e by \V. T. Avery Ltd., Soho Foundry, Birmingham. of conversion or from different parts of the tree to p of th e reflector. The cable from the control box havin g distinctive tones or colours. Besides the t o the lampholders is protected by detachable standar d name and the name of the botanical channels and the unit is supplied completely wired species, information is given of th e sources of supply and ready for use. A special paint finish is used to an d a comprehensive list of synonyms as applied render the reflector durable in service and the t o each species, not only at home but also in th e standar d colour finish is white inside and green countr y of origin and elsewhere where reference to outside. timbe r is of commercial importance. Th e installation particulars of the lamps are : Th e list as it now stands is the result of con 80-watts ; 200/250-volts; overall length 5 ft. ; siderable research and is likely to prove helpful diamete r 1½ in. ; caps are standard B.C.; initial in identifying timbers, especially when use is made light output 2,800 lumens. of the index with its complete cross references. The applications of a light of thi s typ e to th e needs I t is confidently hoped that the general adoption of the drawing office and workshop are obvious. of a nationally agreed standard nomenclature will Furthe r particulars may be obtained from the result in introducing uniformity and simplicity manufacturers, the British Thomson-Houston Co. in place of the chaotic conditions which have Ltd. , a t Bridle Path, Watford Junction, Herts. hithert o existed. Price 3s. 6d. (3s. 8d . pos t free).
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: May 1, 1940