The Purchase Department.
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Where to Buy your Supplies,
You Can Get It At " W.B." (Duastable).—The Self-aligning doublerow ball bearings you mention can be obtained from the Skefko Ball Bearing Co., Ltd., Luton
"M.J." (Windsor).—The Portable shop crane for which you inquire is marketed by the Alldays and Onions Pneumatic Engineering Co., Ltd., Birmingham.
" Petrol " (Eastbourne).—You can obtain full particulars of the petrol-storage system for which you ask from the Steel Barrel Co., Ltd., Uxbridge, Middlesex.
" Y.S." (Birmingham).—The •tire you mention is American-made and can be obtained in this country from the Firestone Tyre and Rubber Co., Ltd., 14-15, D'Arblay Street, Great Marlborough Street, London, W.
Pyrene Fire-Extinguishing Tests.
• We were recently afforded an opportunity of witnessing a number of interesting and convincing tests with the Pyrene fire-extinguisher. The operations were carried out on a piece of waste land facing the Aldwych end of Kingsway, W.C., a frequent scene of such tests.
The first trial was on burning petrol, two quarts were set on fire and extinguished easily, after being allowed to burn for 10 seconds. For the second test a quantity of calcium carbide and water was added to the petrol already in the bucket, whilst an addition of many yards of loose celluloid films was made for the third test. In each case the fire was successfully tackled and extinguished in less than 30 seconds.
For a further test two gallons of petrol were pouted into an open-top tank, and a tap on one side of the tank was turned on and the petrol allowed to flow on the ground. The liquid inside and outside the tank was then ignited and allowed to burn 30 seconds, and again the flames were put out in a very short space of time.
Half-a-gallon of bi-sulphide of carbon was next poured into a pail, and the liquid in this instance was allowed to burn 10 seconds. The rapidity with which the flames from this highly-inflammable chemical were extinguished was remarkable ; in fact, the fire was almost instantaneously quenched.
. Further tests were made using coal tar, turpentine, paraffin, wood shavings, cotton waste and rigs saturated with petrol, and in every instance the Pyrene liquid satisfactorily tackled and quickly extinguished the flames.
It would be difficult to attempt to give the actual time taken for the various tests, but in every case the flames were put out in well under a minute.
The Pyrene liquid is a combination of purely organic materials, -having an aromatic odour and a high specific gravity. It is absolutely clean, and will not freeze at a temperature of 60 degrees Fahr. below zero.
When the liquid is subjected to a temperature of 200 degrees Fahr. or over, it is immediately. transformed into a heavy, dry, cohering, non-poisonous gas blanket, which surrounds the burning material, preventing the access of air and thereby extinguishing the flames. Hoffmann Roller. Bearings.
It is, of course, a well-known fact that the roller bearings produced by the Hoffmann Manufacturing Co., Ltd., Chelmsford, are a radical departure in design and manufacture from the majority of bearings of this• class hitherto familiar to engineers. They arc the outcome of eptitinuous experimental work covering a lengthy period.. The successful results of the tests which the company has carried out have been, in. all respects, substantiated by the experience of Many users who have had these bearings in actual service.
The Hoffmann bearings consist of an inner and outer race with a row of rollers, which are separated by means of a retaining cage. The inner race is channelled so as to form a groove or trick for the 'rollers; the sides or shciulders of this race being accurately ground, and the rollers, being a good fit between these shoulders, are held in true parallelism With each ' other. It is on this principle, combined with -great accuracy in manufacture, that the success of this class of bearing depends. The outer race is a straight cylinder, so that the rollers are free to take up their correct position longitudinally. The separating cage is made of good-quality gunmetal and is accurately machined. It is so designed as to float freely on the rollers, so that there is no friction between the cage and the races.
It will be noticed from our illustration, reproduced herewith, that the rollers are of the .same length as diameter. Many attempts have been made to design satisfactory roller bearings with long rollers with varying success. The roller-bearing races are made from the same . material and preciselythe same prOcesses as are employed as in the production of Hoffmann ball races. The rollers are made from high-carbon chrome steel, and they are treated so as to ensure a uniformity of hardness and temper, and they will stand heavy loads over a lengthy period. The Hoffmann Co. has found that there is an increasing demand for these roller bearings which should appeal to the commercial-vehicle builder on account of their heavy-load carrying capacity.