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Valuable Features in Timber for Passenger Vehicles
Page 103
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An Expert Deals with the Claims of Oak, Ash and Other Woods, as Framing Materials for Coaches and Buses. Features of Some Noteworthy Empire Timbers for Decorative Purposes By A Timberman
UN the early days, vehicle builders had La relatively small number of woods from which to choose, as, of course, many of the forests of the world were then unexplored. To-day, augmented with many new and attractive Empire timbers, a brief description of the variety of woods on the market would fill a volume, and it is doubtful whether there is any other material which presents such a variation of colour, texture and utility, either for constructional or decorative purposes.
With the exception, perhaps, of longdistance coaches, passenger vehicles generally, by reason of frequent stoppingand starting, are, possibly, subjected to more stress than are other commercial vehicles. Therefore, the framework should be only of first-class timber. Railway companies have always recognized it to be false economy to use any other.
Merits of Oak and Ash.
Oak and ash are generally used in this important capacity on all road vehicles, with a preference for the latter timber. There is, however, great divergence of opinion on the matter, and a few details of the characteristics of those two valuable woods may be helpful.
Every Briton has warm affection for oak—that wood which has played so great a part in the history of the Empire—and likes to think of it as the strongest wood in the world Although of great strength, it would be more accurate to say that oak is the most durable wood known. Under certain conditions its durability is almost unlimited; under any condition it will last a lifetime.
That is its chief advantage, when compared with ash, which is of greatly inferior durability. In the matter of strength, which is of paramount importance in framing, it may surprise many readers to know that ash is the stronger wood.
Strength of Oak and Ash,
The following are the results of official tests, carried out with quarterings, 2 ins. by 2 ins., placed on hearers 4 ft. apart. The ash broke with 862 lb. and the oak with 837 lb. The deflection at breaking point was: Ash 81t ins., and oak 7* ins. The specific gravity of ash is .736, whilst that of oak is .827.
will thus be appreciated that, although ash is lighter than oak, it is stronger and more elastic. Indeed, one authority on coachbnilding woods has stated that, in proportion to its weight, ash will withstand greater stress than will steel. Nevertheless, its great enemy is the worm, to. which it is highly susceptible, and, once attacked, it will quickly decay. Not so the oak, the diehard of the timber world. Its natural acid will keep all wood pests at bay for many years, which proves it to be a king of woods.
But in these days of quickly changing fashion, the question of durability has lost much of its importance. Passenger vehicles are neither wanted nor expected to last a lifetime. Utility and comfort are primarily demanded.
Ash, by reason of its great resiliency, which absorbs the shock of sudden starting and stopping, and thus relieves the whole vehicle of stress, is still, in the writer's opinion, supreme as a material for framing, enabling the vehicle to afford a maximum amount of comfort to passengers.
Moreover, as pointed out in an article which recently appeared in The Commercial Motor, the possibilities of bent timber in body construction have now been proved, and ash has long been recognized as the best wood for this purpose, losing little, if any, strength in the process. Of the oaks, American oak is the best wood for steaming and bending, showing extraordinary elasticity. It is considerably cheaper than ash, but is not so strong or tough, nor is it so strong as English oak.
Another constructional timber of great utility, which might be used mole often, is pitch pine—not to be confused with British Columbian pine. Pitch pine is a long-grained timber possessing great strength and toughness. It is usually sound, clean in appearance, free from knots, and is easily worked. Containing an abundance of resinous matter, it will resist water and is highly durable.
Unlike most woods, it is almost immune from climatic changes, which suggests its suitability for vehicles going overseas. The wood is rather heavy, which is apparently its only drawback, but it finds great favour with railway and shipping companies for all-round constructional work. It can be used for purposes where the cost would preclude the employment of ash, for which it is an excellent substitute.
Apart from structural purposes, wood lends itself especially to decorative work, and it is surprising that the numerous handsome timbers are not used to a greater extent. For decorative woods we can now look to the Empire market with complete confidence. A wide range of choice is offered, whilst supplies are xegular and prices are reasonable. Moreover, much more attention is now given to the seasoning of these timbers. The following are hut a few of the many now on the market : Features of Empire timbers.
NIGERIAN WALNUT is a wood usually showing a golden-brown lustre, with a dark-brown or black-streaked figure. It is not difficult to work and the usual technical qualities are quite satisfactory; it is also excellent for both high and dull polishing, and is most attractive as panelling. It is recognized by the London County Council as a fireresistant.
IATHITE BOMBAY is a firm, hard, close and even-grained Indian timber, yellowish-grey to light brown in colour, often with darker streaks, and lustrous. It works well, especially with machine tools, finishes satisfactorily, and takes a good polish. This timber does not warp or twist and is light of weight, being suitable for interior work of the highest class.
SILKY isms from Australia is light brown in colour ancl moderately hard, with a striking wavy figure. Tough and elastic, it is durable when under cover, and neither splits nor, warps when well
seasoned. It gives little trouble in working, finishes to a smooth surface and takes polish well, making an excellent wood for interior fitting and 'panelling.
CRABWOOD, a moderately soft, lustrous wood from British Guiana, closely resembles 'mahogany in colour and appearance. The grain is fairly open and requires care in planing, as the wood is apt to "pick up." However, it gives excellent results when stained and polished, and has already been satisfactorily tested as a body-building
material. .
PLYWOOD S, of course, now largely used for decorative work, but few users seem to know that it can be obtained in the following ornamental woods:— Black bean, blackwood, greywood, lacewood, laurel, sapele mahogany,' sycamore, satinwood, teak, rosewood, alroondwood and ebony.