RESILIENCY WITH RELIABILITY. •
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Reasons Why the Cushion Tyre Is Proving a Popular Mean Between the Pneumatic Tyre and the Ordinary Solid. Efficient Examples.
WHEN considering the adoption of tyre equipment on a vehicle there are many points which should receive careful study so that the utmost efficiency and reliability can be obtained. Many users, or potential users, go no farther than to deal with the points for and against pneumatic-tyre equipment as compared with the employment of ordinary solid tyres, and they fail to give sufficient attention to that most useful mean, the cushion tyre.
Amongst the most popular and prominent of cushion tyres there is the N.A.P. made by the N.A.P. Pneumatic Tyre Co., Ltd., of Stonhouse Street, Clapham, London, S.W.4, and by Chas. Macintosh and Co., Ltd., Cambridge Street, Manchester.
In a sense, the N.A.P. is a pneumatic, in that it embodies an air core. This, however, is at atmospheric pressure. It is manufactured in sizes from 750 mm. by 90 mm. upwards. In the case of Ford vehicles, the tyres are supplied on Hayes or Kelsey rims, which fit direct on to the front and rear wheels of the ton truck. The N.A.P. tyre in the press-on type can be fitted to any existing wheel intended for solid tyres, and is suitable for loads up to 6 tons on the rear axle.
Very little attention is required to this equipment provided the treads are occasionally looked over and any small stones removed from the triangular cavities. If not seriously overloaded, mileages of 20,000, 50,000 and even 100,000 can be obtained. All are guaranteed for 10,000 miles, but it is considered, safe to assume an average of 20,000 miles.
A new and special design of cushion tyre was produced recently by the Dunlop Rubber Co., Ltd., Fort Dunlop, Erdington, Birmingham.
In all cushion tyres the extra comfort is provided by allowing spaces or cavities which enable the rubber to flow or to displace freely under load, and the cushioning depends on the size, design and area, of these spaces. By taking advantage of the opportunities for rubber displacement presented by having the cavities on the outside of the B46 tyre, very effective cushioning has been .obtained in the Dunlop tyre without impairing in the slightest degree the durability, load capacity and base adhesion. The tread forms a very effective and permanent non-skid design, the value of *which does not disappear as the tyre wears down.
The Ducasble tyre is made by the Ducasble Tyre Co., Ltd., Bank Buildings, 16, St. James's Street, London, S.W.1. Its construction necessitates the use of almost exclusively pure rubber, as the internal stresses and continuous work which make it an effective shock absorber would cause splitting round the air cells should
inferior material be employed. Free egress and ingress of air ensure selfcooling, and these cells 'permit free spewing of the rubber towards the centre of the tyre, which retains its shock-absorbing properties to the end and is not rendered useless when wear reaches the air cells; that is, the tyre does not split in half ; furthermore, the rubber partitions between the air cells are claimed to prevent any side-rolling effect. The square profile of the tread assists in preventing ,skidding.
The Ducasble cushion tyre being partly hollow necessitates a larger section for a given solid, and this, by eliminating the narrow solid, necessarily protects the road surface, as the load per tyre is spread over a much greater area.
Several very interesting examples of cushion and super-resilient tyre are manufactured by the St. Helens Cable and Rubber Co., Ltd., Trading Estate, Slough, Bucks. The true cushion typo is•known as the Air Chamber. Concertina tyre. The patented tread design which is employed obviates the use of circumferential grooves which are apt to catch in tramlines, etc. By the vse of a special form of protuberance at the sides of the tread, side slip is practically impossible under normal conditions.
The arrangement is such that when the first tread has worn away, a second complete tread comes into use, and thus the non-skid properties are retained throughout its life. The air chamber is also of special design. It is unpuncturable and contains air at normal pressure. It, like the exterior, has cor
rugated walls, and these when the tyre is heavily laden make contact, and this gives a reinforcing effect.
These tyres are made in 32-in. by 4i-in. size for Hayes rims, and are interchangeable on the re'ar wheels of Ford tanners fitting this type. This type for Fords is being generally marketed at the present time, but the company are also developing tyres of this type in the press-on sizes suitable for replacing solid tyres on passengercarrying vehicles, etc.
Another cushion tyre which gives effective resilience and freedom from trouble is the Goodyear Pneumatic Cushion, which is marketed by the Goodyear Tyre and Rubber Co. (Great Britain), Ltd., Chelsea Wharf, Lots Road, London, S.W.10. It has central air-core cushions, indented side walls and deep springy rubber tread blocks. It is claimed that this type of tyre will not chip at the edges, skid or lose its cushioning through wear.
A tyre which is the result of several years' experience of road tests with cushion tyres of various designs is. the Harboro', manufactured under licence at the works of the Harboro' Rubber Co., Day and Night Mills, Market Harbarough. The tyre is formed with specially designed cavities arranged alternately at each side so that under action the rubber can be displaced into them. The cushioning effect is obtained without tubular conStruction, and the large suaace presented to the air ensures adequate cooling. Each tyre is built on a single steel band for fitting in the ordinary press in the same manner as a band tyre.
In the Goodrich Semi-Pneumatic tyre manufactured by the British Goodrich Co., Ltd., 50, Pall Mall, London, S.W.1, there a central air chamber, a press-on steel base and an anti-skid grooved tread. The sides of the tyre are formed into projecting buttresses which afford a better grip on the road surface and a considerable measure of protection against kerb abrasion.
The leading features of the efficient cushion tyre, made by Henley's Tyre and Rubber Co., Ltd., 20-22, Christopher Street, Finsbury Square, London, E.C.2, are a large air space, staggered grooves each passing half-way across the tread and a steel base in halves keyed together.