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USERS' EXPERIENCES WITH TYRE EQUIPMENT

7th February 1928, Page 127
7th February 1928
Page 127
Page 128
Page 129
Page 130
Page 127, 7th February 1928 — USERS' EXPERIENCES WITH TYRE EQUIPMENT
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Which of the following most accurately describes the problem?

The Tyres Employed on Passenger Vehicles. Modern Tendencies. What the Future May Hold. What Operators Have Learnt.

S0 FAR as the tyre equipment of passeuger vehicles is concerned, we are approaching the end of a transitionary stage in which the solid tyre is rapidly losing the fight, except for certain of the largest vehicles other than rigid six-wheelers, and, in particular, the majority of the buses running in the Metropolis.

There is still a certain amount of doubt as to whether the cushion tyre will not come forward as a more important rival of the pneumatic than it is atpresent So far, the call of the public has been all for vehicles with pneumatic tyres, and a disadvantage of the majority of air-cushion tyres has been that they so closely resemble the solid variety that most people think they are of the solid pattern, but we believe that progress is being Made in the development of cushion tyres which will closely resemble in shape and size their pneumatic rivals Su great has been the progress made with the large pneumatic tyre that average mileages almost equivalent to those of solid tyres are now being achieved; whilst the improvement in construction is decreasing the stoppages due to punctures and bursts—extremely important points in the passenger vehicle, delays with which may become exceedingly annoying and dislocate important services.

Advances are also being made in the direction of the tyre with the comparatively low pressure, say, 40 to 50 lb. per square in., as compared with the 100'to 110 lb. of the large high-pressure type. These tyres are already being used in a

fair number of cases and afford excellent riding comfort.

Many small and medium-capacity vehicles are equipped with single pneumatics on the rear wheels, but there is a tendency with some of these towards reverting to the former practice of fitting twins, as, in the case of one or two tyres failing, the vehicle can carry on for some distance on the remaining tyres.

With the idea of ascertaining the experiences of actual users in respect of the tyre equipment of passenger vehicles, we recently obtained the views of a number of prominent bus and coach operators, both municipal and private.

The Experiences of Private Users.

S.O.S. Daimler and .Tilling-Stevens buses with an average seating capacity of 32 are employed by the Trent Motor Traction Co., Ltd., and all these have ptieumatic-tyre equipment, the reason given for this selection being the demand of the public. The road surfaces over which the vehicles rim are good, and the average mileages are :—Front tyres, 26,000; rear tyies, 30.000. Pneumatic and cushion tyres have been found preferable to the solid variety from the point of view of skidding. No serious effects have ever been experienced as the result of tyre failure. Punctures are very infrequent, and regular inspection is carried out to ensure the correct air pressure. Only a few vehicles have twin tyres at the rear. When a puncture takes place, the vehicle is driven carefully to the end of its journey.

The tyres are bought outright and kept up to pressure by portable r bottles working on the Luchard syste Keith and Boyle (London), Ltd., t company running the well-knot Orange coaches, uses 28 and 32-seat Malays and 25 and 30-cwt. Guys, t majority of the tyres being 32-in. 6-in. and 38-in. by 7-in. pneumati4 These are employed to give extra coi fort on the coaches, and more speed wi less damage to goods on the fleet vans. They run on all kinds of re: surface within 100 miles of London, t average mileage for all four whet being between 18,000 and 20,000.

What small experience the compal has. had with cushion tyres has not be' satisfactory, as those they have us' have been found to wear out too rapid!

The cost of pneumatic tyres vani between .5d. and 1.0d. per mile accor tag to size. One man does nothing el. but attend to air pressure.

No serious trouble has been expe, enced with bursts ; punctures are infr quent, but, where experienced, cause delay of about 20 minutes. No i effects have been found from small ore loads, and a special pumping plant in been installed in the garage.

Pneumatics of 38-in. by 7-in., 364 by 6-in. and 36-in. by 8-in. dimensiot are used by the Thames Valley Tractie Co., Ltd. The vehicles in the fleet to Thornycroft and Tilling-Stevens singl. deck buses with a seating capacity ( between 29 and 35 people, and a fe, double-deck buses of Thornycroft mali each seating 54 passengers.

The tyres are purchased under spech p53 contract on a mileage basis. The pressure of every tyre is taken each morning. In over 60 vehicles with pneumatic-tyre equipment during the past few months an average of only one puncture per week has been recorded. Very little trouble has been experienced with punctures of twin tyres at the rear, but, in such cases, the vehicle would not be run home on the sound tyres. Special pumping plant for inflation is used at each depot.

Instructions. are issued to the staff not to carry excessive loads ; but overloading is bound to occur at times, and, so far as the company is concerned, no trouble with regard to tyres has been traced to this cause.

Front tyres approximate 20,000 miles and rear tyres 25,000.

Twin pneumatics at the rear and singles at the front are utilized by the Scottish General Transport Co., Ltd., the vehicles of which run over all kinds of roads from waterbound macadam in country districts to modern bituminous surfacing and granite setts, whilst tramlines are found in many areas.

No separate records are kept of front and rear tyres, as they circulate in the fleet irrespective of position. The average mileages of the tyres for the various vehicles are as follow :-38-seaters, weighing 5 tons 8 cwt., with 38-in. by 7-in. tyres, 28,000 miles ; 82-seaters of 41tons weight, with 86-in. by 6-in. tyres, 24,000 miles ; 30-seaters weighing 4 tons 15 cwt., with 38-in. by 7-in. tyres, 32,000 miles. The largest of the vehicles are Leyland, the 32-seaters are Tilling-Stevens, Express and Albions, and the 30-seaters of A.E.C. make.

Seventy-five per cent, of the fleet has been converted from solid tyres and the selection of the equipment has, in those cases, been determined by constructional considerations. . .

In the opinion of the company, from a traffic point of view pneumatic tyres are considered to be essential, whilst, from the engineering aspect, they undoubtedly assist maintenance; also the liability to skid is reduced with penanestles,

Only one minor accident has occurred through a burst tyre, -when this damaged a wheel-arch. Breakdowns caused by pneumatic tyres average one in 50,000 miles, the delay pulsed thereby depending upon distance from a garage, as no spare wheels are carried vcept on private cars and long-distance work, such as tours.

Pneumatic tyres will not, says the company, stand so much abuse in the direction of overloading as cushions or solids, but the mileage figures given are the result of normal working conditions where a certain amount of overloading is at times inevitable.

The opinions expressed by the United Automobile Services, Ltd., are terse hat to the point. It is considered' essential, so far as passenger work iS concerned, to run the company's service vehicles on pneumatic tyres. As a matter of feet, the company pioneered this method, being the first in the -country to fit pneumatic tyres to its buses on any large scale... The first of its vehicles with such equipment commenced to operate in March, 1020, and since then the number has been steadily increasing until the whole fleet, with the exception of one or two vehicles (for which there are special reasons why pneuMatie tyring has not been adopted), are now so equipped.

What Municipal Users Have to Say.

The makes . of vehicle which arc run by the muniei

panties mentioned will be found in our tabulation given on pages 894 to 898.

Wolverhampton runs single-deck buses with a seating capacity of 30 to 40 and double-deckers holding 55 to 61, use being made of solid, pneumatic and cushion tyres, but the latest practice is to standardize on the pneumatic type.

It has boon found that pneumatic tyres are less liable to skid and provide better adhesion in ice and snow than solid or cushion tyres.

Daily tests are made of the air pressure. No accident has occurred through bursts, but punctures are more frequent than is desirable, and it is. pointed out that the tyre manufacturers should concentrate on this point. The practice of running home on the single tyres of twin wheels is not considered advisable, especially with loaded buses.

Inflation is carried out at present by means of a motor-driven tyre pump.

Although a considerable number of pneumatic tyres is used on the buses run by Liverpool, their employment has been of short duration only, and reliable data cannot, yet be given. It has already been found, however, that they are superior to the cushion or semi-pnermatic pattern.

Inflation is carried out at the central garage, whilst an employee iS detailed to test the pressures of all tyres each day before they are put into service. Special air-pressure plant is utilized.

Oldham runs single and double-deck buses with from 26 to 72 seats, and 17 of these are six-wheelers.

The question of vibration both of the vehicles and of property has been very serious in this town, as the road surfaces are largely stone setts. For this reason, pneumatic tyres are utilized, as it has been found that cushion tyres did not reduce vibration sufficiently, whereas experience with the pneumatics has been satisfactory and they are not so liable to skid as cushion tyres.

No serious effects have been experienced owing to bursts ; punctures are infrequent, and all tyres are purchased on a mileage basis, the Cost per mite covering all types of vehicle and averaging .94. per bus-mile.

The experience of the authorities has been that no tyre will satisfactorily stand up to much overloading without failures.

Compressed-air cylinders are employed for maintaining pressure in the fyres, responsibility for the -maintenance of correct pressures being placed upon the garage foreman.

Single-deck and double-deck buses seating 32 to 55 passengers are employed by the Birkenhead Corporation. Some of these vehicles have solid front tyres and air-cushion rear tyre's, whilst others are equipped with pneumatics.

The roads consist of stone setts, tarmac and tar-sprayed vraterbound macadam.

The pneumatic tyres are interchange able and rear and average 30,000 mil;

It has been found that both cushion and pneumatic tyres are better than solids from the point of view of skidding. No accident has been caused by. tyre failures, and 'the correctness.of the air pressure is ascertained daily. Punctures are infrequent, and vehicles. With twin. tyres at the rear run home on the sound tyres in case of puncture. No

failures have been traceable to overloading.

Halifax runs its vehicles mainly over secondary roads. Its single-deck 20seaters, including 13 six-wheelers, mostly run on 34-in. by 7-in. tyres, but 38-in. by 7-in. are also used.

Pneumatics have been found to give more comfort to riders, and the large sizes used have proved more economical than those normally fitted.

Pressures are tested daily, and there have been no serious effects due to tyre failures. Punctures are few, and the vehicles run home on the sound tyres in case of puncture, except, in some cases, where wheels are changed on the road.

The tyres are bought on a mileage basis, and, owing to being oversize, stand up fairly well to overloads.

About 35,000 miles' average for front and rear tyres is the excellent result obtained from the 82-in. by 6-in, pneumatics employed on the one-man-operated 26-seater vehicles used by Ashton-under-. Lytle, where the road surfaces are chiefly stone setts with tarmac in the country areas.

It has been found that a much longer life is obtainable from pneumatics than from solid tyres, punctures are seldom experienced, and on bus routes which do not extend for more than four miles a replacement vehicle is sent out in case of puncture and the necessary repair curried out at the depot.

An electric pump is employed for providing the pressure ; it has been found light, convenient and rapid in action. Considerable overloading has to be dealt with, and the pneumatic tyres stand up well to this without failure.

The greater part of the fleet of buses run by Manchester is equipped with pneumatic tyres, which give very satisfactory results. The only make employed so far has been the Dunlop straight-sided pattern, although trials are now being carried out with other makes.

A 'large proportion of the roads is paved with setts, and, in view of this fact, the nverage mileage of 32,450 Which has been obtained is very satisf(actory.

So far as can be ascertained (because the original tyres are still running) the cost should not exceed .75d. per mile.

Considerable importance is attached to correctness of air pressure and to wheel alignment.

Punctures are infrequent and no serious effects have resulted from bursts, svhilet skidding has not been found a serious matter. No spare wheels are carried and a puncture is treated in the same way as a mechanical breakdown,. being dealt with by the garage emergency staff. Every vehicle has twin rear tyres, and it is quite feasible to run to the garage on the sound tyres in case of a puncture.

In the opinion of the general manager, it is better to buy pneumatic tyres outright than on a mileage basis.

For inflation, compressed-air cylinders are charged from a central plant and sent to the various garages. Reasonable overloading due to standing passengers has not been found to have any serious effect.

Air-cushion and giant pneumatic tyres are used on the single-deck 30seater buses run by Chesterfield Corporation. The road surface is fairly good, and the average mileage for both classes of tyre is 25,000.

Pneumatic tyres are favoured, as they provide more comfort and give an equal mileage. The pneumatic tyres are also less liable to skid than the air-cushion variety, and the average cost works out at .S1d. per mile. All the vehicles forming the Rotherham fleet not already so equipped are being converted to pneumatic tyres. The types of vehicle employed are 20, 32 and 39-seaters. For the front tyres the average mileages are : -Pneumatic, 38,000; cushion, 30,000. For the rear tyres :—Pneumatic, 35,000; cushion, 30,000.

There is no appreciable difference noticeable between the resistance to skidding offered by either the pneumatic or enshion tyres. Cushion tyres are somewhat cheaper, working out at .569d. per mile, as compared with .778d. for 34-in. by 7-in. pneumatics. Punctures are not frequent, but cause about halfan-hour's delay when they occur.

All the single-deck vehicles run by Sheffield are on pneumatic tyres, but there is a number of double-deckers on cushions. The pneumatics are preferred although the cushion tyres give good results, especially during rough weather. During the recent period of snow and ice the cushioned-tyred yehicles were run without chains and without any dif ficulty occurring through skidding or wheel slip ; incidentally, the roads are mainly macadam and asphalt.

The general manager points out that correctness of air pressure does not appear to be so important to-day as a little while ago, and that we are rapidly reaching the time when low-pressure tyres will be available; judging by the results from tyres in which the pressure has not had :special attention. Punctures are more erratic, but not too serious, and the delay:depends upon the distance from the depot; as spare wheels are not carried, vehicles running home on their sound. tyres.

It is his opinion that Purchasing tyres on a mileage basis retains the interest and attention of the manufacturers to a greater extent than when purchased outright.

The pneumatic tyres stand up well to overload, and credit is due to the way in which the makers have handled their work during the past three years. Walsall makes use of single-deck vehicles seating 32 persons, and employs on these machines 38-in. by 7-in. and 36-in. by 6-in. pneumatics, the reason for the selection being lightness, non-skidding and resilience.

The average mileages are

20,000; rear, 26,000; and, in the opinion of the general manager, pneumatics are far better non-skids than cushions, whilst the average tyre cost per mile has proved to be only .55d.

The buses are run home on the sound tyres in cases of puncture, and have actually carried on in service, in some instances, without the driver being aware of the fact that one tyre was deflated.

The single-deck 30-seaters owned by Newcastle-on-Tyne are equipped with 36-in. by 6-in, pneumatic tyres, which average 22,000 miles, the present tyre cost being .65d. per bus-mile.

All tyres are kept pumped to 85 lb. per sq. in. Puncturee are not frequent, but wheels can be changed in 10 wins.

The whole of the passenger fleet run by Plymouth was equipped with pneumatic tyres in 1922, this having been done primarily for the purpose of securing quieter running in the streets, reducing the maintenance and affording greater comfort to the passengers. The average mileage obtained is between 22,000 and 24,000, and it must be remembered that the services are entirely in town, with frequent stops and severe gradients. As the rear tyres become partly worn they are brought to the front, so that those covers with the best road adhesion are on the rear wheels.

The vehicles are of the one-man-controlled pattern, seating from 20 to 26 people, and the experience with pneumatic tyres has thoroughly justified their adoption. It has also been found that

the cost of chassis maintenance has been considerably reduced, whilst the tyreshave been the means for permitting a very material speeding-up of the services.

After the whole fleet had been converted the maintenance costs greatly declined, until they now stand at 9d. per bus-mile. The cost of solid tyres averaged .163d, per tyre-mile, and recent records show the cost of the pneumatic tyres to be .089 per tyre-mile. It will, of course, be understood that tyre prices have been very considerably decreased during the past few years and this must be allowed for.

Supervision of the air pressure is considered a most important factor to secure long life, and this duty is allocated to a particular individual. To avoid front and rear wheels being changed, so obtaining wrong pressures on respective wheels, the discs have special indicating marks, whilst the spares in the garage are kept in separate compartments.

The average numberof burst tyres is one in 700,000 tyre-miles. Punctures average one per 29,000 tyre-miles, and vehicles have run home on the good tyres of the twin-tyred rear wheels. This proves far more economical than carrying the dead weight of spare wheels for thousands of milee.

Cylinders containing air under high pressure are used for inflation, these being more convenient to handle amongst vehicles.


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