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From Cardiff to linburgh on One Foot

6th August 1965, Page 48
6th August 1965
Page 48
Page 49
Page 51
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Page 48, 6th August 1965 — From Cardiff to linburgh on One Foot
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Which of the following most accurately describes the problem?

AT the mention of automatic transmission on heavies. many if not most of the hauliers in the UK pull a wry face and shake their heads, saying: "I can't see it happening in my lifetime." In the latter part of last month I was given the opportunity to do a journey from Cardiff to Edinburgh with an ERF 68 GX/3.fitted with a Bristol Sicldeley SRM gearbox which has been in service with Scottish Brewers Ltd., of Edinburgh. for just on nine months. With constantly worsening road conditions, and a slowly but surely diminishing number of good drivers of the right type, it is becoming increasingly more ,evident that the simpler a vehicle can be made to drive, the 'greater is the chance that it will earn a reasonable return on the capital invested in it.

It would seem fair to say that although the Bristol Siddeley SRM gearbox, which was fitted in this vehicle, has not been the most reliable piece of equipment since it was first installed in the autumn of 1962, it has now been brought to a fairly high level of reliability, and that the programme of development on which the makers have embarked is progressing satisfactorily. This has not only been concerned with getting the unit reliable. but also in achieving reasonable and economical manufacturing techniques which alone can have the desired effect on the selling price. Much has been done also to decrease the weight. and whereaS the unit fitted in the test vehicle weighed 840 lb. the latest models scale only 520 lb.

Much credit must go to ERF Ltd. for its perseverance in the project, and also to the fleet operators who have suffered the inconveniences of unscheduled stoppage. But I feel that everyone who has been involved in the development of the unit, its installation or its operation, can take a slice of the credit.

The transmission is by no means the only unusual feature of this machine: it also has disc brakes on the front axles and

twer-assisted steering and handbrake. A Hendrickson walkingam, steel-spring suspension carries Eaton two-speed axles corporating a third, lockable differential. The power unit is Gardner 6LX. and after completing the 410 miles from 1rdiff to Edinburgh in two stints—of 187 miles to Eccles. tries, and 221 miles to Edinburgh—at an average speed of

m.p.h. over some of the best (and worst) road conditions at exist in this country today. 1 was convinced that there is place in the heavy vehicle market for automatic transmission.

ood consumption figures Contrary to my expectations the fuel consumption proved to extremely good. Unfortunately the return load was only cargo of empty beer kegs weighing 5 tons 18 cwt. but as the iver had been aware that we were going to do fuel consump m tests on the outward run he had filled his tank to the neck at r. start of the journey and we were able to get a reasonably curate check for the laden part of the trip. With a load of 11 kegs weighing 14 tons 4 cwt, making a gross vehicle weight 21 tons 12 cwt. this figure proved to be 925 m.p.g., which is achieved at an average speed of 24.5 m.p.h. On the return n where, as I have remarked, the average speed was 30.5 ph.. the fuel consumption proved to be 13.5 m.p.g. and the erage was made without exceeding 40 m.p.h. at any time. Hauliers will quite rightly ask: '' What will it cost? " and Nhat will we as operators get out of it? " Well, to answer the first question. the cost of the box at the present stage of development is £850 and it is expected that this will be considerably reduced once output gets beyond the present preproduction stage. I can hear the groans—but remember that from this must be subtracted the cost of the standard gearbox. the clutch and flywheel and the gear-change mechanism, and these together cost approximately £338. This leaves £512 and, if the immediate savings of annual clutch replacements at around £45 a time are then subtracted the picture begins to look much healthier.

As with all automatic transmissions, the first impressions when driving this vehicle are that the clutch is slipping, and any driver who has an ear for mechanical things rebels at the thought: it is this, and the initial feeling of not being in full control of the machine, that is mainly instrumental in the driver's reluctance to accept anything he does not fully understand. Once the initial feeling of slip is accepted, it is but a short step for the driver to become completely enthusiastic

icing the new Bedford KHE, latest addition to the KH series.

.new feature is length: the KHE has a 193" wheelbase, red for a 21' 6' body. This is the first time ever that a f Bedford chassis has been designed for a 21' 6" body.

re the other key facts about the new chassis? Gross ?8,000 lb. (12 tons 10 cwt). Kerb weight with 21' 6" body ). (4 tons 10 cwt). Designed for a full 8 ton load, 400 cu. in. 131 b.h.p. diesel. Clutch: 14 inch diameter. <: 5-speed overdrive top, direct fourth, and mesh on top four gars. Frame: heavy duty with flitch Rear axle: 20,000 lb. capacity. Single speed standard d optional). Wheels: welded 3-piece wheels with 9.00 P.R. tyres.

the advantages of the TK cab : good vision, driver , easy entrance, easy maintenance.

)ut the two-pedal control. At this stage the automatic (ransmion starts to pay dividends and, through its extremelk gentle !ration, it allows for almost every eventuality, leaving the ver completely fret to give his undivided attention to the iness of piloting the vehicle through the often difficult canons that prevail on the highways today. Thus, a vehicle ich—towards the end of a long and tedious journey when !..d with manual transmission—will suffer a great deal of taSe simply because the driver has had enough, will, with omatic, continue to be in the right gear at the right time. h the power being applied and removed from the propeller ft and differentials just as gently as when it left the depot h the driver fresh and keen.

t is here that I can see the biggest savings being made in !rating costs, because it is likely that the sort of treatment led out to the final-drives by the SRM automatic box will alt in their lasting the full life of the vehicle, a very unlikely urrence with manual-change boxes. Moreover, the effects gentle progress do not end with transmission parts; there far-reaching end results of roughly handled transmissions ich are often at a first casual glance not directly connected. efer to such things as broken driving-axle springs, loose es, loose spring hangers and adjacent crossmembers. In st cases these faults can be traced to rough handling having sed the first bit of movement in an axle or spring hanger ich, if not given immediate attention, results in everlasting able and, more often than not, in a complete failure of one ather of the parts concerned. Particularly on tanker vehicles. se crossmembers invariably result in excess whip in the ssis which in turn causes extensive tank damage. Tractive ts suffer in exactly the same way from this type of treatIt but, whereas the rigid shows extensive wear, the tractive t becomes dangerous through very quickly getting out of ;nment should an axle come adrift: quite often the end result ,n accident.

Fective Retarder

)ver the past couple of years there have been introduced the UK a small number of transmission retarders. Whilst rs have found these extremely effective, they are also expen: and undesirably heavy. The SRM gearbox is equipped standard with a retarder which is so effective that during whole of the test I found it necessary to apply the wheelkes on only two occasions. Although the treatment given braking systems depends largely on the driver, I think it 'air to say that, given powerful brakes most drivers will

reasonably accident-free operation. Given inadequate kes, accident frequency will rise—and fast. There are snags vever, with the powerful braking system as well, in that rig life can vary from astonishing to abysmal, and a re-line in all probability see replacement of the drums required. zing is usually the reason for this, and the cause of crazing prolonged overheating through long periods of medium lication at relatively high speeds, such as when descending mg, severe gradient. Therefore the hydraulic retarder which s nothing to thc unladen weight of the machine and has no ring parts is, I feel, the obvious answer to the problem. h is the retarder built into the SRM gearbox.

ty reversing the direction of rotation of the stator blades-is achieved by applying the double-rotation brake-band the direct-drive clutch at the same time—the torqueverter produces a braking effect of up to 30 per cent of the dmum transmission input power. In operation, negotiating south side of Shap Fell the retarder will hold 22 tons down speed of between 16 to 20 m.p.h. What is more important. inclusion of a heat exchanger stabilizes the temperature of transmission oil, enabling the most arduous duties to be t'ormed without undue overheating. In the event of overling occurring, a warning light comes on in the cab. when driver can take the appropriate action.

;tit throughout the whole of the test it was the retarder that :ated me. for, try as I might. f could not apply it as gently would have liked. Even with the most gentle pressure on brake pedal. the actual operation of the retarder _could be inctly felt. When the test was aer I 'spoke to a Bristol Siddeley engineer on this point and was told that this had been a common complaint, especially from p.s:v. operators. He also said that it was a point high on the list of future development.

Nevertheless, it says something for the efficiency of the retarder that since the vehicle joined the Scottish Brewers fleet there has not yet been any need to adjust the wheel brakes, and as the mileage at the end of my run read 29.296 I got the impression that 200,000 miles might be a fair life to expect from linings, and without the need to replace drums. Mr. N. Robertson, fleet engineer of Scottish Brewers Ltd., told me that on standard vehicles brake relines became necessary at between 60.000 and 80,000 miles and those fitted with discs on the front axles (as was the test vehicle) required new pads at about 28.000 miles. Driver John Johnson, handler of the test vehicle. told me that he has never, during the time that he has had this machine, felt that an emergency could not be coped with, and we all know that these occur at least daily.

Some of the most enlightening moments with the automatic came when negotiating the Wye Valley in torrential rain whilst traffic was being held down to a crawl by an obviously overloaded and under-powered low-loader, the belly of which was bowed almost to the point of scraping the ground. As this machine puffed its way up the valley in crawler-gear, and whilst everyone else in the queue clutched and declutched, and their rear axles shuddered and clattered their suspensions as drives were taken up, the automatic smoothly wended its way up to the accompaniment of an easy conversation between driver Johnson and myself.

Contrasting Calm

The same was noticeable at the foot of the steep hill on die bend just after leaving Kendal, where the authorities had deemed it necessary to lay a cable, with the consequent chaotic results to traffic.' A 22-ton artic, fairly well loaded,: jumped nearly a foot in the air and spun its drive wheels as it got away in front of us, and I shuddered to think what could have happened had it chosen that moment to break either a spigot shaft or half-shaft. In contrast, the ERE smoothly, and without fuss, moved off, calmly selecting and holding the gear it needed to do the job in hand; and while we waited on the gradient for the lights to change it was not even necessary to apply the handbrake, let alone try hard to get away without rolling' backwards. It is here—in the complete absence of the need for the driver to spend his energy on things which, in current vehicle designs when operating in difficult conditions, are a must—that the automatic transmission will more than earn its keep.

A parting shot from Mr. Robertson was: "Could I, do you think, afford to save £100 on a new machine incorporating the SRM gearbox/retarder by dispensing with disc brakes?"

My answer was: "Were 1 in your position, that is just what I would do."

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Locations: Bristol, Cardiff, Edinburgh

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