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Kelvin Hall Shows Them All
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New models introduced in the past year join those featured in 1964 at Earls Court to make this year's Scottish Show the most interesting to date
IT is not unusual for the Scottish Motor Show to contain little of real interest in the commercial vehicle field, so ‘ this year's event must be one of the most noteworthy in its long history. The 45th Scottish Motor Exhibition, to give the Show its full title, which closes tomorrow at Kelvin Hall, in Glasgow, in many ways has more of interest than the London Commercial Motor Show last year. Not only does it display all the new models introduced for Earls Court but also the important new Ford and Dodge goods ranges brought out earlier this year, the new AEC and Scammell twin-steer tractive units for 32 tons gross, and Albion, Commer, Dennis, Ford Transit and Seddon ranges . announced in the past two months.
The new Seddon—the 16: four—is probably the most interesting of these as it is the first standard model fitted with the Perkins V8.510 engine to be announced. It shares this feature with the Dennis Maxim 6 x 4 exhibited at the Show. But the Dennis is a prototype and the vehicle actually belongs to Perkins Engines Ltd., the Cummins VALE V8 being the standard fitting in the Maxim. A prototype ERF with the Perkins V8 should be on the demonstration park; I had hoped to have a test run in this but, unfortunately, the vehicle had been delayed by some mechanical trouble and had not arrived by the time I left Glasgow.
Assessing the Trends An important aspect of the Glasgow Show is that the exhibits give an opportunity of looking at what has happened since the preceding Earls Court Show and assessing possible changes before the next. The three main trends at the 1965 Commercial Motor Show were towards vee engines, tilt cabs and improved brakes. The new Perkins continues the move to vees and I would not be surprised to see another commercial vehicle diesel engine with this cylinder configuration announced before next autumn—or for that matter at least one other vehicle maker go for the lighter-weight Cummins vee diesels in new models.
There is considerable interest by vehicle manufacturers in the Perkins V8, but I know some who are disappointed that it is not a little larger. With a maximum output of 170 b.h.p., and with most vehicle makers working nowadays to a figure of at least 6 b.h.p. per ton, the engine is unlikely to be used for vehicles grossing more than 28 tons. It is significant that the Seddon exhibit with the unit is the 28 ton-gross tractive unit from the 16 : four range. But the engine looks to be a very good design and if it Can emulate the 6.354 on serviceability and so on, it is certainly going to have a big future.
The new Ford and Dodge truck ranges announced this year (the Ford D Series and the Dodge 500 Series) have two main things in common—tilt cabs and a wide Variety of versions to meet all possible requirements within their weight ranges. Both cabs are well designed and well fitted and have a quick and easy tilting system with no dismantling required.
So far as model ranges go, it would be too much to expect many big announcements in the next year, as so, much has happened in the past 12 months with almost every maker having made important introductions. But chassis designed for specific Purposes can be expected. Recent examples are the AEC Mammoth Minor andScammell Trunker II tractive units for 32 tons gross featured in Kelvin Hall. Both of these are twin-steered chassis but of basically different designs, with the AEC having a conventional steering bogie and the Scammell its second steering axle positioned close to the driving axle. A useful aspect of the Scammell Trunker is that the second steering axle has combined airand leaf-spring suspension and when the air springs are exhausted 2.5 tons is transferred to the driving axle in the fully laden condition. This gives improved traction in difficult conditions.
The use of a four-axle artic at the maximum permitted weight of 32 tons is somewhat impractical because of the 38 ft. outer-axle spread required. It is not impossible, as shown when an American Kenworth two-axle tractive unit and York tandem-axle semi-trailer outfit was tested by The Commercial Motor. But is a 10-ton axle load (the maximum) sufficient to give adequate traction? This thought is very common on the Continent and used as an argument in efforts to get the maximum permitted axle load increased to 13 tons—as in France now and probably in Italy soon—not primarily to get more gross weight but more traction. The Scammell Trunker 11 gives this feature now when it is required.
Braking Confusion Braking has been very much in the news since the changes in the regulations last year and the introduction of brake efficiency requirements for main and secondary systems on vehicles designed to take advantage of the higher weights. This year, details have been announced of the proposed annual testing scheme and plating for all goods vehicles which will bring them under the same braking obligations. And a draft has been issued of a " code of practice" for vehicle design, mainly braking, which will come into force eventually.
The manufacturing industry is obviously in a confused state on braking at the moment, and naturally so, with so long being taken in deciding what the final requirements will be. A detailed look at the exhibits around Kelvin Hall illustrates this. No two manufacturers are using an absolutely identical air system and many of those on the models for the new weights are completely different.
There is some similarity in the rigids, with most makers having multi-diaphragm chambers at the rear axle or bogie for secondary braking. The Commer Maxiload, Dodge 22-ton-gross 6 x 4, ERF 16-ton-gross four-wheeler and Atkinson 22-ton-gross six-wheeler have dual diaphragms, whilst the ERF 26-ton eight-wheeler and the Albion Super Reiver 19 have triple-diaphragm chambers.
The Dennis Maxim 22-ton-gross six-wheeler has triples c12 all round and on this model the secondary brake system is a complete duplication of the main—the use of a biased dual foot valve means that in the event of failure in the service brakes the secondary system is brought into operation without any extra action on the part of the driver. In all the others the secondary system is actuated by a separate control—on the Albion and Atkinson by a handreaction valve and on the Commer, Dodge and two ERF chassis by a valve linked to the handbrake.
Split service-brake systems are popular. The front and the rear brakes of the Commer and ERF four-wheeler are on separate circuits and the front and rearmost axles of the Albion Super Reiver 19 are on one circuit and the forward rear axle on the other. On the Atkinson sixwheeler the front axle and the forward rear axle are on one circuit and the front and rearmost on the other, the feeds to the front-axle diaphragms being connected through shuttle valves. On eight-wheelers, Atkinson use separate circuits—one for the front-axle and forward rear-axle, the other for the second front axle and the rearmost rear axle— and this layout is used by ERF on its eight-wheeler at the Show.
True secondary systems are not employed by the manufacturers of lighter-weight goods chassis. But Austin and Morris FJ models have as standard an air-assisted hydraulic system which incorporates a Clayton Dewandre dual actuator coupled to a Girling tandem master cylinder which powers separate hydraulic circuits for the front and rear brakes. The dual actuator has independent air circuits for the front and rear portions, which ensures that a single failure does not result in a complete loss of brakes. On the FJ the handbrake is power assisted by an air chamber acting on the linkage.
An alrnost identical air/ hydraulic system is offered by Ford as an option on some D range models, but the handbrake is not air assisted. Bedford has always used a split hydraulic system (air or vacuum assisted) on the TK design with a tandem master cylinder, and this is carried on for the new models added to the lower end of the range recently and shown at Kelvin Hail.
These systems on the BMC, Bedford and Ford models conform to the proposals in existence for vehicles grossing 12 tons or less, but there is no provision for secondary braking of the semi-trailer on tractive unit models and it is not certain what will happen here when further regulations Are issued. A split system on the tractive unit will not be acceptable if the outfit grosses more than 12 tons.
All the vehicles plated for the new weights at Kelvin Hall naturally have secondary brake systems and provide a third line for the semi-trailer. On the Dennis Maxim 28-ton, ERF 30-ton, Seddon 28-ton 16 : four and the Commer and Dodge 22/24-ton tractive units, the secondary system is a complete duplication of the main. The Dennis uses triple-diaphragm chambers all round, whilst the others have dual actuators at each wheel. The Dennis, Cornmer and Seddon have biased foot valves which bring the secondary brakes into operation automatically, whilst the Dodge and ERF have hand reaction valves for this purpose.
On these last two there is no separate actuation of the semi-trailer brakes and on the Seddon a hand reaction valve provides an alternative means of operating the secondary system. In the case of the Seddon the actuating chambers are the new Clayton Dewandre De diaphragm and piston units introduced at the Scottish Show, not the
dual diaphragms used on other models. And on the ERF 30-tonner a dual foot valve provides for a split system between the tractive unit and the semi-trailer.
No power assistance is provided for the handbrake of these models, except for the Dodge and Commer. On the former, a valve in the linkage applies air to the secondary side of the rear diaphragms, whilst actuation of the handbrake on the Commer powers all the tractive unit diaphragms; there is a hand reaction valve for separate actuation of the semi-trailer brakes.
The two Seddon 30-ton tractive units at Kelvin Hall use Berg piston/diaphragm dual actuators which are now made by a UK subsidiary of the American company at a factory in Scotland. This is the first time these units have appeared on a British show vehicle and the piston portion provides the secondary brake function. In the case of the Seddon, the Berg actuators are used at the driving axle so that the secondary system gives brakes on'the rear axle and the semi-trailer axles; application is by a hand reaction valve and the handbrake is purely mechanical.
Triple-diaphragm chambers are used on the AEC Mammoth Minor and the Scammell Trunker—on the AEC all round and on the Scammell at the front and driving axles. The secondary system on the AEC employs the two steering axles and the semi-trailer axles through a hand-reaction valve, whilst the secondary side of the driving axle triple-diaphragm units is used to give assistance to the handbrake.
Service braking is on a split system, a dual foot valve actuating the first and third axles on one circuit and the second and semitrailer axles on the other. The triple diaphragms at the driving axle of the Scammell are also used for handbrake power assistance. The secondary system—the front axle with a hand reaction valve, too.
Leyland Beaver and Badger tractive units have dual diaphragms at the front axles and on these models the secondary system is applied to the front and semi-trailer axles. Actuation is by a hand-reaction valve and a dual foot valve gives a separate circuit for the tractive unit and semi-trailer connections. The handbrakes are air assisted by an actuator acting on the mechanical linkages. Fodens do not have a plated tractive unit in Kelvin Hall, but the Twin-Load artic is on demonstration. This has triplediaphragms at the front axles and semi-trailer axle for the secondary system. The handbrake acts on the transmission.
The Show Atkinsons have brake systems which will be superseded shortly by a design which has dual diaphragm chambers at the front axle for the secondary system in conjunction with the semi-trailer axles. A split system is used—a dual foot valve actuating the front and rear axles separately—and the feed to the semi-trailer connection is through a valve which ensures that the semi-trailer is braked if one of the circuits fails. The mechanical handbrake on the Atkinson design is fully compensated and is designed to give 20 per cent on a 30-ton-gross outfit without power assistance. The air-brake system used on the Guy Big I includes triple-diaphragms all round, with those at the front axle providing for the secondary system in conjunction with the semi-trailer brakes. A dual footbrake valve feeds the tractive unit's brakes and the semi-trailer connections on separate circuits, the secondary system being actuated by a hand reaction valve. The secondary sides of the driving-axle triple-diaphragms are used to give handbrake assistance. A completely different system is used on the Invincible Mk. III shown by Guy. This has dual diaphragms at the front axle and singles at the rear. A hand reaction valve is used for the secondary braking system—the front axle and semi-trailer third-line connection—and the brakes for the outfit are on a single circuit. The multi-pull handbrake is unassisted.
Not only in respect of the systems used is the braking of vehicles at Kelvin Hall interesting. A recent development by Leyland is that the Adlife brake drums used for some time on p.s.vs are now being fitted to goods chassis. These are of an improved cast-iron material and give better resistance to crazing, which is still a problem.
One of the disappointments at Kelvin Hall is the almost complete absence of semi-trailers--none in the hall is for the new regulations. There is only a Taskers single-axle boxvan and a small Minatic unit, but in a marquee not far from the hall Northern Trailers Ltd. are showing six examples of their range—three single-axle and three tandem-axle. Berg piston/diaphragm brake actuators are fitted to all these models and the British Berg company also has a display in the marquee showing the various items of brake equipment being manufactured in Scotland.