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Second annual exhibition for commercial vehicles organised by the SMMT and held at Olympia
COMMERCIAL MOTOR VEHICLE EXHIBITION 
The second International Exhibition of commercial motor cars promoted by the Society of Motor Manufacturers and Traders (SMMT) was opened at Olympia on Friday last. Although it compares very favourably with its predecessor as regards interesting features, there is a marked change in the exhibits. Last year the attention of the industry was largely absorbed by the motor omnibus, and a large number of builders devoted their exhibition space to this type of vehicle. As is well known, however, the demand for the motor omnibus, as the result of the somewhat brief and often unsatisfactory trials, has fallen away very considerably. So it is that the motor car builders have this year to turn their attention to other fields for their products. Now, owing largely to the success of the "taxicabs" in London, the motor cab is much in evidence, and seems in a fair way of being over exploited in the near future.
In the strictly commercial vehicle section of the show visitors this year have an opportunity of comparing the heavy steam wagons of practically all the leading makers, petrol-electric omnibuses — built on several systems — about which much has hitherto been heard but not much seen, steam tractors, light delivery vans, and motor cabs.
The marine section will be found particularly attractive by users of the rivers on account of the interesting display of motor boats for pleasure purposes, and the effect of competition is here already becoming increasingly evident in the remarkably low prices asked for some of the exhibits.
In view of the importance evidently attached to the motor cab by the exhibitors mention ought first to be made of the exhibits under this head. As a matter of fact, however, with one or two exceptions the makers have merely adapted the frames and mechanism of the light pleasure cars to the new purpose. Some modifications, of frame and steering is, of course, necessary on account of the small radius in which these vehicles have to operate.
The Austin Motor Company has departed from its own pleasure car design. The bonnet has been dispensed with, and the 15 horse-power four-cylinder engine is placed under the driver's seat, but is nevertheless accessible. The engine, clutch, and gear-box are in one piece and suspended at three points. The power is transmitted through the usual change-speed gear and cardan shaft to a live back axle. The water circulation is on the thermo-syphon system.
In the heavy section of the Exhibition the chief features of interest are to be found in the petrol-electric systems of transmission, and in a new steam system for lorry and omnibus work. The latter is shown on a chassis by the Critchley-Norris Motor Company — a branch of Peter Pilkington, Limited, of Bamber bridge, Preston. This vehicle — Fig. 1 — has a three-cylinder vertical single-acting engine and a boiler of the water-tube pattern made by the Lune Valley Engineering Company. These are placed under a bonnet like a petrol vehicle, and a condenser is situated in front. A view of the chassis of this vehicle is shown herewith. Commencing with the engine, the cylinders are 4.25 in. diameter by 5 in. stroke, and have mushroom valves operated by a cam shaft. The engine is designed to run at 500 revolutions per minute, and forced lubrication is provided for the bearings. The pistons have each seven rings, and between the fourth and fifth ring a groove is cut in the piston which enables any steam that has passed the higher rings to escape into the atmosphere instead of finding its way into the crank chamber. The lower rings are intended to prevent the access of lubricant from the crank chamber to the steam space, and ultimately to the boiler via the condenser. The valves are arranged on both sides, and the cam shaft on the inlet side is capable of longitudinal movement to vary the cut-off or reverse the engine. The crank shaft is of vanadium steel. The water-tube boiler consists of a central drum pressed out of a single steel plate, and external coils of mild steel tubing arranged so as to break up the passage of the gases to the flue. Each coil makes three turns, and the ends are expanded into the central drum. It will be gathered from this brief description that the form of construction allows of free expansion and contraction without inflicting damage on the boiler. The coils are surrounded by a suitable casing, and a downtake discharges the products of combustion below the frame of the vehicle. The boiler also contains a feed-water heater and a superheating coil. The latter is placed round the paraffin burner, and is calculated to raise the temperature of the steam to 500 deg. Fah., equivalent to approximately 100 deg. of superheat.
The burner is also made by the Lune Valley Engineering Company, and is constructed so that the oil is vaporised in a coil, afterwards issuing in the form of gas from a jet or nozzle where it is lighted. The jet impinges on an inverted dome-shaped deflector, over which it spreads in a thin film, taking up the right amount of air for complete combustion and producing a white, smokeless flame. The flame is regulated by means of a needle which projects through the nozzle, and is operated by a hand lever. This is the only working part of the burner, and, in addition to regulating the flame, the needle also performs the action of clearing the nozzle, preventing the liability to clogging, which is by no means an unknown feature of some types of burner. Although partially enclosed by the sheet iron casing shown, the boiler is easy of access.
An objection to this type of steam generator, which has hitherto been incontrovertible, is the difficulty of cleaning the inside of the tubes. This has now been overcome by the invention of a cleaning device, in which a pitch chain is caused to pass round and through the spirals. On the free end of this chain is attached a small brush which can be drawn back through time tubes by means of a handle and gearing. The feed-water tank is situated under the rear of the frame, and the fuel tank under the driver's seat. The condenser is built up of gilled tubes which connect upper and lower chambers. It is cooled by means of a fan driven by a chain. The lower chamber contains filters for removing any objectionable matter which may be carried over with the steam from the engine, and the upper space contains the feed-water heater coil. From the engine motion is transmitted to a coupling in an oil-tight casing - seen under the driver's seat — by means of a shaft. A second cardan shaft transmits this motion to the differential shaft from which chains communicate motion to the road wheels. Skew gearing inside the box operates a crank shaft for driving the air and water pumps. The main frame is of channel section steel, and the steering gear arranged so as to be readily adjustable.
Messrs. J. and E. Hall, Limited, Dartford, show a chassis propelled by a petrol-electric system. The method of transmission is a modification of the Steven's system, which was illustrated and described in THE ENGINEER of March 15th, 1907. The chief feature of the modified system is the situation of the two series wound electric motors outside the main frame of the vehicle. The motors drive the back wheels by means of worms and worm wheels, and are easy of access. The motors can be worked either in series or parallel, according to the load and nature of the road. On level roads the motors run in parallel, but on heavy gradients they operate in series. The dynamo is situated immediately behind the petrol engine, to which it is connected by a universal joint. It is a shunt wound interpolar machine giving a continuous current. The controller is placed between the dynamo and motors. The system of control is simple. The transmission resembles that of the ordinary electric car, the storage battery being replaced by the engine and dynamo, and the output varies in accordance with the demands of the motors without breaking the electrical circuit. The effect of throttling down the engine to a slow speed causes the dynamo to lose its excitation, which is immediately increased with the acceleration of the engine through the action of the interpoles. The speed of the engine is regulated by a pedal operated by the driver's foot, and this pedal in its normal position reduces the speed of the engine below that for exciting the dynamo. By the depression of this pedal the throttle is opened, and the speed of the engine is increased. In series with the shunt field of the dynamo is a small shunt resistance operated by a lever on the steering wheel. By means of the resistance the voltage of the generator is controlled, and the driver is enabled to get the most suitable results at any speed of engine or vehicle. We understand that this system has been severely tested, and has proved successful and economical.
The chassis of a motor omnibus exhibited by Milnes-Daimler, Limited, Tottenham-court-road, London, is a piece of remarkable workmanship, and embodies several new features of design. Fig. 8 shows a general view of this chassis, which is furnished with a 35 horsepower petrol engine with four cylinders, 115 mm. X 140 mm. In order to obtain decided flexibility throughout the whole transmission system a three-point suspension of engine, gearbox, and back driving axle has been adopted. This is clearly shown in Figs. 4, 5, and 6. Fig. 4 shows the engine viewed from the fly-wheel end and the ignition gear, means of suspension and air cooled crank ease are plainly seen. Fig. 5 is the gear box and the three-point suspension and controlling gear, which is now part of the top cover, are shown. Fig. 6 represents the new perch bar arrangement and new pinion brake. Forced lubrication is provided on the engine by means of a pump driven from the cam shaft, and this forces oil through the crank shaft. The cylinders are east in pairs, and the valves are placed on either side of the engine, and are easily accessible. The clutch is of aluminium, working in a steel ring.
One special feature of the chassis is the design and section of the main frame, which is clearly shown in Fig. 3. Another feature is the method of spring suspension, whereby the usual fixed pin becomes movable vertically, giving increased spring movement. The ignition system is magneto, with the sparking position fixed. A further good feature is the method of supporting the radiator so as to compensate for any slight deflections of the frame. The ststem of driving fronm the differential shaft to the back wheels is substantially the same as previously used, namely, by pinion driving internal teeth on the road wheels.
A compact form of engine which has some features peculiar to itself is exhibited by the Gaggenau Motor Vehicles Company, Regent-street, London. It is shown in Fig. 7. There are four cylinders 120 mm. by 140 mm. in the 40-50 horse-power engine, and all the valves are on top and actuated by a single cam shaft; the latter is driven by vertical shaft and enclosed bevel gear off the crank shaft. The valves are contained in pockets, which can easily be removed and replaced; the cooling fan, the pump, and the magneto ignition are all driven by gears off the vertical shaft which operates the cam shaft.
The "auto-mixte" petrol electric system is shown applied to a motor omnibus by the Daimler Motor Company. In this omnibus the motor mechanism and the body are mounted on two separate frames. In the "auto-mixte" system there is a petrol engine driving a dynamo, the latter being controllable in such a way that any surplus current given off when running on the level is conveyed to a battery of accumulators, where it is kept in reserve for starting and hill climbing. The engine drives the dynamo by means of a special coupling, and behind the dynamo is a magnetic clutch through which the transmission of the power of the engine or dynamo to the road wheels takes place by worm and speed gearing. The magnetic clutch and coupling are operated by a pedal with three positions, in one of which the engine and dynamo are coupled, and the motive mechanism is in gear; in the second position the engine and dynamo are running together, but are disconnected front the transmission gear; and in the third position the engine is disconnected from the dynamo. The cells are of the Plante type.
It is well known that the greatest source of trouble in steam omnibuses has hitherto been the boiler, Quite a number of steam omnibuses have been tried and found wanting in London in this respect. Mr. Clarkson, of the firm of Clarkson, Limited, Chelmsford, evidently still adheres to the conviction that the steam engine is capable of holding its own with other forms of motive power for the driving of omnibuses. The firm shows an omnibus with a new type of boiler which is claimed to be superior to any yet tested. It is of the water tube pattern, and the tubes are easy of access for cleaning - a necessity where bad water has to be used. There is a thermostatic system of control for the water supply, and the paraffin burner is controlled by the boiler pressure. The engine has been stiffened up and the lubrication improved so that 5/8 gallon per working day is not exceeded. The boiler works at 300 lb. pressure. We understand that omnibuses fitted with this new generator are now in use in London, and are giving great satisfaction.
Amongst the exhibitors of heavy steam wagons and tractors are:
There is no doubt that the first cost of self-propelled vehicles, although justified probably by the large amount of work and high class material which are put into them, is a great impediment to the progress of the industry. There would undoubtedly be a large demand for these vehicles if they were less costly. Makers should aim at producing something equally durable on simpler and cheaper lines. We think the lines of the two-ton wagon with a two-cylinder 16 horse-power engine shown by Thornycroft goes some distance in the right direction. There are no superfluous ornate features in the design, which is just straightforward and simple — no pumps for water circulation, no accumulators to run down, chain-driven wheels on which a certain amount of overload can be taken without undue trepidation, a disc clutch, accessible gear-box, easily filled fuel tank, all seem to point to a well-considered design suitable to place in the hands of none-too-skilful drivers.
A new, and what seems to us excellent, design of radiator mine under our notice on the petrol vehicles shown by the Ryknield Motor Company, Limited. Brewtnall’s radiator is made up of vertical straight flat tubes in between which are placed flat copper coils for deflecting and thoroughly distributing the air over the surface of the tubes. This should give a better cooling medium than many radiators now in use.
In the marine section the Thames Ironworks and Shipbuilding Co, Greenwich, is showing the Clift paraffin motor. This is a vertical four-cylinder engine, with a special compression release device to enable any of the valves, sparking plugs, carburetters, etc., to be removed while the engine is running. Another feature of the engine is the pump gear, fitted to enable either of the two water pumps to be removed while the water circulation is maintained by the other pump. One of the difficulties of using paraffin has been overcome by fitting the exhaust valve-boxes with self-cleaning vaporisers.
The "Villinger" propeller shown on the same stand is reversed by means of cranks and links, which work on pins formed on a block sliding within the propeller boss. The driving shaft is hollow and made of manganese bronze. Through it is carried the brass reversing rod, which moves the sliding block inside the boss. The block also serves as a second bearing for the extended shanks of the blades.
John I. Thornycroft and Co., Limited, of Chiswick, amongst other exhibits in the marine section, show two fine examples of petrol and paraffin marine motors of 50 and 105 brake horsepower respectively. The chief features of these engines are already known to our readers.
The Lune Valley Engineering Company, of Lancaster, shows its well-known boilers and engines for marine work.
Messrs. Norris and Henty, 87, Queen Victoria-street, London, exhibit, in addition to several sizes of the Gardner marine oil engine, a 17.5 horse-power two-cylinder vertical motor for operating on suction gas. The cylinders are 6.5 in. diameter by 6in. stroke, and the engine gives its full power at 600 revolutions per minute.
The Exhibition closes to-morrow, Saturday.