A New Commercar Model.
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First-published Particulars of the Interesting One.tonner now being Constructed at the Luton Works. A New Gearbox.
It is a trite but nevertheless indisputable truism, and one which particularly holds good in the field of industrial-vehicle production, that there is always room on the market for something good. A product sound in ,first principles, both as regards design and construction, must necessarily appeal to the potential user, who is, nowadays, almost. on every hand, fully cognisant of the exact degree of efficiency that can be placed to the credit of any class of machine he may desire to handle.
There are many sound constructional features cangoodied in this new Commercar model which are characteristic of this well-knowv manufacturer ; each of them will at once inspire confidence as to the capability of the machine to afford efficient service under all working conditions. Those responsible for its introduction are to be well eom. mended, and that we are fully justified in making these remarks will be to a large extent gathered from its description and the series of illustrations, included herewith, which were taken at the Biseot Road works during our recent visit.
Details That Count.
The primary feature on the model -which impressed us was the substantial yet not unduly heavy construction throughout. It is, of course, important to recall in chassis design that " it's the details that count," and a close inspection of the detail and assembly drawings submitted to us at the. Luton works gave much proof that this new unit has been evolved equally to afford the efficient service which has so long been associated with Commercar productions. The normal brake-horse-power developed by the power unit, the cylinders of which are cast in pairs, is -20, the bore and stroke being 90 mm.. by 120 mm. respectively. This constructor't; feature of mounting the crankshaft on ball bearings holds good in this instance. Considering the varied climates in which Commerears are used, it is naturally to be expected that the designers have paid particular attention to the provision of a satisfactory cooling medium for the engine. On this model the the.rmo syphonic principle is brought into use. A noticeable feature is the a.bse.nce of unnecessary pockets and sharp bends, likely to set up eddies in the water circulation, in the water jacket and pipe work. The Lamplmigh type of radiator, constructed on the castheader and base system, is connected up to large-sized cast pipes. The outlet pipe, bolted on top of the cylinders, is provided with two
flexible connections, so that any tendency to distortion of that com ponent is entirely prevented. A four-bladed fan, mounted behind the radiator, assists cooling. The interchangeable inlet and exhaust valves are disposed on the nearside of the engine.
The Claudel-Hobson make of carburetter is responsible for supplying the engine with explosive mistture, and the main air intake ii very effectively heated by means of a large-diameter pipe, conducting hot air from, a " muff " fitted around the exhaust pipe. This pipe passes between the two pairs of cy linders to the carburetter. Thi ignition is effected by means of a high-tension Bosch magneto, which is mounted on the same side of the engine as the valves, but positioned so that it in no way interferes with ease of access to the adjustable tappets. A leather joint couples
up the magneto drive. A neatlydesigned gear pump is utilized to circulate the oil under pressure to the main hearings of the engine. It is submerged and driven of the camshaft. through a vertical shaft and spiral gearing. There is another interesting detail of construction here worth noting: a light tube is brought into use to connect up the pump spindle with
its driving shaft, thereby affording a simple yet effective flexible coupling to the pump.
A Feature in the Oil Service.
Ready means are afforded for taking out the filter for cleaning purposes, and, moreover, upon attaching the covering which holds the filter in position, a small springloaded valve at once faces up to a cone seating in the main supply duct, so that, when the filter is taken adrift, not a. drop of oil is spilled from the crank chamber. This feature is quite old practice with the Commercar people, and one which is now being utilized on many other makers' chassis. A leather-to-metal cone clutch transmits the engine power to the gearbox, a leather type of double universal joint beinga feature here. A plate spring faced with leather is provided as a clutch stop, and, in order to effect the quick and easy changing of gear, both the male member and the stop ta.avel towards one another when the clutch pedal is depressed.
A New Type of Three-speed Gearbox is Embodied.
An interesting departure from usual Comm ercar practice is noticeable in the gearbox which is fitted. It differs much from the usual form of component associated with this maker, although dog engagement of all gears is still retained. The unit is much smaller in size, so that the distance between the ball bearings on which the shafts are mounted is kept down to minimum; upon measurement we found it to be but 7-ins. This desirable feature has been greatly assisted by the manner in which the different wheels are brought into mesh, in. that the selecting gear picks up two wheels at one time in order to effect the speed desired, so that clearance distances, equal to the width of certain of the gears, have been eliminated.
One illustration will afford some idea of the unique construction of
the selecting gear. Its design is quite sound in principle, and we found it absolutely impossible to miss gear." The mechanism is positioned well up to its work, and there was no whip discernible when we operated the change-speed lever, which is mounted transversely across the frame and well housed in substantial brackets bolted to each side of the frame member.
Means are provided for giving three. speeds ; the first is Si m.p.h., the second Me m.p.h., and the top, -which is direct drive, 20.4 m.p.h. A noteworthy point is that there is but one sliding-member utilized, and engagements take place quite close to the shaft bearings. All gears are of ample width, and are machined out of Ubas steel, a production which has found favour with the chassis builder for many years, and a steel which is thoroughly understood so far as the average case-hardener is concerned. The box itself is mounted on the thrce•point-suspension principle,‘ as is also the engine. 11,,--,mted behind the gearbox, and with the minimum amount of overhang, is the foot-brake and forward universal-joint of the propeller shaft. The brake is of the loco type, and is actuated by means of spring-loaded face-cams east in pholthor-bronze. These cams, mounted on a transverse shaft which runs across the top of the brake-drum, are coupled up to large-sized east " cheeks.," to which
are bolted the shoes themselves. Upon unscrewing a couple of bolts, each cheek can be readily withdrawn to allow for inspection and replacement of that particular part of the construction. Good-sized wing nuts, placed in a very accessible position, afford an opportunity for brake-shoe adjustment.
The Final Drive is Through Worm..gearing.
A propeller-shaft transmits the drive to a worm-drive type of back axle, the worm of which is placed on top, thus affording ample ground clearance at ,this portion of the chassis. As would be expected, the axle unit is quite a sound combination, and there are many interesting details embodied in its construction much to the advantage of the user. The provision of means for efficient lubrication of all parts of the component is only one of the many points which the designer has kept in view with effect.
How the Worm-shaft Ball. bearings are Lubricated.
A particular instance which is worthy of note is the means provided far lubricating the ball bearings of the worm shaft, which, being placed on to of the axle, and away from the ordinary supply of lubricant, calls for special mention. To effect this, the designer has provided pockets cast in the walis of the casing adjacent to the teeth of the worm, and, as this member revolves, lubricant is flung into these receptacles, and thence led through ducts to the forward and tail end bearings, from which it can again find its way into the main casing.
Some Constructional Points of the Back Axle.
The differential gear, which is housed in a steel stamping, together with the worm geirr, is enclosed in a good, stiff, malleable cast-iron casing ; this cover is split horizon.. tally at the centre line of the axle. It is provided with large-sized flanges, for the purpose of bolting up the cast-sleeves, which form the remaining portion of the cover for the nickel-steel differential shafts. The sleeves, which, at their outer ends, carry the main suspension springs, are, of course, of ample construction ; the design of these should satisfy the most exacting. They are webbed on their undersides, the webs terminating in a large bass for the purpose of accommodating a tie-rod, The peculiar construction of this is readily discernible in our illustration of the ba.ck-axle anit. Sensible means are provided for supplying the gear with lubricant, a good-sized branch being cast in the bottom half of the casing, and the top of this is well clear of any part of the axle likely to hamper the " " process. A similar facility is afforded on the change-speed box.
The hand-brake takes effect on both rear road-wheels through the medium of east-steel drums and externally expanding cam-actuated brake-shoes.
The chassis framing, together with the main suspension, is quite in keeping with the general features n14 of the machine. The main frame members consist of rolled steel channel of ample section, and the construction is well tied by crossmembers, suitably positioned throughout the chassis length.
Cast-steel Wheels are Standard.
The rear road springs take up the drive, so that a torque rod is not fitted. Cast-steel wheels, which run on ball-bearings, will be supplied with the standard model, the tire sizes they accommodate. being 860 mm. by 90 mm. ; the rear wheels are mounted with twin bands. Two different whe.elbases are listed, viz., 9 ft. 6 ins. and 10 ft. 6 ins., respectively. These dimensions allow for a platform length of 7 ft 6 ins. and
9 ft. 6 ins. The specified useful loads the machine will carry are one ton net, or 30 cwt. gross.
We "Try Out" the Machine.
We took the opportunity.of a trial run on the model, and .during the trip the machine mounted a long and trying incline of 1 in 7.2 on second speed. We were well satisfied that the pulling power of the engine is quite ample for all the work it is likely to be called upon to perform in service. The operating levers for both engine and chassis control are particularly handy, and the driver was in no way called Ilion to exercise any bodily exertion in their manipulation. Moreover, the whole machnet responded to his will with remarkable effect.
Easy Maintenance has Been a Consideration.
'There has undoubtedly been a -consistent endeavour on the part of designers to ensure, as much as possible, the easy road-trim of the machine, this, of course, being a very desirable feature, in that it enables the driver quickly to get 'away with the load without having to spend valuable time in preparing for " filling up" or making sundry abortive attempts at getting lubricant into awkwardly-placed grease and oil cups. In addition to this, certain component parts, which, in the ordinary way, call for periodic attention, are readily accessible.