Clean Sweep in New Brush Body
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Wi-AT is undoubtedly a definite sitep in the direction of the complete chassisless, all-metal bus is now coming off the line at the Loughborough factory of Brush Coachwork, Ltd. It is the Brush pop-riveted, allmetal single-deck bus body, 300 of which are on order for the Birmingham and Midland Motor Omnibus Co., Ltd.
Although the Brush concern has been responsible for the final design and construction of this new and original body, much of the credit for its ultimate production in large quantities goes to Mr. Donald Sinclair, the general manager of the R.M.M.O., for his enthusiasm for pop-riveting and his conviction that'this type of construction would bring both the manufacture i and the operator nearer to the ideal all-metal bus body, as opposed to the orthodox compositeconstructed type. In the Brush body the timber furrings have been entirely eliminated. The only timber used is, in fact, the main floor, although there is no reason why even this should not be of metal construction.
The body framing, formed by the constructional members and the " inntr skin," are riveted together in the normal manner with solid rivets to obtain the usual firm foundation. Flow production, however, is obtained by constructing all sub-assembly units of the sides. ends, roof, cab, partition, floor framing. doors, etc., in jigs, each part for the sub-assemblies being shaped and machined to a template, thus ensuring
complete interchangeability. It is in the securing of the exterior panels that poprivets are employed, providing an "outer skin " which can now take its full part in the strengthening of the whole structure. The pop-rivets pull the panels together in a positive metalto-metal connection under a pressure of approximately 1,000 lb. per sq. in. during the setting-up action.
Pop-riveting, a simple, one-man operation, is not new. It has been
proved in aircraft construction, and in many other spheres during the war years. Its application to the building of bus bodies, however, is important, in that the time requised to replace a damaged panel is considerably reduced. The rivets of a damaged panel are removed by a drill about 1-64 in. undersize, so that when the repaired panel is put back, new rivets are inserted without enlarging the hole, thus ensuring the same 'tight joint and retaining the tension of the exteriot sheeting on the main frame structure.
The main pillars are of H-section steel, formed from a solid-drawn tube, with flanges on both inner and outer sides. The inner constructional sheets are solidriveted to the inner flanges, and the exterior aluminium panels and alloy cover mouldings are pop-riveted to the outer flanges. Cantrails, waist rails and seat rails are of channel-section drawn steel, with the open edges turned inwardly to give greater strength and to prevent holes occurring too near to the edge of the section.
It has been found that a saving in weight of at least 5 cwt. is effected and that, by the elimination of the timber furrings, there is a considerable saving • of labour. With this design, and by t'he constructional methods employed by the Brush concern, it is estimated by the chief designer to Brush Coachworks, Ltd„ that the output of bus bodies will be increased by at least 10 per cent.
The 40-seater bodies for the B.M.M.O. are carried on Silentbloc mountings on a most interesting chassis which was developed and built by the . Birmingham company during the war years. Its particular feature is that the engine and gearbox are carried amidships in a flat position, with the cylinder heads and valve gear, fuel pump, etc., lying slightly outside and beneath the off-side longitudinal frame member. The wheelbase is 16 ft. and the maximum depth of the frame members is 8 ins. The six-cylindered oil engine is of B.M.M.O. design and manufacture, with a 4.45-in. bore and 5.25-in. stroke, It has the excellent output of 100 b.h.p. at 1,750 r.p.m., with a maximum torque of 350 lb.-ft. at 1,000 r.p.m.
Rubber mounted Engine The engine unit is supported at the • front by twin cylindrical rubber bushes, and at the rear by the cast-iron clutch housing, carried in a circular cradle upon rubber segments. The air supply is obtained from above the driver's cab, from where it is conveyed by ducting to the Talflow filter carried on the valve covers of the engine. A 16-in, singledry-plate clutch is employed, in a castiron housing cut away to give access to the clutch mechanism for adjustment and to provide adequate ventilation. The constant-mesh gearbox is a separate unit, flexibly mounted on rubber
bushes. The ratios provided are:— First, 4.55 to 1; second, 2.74 to 1; third, 1.617 to 1; top, I to I. The reverse ratio is 5.88 to 1.
The fully floating rear axle is driven by overhead-worm gear, set to the off side of the chassis and having a ratio of 5.2 to 1. Four-wheel hydraulic Lockheed braking is assisted by a continuous. flow servo pump driven off the propeller shaft from a point behind the gearbox and giving a three-to-one boost. The hand brake operates through separate linkage on the rear shoes only.
Chassis lubrication is designed on the grouped-nipple principle, with the two batteries of nipples located one on the near-side front end of the frame and the other on the off side, slightly to the rear of the engine. Both are easily accessible. The tyres fitted have dimensions of 9.00 by 20, with singles in front and twins at the rear.
In the layout of the completed vehicle, which we inspected last week at the Brush works at Loughborough, there is ample seating capacity for the 40 passengers, all of whom face forward. The full-fronted body, moreover, imparts a striking and pleasing appearance. Two safety factors we noticed in the construction of the halffloating cab were, first, that the driver has complete visual control of the entrance and exit, which is at the front near side immediatelyto his left, and, secondly, that the windscreen is set back to obviate glare from the headlights oncoming vehicles.
During a short run in one of these buses through the streets of Loughborough, we were impressed by the absence of both drumming and engine noise, particularly so when the cornrnunication door between the entrance and main body was closed. And to those who have any doubts about the durability or suitability of pop-riveting for bus bodies, Mr, Donald Sinclair has
this ready answer. . One of his double-deck buses which has been in operation in Birmingham for the past three years has one complete side-section built up of pop-riveted exterior panelling, and in that period there has been no distortion, or signs of wear or weakening at the panel joints.