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AC Cars Railbus

Principal Dimensions

Overall length (buffers free): 37' 0"
Length over body: 36' 0"
Outside width over panels: 8' 11"
Overall height from rail (laden): 12' 2 1/2"
Inside width at waist rail: 8' 6"
Floor height from rail (laden): 4' 3"
Interior height, floor to ceiling: 7' 4"
Wheelbase: 19' 0"
Wheel diameter: 3' 0"
Tare weight: approx. 11 tons
Seating capacity: 46
Maximum speed: 55 mph

The vehicles could be considered as two separate parts, the chassis (with the power train) and the body.


The underframe was designed as a lightweight steel unit formed mainly of mild steel channel section electrically welded together, the whole being stiffened with diagonal members and generously gusseted. Lightweight rolled steel disc wheels were mounted on two axles carried in SKF self-aligning roller hearings in cast steel axleboxes. Wheels and axles were supplied by Owen & Dyson Ltd.


The axlebox suspension followed the Metalastik principle of supporting the axlebox in two chevron shaped rubber-bonded-to-metal shear-compression spring units. The design of the springs and the angle in which they were set allowed freedom of movement in a vertical direction, but exercised the necessary constraint in transverse and longitudinal directions. The springs were set at an included angle of 40 degrees (which determined the ratio of shear to compression) and provided a static deflection of 1 3/16 in. under the maximum design load. The ratio of stiffness of the suspension in vertical, transverse and longitudinal directions was 1:2:7.

This Metalastik axlebox suspension eliminated all metal-to-metal contact and the need for lubrication. The springs interposed a barrier of rubber between the tyres and the bogie, or the body underframe, absorbing high-frequency vibration and noise set up by tyres in contact with the rail joints.

The brakes of normal clasp type were operated by a straight air system and incorporated an emergency feature, and were supplied by Clayton Dewandre Co Ltd.

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