Bristol MW

Bristol MW
A Bristol MW with standard ECW bus bodywork
Overview
Manufacturer	Bristol Commercial Vehicles
Body and chassis
Doors	one
Floor type	Step entrance
Powertrain
Engine	Gardner
Dimensions
Length	30 ft (9.1 m)
Width	8 ft (2.4 m)
Chronology

The Bristol MW (MW stands for "Medium Weight") is a bus and coach chassis. designed and built between 1956 and 1964 by Bristol Commercial Vehicles Ltd (BCV) at Brislington, Bristol.

It had a horizontally mounted engine under the floor between the two axles allowing an entrance ahead of the front axle and a flat floor for its entire length and thus suitable for "one-man" operation. The chassis then had a body mounted upon it by a bodybuilder, either a bus body or a coach body. The MW replaced the earlier LS (Light Saloon) which was designed to be built into an integral bus or coach only by sister company Eastern Coachworks Ltd (ECW) based in Lowestoft. This prevented the sale of the mechanical underframe to other bodybuilders when a change in control of the company allowed this to happen. A few chassis were sent to Alexander at Falkirk to receive bodies to the specification of companies within the Scottish Bus Group.

Unlike the earlier LS, which experimentally housed AEC and Rootes TS3 engines and the later RE experimentally using a horizontal and turbocharged version of Bristol’s own BVW engine, all MW chassis were fitted with Gardner 5HLW (5-cylinder) or 6HLW (6-cylinder) engines. The chassis type designation was either MW5G or MW6G. These engines were deep in their horizontal form causing the floor height of the finished vehicle to be high, resulting in steep steps at the entrance. The transmission was by way of a manual 5-forward speed gearbox made by the company. It incorporated synchromesh cones, but these did not wear well and gear changing still required drivers to adjust engine to road speed. The rear axle was available in three ratios 5:1, 5.5:1 and 6:1. 5.5:1 was by far the most popular and 6:1 was the standard for bus versions built for Bristol Omnibus Company Ltd.

The vehicle was built to the contemporaneous legal maximum limits of size, namely 8 ft wide (2.4 m) and 30 ft long (9.1 m). When regulations allowed longer (36 ft or 11 m) and wider (8 ft  2 ¹⁄₂ in or 2.5 m) vehicles, BCV did not extend this chassis and moved to a new concept with a rear engine. Despite this, as late as 1962, an option was designed to incorporate major modifications to the chassis to fit air springs instead of the traditional multi-leaf springs. The air sprung version was popular for chassis intended for coach bodywork, just before the 36 ft model for fitment to the RE chassis. Few customers specified air springs for bus versions. Bristol Omnibus Company was the main one and it was on the basis that the better suspension caused less stress and damage to the chassis and bodywork and reduced lifetime costs of operating the vehicles would outweigh higher initial purchase price. Their chief engineer at the time, Mr E Hardy, was sorely displeased when the option was withdrawn for the last year of production.