Nick Cleak: "I do remember seeing one cleaning the streets when I was
on the bus going to school. They made an Imp type noise"

The Imp Site

based on:
Pathmaster 42, mark 3 / Derek Couldry. - Impressions Aug. 1986

Pathmaster 42

In 1973, a hundred Imp short motors were sent to a South London Borough Council for their road sweepers.

The Blaw Knox Pathmaster 42 is a little three wheeled road sweeper. It measures just 4'6" wide and it is powered by an 875 cc Mk II Imp engine governed to 4200 rpm and mounted in the usual way. Transmission is by way of a standard Imp clutch and gearbox with Blaw Knox reduction boxes in each of the rear hubs.

Top speed is around 20mph when not sweeping but around 12mph when the brushes are in use. Fuel consumption is around ½ gal./hour. It has the familiar Imp gearchange on the right and steering column controls from a post '69 Imp. The instruments include a combined tachometer/speedometer, fuel and temperature gauges, switches for lights, wipers, amber beacon and heater blower.

It has a brush on each side of the front, that can be seen from inside the cab. These can be controled independently. The one brush in the centre, behind the cab. These brushes are driven by hydraulic motors, which are driven by the Imp engine.

Noise is very little, but if the Pathmaster is to be used in a confined area, an optional LPG conversion can be fitted with the bottle behind the cab. A switch is fitted to change from petrol to gas when required.

The PM42 ceased to be made in 1982, with some 870 units made. Many were exported: France and Italy were the best markets, but they were sold all over the world. After 1982 some 20 or 30 units were made using reconditioned engines.

taken from
Municipal Imps / Kevin Horn. - Impressions June 1986. (former Technical Advisor at the Blaw-Knox spares " services division in Watford, between 1974 and 1979):

It was called 42 as the width of the main centre brush was 42 inches.
I remember the ripple that went through the firm whe the Linwood closure was announced - we felt that was the end of the PM42, although production at Rochester continued for a while longer...
We had quite a good selection of Imp parts in our store and, with security being practically non-existent, at one time it became apparent that three complete engines had disappeared into thin air !
I believe that most PM42s had a low compression engine and were most definitly fitted with an engine governor.


Cleaning appliances to meet changing conditions. - Commercial Motor 1970, June 5th, p.69-71. - [Municipal and Public Utilities]
a small photo from the brochure on p. 70 and two sentences

A fresh range of optional equipment is available for the Blaw Knox Pathmaster 42 sweeper which is powered by a Hillman Imp engine, giving travelling speeds up to 20 mph. Heavy duty polypropylene side brushes, for use in the removal of deep deposits, are among the extras mentioned, others being a water-sweeper system with a 25-gal. tank located on the top of the hopper, and an engine-hour meter.

Blaw Knox Ltd, Rochester, Kent, ME1 3AP. - Commercial Motor 1978, January 13th, p.45. - [Municipal and Public Utilities]

The Pathmaster, the smallest of the Blaw Knox ride-on sweepers, measures 1.37m (4.5ft) wide and 2.99m (9.8ft) long and is designed to work in confined areas. A tapered cab with sloping side allows the machine to be manoeuvred close to obstructions in safety as the large windows provide good all-round visibility.

The hopper has a working capacity of 0.56cum (20cuft) which can be checked from within the cab. Discharge is achieved using the controls mounted in the cab to operate the twin hydraulic tipping rams.

Water, which is stored in a 250-litre (55gal) tank, can be delivered under pressure to jets located above the two circular side brushes and the one main brush, which can be used in a choice of combinations and raised to enable the machine to mount a six-inch kerb, while the maximum swept path is given as 1.93m (6.3ft).

An 875cc (53cuin) Chrysler petrol engine, positioned below the hopper, provides motive power for the road wheels and the brushes. The average sweeping speed is given as 4 to 9km/ h (3 to 6mph) while top travelling speed may be as high as 32km/ h (20mph).

A turning circle of 5.4m (18ft) allows good manoeuvrability, but for those areas too confined for the brushes to reach, a wander-hose facility is provided.

The Road Master is a larger and more powerful machine fitted with a 1,600cc (98cuin) Volkswagen four-cylinder aircooled petrol engine or alternatively a Perkins 1,760cc (107cuin) diesel engine.

The working capacity of the hopper is double that of the smaller machine. Brush speeds on both models are variable to cope with the density of the deposit being swept. With an overall length of 3.7m (12.2ft) and brush width of 1.9m (6.3ft) the turning circle measurement comes out at 6m (20ft).

The wander-hose option is mounted on top of the hopper to allow 360 degrees of movement around the vehicle and the hydraulically operated fan provides sufficient suction to cope with litter the size of bottles and cans.

All petrol engines models are suitable for an lpg conversion and by means of a simple selector switch either fuel may be used as required.

Imp Club News sheet, March 1986. - Mike Hanna and Alan Ramsey

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© Franka
Edition: 21 Jan. 2017
File started: 10 July 1997