Scammell Automatic Coupling Gear
operators were quick to realize the advantages offered by the Scammell automatic
trailer coupling system and the use of articulated semi-trailers. Bedford (OSS model). Austin, Morris
and Karrier were the
most popular, but other makers chassis could also be fitted with the coupling including Thornycroft,
Dennis, Seddon, Dodge, and Ford. The
four-wheeled tractor units were mainly used on town-to-town haulage work leaving
the three-wheeled Mechanical Horses to take the trailers on local and town
The Scammell coupling
continued in regular use until the 1970s when the increasing gross train weights
and the increased use of the fifth wheel coupling, caused it to fall out of
favour with haulage operators. The Ministry of Defence and one or two small companies
continued to use the Scammell coupling gear until the late 1980's and it
was believed that these were the last users, however club member and author
Bill Aldridge found the Scammell system still being used well into the
21st century. For further details please right click
here and select 'Save target as ...'
The coupling consisted of two ramps attached to the rear of the tractors chassis and coupling hooks situated in front of the rear wheels. The trailer had an undercarriage mounted below the turntable with two rollers that ran up the tractor ramps. Under the beam holding the rollers was a narrow twin legged frame (with jockey wheels at its extremities) which folded back as the rollers ran up between the tractor ramps and striking the release plate situated below the ramps.
The hooks on the tractor unit engaged with the lugs on the trailer, attaching it to the tractor unit. Most importantly the trailer brake and trailer light connections were made automatically and all the driver had to do was release the trailer hand brake and connect the registration plate to the rear of the trailer.
The two ramps or runways fitted at the rear of this
Scammell Scarab are shaped to take the flanged wheels of the trailer
undercarriage at what ever angle the unit may be coupled to the trailer. At the
front end of the ramps are two adjustable sprung buffers,
which absorb the shock of 'coupling up' and load the coupling hooks in order to
keep the trailer securely locked to the unit. The double locking hooks are
provided so that should the initial coupling be incorrectly carried out the rear
hook will prevent the trailer breaking away.
For a larger version of this image please click here (opens a new window)
Pictured here are the Scammell Jockey wheels fitted to the trailer unit. Note the plate situated in the middle of the Jockey wheels. When this plate comes into contact with the S-type hook fitted in the centre of the running ramp on the tractor unit it causes the wheels to fold back and clear the ground. A trailer release lever is fitted in the cab, when this is operated the coupling hooks are tripped and the unit may be driven clear of the trailer.