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Guy Preselective Control

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8th November 1935

Page 122

Page 122, 8th November 1935 — Guy Preselective Control

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for Cotal Gear

Ingenious Automatic Speed-change Mechanism Incorporated in Electro-magnetic Epicyclictransmission Installation

QNE of the most promising rivals to the gearbox of orthodox type is the Cotal. It is, therefore, of great interest to learn that this unit has been 'embodiedby Guy Motors, Ltd., Wolverhampton, in a bus chassis built for Southampton Corporation. The vehicle, with a Park Royal body, is exhibited at the Show.

The great novelty of this gearbox installation is the Guy patented system of control which is employed. It is admirably adapted to the requirements of bus service, for such operating conditions demand a simple and easily actuated mechanism, in which the characteristic of smooth ness is predominant. . The driver is provided with a finger-tip preselective control, which forms a small unit and is mounted on the steering column. By this the four forward and single reverse speeds can be preselected. It is not until the clutch pedal is depressed, however; that the gear is actually changed. At the end of its travel the pedal completes the necessary electric circuits to excite the appropriate electromagnetic clutches of the gearbox.

The last-named is used in conjunction with a two-plate clutch, arranged between it and the engine. This possesses the feature of extremely smooth operation. A certain slip is also allowed by the magnetic clutches, as they come into action, because the oil has to be squeezed out from between their faces as they engage. Consequently, the drive is taken up very sweetly, whilst the magnetic clutches are subjected to the minimum of wear.

A refinement to be found in the control gear is a neat device the object of which is to make night driving easier. A number on the control panel is illuminated as the gearchange is effected, so that the driver can tell at a glance which gear is being used.

Handled now by the Cotal Chadburn Co., Ltd., 9, Cloak Lane, Cannon Street, London, E.C.4, the Cotal gear was marketed during the years 1927 to 1929 by the Guy company, which was then the sole concessionnaire in tills country. Guy engineers then had considerable experience of the gear, but encountered certain mechanical difficulties which retarded its development.

The present design differs materially from the original,* and all the weaknesses have been eliminated. it is stated by Guy Motors, Ltd., that no difficulty was ever experienced with the electrical partof the equipment.