AND WINDING DKUM. 107 



cables, 98 feet in length, fixed to an anchor. A man passes- 

 the small cable over a pulley fixed on the frame, and pulling 

 backwards readily displaces the system, as it travels easily on 

 rollers and rolled joist iron girders. These girders must be 

 sunk in the ground. If it is too hard, they require to be 

 steadied by means of pegs. 



The drums must always be provided with brakes (auto- 

 matic or otherwise) to steady the unwinding of the cable ; if 

 not, the latter, unwinding by jerks, becomes entangled in the 

 different parts of the machine, and occasions great loss of 

 time. The most simple automatic brakes consist of a 

 weight, which may be displaced along a lever, at the end of 

 which a shoe is fixed, compressing against the flange of 

 the drum. 



Stationary winding drums are generally made with a 

 vertical shaft, so as to allow the cable to unwind in different 

 directions, without requiring an arrangement of pulleys, 

 but this requires the use of bevel pinions to transmit the 

 movement from the engine to the drum. In the direct 

 traction system the drum generally revolves round a hori- 

 zontal shaft, the cable winding with or without the aid of a 

 pulley arrangement, according to the direction of the 

 traction. 



Finally, for travelling on roads, the drums are usually 

 mounted on four wheels. 



Guyot's winding drum (Fig. 26, page 51) consists of a large 

 rectangular frame, made of rolled joist iron girders, upon 

 which the portable engine is carried ; the fly-wheel of the latter 

 is connected by means of a belt to the pulley of the capstan, 

 which is fixed at the other extremity of the frame. A pinion 

 is keyed on the shaft of the pulley, gearing with a cog- 

 wheel keyed on another shaft, together with another pinion, 

 gearing with the large crown-wheel of the drum upon which 

 the cable winds direct. 



The large frame is . carried by four rollers, travelling on 

 rolled joist girders. The displacement of the system is easily 

 managed by means of levers* ; the latter may be inclined at 

 an angle to allow the system to turn about if the headland 

 is not straight, or at the end of the headland, in order to 

 plough it. 



* Guyot tried to displace the system automatically by means of a belt, 

 pulleys, and gearing system, revolving the axle of the rollers when required. 

 This complicated mechanism (1891) has been discarded. 



