492 Report on the Trials of Implements at Wolverhampton. 
amount of pull may be exerted by the engine. Buhbinp; friction is to a great 
extent avoided ; as the jaws or clips close upon the rope by its directly central 
l^cssure upon their curved parts Ibrmin"; the bottom of the groove, and when 
arrived at the jioint where the rope begins to leave the groove, fall open of 
their own accord. Experiment has not determined whether the consolidation 
of the rope, and the preservation of its form by continually closing down any 
jirotruding wires, which fire effected hy the pressure applied around a con- 
siderable portion of its circumference, are more conducive to durability than 
the tendency to flattening which is observable when wire rope is pressed 
upon the bottom of an ordinary open groove ; but there can be little donbt 
that the treatment of wire-rope by the clip-drum is less damaging than the 
constant grinding of coil against coil, and the severe pressing of outer strands 
\\\)iya. the sharp angles of outer strands, which are always an effect of im- 
lierfect coiling upon a winding-drum. A Report on " The Underground 
Haulage of Coal," by a Committee appointed by the North of England 
Mining Institute to investigate the subject, gives examples of steel-wire rope 
lasting three years in collieries, when in daily and incessant action upon clip- 
drums in hauling trains of heavily-loaded " tubs " up and down inclines. 
]jut there is an advantage in the clip-drnm which is wanting in the winding- 
drum. An efficient coiling-gear maj^ insure regular and uniform coils, free 
from over-wrapping, so long as the rope be new and not unevenly worn ; but 
at present, no coder, however ingenious, has mastered the difficulty of accom- 
modating its speed of traverse to the thinner dimensions of an old rope. In 
the clip-drum, however, is provided a means of adjusting to a nicety the 
calibre of the groove to any altered size of the rope, as exhibited in section 
Fig. 8. A and B are one pair of the clips, which surround the entire circum- 
Fig. 8. — Section of the Clip-Drum attached to Messrs. Fowler and Co.'s 
12-IIorse-powcr Engine, No, 6482. 
fcrencc of the drum ; the upper clip A hinged or centred upon the maiu 
flange G G, and the lower clip B upon a ring D, which is screwed upon the 
flange or body of the drum by a thread chased round its periphery. Thus, by 
slii)ping the ring, D, part of a revolution upon the drum, it) is gradually 
shifted a slight distance nigher or lower, with the effect of diminishing or 
increasing the space biicwcen the centres of all the upper and lower clips 
