Concrete Roads
and Their Construction
År: 1920
Serie: Concrete Series
Forlag: Concrete Publications Limited
Sted: London
Sider: 197
UDK: 625.8 Con-gl.
Being a Description of the concrete Roads in the United Kingdom, together with a Summary of the Experience in this Form of Construction gained in Australia, Canada, New Zealand and the United States of America.
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MECHANICAL DEVICES FOR MAKING ROADS 125
have now been modified so as either to remove a relatively thin slice
of material or to cut their way through a hill. When used for
levelling a rough piece of country—as in working a wholly new
road or in widening an existing one—steam-shovels are found to be
much cheaper and quicker than hand-digging, and far less super-
vision is required.
A British firm of steam-shovel manufacturers is Ruston
and Hornsby, Ltd., Lincoln, whose No. 5 Excavator (Fig. 78),
by reason of its remarkable mobility, wide range of move-
ments, ease of control and general utility is particularly suitable
for road-making. This excavator is capable of taking a maximum
depth of cut of 20 ft. without breaking the top down, by hand,
and will also successfully deal with very shallow cuts for grading,
With the standard bucket-arms this machine can excavate a
trench to a depth of 6 ft., and, by the simple expedient of letting
out the jib ties and fitting slightly longer bucket-arms, up to
12 ft. The minimum bottom width of cut with 1 to 1 slopes is
12 ft., and the maximum height of open bucket door from rail
level 12 ft. 9 in., the maximum and minimum discharging centres
being 22 ft. and 15 ft. respectively.
Small revolving steam-shovels have been in use in the
United States for road-making with great success. The sizes
which are most popular are equipped with dippers of | or | cu.
yds. capacity. Two such dippers full of material woüld com-
pletely fill the ordinary tip wagon or cart, while three dippers
would load a 2-yd. wagon or cart to its maximum capacity.
The shovels revolve through a full circle, permitting the ma-
chine to dig or dump at any angle and enabling them to operate
successfully in limited space. The latter feature is especially
valuable when it is necessary to build one-half of a roadway while
the other half is open for traffic. These steam-navvies will
excavate any materials which can be penetrated by picks and
shovels, and they are also valuable in handling properly blasted
rock.
The shovels have capacities in ordinary roadwork varying from
15 to 60 cu. yds. per hour, depending on the depth of cut, class of
material, and manner in which disposal of the material is organ-
ized.
Traction wheels are generally used on this class of navvy, but
any of them can be equipped with standard gauge car wheels, and
on some of the shovels continuous tread traction can be substi-