A Treatise On The Principles And Practice Of Dock Engineering
Forfatter: Brysson Cunningham
År: 1904
Forlag: Charles Griffin & Company
Sted: London
Sider: 784
UDK: Vandbygningssamlingen 340.18
With 34 Folding-Plates and 468 Illustrations in the Text
Søgning i bogen
Den bedste måde at søge i bogen er ved at downloade PDF'en og søge i den.
Derved får du fremhævet ordene visuelt direkte på billedet af siden.
Digitaliseret bog
Bogens tekst er maskinlæst, så der kan være en del fejl og mangler.
POWER OF GATE MACHINES.
527
greenheart gate, nioving at a much slower rate with conical rollers over
splayed tracks, and it will still further be augmented by a certain amount
of friction at the heel-post. On tlie other band, there is the diminution of
the load on the rollers due to flotation, which will, of course, vary witli the
depth of water at the time of working. Further, there is the ratio of
the diameter of the roller to that of its axle, and the proportion of weight
which the roller carries. With a ratio of 4 to 1 and a coefficient of -15,
the friction due to that portion of the gate borne by the roller would be
2,240 x -15 „
- ----------= 84 Ibs. per ton. Allowing for flotation and dealing with the
question, as is inévitable, in a somewhat rough and ready way, it will pro-
bably not prove an excessive estimate if we take the frictional resistance of
the gate at 20 Ibs. per ton on its gross weight, in which case
150 x 20
2,240
= 133 tons.
For the resistance offered by salt water to displacement we have
/3
55 X 40 X 64 X 1-85
64 x 2,240 “
= 1'81 tons.
Hence the maximum tension in the chain, exerted at the moment of
starting the movement of the gate, will be
T ^ +/2 + /3 = 3-47 tons.
This figure will need some additional margin to cover uncertainties in
the frictional resistance. Under circumstances only too common in con-
nection with the working of dock gates, the resistance may easily be
increased to double the amount calculated above, for which fair conditions
of track have been assumed.
The following table exhibits data relating to several existing examples of
machinery for greenheart gates. For metal gates with buoyancy chambers
the friction of movement will be much less, and the amount of power to be
applied will accordingly be considerably reduced.
TABLE XLIII. —Gate Machines.
Width of Entrance. Greatest Working Head. Least Working Head. Area of Surface of Leaf. Diameter of Ram of Gate Machine. Diameter of Chain. Gear. Accumu- lâtor Pressure.
Feet. Feet. Feet. Square Feet. Inches. Inches. Lbs.
40 36-5 26-5 766-5 12 1 6 to 1 750
80 41 31 1722 17 1^ 6 ,, 1 750
80 40 30 1680 17 1A s,, 1 850
90 41 31 2091 18 li 6 ,, 1 750
94 34 24 1768 18 li 6 ,, 1 750
100 41 31 2316-5 19 14 6 „ 1 750
100 40 30 2-260 19 14 6 „ 1 850
100 39 29 2203-5 20 li 6 „ 1 1000