New-York tribune., 1919-04-20
Lifting 900 Tons {
Day Simple for
Magnet

I terial, the current turned on and the
hoist made Immediately. When the load
has been dumped 1t is released instantly
by switching off the current. The delay
involved both in singing and in unsling-
ing is avoided, and the man who drives
the crane controls the current Many re-
corded tasks reveal immense gains over
the old slow methods. One record is at
the rate of 800 tons of pig handled per
day OF ten hours by one magnet and one
man. magnet is shown to have saved
its cost in fortnight. Loads have been
handled at the rate Of one per minute, a
rate which has again been doubled and
costs cut down to a penny and a half
penny per ton. Again, the electromagnetic
will perform one section of work that
cannot be dealt with by the singer In
rolling mills it will lift materials which
at temperature much too high for
men to handle, and without damage to
the magnet in those designs where the
coil insulations freproof. Rails and
other sections can be lifted from the hot
banks and transported to the cooling beds
and thence to the Strengthening machines
and other destinations. The magnets will
lift small articles incosed in packing
cases, still without singing, the magnetic
force passing through the wood, and they
will pick up such cases if submerged in
water.
"Most lifting magnets are of circular
outlines, disk-like in external appearance.
A few made for dealing with special work,
such as long plates and bars, are oblong,
and more than one may be associated in
such duties. A few are ellptical. The
essential construction includes the copper coil
inclosed in a with north and south
poles, a terminal box through which the
current is conveyed, a shield which pro-
tects the lower face of the COIL lugs or
eyes to which the lifting chains are at
tached, and pole shoes on the bottom with
which the work to be lifted makes con-
tact. These shoes are renewable, an ar
rangement necessary because their
faces the wear and tear of very rough
service is concentrated.
"The attractive force, the strength Of
magnet depends on the quantity of cur
rent that passes through it's coils. The
larger the number of turns multiplied by
the current the greater will be the lifting
capacity. Since it is desirable always to
reduce the dead weight of the magnet In
order to afford the largest margin of live
load for the crane to carry, the problem
is to get the maximum number Of coils
in the least possible space and to put the
maximum current into it. This explains
why in place of coils of wire copper strip
of rectangular section is preferred for the
larger magnets.
"In considering the economical aspect
Of magnet it is not correct to regard
the consumption of current alone. because
then no account Is taken Of the power
consumption Of the operating crane, or
of the time occupied in loading and un-
loading, of the wages of the crane
driver. The cost of large supply of
current will be found to be cheaper than
these other items. Hence the most eco
nomical magnet may we'll prove to be that
which consumes the most current, because
it lifts maximum loads at maximum rates,
and handles them the most rapidly. Es-
pecally when ships being loaded and
unloaded the saving in dock dues becomes
very considerable item"