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Editor's
Note: The following article is presented in it's entirety.
While only two or three paragraphs deal with the actual
workings of the davit, I thought the reader would be interested
in some of the background involved with the development
of these davits, and the general attitude of the time regarding
the emphasis on deck space over actual life-saving capacity.
One gets the impression that the presence of lifeboats was
almost considered a "nuisance". Of course, attitudes
would change in just a couple of years...
The
last paragraph deals with the davits' installation on Olympic
and Titanic. Some "specifications" obviously changed
after this article was written, which will become clear.
While
I realize that much of the material in the article and the
accompanying scans are of little practical use to a modeler
building a 1/350th model, it is always fun to know how these
things worked. I for one have always wanted to know what
the front of the davit looked like up close, and how the
double sided davits were operated. All known photos only
show a glimpse of that area. So I was thrilled to find the
plans you are about to see.
Links
are provided in the text when an illustration is referenced.
Figures 4/5 and 7/8 are combined on their own pages. You
may also access all of the illustrations via the links at
the bottom
of this article. The scans are large, but the file size
is managable, and you should be able to print them by setting
your printer to Landscape.
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It
is some years since we published particulars of the standard
pattern of the Welin Quadrant davit for lowering boats on
board ship.*
The first trial set had just been fitted on board the cargo
steamer Kortnaer. Since that date the advantages claimed
for the gear have been so well substantiated in practice
that at the present time some 3000 davits are in use.
In addition
to what may be termed the mechanical superiority of this
type of davit over the older form, the use of this gear
renders possible a considerable saving in deck space. To
all familiar with the conditions of modern ocean travel,
it will be patent what this really means. Nowadays the success
of a line of passenger-carrying steamers depends (at least
on certain routes) largely upon its popularity among the
traveling public. Competition has in many instances afforded
a wide choice of routes, and passenger lines must provide,
at the present day, vessels not only as safe and well found
as possible in all respects, but also boats which are attractive
and offer special facilities for the pleasurable occupation
of the long hours of enforced leisure. For these and other
reasons saving in deck space is a distinct advantage, and
it may be taken that any gear which renders this possible
has much to recommend it.
Of the
many propositions put forward from time to time whose objectives
have lain in this direction, probably the most obvious is
that of "double banking" the boats on convenient
portions of the deck ; in other words, to carry them in
a double row, one inboard of the other, on the less valuable
part of the deck. Up till the present, any proposal embodying
this arrangement has been checked by the fact that the Board
of Trade has refused to recognize the inboard boat as fulfilling
the clause in it's regulations, which requires a boat to
be "under davits", as it is termed. Double-banking
has, nevertheless, been practiced to some extent; but owing
to the above clause, only in the case of such life-boats
as have been carried over and above the regulation complement.
Thus it has assisted in no way in reducing the long file
of regulation boats to port and starboard, which obstruct
a space that might otherwise be advantageously devoted to
recreation, etc. The sea going public unquestionably thoroughly
appreciates the advantages presented by clear deck space,
as well as unrestricted view, and as both these are rendered
more easily possible by double-banking of the boats, shipowners
will doubtless not ignore a decision, recently reached by
the Board of Trade, on this point. In conformity with this
decision, the Board's rules have been amended in such a
way that, in certain cases, the inboard boat of two double-banked
boats shall now count as forming part of the regulation
complement, when fitted in an efficient manner.
A modified
pattern of davit, recently brought out by the Welin Quadrant
Davit, of Hopetoun House, Lloyd's-avenue, E.C., complies
with these new conditions. This gear we illustrate in Figs.
1 to 8 herewith. The new design of
quadrant is similar in operation to the old, and there is
no need, therefore, to enter into a description of the principles
on which the system has been worked out. The general arrangement
of the new form of gear is shown in Figs. 1 to 3. From Fig.
1 it will be seen that for this double gear the quadrant
is a much larger sector than formerly. The davit arm practically
bisects the angle formed. The travel for the screw block
is much greater than in the orginal pattern and allows the
davit-head to move from an extreme outboard position into
an extreme inboard position, in which it stands plumb over
the keel line of the inboard of the two double banked boats.
The larger sector and the lengthened rack and screw are
necessary, of course, to this greater travel. The extreme
positions are shown in dotted outline in Fig.
1. The lead from the block is taken over and round a
sheave shown on the inboard end of the frame, and thence
to a bollard on deck, as may be seen in Figs. 1 to 3. This,
when the boat is being swung out, tends to raise it and
keep it clear of the deck. When swinging in, after a certain
point, the weight exerted by the boat actually tends to
raise the davit, while the falls are paid out at the same
time.
With
a view to gaining further fore-and-aft deck space, twin-frames
are sometimes employed for the gear, as shown to the right
hand in Fig. 2 and Fig.
3 . Under these conditions a special driving gear is
used, which is further shown in detail in Figs.
4 and 5. It will be seen from these latter figures that
the driving-pinion for the screw gear is carried on a swinging
frame, the lower end of which is forked. Between the limbs
of the fork is an eccentric which can be thrown over by
hand, so that the pinion will mesh with the gear of whichever
screw it is desired to operate. This eccentric has a throw
rather greater than that corresponding to it's maximum eccentricity,
so that it remains automatically locked when thrown over
one way or the other.
The first
twelve sets of this type of gear have recently been fitted
on the new boats of the Union-Castle Mail Steamship Company,
but in this instance they were applied only to boats carried
on the poop-deck, the remainder being fitted with standard
Welin davits. Fig. 6 is a photograph
taken on board the R.M.S. Balmoral Castle, of which we recently
gave illustrations. The view we now give shows the outboard
boat being handled in the davits.
A more
extensive application of the new system is being made on
the White Star liners Titanic and Olympic, now in course
of construction at the yards of Messrs. Harland and Wolff,
Belfast. These vessels are to be fitted throughout with
double-banked boats operated by the new Welin gear. A plan
of part of the boat-deck of these vessels is shown in Fig.
8, while Fig. 7 gives
a section showing the position and handling of the boats.
Half the number of the boats fitted on these ships will
be in excess of the Board of Trade requirements. Adequate
provision on this scale could only be rendered possible
by the adoption of some such scheme as that now sanctioned
by the Board. The outer boats will be provided with shifting
chocks, and at sea will be carried at the half-outboard
position, allowing ample gangway room between the two rows
of boats. The inboard boats might, of course, also be provided
with shifting chocks, and the gangway between the boats
and the deck erections thus increased. It will be evident
that this arrangement might, with convenience, be adopted
in cases where at present boats have to be cleared for coaling
operations. Double gear would obviate such inconveniences,
and we understand that more than one company are considering
the matter with this in view.
*
Volume LXXI, page 815. [I have calculated this be the Jan
to June 1901 volume]
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Additional
Reference and Comments
The
design of the davit is quite elegant. To understand what
happens as the arm is raised and lowered, extend the curve
at the bottom of the arm (the quadrant) into a complete
circle. You will find that the pivot point (screw block)
is at the exact center of that circle. As the screw is turned,
the screw block travels forward or backwards while always
staying the same height, just as the axle of a car travels
in a straight line as the wheel turns. To keep things from
slipping, a rack (row of teeth) on the davit frame meshes
with teeth on the inner edge of the quadrant as seen here.
The outer edge of the quadrant has a wider rim with no teeth.
The weight of the boat forces the quadrant towards the centerline
of the davit frame, ensuring the teeth always mesh, and
the arm stays locked in position.
Note
that all the diagrams only show a "half" chock,
on the inboard side of the lifeboat, not an outboard one.
This can be confirmed in most photos of Titanic, such as
this.
There
was a "sheath" covering the screws that can be
seen on most photos and was obviously there to keep the
screws as free from dirt and corrosion as possible. This
appears to have been a permanent attachment, as photos show
it in place in a variety of arm positions. There may have
been a wire wound inside that kept it expanded throughout
the arms' travel. You can make out a spiral structure in
this
photo.
The
crank was stowed by removing it from the center drive
shaft and turning it around backwards, so the end rested
on one of the pulley mounts. The center of the crank was
just a square hole that fit the square end of the shaft.
It's unclear if the outer circular object opposite the handle
is another hole for mounting the crank further from the
center for more leverage or if it was a counterweight. To
keep the crank from getting lost, there was a small chain
connecting the crank to the davit frame as shown here.
Figure
4 - 5 shows
the ring. It may have turned with the drive shaft, eliminating
the need to unclip it.
Finally,
for those of you that have a hard time deciphering the diagram
of the fork assembly on the davit end, I have removed all
the extraneous lines from Fig 4/5 and present you with this
diagram.
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