IMPROVEMENTS IN THE CONSTRUCTION OF CRANK SHAFTS
Year: 1884

page_text: I, THOMAS WILSON of Wallsend, in the County of Northumberland, Engineer,
do hereby declare the nature of said invention for "IMPROVEMENTS IN THE
CONSTRUCTION OF CRANK SHAFTS" to be as follows :-
My invention relates to what are known as "built up" crank shafts and is
applicable to,
1. Shafts in which the main shaft, the webs and the pin form separate pieces.
2. Shafts in which the webs and pin form one piece separate from the main
shaft.
•
3. Shafts in which the pin and one web form one piece, the other web and the
main shaft being also separate pieces.
4. Shafts in which one web is solid on a portion of main shaft, the other web
being separate from the next portion, the pin being either a separate piece or
formed solid with one of the webs.
The first named is the form to which I consider my mode of construction is
specially advantageous.
My invention consists in connecting the straight pieces forming the main shaft to
the webs by flanges or collars, fitting into recesses in the outer faces of the webs
and secured therein (except in cases hereafter specially named) by bolts in the
nanner already practised, but I form on the end of the main shaft a projecting
stud or "spigot" which is turned and fits truly into a hole, preferably entirely
through the web, bored out to accurately fit the stud or "spigot." This stud or
'spigot" is eccentric to the axis of main shaft having its centro, preferably, toward
to the crank pin and it will be convenient to make its radius less than that of the
main shaft by exactly the amount of its eccentricity.
"
The effect of this eccentric stud or "spigot" is to relieve the bolts, which secure
the flange or coupling on main shaft to the web, of all (or nearly all) shearing
strain, the coupling flange being rigidly fixed and prevented from turning round in
the recess in crank web by its eccentricity to the stud or "spigot."
The bolts have thus only to keep the crank web and main shaft united longi-
tudinally and in some cases I propose to dispense with coupling bolts, such as when

page_text: the crank webs may be shrunk on the end of main shaft or where any of the
ordinary methods of securing them against longitudinal movement may be
adopted.
Shafts constructed according to my invention will be much less liable to
injurious strains while in process of being machined, especially in the case of very
large shafts, as the tranverse strain on the coupling bolts, tending to distort the
threads of their screwed parts, is to a great extent neutralised by the support given
by the stud or "spigot," in conjunction with the coupling collar, each fitting truly
into hole and recess respectively in crank web.
1004

page_text: I, THOMAS WILSON of Wallsend, in the County of Northumberland, Engineer,
do horeby declare the nature of said invention for "IMPROVEMENTS IN THE
CONSTRUCTION OF CRANK SHAFTS," to be particularly described and ascertained
in and by the following statement :—
My invention relates to what are known as "built up" crank shafts and is
applicable to,
1. Shafts in which the main shaft the webs and the pin forms separate pieces."
2. Shafts in which the webs and pin form one piece separate from the main
shaft.
3. Shafts in which the pin and one web form one piece, the other web and the
main shaft being also separate pieces.
4. Shafts in which one web is solid on a portion of main shaft the other web
being separate from the next portion, the pin being either a separate piece or
formed solid with one of the webs.
The first named is the form to which I consider my mode of construction is
specially advantageous.
My invention consists in connecting the straight pieces, forming the main shaft
to the webs by flanges or collars, (concentric with axis of shaft) fitting into recesses
in the outer faces of the webs and secured therein (except in cases hereafter
specially named) by bolts in the manner already practised, but I form on the
flange or collar of the main shaft a projecting stud or "spigot" which is turned and
fits truly into a hole, either entirely or partially through the web, bored out to
accurately fit the stud or "spigot." This stud or "spigot" is eccentric to the axis
of main shaft and it will be convenient to make its radius less than that of the
main shaft by exactly the amount of its eccentricity.
The effect of this eccentric stud or "spigot" is to relieve the bolts, which secure
the flange or coupling on main shaft to the web, of all (or nearly all) shearing
strain, the coupling flange being rigidly fixed and prevented from turning round
in the recess in crank web, by its eccentricity to the stud or "spigot."
The bolts have thus only to keep the crank web and main shaft united longi-
tudinally and in some cases I propose to dispense with coupling bolts, such as when
the crank webs may be shrunk on the end of main shaft or where any of the
ordinary methods of securing thein against longitudinal movement may be
adopted.
I apply the principle of my invention also to fix the crank pin and prevent it
from turning round when fitted separately from the webs of crank or from one
web by inserting it into a recess formed in one or both webs and passing through
it and the webs a strong bolt the centre of which is eccentric to the centre of pin
this bolt in this case being the equivalent of the spigot on collar of shaft.
Shafts constructed according to my invention will be much less liable to injurious
strains while in process of being machined, especially in the case of very large
shafts as the transverse strain on the coupling bolts, tending to distort the threads

page_text: of their screwed parts, is to a great extent neutralised by the support given by the
stud or "spigot," in conjunction with the coupling collar, each fitting truly into
hole and recess respectively in crank web.
The advantages of my mode of construction of shafts may be briefly stated as
follows.
First. Elasticity in motion combined with strength; smooth working and less
liability to heating, hence a longer lifed shaft, the shaft being built in such a
manner that the bolts give elasticity and the eccentric spigots take the torsional
strains.
Second. Economy in repairing without the necessity of taking the shaft out of
the vessel.
Third. Reduction of material through lessening the number of bolts as the
cc.entric spigots take up the strains and doing away with the couplings between
cranks.
-
Fourth. There being no couplings the eccentrics can be put on shaft between
cranks and the shaft arranged in the least possible space to suit centres of
1°
'
DESCRIPTION OF DRAWINGS.
On the accompanying sheet of drawings I have illustrated my invention as it
may be best practically applied in the construction of shafts built up in a variety
of ways but other modifications may be adopted still preserving the leading
features.
Figure 1. shews an elevation of a three throw crank such as is now commonly
used for triple expansion marine engines and Figure 2 is an end view of same in
section through line A. B of Figure 1.
Figures 3.4 and 5 shew sections of various modes of applying the invention to
different forms of built up cranks. The same numerals indicate corresponding
parts on all the Figures-Figure 3 shews the two webs separate from the main
shaft and the crank pin also a separate piece-Figure 4 shews the two webs also
separate from the main shaft the crank pin being solid on one web and loose in the
other Figure 5 shews the two webs separate and shrunk upon the crank pin-
I have not illustrated that form in which the webs may be shrunk on collar and
spigot of shaft so as to dispense with bolts, as that mode of construction is
sufficiently obvious, nor that form in which the webs and pin are in one piece
either cast or forged.
On Figure 1. 1. 1 are the ends of straight portions of main shaft with collars 2.2*
formed upon them fitting into recesses in outer faces of the crank webs 3. 3* in
the bottoms of which are smaller recesses 4. 4ª eccentric to axis of shaft into which
the projecting studs or "spigots" 5. 5* formed upon the collars fit accurately.
6. 6ª are tapered bolts (with sunk nuts 7. 7" and guard plates 8. 8*) to unite the
webs to collars longitudinally. The crank pin 9 is fixed in the webs in a novel
manner, the same in principle as that in which the webs are fixed on shaft, the
ends fitting accurately into recesses and a strong bolt 10, the equivalent of the
spigot on collar of shaft, unites the pin and webs but this bolt, instead of being
concentric to the axis of pin, is eccentric to it and thus the pin is prevented from
turning round in the webs in which it has yet a certain degree of freedom.
Figure 4 shews another form of applying my invention the crank pin 9 being
here formed solid on one of the webs 3 and recessed into the other web 3*, the
eccentric bolt 10 uniting the whole as before and keeping the two webs accurately
opposite each other, both when the shaft is being machined and when working.
Figure 5 shews a rigid crank pin 9, the webs 3. 3* being contracted upon it with
or without a key or steady pins.
It will be seen by referring to Figure 1 which shews the mode in which I prefer
to construct a shaft according to my invention, that all the cranks and three of the
straight lengths 1, 2 and 3 are exact duplicates of each other and therefore inter-

page_text: changeable and the fourth straight length 4 may also be a duplicate of the others
and thus one straight length one web and one pin will suffice as spare pieces for
any contingency likely to arise from a break down.
It is obvious that a shaft may be constructed with one, two or any number of
cranks on this principle, also that one portion of a shaft may be so constructed and
work in conjunction with another portion made in any other form.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
募
First. Constructing built up crank shafts by fitting the web or webs of crank
to the main shaft by a concentric collar or flange recessed into the web, and a
'spigot" or stud, further recessed into the web, the centre of which is eccentric to
the centre of the collar or flange for the purpose of transmitting the power applied,
with or without coupling bolts, substantially as shewn and described.
Second. Fixing the crank pin, when formed separately from the web or webs,
and preventing it turning round by means of a bolt, passing through it and the
web or webs, having its centre eccentric to the centre of pin substantially as shewn
and described.
Third. The construction of built up crank shafts in which the webs are fitted
to main shaft by a recessed concentric collar or flange and a further recessed spigot
or stud, eccentric to said collar or flange; combined with crank pins recessed into
webs and secured so as to prevent the pin turning round by bolts eccentric to
centres of pins substantially as described and shewn by Figures 3 and 4 of
drawings.
Dated the fourth day of September 1885.
Witness,
I. J. DAWSON, F. Inst. P.A.,
Consulting Engineer & Patent Agent,
Newcastle-upon-Tyne.
THOMAS WILSON.