RANGING CIRCULAR CURVES
Year: 1886

page_text: HARLEY HUGH DALRYMPLE-HAY Engineers Office, London & South Western Ry.
Bishopstoke, Civil Engineer, do hereby declare the nature of my invention for
RANGING CIRCULAR CURVES, to be as follows:-
A disc or wheel capable of moving along & also of being clamped to a graduated
bar is made to revolve on a plate with which it is in contact by turning a shaft
thro which the bar passes-A graduated dial is fixed to the shaft and that end of
the bar that passes thro the shaft also passes thro the dial-An index arm fixed to
this end of the bar revolves when the disc or wheel is made to develope its
circumference on the plate the index arm then makes one complete revolution-
The opposite end of the graduated bar is supported by a bracket fixed to the shaft.
A telescope surmounts the shaft-There are various clamps & slow motion screws
& the instrument is fitted to parallel plates fixed on a tripod stand.

page_text: An Improved Instrument for Ranging Circular Curves.
I, HARLEY HUGH DALRYMPLE-HAY Engineers Office, London & South Western Ry.
Bishopstoke, Civil Engineer do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement:-
The instrument is for laying out or ranging circular curves according to the
method suggested by Professor Rankine and now generally adopted by Engineers.
This method of laying out curves is illustrated at Diagram 1 of the drawings
hereunto annexed.
at which the curve is to commence.
In this figure let A. B be the straight portion say of a railway and B the point
Let the curve to be set out be for example a
curve of 80 chains, radius and the points D. E. F. be points on the curve at the
usual distance apart that is one chain.”
"The method of ranging the curve is as follows:-A theodolite is set up at B and
adjusted and the telescope made to point to C, the tangential angle for the first
chain of the curve is then ascertained by reference to a table of tangential angles.
By the table it will be found that the angle C. B. D. = 0°, 21', 29"-Then set
the vernier of the theodolite so that the telescope points in the direction B. D. the
instrument having been clamped to zero when first set up at B. Now measure a
chain from the plumb-bob under the theodolite to D then this distance measured
along the straight line B D. determines the first point D in the curve.
look up in table of tangential angles the angle for the second point namely the
angle C. B. E, this will be double the first angle viz 0°, 42, 58" then set the
vernier to read this angle and measure a chain from D towards E-The position
of E is then determined by the angle C. B. E. and the distance D. E. this gives the
second point E of the curve-and so on.
Now
After laying out a certain number of points in this way it is often necessary to
range a new tangent and start afresh either because of obstacles being in the way
or because another curve bending on the opposite side of the tangent is required
to be set out.
The laying out of a new tangent is effected in the following way-see
Diagram 2.
The 80 chain curve bearing to the right of first tangent having been set out say
as far as D the 10th peg from B, the last angle to which the vernier was set will
be the angle C. B. D. = 3°, 34', 52".
C. D. E. is the new tangent required.
To set out this subtract the angle 3° 34′, 52" from 360° which equals 350°, 25', 8″
the angle to which the vernier must be set when the theodolite is set up at D; the
horizontal circle is clamped when the telescope is directed to the pole at B and
the bisection of the cross hairs with this pole perfected by the tangent screw.
The telescope is then taken out of the Ys and reversed end for end. The vernier
is now set to read zero on the horizontal circle, in which position the telescope will
point along a tangent to the curve at D.

page_text: If the same curve has to be continued proceed as above; but if the curve to be
set out now bears to the left of the tangent as shown in Diagram it is then
necessary to subtract the tangential angles given in the tables from 360° and then
set the vernier to these calculated angles to obtain the tangential angles for each
peg in the left hand curve.
The object of the instrument designed by me is to do away with the use of the
curved tables altogether and with the repeated setting of the telescope by the
vernier to the required angles and to substitute therefor a mechanical means for
pointing the telescope to each successive chain.
This I do by the use of a wheel the spindle of which lies along a horizontal arm
which extends from the vertical axis above which the telescope is mounted. The
wheel can be set on the spindle at any required distance from the vertical axis→
the distance depends on the radius of the curve to be set out. The wheel is made
to rest on a horizontal plate with which it is in contact and is consequently made
to revolve whenever the vertical axis carrying the telescope is turned. The
spindle of the wheel carries an index arm in front of a dial face and enables the
angle through which the telescope will have been turned after the wheel has made
one complete revolution to be divided into any desired number of equal parts say
for example 100 parts if the fixed dial face has 100 divisions upon it-so that if
desired 100 consecutive points in a curve can be set out simply by turning the
vertical shaft upon which the telescope is mounted and making the index hand to
point in succession to each division of the dial face.
The drawing annexed shows various views of an instrument constructed in the
manner I prefer for carrying out my invention.
Figure 1 is a plan view of the instrument with some of the parts removed and
Figure 2 is a side elevation partly in section. In these figures A is a vertical axis
turning in a coned socket B. Above the socket it is forked as shown at Figure 3 to
form bearings for the trunnions of a telescope C.
Each trunnion has fixed upon it a toothed wheel D, a pinion D' gears into one
or other of these wheels so that by turning the pinion the telescope can readily be
set to any inclination required.
Standing out from the fork are projections carrying two spirit levels E at right
angles to one another for setting the spindle in a vertical position-these spirit
levels are only shown in Figure 2-another spirit level F is mounted on the
telescope for setting the telescope into a horizontal position. G is a dial fixed to
one side of the fork and H a horizontal arm extending from the opposite side.
His a spindle one end of which turns in a bearing at the centre of the dial face
and the other end in a bearing at the outer end of the arm. I is a slide capable.
of being moved to and fro along the spindle and of being clamped to it. J is a
disc or wheel fixed on this slide. The spindle is formed with a flat side and the
slide fits to it so that if the wheel be turned the spindle turns with it. The
flattened side of the spindle has a scale marked upon it as shown so that the
wheel may be fixed upon the spindle at any required distance from the vertical
axis A. K is a flat horizontal table against which the wheel J bears with
sufficient pressure to cause the wheel to roll over it whenever the arm H is moved
to one side or another. This table can be adjusted vertically by means of three
adjusting screws. W is a small milled head by which the spindle can be turned
and the needle set to any position on the dial face. L L are clamps one of which
can be made to clamp the vertical axis A and the other to clamp the exterior of
the fixed socket bearing B. One clamp carries a screw M and the other a nut N
for the screw to screw into as shown at Figure 4. This permits of a slow revolving
motion being given whenever required to the vertical axis. A. If one clamp is set
free the axis can be turned quickly-if both clamps are set free they can always
be turned into such a position that the heads of the clamp screws are accessible in
whatever position the axis may have been turned into. The flat table K is carried
by an arm which extends from a tube K¹ which can turn around the exterior of
the socket bearing B.
از

page_text: The end of the table which is towards the vertical axis A is made concentric
with it as shown at Figure 1. A divided circle is marked on the surface of the
table and by a vernier marked on a projection A¹ from the fork of the vertical
axis A the angle to which the telescope is turned can readily be read off or the
axis can readily be turned through 180°. T is a magnifying glass for reading the
Vernier. A vernier and magnifying glass may if desired be carried by each limb of
the fork as shown at Figure 1.
The table can be locked and held in any position desired by a clamp O, and
slow motion screw gear a side view and plan of these parts are shown separately
at Figures 5 and 6. The flange B¹ fixed around the exterior of the coned socket
has four screw legs P passing downwards from it the lower ends of which bear
upon a flange R¹ which extends from an inverted cup bearing R.
By these screw legs a nut S on the lower end of the vertical axis A is held
up into the cup bearing. The cup bearing is made to screw on to the top of
an ordinary tripod stand and when it is so erected on the stand the axis A can
readily be brought into a vertical position by the screw legs.
In using the instrument for ranging or setting out a curve the instrument fitted
to the tripod is erected at the point from which the curve is to commence say the
point B Diagram 1. The slide I which carries the wheel J is moved along the
spindle H¹ until it is seen by the scale on the spindle that it has been brought to
the proper distance from the vertical axis for the curve which it is required to set
out. Then make the zero marks of the divided circle and vernier on the table and
vertical axis to coincide and bring the telescope in a line with the line A B. The
index hand of the spindle H¹ must then be made to point to zero on the dial face
by the thumb screw W Figures 1 and 2.
The table must now be clamped and the vertical axis A turned by the slow
motion gear until the index hand points to the first division on the dial face the
telescope will then point along the line B D. Now measure a chain from B to D-
this determines the 1st peg in the curve. Afterwards turn the vertical axis A
until the index hand points to the next or 2nd division of the dial face the
telescope will then point along line B E and similarly set out the next point on
the curve and so on.
The method of setting out a new tangent is equally simple and is effected by a
series of easy mechanical movements. No calculation is required for setting the
instrument in its new position.
The vernier carried by the axis and the scale marked on the table enable the
telescope to be shifted with accuracy.
Supposing the new tangent to be required at the 10th peg marked D on
Diagram 2 the index hand would have been pointing to division 10 on dial.
When the instrument has been set up at D make the zeros of table and vertical
axis to coincide and direct the telescope to B also set the index hand to zero on
dial then clamp the table and turn the vertical axis until the needle indicates
division 10 on the dial the telescope will then point in the direction D. C. and
clamp the axis in this position. Now unclamp the table and turn it through 180°
and clamp it when the zero of the vernier on vertical axis coincides with 180° on
the table and when in that position release the clamp of the vertical axis and
make its zero coincide with that of the table. The telescope is now in position to
continue the curve as before-the curve may either be continued of the same
radius as before or to a different radius or it may be continued to any desired
radius inclining to the left instead of to the right.
To facilitate the graduation of the scale on the spindle it is convenient to make
the disc or wheel of a diameter of 1 inch.
The distances at which it is required to set the wheel from the vertical axis A
can be found by calculation. If for example it is required to range a curve of
80 chains and that it is also proposed that the instrument shall be capable of
setting out say 100 consecutive chains in a curve-it may be ascertained that the
tangential angle for the 100th chain of the curve is 35° 48' 39"
35°- 82.

page_text: Now the diameter of the disc of the wheel being taken as unity it follows that
the radius required will be equal to 18 = 5.03 inches.
If therefore the disc or wheel be set and clamped at 503 from the centre of
revolution it will by developing its circumference on the "table" have described
an arc = 35, 48, 39 and as the dial is divided into 100 equal divisions the
instrument is capable of dividing up this angle into one hundred equal parts.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I would have it
understood that I do not confine myself to the exact construction of instrument
shewn in the drawings hereunto annexed as the construction may be varied and
the improvements may readily be adapted to theodolites of existing form-one way
in which this can be effected is by clamping to the upper plate which carries the
telescope an arm to carry the dial G and spindle JH whilst the table K is
clamped to the upright which supports the lower plate I declare that what
I claim is :-
1. An instrument for ranging circular curves in which a telescope or other
sighting appliance is mounted on a vertical axis and in which a wheel mounted
on a radial horizontal axis so that it can be set nearer to or further from the
vertical axis is made to roll over a flat surface as the vertical axis is turned-and
in which a finger on the axis indicates on a dial face the turning of the wheel so
that the arc described by the wheel in developing its circumference on the flat
surface can be thereby divided into any desired number of equal parts.
2. The construction of instruments for ranging circular curves substantially as
hereinbefore described and illustrated in the drawing annexed.
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1
1000
CARPMAEL & Co.,
Agents for the Applicant.