Improvements in Instruments for Guiding Tunnelling Shields.
Year: 1896

page_text: Date of Application, 31st July, 1896
Complete Specification Left, 13th Oct., 1896-Accepted, 14th Nov., 1893
PROVISIONAL SPECIFICATION.
Improvements in Instruments for Guiding Tunnelling Shields.
HARLEY HUGH DALRYMPLE-HAY 20 Victoria Street Westminster Civil
Engineer do hereby declare the nature of this invention to be as follows:-
The object of my invention is to provide a simple means of guiding tunnelling
shields. This I perform in the following manner. First assuming the tunnel under
construction is to be straight. A theodolite is set up at any convenient point on the
centre line of the tunnel say 10 feet back from the shield. A line square to the
centre line is then set out from this point & marks indicating it are made on pieces
of wood fixed to each side of the tunnel. These marks I call zero marks. Two
similar scales of any desired length & made of any suitable material are then
temporarily attached to the shield at convenient points. These scales are graduated
in feet & inches or other suitable measure & extend on both sides of the zero
marks. When the shield advances the scales are drawn along with it & by observing
the zero marks on each side of the tunnel it can be seen if the shield is advancing
evenly. If however it is desired to construct the tunnel on a curve all that is
necessary is to replace one of the scales by another of such a length that calling r
the radius of the centre line of the tunnel & d the diameter of the tunnel then the
1(2r-d) where is the length of
(2r+ d)
required length of the scale will be equal to-=-
the original scale.
Improvements in Instruments for Guiding Tunnelling Shields.
HARLEY HUGH DALRYMPLE-HAY 20 Victoria Street, Westminster 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 ascertained in and by
the following statement:-
The object of my invention is to provide a simple means of guiding tunnelling
shields. This I perform in the following manner. First, assuming the tunnel under
construction is to be straight. A theodolite is set up at any convenient point on
the centre. line of the tunnel say 10 feet back from the shield. A line square to
the centre line is then set out from this point & marks indicating it are made on
pieces of wood fixed to each side of the tunnel. These marks I call zero marks.
Two similar scales of any desired length & made of any suitable material are then
temporarily attached to the shield at convenient points. These scales are graduated
in feet & inches or other suitable measure & extend on both sides of the zero
marks. When the shield advances the scales are drawn along with it & by
observing the zero marks on each side of the tunnel it can be seen if the shield is
advancing evenly. If however it is desired to construct the tunnel on a curve all
that is necessary is to replace one of the scales by another of such a length that

page_text: calling the radius of the centre line of the tunnel & d the diameter of the
tunnel, then the required length of the scale will be equal to
the length of the original scale.
1(2-d)
(2r+d)
where is
I have explained the method I prefer for setting out the positions of the zero
marks on each side of the tunnel where such is straight.
If however the tunnel is to be on a circular curve the setting out of the positions
of the zero marks is performed in the following manner.
Suppose the tunnel has been driven for a certain length on the straight & enters
on a circular curve bending to the right. Assume it has advanced some distance on
this curve & it is desired to set out the positions of new zero marks so that the line
between them may be normal to the curve & at a distance e measured on the chord
of a circle of radius r. I first calcu!...he value of the angle of deflection
formed by the chord c and the tangent the curve at its commencement & then
set up a theodolite at the springing of the curve & from it lay off to the right the
angle & measure the distance c along the chord line so laid off.
This determines a point on the centre line of the tunnel whose radius of
curvature is r. Now setting up the theodolite at this new point I look back &
direct, the telescope to the springing point of the curve, i.e. the end of the straight
portion & from it lay off an angle to the right.
$
The angle so set out determines the position of the tangent line to the curve at
the leading end of the chord c. I now set out a line at right angles to this new
tangent by turning the telescope thro' 90° right and left and make marks on pieces
of wood fixed to each side of the tunnel. The line joining these two marks is
normal to the curve at the point where it intersects the centre line of the tunnel.
Two dissimilar scales are now attached to the shield & by noting the distance on
the scales that each side of the shield is from its respective zero mark it is at
once known if the shield has been advancing evenly.
When the shield is about to be moved forward the two guide scales are attached
to it at about the level of a horizontal diameter, & when the shield advances the
reading on each scale as indicated by the zero marks should be alike. If this
be so it is at once known that the shield is moving forward correctly.
It will be apparent therefore that I can by means of these zero marks & guide
rods or scales at once determine the rectangularity of the plane of the cutting edge
of the shield with reference to the centre line of the tunnel.
At the same time it is possible by means of the guide rods or scales & the zero
marks to determine the rectangularity of the leading face of the tunnel with
reference to the centre line of the tunnel.
This I do by placing the leading end of each guide rod or scale flush with the
leading face of the tunnel & reading the distance on the divided face of the guide
rod or scale opposite the zero mark on each side.
The guide rods or scales I prefer to make of timber and about 20 feet in length
by 3 inches broad by 1 inch thick.
Each rod is attached by suitable means to the shield at about the level of a
horizontal diameter.
Having now particularly described and ascertained the nature of my said inven-
tion & in what manner the same is to be performed, 1 declare that what I
claim is :
1. An apparatus for guiding tunnelling shields in which two rods are attached to
the shield, one on each side at about the level of a horizontal diameter.
2. The graduation or division of these rods into fect & inches or other suitable
measure. If the tunnel is straight the divisions on each of the rods are similar;
but if the tunnel be curved then the divisions of the two rods are dissimilar.
3. Marking on each side of the tunnel a point somewhere in the length of the
guide rods or scales such that if the two points he joined the line between them is
at right angles to the centre line of the tunnel where such is atraight, or if the

page_text: centre line be curved then the line between the two points is normal to the curve
at the point where it intersects the centre line.
4. The means by this apparatus of determining the rectangularity of the plane
of the cutting edge of the shield or the leading face of the tunnel with reference
to the centre line of such tunnel.
Dated this 30th day of October 1896.
HARLEY HUGH DALRYMPLE-HAY.