Engine 
Graduation. 
Account of 
Ramsden’s 
straight line 
engine, 
358 
drawn on it, or on any instrument fastened on the plate, 
with the greatest accuracy, by .a point or tracer fixed 
in’a proper frame, whereby it has a rectilinear motion, 
without any lateral shake.) >: “iy wt 
Sometimes it may be necessary ‘to lay down lines:on 
instruments which are not commensurable with English 
inches ; such as-are the feet, inches, &c. of most other 
countries: this is done by inclining the line to be di- 
vided to make an angle with the direction’ of motion 
of the plate, by an apparatus to be described hereafter; 
if the tracer be set to draw lines at right angles to the 
direction of motion, or to the side of the plate, then 
the line to be divided will ‘be as much longer than the 
space the plate has moved; as the secant of the angle 
of inclination is longer than the*radius; but if the tracer 
be set to draw’ lines at right angles to the line to be di- 
vided, then divisions on that line will be shorter than 
the space the plate has moved along the iron frame, as 
much as the cosine of the angle of inclination is short- 
er than the radius. 2 . . 
PLATE 
CCLXXxX, 
Figs. 1—5. 
Fig. 1. 
Fig. 5. 
Fig. 1, 
Fig. 1. Represents a plan of the dividing engine. 
Fig. 2. An elevation. b 10 Oty 48 
Fig. 3. A seetion on the line AB. 
Fig. 4. A section on the line DE. 
Fig. 5. The underside of the plate A, represented in 
Fig. 1. 
"Note: Like parts are marked with the same letter in 
each of the Figures. : 
A represents a strong brass plate, 27 inches long, 
four inches broad, and.,7ths of an inch thick ; work- 
ed exceeding flat,.and of the ‘same thickness through- 
out, with its two edges exactly parallel. 
B is. a strong iron frame, 48 inches long, ‘having two 
edges a, 4 rising half an inch above its ‘surface; these 
two edges ate made very straight, and in’ the same 
plane; the inside of the edge a is also made as straight 
as possible. Atp9 
The plate A slides on the two edges’ of the iron 
frame ; beneath it are two springs °c, c, each fastened at 
the extreme ends to the. plate A by the screws’ s; at 
the other end of each spring isa roller ¢ of tempered 
steel, turning on an axis inthese springs ; there'is also’a 
third roller d of tempered ‘steel, ‘let into the iron frame 
near where the threads of the endless screw: act; this 
roller hath a long axis, one end turning in the iron 
frame at g, and the other in the lever #; this lever 
turns on a centre at 3, and with it the roller d’may be 
raised or depressed, by turning the capstan-head) screw 
o, which presses on a strong spring. ~ 
The use of the rollers is to diminish the friction of 
the plate A, when moving’ on the iron frame B: for 
this purpose, the strength of the springs is regulated’ by 
turnmg the two screws ”, 7, and of the roller d by the 
eapstan-head screw 9, till the weight of the plate A be 
very nearly carried on these rollers. 
C is the endless screw, which is of tempered steel, 
and has its pivots formed in the shape of two frustums 
of cones joining each other at their smaller end by a 
cylinder, as shewn in the description of the circular 
engine, p. 5, Plate III. of that work. These pivots 
turn in half holes of the same form in the pieces of 
brass DD, which are’ firmly ‘screwed to the iron frame ; 
the half’ holes’ are ‘kept ‘together by the screws m, m, 
which may be tightened at any ‘time to prevent the 
endless screw from shaking. 
On one end of the screw arbour is a wheel h, having 
its circumference divided into 50 parts, and numbered 
at every tenth division with 1, 2, to 5; and these divi- 
sions are again subdivided into five parts by the vernier?. 
GRADUATLON 
‘plate E may: 
Pp 3 
2 On 
_.G, G.represent two frames of steel ; each of these 
frames turn on centres K, fastened to the under-side Gt 
of the plate A, -andbequi-distant from. the» of it. 
In each frame is a roller y.of tempered steel, turned [Req 
very concentric to their pivots,:and ¢ “of the samé an 
diameter.) ,(uxls so! iccze nd ,oderalioie allt, avtivesifias, engl 
. The trames G, G are connected bask Pu 
plate E, which turns;on a stud:in frame; the studs C& 
must be at equal distances from the centres K. ; 
the frames turn, and the distance between the holes in 
the plate E in which: the studs act, must be the same 
with the distance between: the: centres: &, so that the 
the rollers may be always equidistant 
from that edge of ithe plate:A; which is in 
-ratched.. This | to’ press the edge of 
the plate A, with a motion parallel to itself, against'the 
threads of the: endless screw. logge. Quire gl 
the’ and ef"Ehevplate uslishaen 
steel, which acts as a bent lever.» 
‘spring. 
. this lever has'a ketch, which. under the head of 
the stud I, that is on the end of the connecting piece E. 
ee eee the lever is pressed gradually 
down towards the plate A, by turning the finger screw 
F, the connecting piece E is drawn forw: so that 
Pea rp. EN MLS. 
ro may force the side of the plate against the end- 
ess screw. t i svoule t) Ii aa UG 60 
_. Then having two screws of témpered steel:exactly 
of the same diameter and number. of thréads, ‘viz. 20 
in an inch, one of these screws was notched across the 
threads, so as to cut in the mantier of a’saw ; this screw 
was put in the half holes in the pieces D, D; on the 
opposite end of the sctew. arbor ‘to that whereon the * 
wheel is, there is attached .a long rod, of such length, 
_ that the winch on the end of: it, by which the rod and 
endless screw are ‘turned round, may be clear of: the 
‘dren framevodin4 slatsgairiucd : bus vowirev 
i Dhisva’ narrow slip: of brass, having its 
1 . r 
, ne is serewed.on the plate A, and e 
, : £; ‘ » tasatide 
iP isiedge of this slip is parallel to the edge of the 
A; a distance of 25.6 inches was set»off on :a 
ine on the slip parallel to: its edge ; this ‘distance was 
bisected continually, till the distance between each bi- 
section was {ths of an inch. 2.08 ten balsesitod 
A brass cock was fastened to the iron’ frame, which 
passing over the endless screw, applied itself to the 
slip on the brass plate A, a small silver wire was stretch- 
ed across a héle of half an inch diameter in the end of 
the cock. The coincidence of the bisections with this 
wire was examined by’a small magnifier ina brass'tube 
fixed exactly over it, © 9) 0m) > velit aa 
The plate A being on the iron frame, the’ bisection 
marked I, towards the right-hand, was set to coincide 
with the wire, and the division. numbered 50 on the 
wheel, was set to the first division onthe nonius.. . 
The plate A was then pressed! against. the endless 
screw, by turning the finger screw F ; then, by means 
of the winch, the endless serew was turned towards 
the left sixteen revolutions, till the bisection marked 0, 
was brought to the wire ; this done, the plate was de- 
tached from the endless screw, by unturning the finger 
screw F, and the division numbered 2 was set to coin- 
hoe SEA 
- 
cide with the wire, the division 50.on the wheel being 
previously set to its index, and the edgeof the plate 
was pressed against the screw by the 1 
screw F ; then, by means of the winch, the endless 
screw was again turned ‘round jits axis 16 revolutions 
a 14 ; 
t 
. 
Fig. 1 
