STANDARD - Survey Instrument Antique Center!

207
The Berger Tunnel Tripod
Patented
\vitli Centering: ami Aligning Device for moving Transit with three leveling screws
under ov above a given point or onto a given line see cut of No. 1O b.
The above tripod has been designed to facilitate the placing of our Transits with three
leveling screws in the axis of a tunnel or onto a given line of sight. 1-or this reason, in addition
to our centering device, a lateral motion lias been provided, which allows the Transit to be moved
with ease and precision and without disturbing the position of the level bubbles mentioned in describing
the Lateral Adjuster for transits with FOUR leveling screws, page 205.
This centering and aligning device is very simple to manipulate, but increases the weight of
the tripod-head, particularly when the latter is wholly made of brass Thus the tripod-head for si/e
No. 1 and No. 11 Transits is heavier by about 2% to 3 Ibs., that for No. 2 about 2 to 2% Ibs., and
for No. 4 about \ l/2 to 2 Ibs., and in the case of No. 1O and 12 about 5 Ibs.
TO USE. First place the uppermost triangular shifting piece, upon which the instrument
rests, in the center of its motion, which is indicated by equal spaces all around it, and also place
the lateral adjuster, which is the lower slide, in the center of its range, indicated by two small
projections on the tripod head and S!OAV motion piece of the lateral adjuster.
Then place the tripod head in such a position that the motion of the Lateral Adjuster is
about at right angles to the line of sight; after which level up, and center over or below the given
point; then clamp the large winged central nut in the usual manner and apply a slight pressure
by turning milled headed nut which acts against the spring of the instrument fastener. The instrument
is now ready for angle work.
TO USE THE LATERAL ADJUSTER FOR ALIGNMENT. Clamp the milled
headed screAV on top, bearing in mind that, in order to enable the feed screw to move the instrument
during this lateral motion, loth the large iringed central clamping nut on top of tripod and fastener
spring below must first, be released.
'Inasmuch as the pitch of the feed screw corresponds to tenths of a foot, each motion of a
tooth of the star indicating wheel corresponds to a thousandth of a foot. Thus it will be seen that
if the pointing of the telescope on a distant scale requires the instrument to be moved I/ 1000th or
5/1000ths of a foot, as the case may be, that the manipulator turns 1 or 5 teeth around the index
mark and the object will be attained. When the line of sight of the telescope is in the given line
in the tunnel then slightly clamp the large winged central clamping nut on toi> of tripod and a^ain slightly
apply the .spring of the instrument fastener.
If in the course of operations the line of sight must be moved laterally, then the central
clamping nut and spring nut must again be first slightly released from the shifting piece before
any lateral motion should be attempted.
To use the tripod head as a trivet, unscrew the extension legs and screw the three 4-inch iron
legs in the places assigned them. It can then be used on brackets or any other special device
rigged up to receive it in the axis of the tunnel.
To obviate the removing of the legs so that attachment can he used as a trivet, a special
tripod head, having centering and lateral adjuster devices, but without wooden legs, may be ordered.
This extra head complete would have the three 4-inch iron legs heretofore mentioned.
After the Lateral Adjuster has been used, before putting it away, it will be well to clean it,
placing the triangular shifting piece, as well as the lower slow motion slide of the Lateral Adjuster,
again in a normal position, and then clamp both by the central clamping nut and small
knurled nut.
The tripod is made with fine mechanical nicety and should be well taken care of in order to
preserve it in good condition.
This device (for instruments with THREE leveling screws only) is made in four sizes as
follows :
For Transits No. 1, 5 and 11, .... Code Name Topoltuni
" Transits No. 2, 3 and " "
(>,.... Topomara
" Transit No. 4 "
Toponia
" Transits No. 1O and 12 Toposmus
The price of this lateral adjuster over the regular centering device furnished with our transit
tripods will be given upon application.