made to reinforce this area, but failure continued.
This assembly has only one sliding tube, which
The snowblower extension frame was modified
extends 2 m. The normal back and forth move-
slightly to increase ground clearance and reduce
ments of the tunneler are thus translated to the
an interference problem. A cutter blade was added
lighter, more flexible pup truck.
to the front of the snowblower to improve snow
A team of four CRREL engineers and techni-
removal from the floor, and side wing extensions
cians arrived at the AmundsenScott Station on
added to prevent machined snow from passing
15 November 1996 to resume the tunneling effort.
by the sides of the snowblower.
Foul weather, which led to a late opening of the
A 30-kW motor with the correct frame size was
summer season at the Pole, hampered the initial
shipped from McMurdo to the Pole and installed
work planned for arrival. The equipment was de-
on the fan. The equipment was redeployed in the
ployed and modifications to the tunneler were
trench, and tunneling recommenced. Unfortu-
begun with what was available from our cargo and
nately, within two hours, one of the electrohydrau-
on site.
lic pump shafts failed and the equipment was
The cutter drum was reconfigured to allow
down once again. On-site attempts to repair the
more even loading of the teeth during the cutting
shaft were unsuccessful, and after several attempts
process. The cutter arms were rotated such that a
to rectify a seal leakage problem, the operation was
line of cutters, symmetrical about the center chain
terminated. While waiting for the pump shaft to
drive where possible, engages the tunnel face ev-
ery 45 rotational increment. The engaged length
be repaired, the tunneler was returned to the shop
at the Pole and the flexible hose elbow reinforced
is either 41 or 43 cm. This is an improvement over
with angle iron to form a fixed elbow. The ejector
the 10-cm spread in the engaged length on the
tube was modified to allow sliding extension when
original drum configuration and allows smoother
the snowblower was extended. The system, tested
system operation. In addition, the drum drive
with these modifications under diesel power, was
sprocket was replaced with a 21-tooth sprocket,
a vast improvement over the old system. Final
increasing available torque almost 10%. The chain
progress on the tunnel was 7.5 m, about the length
also needed replacement, as the installed chain had
of the tunneler.
galled and no longer flexed freely.
Although somewhat disappointing, the Antarc-
The tunneler tracks were tightened and the
tic trip was very valuable. Important modifications
cleats removed, making travel with the tunneler
to the equipment were made, and operating ex-
much smoother. The roughness of the travel on
perience pointed to several other areas that could
the hard firn and surface snow of the Pole had re-
be improved. Further simplification of the hydrau-
sulted in the failure of some components, most
lics needed to be made, and the source of much of
notably the shoulder bolts and piston rod exten-
the excess heat generation found and rectified: a
sion on the snowblower lift mechanism. An ad-
faulty pressure relief valve for the drum circuit was
justable choke was fabricated and installed on the
not allowing oil to bypass when the drum stalled
impeller opening of the snowblower to limit the
during cutting. Further analysis of the broken
flow of snow into the chip-removal system in an
pump shaft at CRREL and by an independent
attempt to reduce stress on the centrifugal fan mo-
metallurgist could not definitively determine the
tor. The broken hydraulic pump was replaced,
cause of pump failure, but fracture patterns on the
along with the faulty drum pressure relief valve,
shaft indicated the failure mechanism was likely
pump heater coils were installed beneath both tan-
high startup torque.
dem hydraulic pumps, and some of the other
modifications were implemented to simplify the
Operational deployment (199697 season)
Over the course of the summer following the
Testing of the system was conducted on 21
initial deployment, the tunneling system had been
November. The cutter drum worked much more
reexamined and the hydraulics simplified to im-
evenly than during the previous deployment, but
prove reliability. A new ejector chute for the front
the choke seemed to have little effect on the blower
end of the tunneler was designed and manufac-
motor performance. The 30-kW motor was
tured to replace the flexible tube that had been so
switched out for a 37-kW motor. The tunnel ac-
problematic in January. To reduce stress on the
cess trench was completed during the test phase,
system of expanding tubes used for chip transfer,
and the area at the bottom of the trench was pre-
a short duct/truck assembly, called a pup truck,
pared for equipment deployment. At this time, the
was designed for use directly behind the tunneler.
final shipment of cargo arrived and the remain-
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