This season for the sea ice work K5 was allocated the D4 bulldozer which towed 2 "cantago" sledges (carrying Wannigan, equipment and fuel). 2 Snotric toboggans 037 and 036 (later replaced by 039) and two Tamworth sledges.

D4 Bulldozer.

The D4 was initially used this season for the fuel train and Vanda resupply to Marble Pt, and developed a fuel tank leak during this time. After returning to Scott Base the fuel tank was repaired, and the D4 given a general check and oil change by the Army Plant Operators and Malcolm McLeod before it was used by K5.

The only major problem with the D4 was the recurrence of the fuel tank leak in Granite Harbour. An attempt to replace the tank with a 44 gallon drum was not completely successful as vibration eventually sheared off the drum fittings and we reverted to the original tank. Over 4 gal/8 hours of DFA was collected from the leaking tank, while the D4 was stationary and idling. This contaminated fuel was used in the Wannigan heater.

Snotric Toboggans.

SM 037. This toboggan gave few problems in the field. Four bogey springs were replaced during normal use. A complete bogey assembly was damaged when the allen cap screw came out of the bogey axle. This was attributed to a page 39 faulty star washer and the bogey assembly was replaced. The Halda Twinmaster odometer was eadily fitted to the toboggan but was occasionally knocked because it could only be mounted in an exposed position.

The toboggan had a partial dunking in a frozen tide crack near the Mackay Glacier Tongue. Salt water entered the gear-box but was quickly removed by three successive oil changes and no starting problems occurred.

SM 036 was used for 3.5 weeks during which time only 4 bogey springs were replaced. While returning to camp down the New Glacier, the steering shaft sheared off where it attaches to the front ski. The remaining 7km to camp was negotiated with a person sitting on the front and steering with a length of rope and his feet. This toboggan was airlifted to Scott Base and replaced by SM 039.

SM 039 was airlifted from the lower Victoria Glacier, where it had been used by K1, to our camp in Granite Harbour. When it arrived we found the rubber sprockets on the right rear axle to be badly damaged and replaced the complete axle with our only spare. This machine was burning over 1/2 litre of oil per day unlike SM 037 and SM 036 which required only a small top up each week.

The engine on this machine "blew up" while carrying out critical seismic shots off Butter Pt. Piston, con rod and bearing were fragmented into several pieces. The engine was replaced with a new engine by the Scott Base mechanics while at the Blue Glacier five days later. The steering shaft also broke on 039 in the same manner as 036. On this occasion it occurred at a less critical time on flat sea ice one day before our scheduled return to Scott Base.

The distances travelled with each toboggan are listed below:

Sledges.

This is the second season that Cantago sledges have been used on sea ice. On hard multiyear ice and bare firstyear ice the sledges tended to crab sideways which was partly due to a bent and therefore off-centre draw bar. The absence of any chain tensioning devices meant that this could not be corrected in the field. It became evident that loading is crucial to the sledges' performance because of the flexible deck but unfortunately it is not always possible to redistribute the loads daily. Modification of the skis to increase the surface area and rocker forward and aft is still necessary for rough ice and soft snow. Without these sledges however it would not have been possible to carry out our successful sea ice programme of the last two seasons.

The Tamworth sledges towed by toboggans were used to ferry our heavy sampling equipment on the sea ice near the Mackay Glacier Tongue and people on New Glacier. The older sledge fitted with keels was easily controlled and used on New Glacier requiring rope brakes only on parts of the downward journey. A new sledge without keels was extremely difficult to control fishtailing badly on sea ice. All the laminated bridges along the left side were cracked after work in Granite Harbour although the sledge was never rolled with a load on. How this occurred is still puzzling but it is most likely that a sideswipe with a heavy load (800 lb) may have caused the cracks. A new type of longer keel should be considered for Tamworth sledges which permanently protrudes under the ski and does not require a slot cut in the ski like the present adjustable keels.

Helicopters.

All 7 allocated helo hours were used this season. The sea ice reconnaissance to Granite Harbour and erecting beacons in New Harbour used 4.5 hours flying time and 1.5 hours ground time. The remaining 2.5 hours was used transferring 036 and 039 toboggans and flying urgently needed parts and surveyor to Granite Harbour.