Victoria University Antarctic Research Expedition Science and Logistics Reports 1980-81: VUWAE 25
Three 4-stroke Snotric motor toboggans (NZARP Nos. 039, 038 and 016 - a single geared older machine) were used on the sea ice in McMurdo Sound by Event 14. Sno Trac 35 primarily assigned to the Lands & Survey surveyors (K3) was also used for a time by this event. From 26 November to 3 December Snotric 016 and Sno Trac 35 were used off Butter Point by the seismic survey party (Dibble and lies), while the remainder of K14 continued the sediment sampling programme in New Harbour with snotric's 039 and 038. For each vehicle a summary of the mechanical problems, repairs and regular maintenance executed page 39 by K14 are presented below. A Vehicle Itinerary is presented in Appendix V.
During the sea ice sampling programme the helicopter hours used, arranged on an opportunity basis, were mainly for fuel and parts resupply. A helicopter was scheduled for K14's move to Mt. Crean (Lashly Mts.) on 11 December; the return to Scott Base executed on 16 December.
Snotric 016: Carburettor gasket replaced after spraying petrol from faulty gasket (21 October).
Nearly one litre of oil added to crankcase (30 October), burning quite a lot of oil (estimated 1 litre per 100km).
The carburettor air intake disk was lost and replaced with a camera lens cap during the trip to Butter Point (7 November). The head manifold [unclear: of] sheared off (11 November). A new elbow and carburettor disk were fitted after being flown from Scott Base (12 November), the air filter wired on and 0.5 litres of oil added to crankcase. This finished the one litre synarctic oil field pack with no likelihood of receiving more from Scott Base which had also run out.
The spring anchorage bolt on the front ski sheared and was replaced near Cape Chocolate (14 November).
The front ski quide rail was rewelded and turned 180° (cf. 039), a new spark plug fitted and 1 litre of oil put into the crankcase at Scott Base (17 and 18 November). Also the small inadequate manifold guard was removed and replaced by a larger version which was wired on. This was done to stop the burning of holes in the operator's clothing. The wired-on air filter cover was completely removed during this period of maintenance.
On 21 November the trip from Scott Base to Butter Point was aborted because 016 broke down 20km from McMurdo Station. It could be started by blowing into the tank to get fuel into the fuel pump but would die again almost immediately. The pump and carburettor were removed and the party returned to Scott with 037 and 038 which ran very well with only two passengers.
A new fuel pump and cleaned carburettor were fitted. Fuel was now found to be varporising in the carburettor after a kilometer or so when the engine became warm. The cowling vents were removed to give better air circulation. 016 ran continuously thereafter but readjusting the carburettor did not regain the power the machine had earlier in the season when temperatures were cooler.
During the seismic programme one of the sprocket wheels on the rear axle sheared from the axle destroying a rear bearing assembly. A spare rear axle and bearing assembly were fitted. During this period the petrol tank was accidentally run dry. After refilling the machine would not start until the sump was filled with oil to give sufficient impulse for the petrol pump to operate. The front ski guide rail also sheared again leaving 016 without good steerage on the return to Scott (4 December).
Snotric 039: On 22 October this toboggan refused to start when returning to page 40 Scott Base from the desalinisation plant at McMurdo. A small spark was being generated but the engine did not fire when primed with raw petrol or ether. The machine was towed back to Scott where the condenser was replaced next day. A new fuel pump was fitted at the same time. The two air filter brackets broke as on 038 when returning from Evans to Scott (28-29 October).
All three machines were topped up with oil at Scott Base (30 October) and air filter brackets rewelded.
Oil topped up, 0.25 litres (12 November).
Air filter brackets broke again and manifold broke letting exhaust gas escape (warm knee), similar to 016 (15 November). Major repairs at Scott (17-18 November). New manifold made up (no spares at Scott). New single air filter brackets were made by bending strap steel (1" × 3/16") 270° around the filter pipe and welding, then bolting the bracket to the head with two head bolts. Brackets were made for both 039 and 038. The broken front ski guide rail was rewelded, turned 180° and refitted to the ski. New spark plug fitted and 0.5 litres of oil added to the gearbox. A new variator drive belt fitted (26 November) manifold broken once again (27 November). A new manifold fitting made up at Scott Base was fitted the next day (28 November). Oil topped up also and plug checked.
This machine then ran well up until 6 December when it was relinquished to K2.
Snotric 038: During the trip from Scott Base to Evans (24 October) the two brackets (1/2" × 1/8" steel) attaching the air-filter to the engine block snapped. The filter was then wired to the engine block but failed within five minutes of travelling. The fuel tank was accidentally run dry from Evans to Royds. Great difficulty was experienced to restart the engine (0.5 hour) and afterwards all machines were topped up regularly to prevent running dry.
Oil topped up and air filter brackets repaired (30 October) at Scott Base. In the field this machine had already become difficult to start, however, it was found to start better in the warmth of the Scott Base garage.
Oil topped up, 0.25 litres (12 November).
Snotric 038 had become increasingly hard to start (10-20 minutes pulling was not uncommon) cold and was also difficult to start hot, requiring ether on several occasions when hot. The machine was adjusted to run warm and once started did run reasonably well.
Air filter brackets broke once again when returning to Scott (15 November) and the spark plug was replaced making the cold starting slightly easier.
At Scott Base (17-18 November) the new airfilter strap was fitted (cf. 039), fuel pump replaced and the fuel line from the tank refitted to stop a primer bulb leak. Topped up crankcase (0.25 litres) and gearbox (0.5 litres) with oil. The new plug and fuel pump made cold starting considerably easier, although the temperatures were much milder than in October. Regular maintenance; oil, plug checked and a new variator drive belt fitted on 28 November. This machine also continued to run well for the remaining time in the field.page 41
Sno Trac 35: Prior to 25 November four new bogies had been fitted to 35. Two of these new bogies from the front right bogey assembly subsequently broke and were replaced enroute to Butter Point (25 November).
A steering clutch splined shaft was stripped during the seismic survey programme. The Scott Base Mechanic (Bruce Scott) flew to Butter Point where he replaced the steering clutch assembly on the sea ice.
Two further bogies were broken on the return to Scott Base from Butter Point (4 December).
General Summary: The three toboggans were in good condition when they were handed over to K14 on 14 October. This was due to the work done in early October by Nevil Clark and Bruce Scott (Base Mechanic). The assistance both these people gave to this event especially when initially testing the toboggans and then later in the season, was invaluable.
Nearly 1,000 kilometres were travelled by all three toboggans on relatively smooth often bare hard sea ice. The hard conditions were probably responsible for only some of the damage incurred, particularly the sheared axle (016) and steering ski guide rail breakages (016, 039). The other damage and mechanical failures which occurred were related primarily to the Briggs and Stratton engine. The vibration from these engines were responsible for the failure of the air filter fittings (once 016, twice 039, twice 038). This recurrent problem was only solved by building an extremely heavy fitting fastened by two head bolts but attached from only one place on the head. This prevented any opposing vibration which may have caused the two bracket mounting to fail. Manifold failure occurred on three separate occasions and can also be attributed to the engine vibration. The right angle elbow on 016 vibrated sufficiently to distort the male thread entering the block, eventually causing it to shear off. The manifold on 039; a threaded nipple pipe welded to a flange broke twice, in one case leaving part of the sheared nipple pipe in the exhaust port.
The carburettor was adjusted to give the best performance when running warm (after about 1/4 hour from a cold start early in the season). The idling speed was adjusted to prevent the machine stalling even when hot but meant the idling speed was too high for the Salisbury clutch to disengage when changing gears. However, by turning off the engine, changing gears then quickly turning on the engine it was possible to change gears relatively smoothly.
It was always necessary to have at least 2 metres of "slack rope" before being able to start moving a heavy sledge (=900 lbs) on the flat ice. Snow cover or a slight upward gradient made things even more difficult. The Briggs and Stratton engines have a particularly slow pick up so they were developing less than half revs by the time load came on the sledge. At these revs less than 10 BHP was being produced. If the sledge didn't move the moderate torque caused "track spin" and the toboggan "dug in" and made the situation more difficult. The rope starter makes starting these big engines even more difficult. Even when the engine was warm some of the event members could not start the machines consistently.page 42
Sno Trac 35 seems to specialise in destroying bogey wheels. These were all broken when travelling between 10 and 15km per hour on dead flat smooth bare sea ice, for distances of about 30km. The front bogey assemblies accounted for all the broken bogies which were found to be very hot at the time of breaking. This indicates that they were doing a lot more work than the absolutely cold bogies further aft.
Two dog sledges (B5 and B7) and a Tamworth (T1) were used initially to Cape Evans. The dog Sledges which did not have keels were replaced by a new Tamworth (T3) and a double-ended Nansen with keels (B4 on 1 November. The keeled sledge towed significantly straighter on hard snow than the previous dog sledges but was just as difficult to control on bare ice as the non-keeled sledges.
Loading: Both Tamworth sledges carried between 800 and 900 lbs for most of the time. This was probably too much for these sledges on bare sea ice, which is far more rigorous than snow. The alternative to distribute the load on tandam sledges was however impractical because; of the much greater difficulty to negotiate rough ice with two sledges, the limited manpower of our event, and the towing capabilities of the toboggans was often not sufficient to tow two moderately heavy sledges.
B4 was loaded to about 600 lb which was a suitable weight for sea ice conditions. The keels however may have been more effective if located further aft especially when close towing on bare ice.
Damage: T1 is an old sledge with non-laminated steamed timber bridges, and already had two cracked bridges on 15 October. The cracks became enlarged and the remaining bridges cracked during the programme. Hose clips provided a very satisfactory repair for the cracked bridges in the field.
T3 is a new laminated sledge which proved very satisfactory. No bridges were cracked but the laminated runners suffered some damage. Delamination occurred on both runners at all ends where the bridges are housed into the runners. This damage seemed to be a result of the design and could be prevented if the top lamination, which houses the bridges, were laminated further into the curve of the runners.
The proud lashing (thong leather) on the Tamworth sledges became worn from the movement of poorly-fitting sledge tanks. The lashings were replaced without much difficulty in the field.
Broken bridges, especially on an old sledge, worn lashings and towing bridles are all damages which should be expected as normal "wear and tear" in a season. The sea ice even though excellent travelling this season is extremely hard on this type of equipment.
B. MAIN AREAS COVERED
The bottom sampline programme undertaken by Event 14 required several traverses across the sea ice in McMurdo Sound. The areas of interest were from page 43 Scott Base to Cape Royds, across to Butter Point and in New Harbour and south to Cape Chocolate. A more detailed account is presented in the Itinerary (Appendix IV).
Difficult weather conditions restricted the Event 14 programme early in the season (25-29 October) when several southerly storms caused intermittent blizzard conditions in the McMurdo Sound area. Four days were spent tentbound during this period. "Normal" weather conditions for McMurdo Sound prevailed later in the season during the major period of the field programme. A summary of weather observations is presented in Appendix VI.
DSIR Compak SSB radios were used for field communications and worked satisfactorily. During the seismic programme two Compaks were used on a free channel (4700 KHz) between the recording station and shot firing point. The radios were also used to record the shot instant on the recording (see Appendix IF).
E. LOSS/DAMAGE TO EQUIPMENT
The major damage occurred to toboggans and sledges; detailed in the Transport section.
No equipment was lost or damaged. However, the sphincter corer, which was an important part of the operation, did not perform satisfactorily.
The sphincter corer was designed to take a shallow (=300mm long) large diameter (=200mm) minimally disturbed core and retain the sea floor sediment-water interface intact. The main feature of the corer is a cloth sleeve (sphincter) which cuts the sediment in situ and retains the core with a nearly water-tight seal.
Two major types of problems were encountered when operating the corer. A lack of penetration was evident in some areas of the Sound where the sea floor was stoney, e.g. near Ross Island. Thick sponge mat in some areas also contributed to poor corer penetration. Extra lead weights and a short barrel option will be used to overcome the penetration problem.
The second problem was that caused by freezing sea water in the trigger mechanism. This mechanism consisted of a main pin into which was hooked a sprung detent pin. Both pins were greased and enclosed in a close-fitting steel housing. Sea water on freezing ejects brine and forms "fresh water" ice. This ice does not melt in the sea water, which has a temperature of −1.9°C. Because the trigger was enclosed, ice was not flushed out as the corer descended to the bottom. The problem should be solved by opening out the trigger so that it will be self-draining, and can be flushed either in the sea or with alcohol.
In general the other scientific equipment performed well, particularly the winch. The salinity-temperature bridge was difficult to use in the open page 44 where it was impossible to keep unfrozen the water standards used for calibration of the instrument.