(a) Toboggans. Event 12/12A

This event used two snowtric toboggans (NZARP Nos. 16 and 17), powered by Briggs and Stratton 16 h.p. 4 stroke motors. No. 17 had lost its engine cowling during the winter but a new, strong wooden one was made by the carpenter, Doc Livingstone. This cowling survived the trip's knocks well. A new petrol pump on the same toboggan had been incorrectly fitted but once this was established the problem was easily rectified. On the field trial it was impossible to start No. 16 after a night of − 40°C temperatures, although this toboggan usually started easily in temperatures of − 25° and warmer. A petrol burning preheater was subsequently fitted on to the air inlet manifold by the engineer, Jim Rankin, and worked well on the two or three occasions it was needed. Toboggan 17 was more difficult to start in − 25° temperatures and a gravity feed system bypassing the fuel pump was used on a few occasions to start it. Generally, however, the petrol pumps worked entirely satisfactorily in temperatures warmer than − 25° and few starting problems were experienced. The pullcord starting system adopted since 1975 is simple and effective once the operator learns the toboggan's starting characteristics.

The engines on the toboggan generally ran well and carburettor and manifold problems with No. 16 gave the only engine trouble. However mechanical breakdowns occurred on several occasions. These were due to fatigue and the rough terrain, accentuated by the occasional pulling of heavy loads necessitated by time restrictions due to bad weather and a full programme. Incomplete checking and replacement of worn parts by the party prior to leaving Scott Base had its repercussions in the field although the snowtric is fairly easy to work on. Adequate time should be allowed to thoroughly check toboggans, especially swinging arms and brackets, drive sprockets, tracks, and suspension and ski springs and assemblies. Assurances from base staff that "the toboggans (etc.) are in Al condition" should not be taken for granted, nor allowed to lessen the priority of thoroughly checking them. Complete sets of tools and spares should be taken for each toboggan. To the spare parts list for snowtrics in the toboggan manual issued by Antarctic Division, should be added the following: leaf spring for front ski and at least four oil seals and bearings. A good supply of nuts, bolts and washers (compatible with the toboggan, especially the ski assembly), small amounts of metal sheeting, lengths of wire, and rubber tubing, all of various sizes, should be taken.

The new engine mounting system, installed since 1975, is excellent and no problems were experienced with it. Both machines had previously been fitted with ice cleats which were essential since most of the surface of Taylor Glacier is bare ice. The steering of snowtrics is greatly improved, especially on hard ice, when the worn guide rib on the underside of the ski is replaced. Windscreens for both toboggans were made before leaving Scott Base. Simple braces greatly strengthened these, and they survived the field season virtually intact.

It was decided early in the expedition to use sledges as much as possible and not ride two up on the toboggans. The latter practice has been shown (Curphey, 1975) to overload the toboggan causing undue wear and subsequent breakage of the suspension springs. We broke no suspension springs.

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Toboggan covers were used on both toboggans. However they could not be tied down adequately to prevent snow getting into the engine compartment during blizzards. Nevertheless on the one occasion when this was a real problem, snow blown and compacted under the track and around the idler wheels was more of a problem since the cover probably kept some snow out of the engine compartment.

The towing power of these snowtric toboggans seems to have been under-estimated, especially on bare ice. In this situation the reduction in friction between sledge runner and ice more than compensates for the reduced traction of the toboggan. Sledge loads of up to 1000 lbs were easily towed by each toboggan on the glacier even up gentle inclines, without flogging. Heavier loads up to 1500 lbs were occasionally pulled when the situation demanded but this was seldom. Relaying was necessary for loads greater than 800 to 1000 lbs on the steeper sections of the glacier routes. Toboggan 17 performed well at altitude (up to 2720 m on Mt. Morning) and pulled 800 lbs comfortably up gentle tacks on snow and sastrugi. Such weights can be pulled without fear of axle (etc.) failure if the machines are kept in good condition.

Toboggan manuals were kept up to date, listing breakdowns and repairs. This has not always been done in the past. The following lists contain breakdowns etc. on the two toboggans used by Event 12/12A.

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(b) Sledges

The two events required the use of three sledges each. Due to some minor accidents in the spring, dog sledges were at a premium early in the season. However with the assistance of various people, the sledges were prepared. Foot brakes were made, some tufnol replaced and some lashings repaired.

Event 12/12A used one dog sledge with keels, one combination sledge with keels and brakes and one manhauler with neither keels nor brake. The bare ice was too hard early in the season for the keels and they were seldom used at all on the glacier, even on the descents. However the descents off Mts. Morning and Discovery would have been extremely difficult without them. Foot brakes are a very useful addition. The sledges handled the hard ice conditions admirably, and little damage occurred. For details of these see Loss and Damage to Field Equipment, FIELD NOTES, Section E. The orange whistles used were excellent for sledge to toboggan communications.

(c) As in recent seasons air transport in the field was provided by the US Navy using twin turbine UHI-N helicopters. No problems were experienced. The windscreens on the snowtric toboggans had to be removed prior to loading and the removal of skis gave more room inside the cabin. Care must be taken when loading sledges on to the helo skids. They must be lashed so that when the aircraft lands and the skids flex, projections on the body of the helo do not push down on to the wedged sledge. Firm but not over-tight lashings will allow some movement of the sledge. On at least three occasions the Americans made unexpected and much appreciated mail deliveries. For details of helo use see Appendix 1.