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Tractor-Type Transportation Units for Arctic Operation: Encyclopedia Arctica 2b: Electrical and Mechanical Engineering
Stefansson, Vilhjalmur, 1879-1962

Tractor-Type Transportation Units for Arctic Operation

EA-I. (Caterpillar Tractor Co.)

TRACTOR-TYPE TRANSPORTATION UNITS FOR ARCTIC OPERATIONS

CONTENTS
Page
Commercial Usage 1
Military Usage 2
General Specifications of Commercially Available Track-Type Tractors. 3
Thickness of Ice 6
Type of Road 7
Maximum Grades and Grade Resistance 8
Sliding Resistances 8
Tonnage of Pay Load 9
Speed 9
Special Equipment Required for Arctic Tractors 11
Winch 11
Radiator Guard 11
Radiator Curtain 11
Cranckcase Guard 11
Front Pull Hook 11
Headlight Guards 11
Engine Side Shutters 12
Generator 12
Headlights 12
Exhaust-Pipe Extension 12
Cabs and Seat Enclosures 12
Tracks and Roller Frames 14
Fuel System 17
Instrument Panel Controls 18
Engine Heating Devices 18
Underchassis Heater 18
Hot-Air Heater 19
Water Heater 20
Open-Flame-Type Heaters 21
Operation and Maintenance 22
Sled Loading 24
Selecting the Route 25
Assembling the Train 25
On the Trail 26

EA-I. Caterpillar Tractor Co.: Tractor-Type Unites

Contents #2
Page
Fuels, Coolants, and Lubricants 28
Fuels 28
Engine Coolants 30
Lubricating Oils 31
Maintenance 32
Engine 33
Tractor Transmission and Final Drive 34
Tracks and Rollers 34
Sleds and Wanigans 35
Conclusions 35

EA-I. Caterpillar Tractor Co: Tractor-Type Units ✓

LIST OF FIGURES
Page
Fig. 1. Steel and glass can on International TD-18 Tractor 12a
Fig. 2. Canadian-type canvas enclosure on Caterpillar D-6
tractor
13a
Fig. 3. Herman-Nelson hot-air generator, being used to warm
up tractor engine
19a
Fig. 4. Caterpillar D-7 tractor, equipped with two Vapor Car
hot-water heaters
20a
Fig. 5. Using an open-flame-type heater on Caterpillar D-7
tractor starting engine
21a
Fig. 6. Caterpillar D-7 tractor pulling 24 sleighs (each carrying
4 cords) of pulpwood logs
22a
Fig. 7. Caterpillar D-6 diesel tractors and 32 sleighs carrying
approximately 300 tons of supplies
22b
Fig. 8. A Caterpillar D-7 diesel tractor opening a road for
spring traffic
25a
Fig. 9. Caterpillar D-8 diesel tractor, pulling 3 sleds, each
loaded with approximately 25 tons of lumber and other
building materials, went through the ice
27a

EA-I. (Caterpillar Tractor Co.)

TRACTOR-TYPE TRANSPORTATION UNITS FOR ARCTIC OPERATIONS
The track-type tractor provides the most practical, and in some
circumstances the only means of transporting any sizable quantity of mate–
rials and supplies in those arctic areas unreached by roads or open water.
It has the ability to negotiate steep grades and rough country, breaking
its own trail as it goes. Over ice, snow, or deep mud, the wide planklike
tracks provide the necessary support and traction to enable it to maintain
a steady pace. Developed commercially to do the roughest kinds of work under
unfavorable conditions in all parts of the world, it has found a definite place
in arctic operations.
Of course, the track-type tractor has its limitations in what it can do
under arctic conditions. It cannot travel over ice too thin to support its
weight, or in deep snow or mud too soft to keep the tractor and the load it
is pulling on the surface. Equipment is available to overcome, to a large
degree, the operational difficulties imposed by the extreme cold sometimes
encountered, but at the same time special maintenance practices must be carefully
employed if mechanical difficulties are to be avoided.
COMMERCIAL USAGE
The track-type tractor is no newcomer to the Far North. Almost from the
time this machine first became commercially available it has found immediate
application in lumbering the pulpwood operations in the Subarctic, building

EA-I. Caterpillar Tractor Co: Tractor-Type Units

and maintaining access roads, hauling supplies, and dragging the fallen
timber to points where it could be floated or hauled to market. There are
numerous mines in the Far North that have for years depended upon track-type
tractors for digging and hauling dirt and ore, bringing in fresh supplies,
and performing other tasks.
From these early users of track-type tractors in northern regions comes
much of the present knowledge of design of special equipment to fit such
machines for service under the severe conditions encountered, and the suggestions
and recommendations that will be made later borrow freely from their experience.
MILITARY USAGE
The possibility of future wars being fought in the Arctic has not escaped
the attention of the military strategists of various nations, and a great
amount of exploratory work has been done to determine the scope and usefulness
of track-type equipment in arctic military operations.
Early successes of the Japanese in World War II indicated the immediate
need of Ordnance operations in arctic regions, and spurred construction of
the Alcan Highway by the U.S. Engineers. Much of the country traversed by
this highway is typically arctic, and track-type tractors were the major tools
used in construction. Due to the urgency of this project, the U.S. Engineers
had to rely on practices of local operators at first, but immediately launched
an organized test program to bring about improvements in equipment, lubricants,
fuels, and human comfort. Most of the work was done during warm weather and
many new methods and procedures for operating in muskeg were developed. In
the winter, tractors were used for repair and maintenance of the road, and these
operations added much to the store of knowledge of operating over snow, ice,

EA-I. Caterpillar Tractor Co: Tractor-Type Units

and frozen ground at extremely low temperatures. The Alcan Highway project
became a proving ground for laboratory-developed equipment for arctic opera–
tions.
As the war progressed, considerably more knowledge was gained from machine
performance in constructing air bases in Alaska, and in the Aleutian campaign.
Considerable work has also been done by the U.S. Navy, involving both explora–
tion and construction, using track-type tractors in Antarctica and at Point
Barrow, Alaska.
Much work remains to be done to improve and expand further the usefulness
of track-type tractors in arctic regions. Both the U.S. Engineer Corps and
the Canadian Army are continuously investigating these problems in full-scale
field and laboratory tests, and much new knowledge is daily coming to light.
The suggestions and specific recommendations made in this article come
principally from the reports and first-hand observations of factory engineers,
operators, and owners of track-type tractors engaged in arctic operations,
and military reports and personnel. More detailed information on specific
questions can usually be obtained by applying directly to:
2. Individual manufacturers of track-type tractors: Caterpillar Tractor
Co., International Harvestor Co., Allis Chalmers Co., and Cleveland Tractor Co.
4. Military sources: U.S. Engineers (Fort Belvoir, Virginia), Bureau of
Yards and Docks (Navy Department, Washington, D.D.), and F R oyal Canadian Army
Service Corps (Ottawa, Canada).
6. Major oil companies: Standard Oil Co. and Shell Oil Co.
GENERAL SPECIFICATIONS OF COMMERCIALLY AVAILABLE TRACK-TYPE TRACTORS
Commercially available track-type tractors, as offered by the various
manufacturers come in a variety of sizes, ranging from a small machine weighing

EA-I. Caterpillar Tractor Co: Tractor-Type Units

approximately 1.5 tons and powered with an 18-horsepower engine, to giant
construction tractors weighing up to 20 tons and rated at 163 horsepower.
Travel speeds provided on standard models are fairly uniform, with lowest
w s peeds ranging from 1.4 to 1.8 miles per hour and highest speeds from 4.8
to 6 miles per hour. Conventional gear-type transmissions are generally
used, although one manufacturer now offers a hydraulic torque converter on
his largest model. As engines are generally operated at a constant governed
speed, speed selection is made with the transmission, and the operator has
a choice of at least three, and on some models as many as six, forward speeds
within the high and low limits given above.
The amount of tractive effort or drawbar pull the tractor exerts varies
with operating speed and the degree of traction afforded by ground conditions,
but a study of manufacturer’s published specifications shows that, in low gear
on level ground and with sufficiently good footing to prevent slippage, the
track-type tractor is able to exert a pulling force equal to about 90% of its
weight. At top speeds of 4.8 to 6 miles per hour the drawbar pull is reduced
to about 20 to 30% of the tractor’s weight. Complete data is obtainable from
the individual manufacturers.
Most models of track-type tractors currently offered are powered by
semi high-speed diesel engines (1,000-1,800 r.p.m.), although gasoline engine
driven tractors are still made by two of the four major manufacturers. How–
ever, the lower fuel consumption of the diesel engine and its freedom e from
electrical ignition difficulties make it a unanimous choice for arctic operations.
Reduced fire hazard and freedom e from radio static interference are also
important factors.
There is considerable variation in the methods used for starting the

EA-I. Caterpillar Tractor Co: Tractor-Type Units

diesel engine. Battery-operated electric-starting systems are used on some
models, but are not favored for arctic operations because of the high rate
of depreciation of the storage battery under the travel conditions encountered
and its poor performance at low temperatures. Another method utilizes an
independent gasoline-operated starting engine, which finds considerable
favor because it can be hand-cranked, operated as long as necessary to start
the diesel, and while running adds its heat to the diesel engine to help
condition the diesel for easier starting. A third method utilizes an arrange–
ment whereby the diesel engine is started on gasoline as a conventional gasoline
engine, and when sufficiently warmed up is shifted over to full diesel operation.
All of these methods have a low-temperature limitation, below which
satisfactory starting requires external means of applying heat to the engine,
or other special provision to permit the starting method to crank the diesel
engine fast enough to fire. Inasmuch as the frictional resistance of the
engine goes up and battery efficiency goes down with reduced temperatures,
diesel engines relying on conventional battery starting find need for special
aids at about 32°F. and lower. Diesel engines that start on gasoline, using
battery power for cranking, will start with fair reliability as low as 0°F.
The use of a hand-cranked gasoline engine for cranking the diesel permits
considerable lower starting temperatures, in the range of −20° to −30°F.,
before special aids are necessary.
The track-type tractor is so well suited inherently for arctic operations
that few, if any, alterations are required in the basic design to fit it for
such service. There is, however, a wide choice of attachments and accessories
available from the manufacturer as special equipment to improve the usefulness
and reliability of the tractor under the operating conditions encountered, as

EA-I. Caterpillar Tractor Co: Tractor-Type Units

well as equipment to combat the effect of the extremely low temperatures
sometimes encountered. Such items will be covered in detail later on.
As for the selection of the best size of tractor to use for transport–
tation and freight hauling in arctic regions, there seems to be general
agreement that the larger machines are the most desirable, if operating
conditions permit their use. The easiest, and sometimes the only, route is
generally found by following lakes and rivers. The thickness of the ice
becomes the determining factor in selecting the best si x z e of tractor.
Other factors involved are: type of road; maximum adverse grades; sliding
resistance; tonnage; and desired speed.
The t T hickness of i I ce. The thickness will vary with every body of water. On lakes, if
there are currents or if the ice is under a considerable amount of snow, the
ice will generally be thin. Often on shallow lakes the ice will be poor due
to heat from the bottom. The color of ice is usually a good indication of
its thickness, light-blue being the strongest, and shading from gray to
black indicates less and less strength. Although specific information on
the bearing power of ice is not available, the rule-of-thumb data given in
Table I may be of interest.
Table I.
T R r actor model Weight, lb. Safe ice, in.
D-2 6,870 10 to 14
D-4 10,430 12 to 18
D-6 17,330 16 to 24
D-7 24,330 28 to 32
D-8 34,360 36 to 40

EA-I. Caterpillar Tractor Co: Tractor-Type Units

Reconnaissance of the ice is recommended for winter hauling for there
are many possibilities of breaking through the ice: (1) Rocks near the
surface of lakes or streams give a thin ice sheet between the rocks and ice
surfaces. (2) Expansion and contraction of large ice areas produce “rents”
which result in thinner secondary ice. When covered by snow, these conditions
are not apparent to the vehicle operator. (3) Ice fatigue results from con–
stant travel over the same route.
If the ice surface of a lake is not sufficiently strong, there are a
number of ways in which the road surface over the ice may be strengthened. (a) If the
haul road is ice, the tanking may be continued over the lake ice. This will
build the natural ice up and will form an ice bridge across the lake, much
stronger than the surrounding ice. (b) If the road is snow plowed down to
the ice to a width of say 100-150 feet, the ice will thicken considerably
over this area as the insulating blanket of snow has been removed. With this
wide cleared area, if the ice gives at any one point, the road can be moved
fifteen to twenty feet to one side until the road can be repaired. It has
been found that a road grader pulled by a light tractor is very practical
for this purpose. (c) If holes are chopped in the ice the road area can be
flooded, with or without the use of pumps. Each application of water should
be allowed to freeze before more water is added. (d) Another method of rein–
forcing ice to increase its carrying capacity is by adding straw or boughs and
freezing them into the surface. However, being dark, they would be a drawback
in a spring thaw as they would cause faster thawing than normal. However,
occasions may arise where this method of reinforcement is practical.
Type of Road . It is obvious that a tractor must have a firm well-packed
road in order to develop maximum output in the form of drawbar pounds pull.

EA-I. Caterpillar Tractor Co: Tractor-Type Units

Usually several passes of tractors and trains will achieve this condition
but in this connection, the moisture content of the snow is of great
importance. Wet, heavy snow will pack down much quicker and provide more
thrust resistance than the dry, loose snow characteristic of very cold
temperatures.
Maximum Grades and Grade Resistance . When a tractor train is hauled
over a grade, it is necessary to lifet a portion of the weight of the train
in addition to negotiating forward movement. Grades are usually expressed
in percentages equal to 100 times the ratio of the vertical rise to the
horizontal distance, thus a 1% grade is one in which a vertical rise of one
foot is encountered in a horizontal distance of 100 feet. It is generally
accepted that each per cent of grade requires 20 additional drawbar pounds
pull per ton — over and above the pull required to overcome sliding
resistance.
Sliding Rresistances of steel runners on ice and snow are not generally
very well known and the available figures are not completely usable because
of the variety of conditions encountered — sometimes in a comparatively short
distance. The National Research Council of Canada has some of the most reliable
information on this subject. In logging sleds, of great importance are the
length of the runner in proportion to its width and the camber of the front
runner which should be such to achieve a lifting effect on loose snow. The
moccasin-type runner has achieved greatest popularity in the Province of Quebe d c
for snow use. This type utilizes a runner twice the width of the steel shoe.
To give better flotation to the sled, the steel shoe is usually a ah ha lf oval,
about 4 inches wide, and rolled of mild steel. The load weight per unit of
shoe surface should be as great as practical, as the sliding resistance of

EA-I. Caterpillar Tractor Co: Tractor-Type Units

the steel on the snow is reduced by the heat created by friction of the
runner. Commercial freighters are of the opinion that tractive efficiency
is materially increased if the gauge of the sleds is the same as the gauge
of the tow vehicle.
Tonnage of Pay Load . Larger tonnages obviously require more powerful
tow vehicles and increases in speeds bring about decreases in workable
tonnages.
Speed . The available speeds in miles per hour and drawbar capacities
in pounds pull for five types of tractors in five different gears are
given in Table II. An examination of Table II indicates a model D-6 tractor
Table II.
Model Weight, lb. Gear
1st
m.p.h. lb.
2nd
m.p.h. lb.
3rd
m.p.h. lb.
4th
m.p.h. lb.
5th
m.p.h. lb.
D-2 6,870 1.7-6,250 2.5-4,700 3.0-3,800 3.6-3,070 5.1-1,950
D-4 10,430 1.7-9,450 2.4-6,990 3.0-5,470 3.7-4,180 5.4-2,690
D-6 17,330 1.4-15,500 2.3-10,750 3.2-7,320 4.4-4,730 5.8-3,130
D-7 24,330 1.4-21,351 2.2-13,454 3.2-9,090 4.6-5,994 6.0-4,550
D-8 34,360 1.7-28,700 2.3-21,300 2.8-16,800 3.7-12,600 4.8-9,550
in fourth gear at 4.4 m.p.h. has as much pulling ability as a D-2 in second
gear. Similarly, a D-8 in high gear (4.8 m.p.h.) has greater pulling capacity
than a D-4 in low gear.
In regions where the tractors operate over frozen ground or heavy ice,
large tractors in the class of the Caterpillar D-7 or D-8 are used, but in areas
where most movements have to be made over river or lake ice, and there is a
limited number of days in the year when the ice is thick enough to safely support

EA-I. Caterpillar Tractor Co: Tractor-Type Units

a D-8, more work is accomplished with a medium size tractor, such as the
Caterpillar D-6. For comparative purposes, brief specifications of the
Caterpillar D-8, D-7, and D-6 tractors are given in Table III.
Table III.
Over-all dimensions D-8 D-7 D-6 (wide gauge)
Length 15 ft. 3 in. 13 ft. 6 ¼ in. 12 t. 5 3/16 in.
Height 7 ft. 6 in. 6 ft. 8 in. 6 ft. 3 1/4 in.
Width 8 ft. 7 3/4 in. 8 ft. 1 in. 7 ft. 10 1/2 in.
Weight 34,360 lb. 24,330 lb. 17,330 lb.
Horsepower
Belt 144 92 75
Drawbar 130 80 65
Drawbar pull (at various travel speeds, and rated engine speed)
Forward: m.p.h. lb. m.p.h. lb. m.p.h. lb.
1st 1.7-28,700 1.4-21,350 1.4-15,500
2nd 2.3-21,300 2.2-13,454 2.3-10,750
3rd 2.8-16,800 3.2-9,090 3.2-7,320
4th 3.7-12,600 4.6-5,994 4.4-4,730
5th 4.8-9,550 6.0-4,550 5.8-3,130
Tracks
Width (standard shoe) 22 in. 20 in. 16 in.
Length track on ground 97 5/8 in. 93 1/4 in. 85 5/8 in.
Area ground contact 4,296 sq.in. 3,730 sq.in. 2,740 sq.in.
Ground pressure
(standard tracks)
8 p.s.i. 6.6 p.s.i. 6.28 p.s.i.

EA-I. Caterpillar Tractor Co: Tractor-Type Units

SPECIAL EQUIPMENT REQUIRED FOR ARCTIC TRACTORS
Because of the extreme variations in operating conditions that are to
be found in various arctic regions through both summer and winter, it would
be impossible to equip a tractor so that it would give best possible per–
formance under all conditions. Experience has shown, however, that certain
items are generally required or desirable, regardless of season or ground
conditions.
Winch . A rear-mounted winch is essential. When the tractor encounters
ground conditions where there is insufficient traction to move the load, the
winch permits the tractor to be uncoupled from the drawn sleds and move on to
firmer ground, where it acts as an anchor while the winch pulls the load over
the soft area.
Radiator Guard . This is a heavy metal plate, perforated to permit
passage of air, that mounts directly in front of the radiator. It prevents
damage to the radiator when passing through wooded areas. As any damage to
the radiator may result in loss of coolant, and enforced shutdown of the engine,
radiator guards are considered to be essential.
Radiator Curtain . This attachment aids in keeping the engine up to the
proper operating temperature during cold weather.
Crankcase Guard . This is a heavy steel plate that armors the underside
of the engine and transmission case, to prevent damage from stumps, hidden rock, etc.
Front Pull Hook . Principal use of the front pull hook is as a means of
coupling two tractors together, on those occasions when it becomes necessary
to double-head the tractors.
Headlight Guards . These are heavy wire mesh guards to protect the head–
light lens from damage when traveling through wooded country.

EA-I. Caterpillar Tractor Co: Tractor-Type Units

Engine Side Shutters . These serve two purposes: they keep snow from
blowing in on the engine, and they help conserve the heat of the engine to
keep it at the proper operating temperature. Sheet-metal shutters, tailored
to fit snugly, are usually obtainable from the tractor manufacturer. Another
type that has found favor is made locally from canvas. The top edge is clamped
to the engine hood, and the bottom edge is simply weighted to keep it from
flapping. The canvas type has the advantage of making it extremely simple
to get to the engine as it requires no clamps.
Generator . A generator is required to furnish power for the headlights
for night travel. The batteryless-type generator is favored, because of the
previously mentioned objections to batteries. A generator of sufficient
capacity to handle all the lights required should be specified.
Headlights . Each tractor should be equipped with a pair of headlights on
both the front and rear of the tractor. The rear lamps assist the operator
when winching the load at night. In addition, there should be a pair of
spotlights, mounted on the highest point of the tractor seat enclosure. These
spotlights are chiefly used shining to the rear, with the beams converging on
the sled train.
Exhaust-Pipe Extension . At low temperatures, the moisture in the engine
exhaust condenses to form a dense cloud of vapor, and may seriously obscure
the operator’s vision. Eliminating this operational hazard may require suitable
alterations or extensions to the exhaust stack.
Cabs and Seat Enclosures . To afford the tractor operator as much protection
as possible from the elements, one of two types of enclosure is generally used:
( 1 ) a regular tractor cab, made of sheet metal or plywood and with glass
windows totally enclosing the operator’s compartment (see Fig. 1) , or ( 2 ) simple canvas FIG. 81 - Steel and glass cab on International TD-18 tractor. Note how
cold has fogged the glass.
FIG. 7 - Steel and glass cab mounted on Caterpillar D8 tractor.

EA-I. Caterpillar Tractor Co: Tractor-Type Units

shields, sometimes with a glass windbreaker, that transform the operator’s
compartment into an open cockpit . (see Fig. 2). Holes cut in the dash allow engine heat
to circulate around the operator. Each arrangement has its advantages and
disadvantages.
The standard tractor cab has the advantage that it gives the operator
maximum protection from wind, snow, sleet, and rain, and in the summer months,
from insects. On the other hand, it is subject to rather rapid depreciation
under rough operating conditions, and inclined to be somewhat noisy. Visi–
bility is poor due to frost forming on the glass and the wood or sheet-metal
frame, which unavoidably blocks the operator’s view in certain directions.
Also, cabs make it difficult for the operator to escape in the event the
tractor should fall through the ice when crossing lakes or rivers.
Open cockpits, with canvas sides and windshield, offer maximum visibility,
low maintenance, and easy escape in case of accident. However, there is no
protection from the elements or from insects in the summer months. There
is also a problem of keeping pieces of ice, etc., thrown up by the tracks
from filling the cockpit.
The opinion of commercial haulers seems to favor the open cockpit,
canvas-shrouded enclosure over the totally enclosed cab, especially for
cold-weather operation, because of the better visibility and safety features.
It should be noted, however, that most of the objections to cabs could be over–
come by improved design, and investigation in this direction is continuing.
Escape hatches on the cab roof can be provided rather simply. An efficient,
dependable window defroster and windshield wiper, and the use of double-pane,
sealed glass (Thermopane) would improve visibility, as would careful location
of the windows. Such improvements could quite conceivably result in the cab
being given operator preference.
FIG. 102 - Canadian type canvas enclosure on Caterpillar D6 tractor. FIG. 9 - Canvas type enclosure for operator. The track carrier rollers
have been replaced with a hard wood block, to eliminate diffi–
culty in getting carrier rollers to turn in extreme cold and
deep snow. Note also the plywood engine side doors.

EA-I. Caterpillar Tractor Co: Tractor-Type Units

Whether cab or enclosure is used, it should be of sufficient width to
comfortably seat two men dressed in arctic clothing. A width of 48 inches
is about minimum.
Glasspanels, if used, should be of safety glass. Glass on the forward
part of the cab should be protected with some type of metal guard to prevent
the possibility of breaking the glass when removing engine side panels or
doing other work around the engine.
If a canvas enclosure is used, the windshield should be hinged so that
it can be folded down during calm, mild weather.
Tracks and Roller Frames . As has been mentioned before, the great variety
of operating conditions encountered in the Arctic makes it impossible to
equip a tractor so that it will perform equally well, without equipment changes,
in all situations. This is especially true in regard to selecting the type and
size of track plates for such service.
In operating over soft snow or muskeg, the important consideration is to
keep the machine from sinking or digging its way beneath the surface, which
requires that track plates having the maximum obtainable area be used.
Experience has shown that, for satisfactory operation over packed snowdrifts
or average muskeg, the ground pressure (total weight divided by area of track
plates actually on the ground) of the tractor should not be more than 2 to 3
p.s.i. This is less than half the ground pressure ordinarily found with
conventionally equipped track-type tractors (specifications previously given
for the Caterpillar D-6 tractor, with standard 16-inch shoes, show ground
pressure of 6.28 p.s.i. To operate under such conditions, the track-plate
area must be increased by using wider-than-standard plates, or by attaching
to the regular plates auxiliary track pads. The p [: c] atter means, while successful

EA-I. Caterpillar Tractor Co: Tractor-Type Units

in decreasing the tractor ground pressure, has its limitations, as can be
judged from the following excerpt from a report on U.S. Army Task Force
Williwaw at Adak, Alaska (1947).
“Two track-type tractors were reworked to decrease the ground pressure
on each unit. This was accomplished by replacing the standard track pads
with angle iron section pieces. A Caterpillar D7 tractor track was built
up with 6 × 6 inch 5/8 thick angle iron 40 inches in length, which reduced
the ground pressure of this tractor to 2.7 psi. The angle iron type grouser
had an overhang from the outside track link of 25 1/2 inches. An International
TD14 tractor was reworked in similar manner. The angle sections were 5 × 5
inch 1/2" thick angle iron 30 inches long, which reduced the ground pressure
to 4.5 psi. B e y increasing the track pad size as described, the tractors
were found to be very mobile and the units were considered good prime movers.
Trouble may develop in the units as an overload is produced on the steering
system, track frames, links, roller, etc. because of the extra wide grousers.
In rocky sections of the terrain, it was found that the angle iron grousers
became quite badly bent.”
In order to provide as much clearance as possible for the use of extra
wide track plates, wide-gauge tractors should be specified, if available.
Wide-gauge tractors differ from standard tractors only in that the track frames
are spread farther apart, with a corresponding increase in the distance from
the track chains to the side of the tractor chassis. It is desirable that
extra long track plates be attached to the track chain as near the center of
the plate as possible, with equal overhang on each side of the track chain,
which indicates the desirability of the widest gauge obtainable. In addition,
the increased width of the tractor gives it additional stability when travelling
over rough or sloping ground.

EA-I. Caterpillar Tractor Co: Tractor-T G ype Units

Some tractor manufacturers also offer, as special or optional equipment,
extra long track roller frames. As longer frames increase the number of
links in the track chain, with a corresponding increase in the area of
track in contact with the ground, they should be specified if available.
Under some operating conditions, low ground pressure is not an advantage,
and may even be un desirable. For example, when travelling over ice or hard-
packed snow, higher ground pressure may be required to secure sufficient
penetration of the track grousers to give the required traction. Furthermore,
the extra wide shoes required for low ground pressure reduce the maneuverability
of the tractor, and are subject to considerable bending of the ends when rocky
ground is encountered.
Fortunately, in actual practice most of the difficulties mentioned above
can be avoided, by careful choosing of the trail to avoid low, s e w ampy areas
in warm weather. In a report on the joint operations of the U.S. Army and
the Canadian Army near Fort Churchill, Canada, an observer reported.
“By selecting the proper routes, a tractor with a higher ground pressure
can be used and more work done than if a straight cross-country route is taken.
“Commercial freighters are very careful in selecting their routes for
winter time hauling. For terrain as found in the Churchill area, even greater
care must be taken as to route selection during the summer months because the
muskeg becomes very soft, with the water level near the surface.”
The design of the track plates, as well as the size, is of considerable
importance. Over the years, a great amount of experimental work has been done
by tractor manufacturers and commercial haulers alike in an attempt to develop
the “perfect” track plate for snow and ice. While no single answer has been
found, and tractor manufacturers offer a variety of sizes and shapes of track

EA-I. Caterpillar Tractor Co: Tractor-T G ype Units

plate for snow and ice. While no single answer has beenfound, and tractor [] ✓ cf. original p. 25 line 7 from bottom
manufacturers offer a variety of sizes and shapes of track
plate to meet
varying conditions, the so-called “snow and ice semi-skeleton” track plate
seems to be most popular for arctic winter operations. The center of the
shoe is open, so that snow that packs in the chain is punched out by the
track sprocket. The grousers have both single spikes and double spikes,
and the plates are attached alternately to the track chain — first a single–
spiked plate, then a double-spiked plate.
As a general recommendations for equipping a tractor for year-round
transportation service in the Arctic, as far as the track running gear is
concerned, it should have the widest gauge and the longest track frames
obtainable from the manufacturer. The track plates should be of the type
described above, in the widest width furnished. If it is possible to avoid
soft, marshy ground or deep snow by careful selection of the travel route, the
track-plate area can be augmented by bolting on extra wide pads made from such
material as heavy angle iron.
Fuel System. One of the commonest difficulties encountered in operating
tractors in extremely cold weather is the formation of ice in fuel lines. It
is extremely difficult to keep the fuel absolutely free of water, and only a
very small quantity is required to cause trouble.
Fuel tanks and filter housings are customarily equipped with drain cocks,
settling bowls, or other provision so that accumulated water can be periodi–
cally removed from the fuel system. In addition, it is good insurance to
replace all fuel lines of small size with oversized lines (approximately
½ inch inside diameter), and use fittings that have smoothly rounded inside
passages.

EA-I. Caterpillar Tractor Co: Tractor-T G ype Units

Instrument Panel Controls. All control knobs, handles, keys, etc., that
the operator uses should be spaced and of suitable shape so that they can be
worked by the operator without removing his heavy gloves.
Engine Heating Devices
ENGINE HEATING DEVISCES
As mentioned before, the low-temperature limit for satisfactory starting
of the engine on commercial crawler tractors without special eating equipment
is about 0° to −10°F., assuming that the engine is in good operating condition
and has been properly services with correct fuels and lubricants for low–
temperature operation (see “Operation and Maintenance” section). For lower
temperature it is usually necessary to apply heat to the engine from some
external source.
The most obvious solution is to keep the tractor in a heated enclosure
when it is not in operation, but under arctic conditions such a solution is
not often practicable, and the tractor must be parked in the open.
There are several means of applying auxiliary heat to the engine to
facilitate starting. In general, the selection of the most satisfactory
arrangement to meet existing conditions depends upon two factors: how low
a temperature the engine reaches, and how fast a start is desired.
Underchassis Heater. Perhaps the simplest scheme for maintaining the
temperature of a tractor parked in the open high enough to permit starting
consists basically of a tarpaulin closely fitted around the tractor or engine,
and a conventional-type gasoline-burning space heater which is hung beneath
the tractor chassis. Such an arrangement was furnished for military machines
for arctic service during World War II, as part of a so-called “winterization
kit.”

EA-I. Caterpillar Tractor Co: Tractor-T G ype Units

On paper, this arrangement would appear to be capable of doing a
satisfactory job. It is simple, lightweight, and operating principle
is obviously sound. However, actual tests brought cut a number of objections.
Under conditions of extreme cold the heater may go out, either from the wind
or from the heater fuel line freezing up. The products of combustion of the
fuel condense on the ignition system of cold engines. If the engine has
reached an extremely low temperature before the heater is lit, the heat is
slow in penetrating and an excessively long period of time is required to
achieve starting temperature.
Hot-Air Heater . One of the developments of World War II was a high–
capacity hot-air generator, specifically designed for warming aircraft
engines. Perhaps the best-known machine of this type is the Herman-Nelson
heater (see Fig. 3) , which consists basically of a high output (100,000 B.t.u. per hour),
gasoline-fired burner, and a 4-cycle air-cooled gasoline engine, which drives
a fan to force the hot air through flexible conduits to the point where heat
is needed. The whole machine is mounted on a portable, four-wheeled cart.
Operational reports indicate that this type machine does a very satis–
factory job of warming up cold engines, even under extreme conditions. By
using canvas shields around the engine, it is a simple matter to insert the
hot-air conduit to direct the heat where most needed. However, the problem
remains of getting the engine on the heat generator started, assuming the
tractor is on the trail and there is no heated shelter for the heater.
It would seem, then, that the Herman-Nelson type heater is very satis–
factory for arctic operations where the machines to be started are bivouacked
near permanent or temporary headquarters, and the heater can be put into
operation without much difficulty. On the trail, such an arrangement presents FIG. 133 - Herman-Nelson hot air generator, being used to warm up
tractor engine. the fuel condense on the ignition system of cold engines. If
the engine has reached an extremely low temperature before the
heater is lit, the heat is slow in penetrating and an excessive–
ly long period of time is required to achieve starting temperature.
Hot Air Heater
One of the developments of World War II was a high capacity
hot air generator, specifically designed for warming aircraft
engines. Perhaps the best known machine of this type is the
Herman-Nelson heater, which consists basically of a high output
(100,000 B.T.U./hr.) gasoline fired burner, and a 4-cycle air
cooled gasoline engine which drives a fan to force the hot air
through flexible conduits to the point where heat is needed.
The whole machine is mounted on a portable, four wheeled cart.
Operational reports indicate that this type machine does a
very satisfactory job of warming up cold engines, even under ex–
treme conditions. By using canvas shields around the engine, it
is a simple matter to insert the hot air conduit to direct the
heat where most needed. However, the problem remains of getting
the engine on the heat generator started, assuming the tractor
was on the trail and there was no heated shelter for the heater.
It would seem, then, that the Herman-Nelson type heater is
very satisfactory for Arctic operations where the machines to be
started are bivouacked near permanent or temporary headquarters,
and the heater can be put into operation without much difficulty.
On the trail, such an arrangement presents an additional engine
starting problem, and in addition it becomes another piece of
freight to be transported by the tractor train, deducting just
that much from the pay load.

EA-I. Caterpillar Tractor Co: Tractor-T G ype Units

an additional engine starting problem, and in addition it becomes another
piece of freight to be transported by the tractor train, deducting just that
much from the pay load.
Water Heater. This arrangement consists basically of a gasoline burner and
a hot water coil, generally mounted on the exterior of the engine. The water
coil is directly connected to the cooling system of the engine, and in addi–
tion there may be auxiliary heating coils in the oil sump and around the
battery box. The burner and hot water coil are mounted low on the engine,
and act as a thermosiphon to maintain circulation. As the engine coolan d t is
heated, it rises in the system, forcing cold coolant into the heater. The
best-known heaters of this type are the Vapor Car Heater (See Fig. 4) and the Superfex.
This type heater, if put into operation immediately upon shutting off
the engine, will maintain a sufficiently high engine temperature for immediate
starting. If the engine is cold to begin with, it may take from 6 to 8 hours’
operation of the heater to bring the engine up to a satisfactory starting
temperature.
Field tests indicate that this type heater, if it operates properly,
gives very satisfactory results. In a test at Fort Churchill, a Caterpillar
D-7 tractor was started in slightly more than one minute in a temperature of
−38°F. However, numerous operational difficulties sometimes arise, and in
this same test it was reported that the operators were somewhat discouraged
by the heater fuel lines freezing up, snow being blown into the heater, and
the uncertainty that proper circulation was taking place, due to the formation
of vapor locks.
Development work is still progressing and undoubtedly most of these
operational problems will eventually be overcome. If so, this type heater FIG. 144 - Caterpillar D7 tractor, equipped with two Vapor Car hot
water heaters. Note the escape hatch built into the cab
roof.
Water Heater
This arrangement consists basically of a gasoline burner and
a hot water coil, generally mounted on the exterior of the engine.
The water coil is directly connected to the cooling system of the
engine, and in addition there may be auxiliary heating coils in
the oil sump and around the battery box. The burner and hot water
coil are mounted low on the engine, and act as a thermo-siphon to
maintain circulation. As the engine coolant is heated it rises
in the system, forcing cold coolant into the heater.
The best known heaters of this type are the Vapor Car Heater,
and the Superfex.
This type heater, is put into operation immediately upon
shutting off the engine, will maintain a sufficiently high engine
temperature for immediate starting. If the engine is cold to be–
gin with, it may take from 6 to 8 hours operation of the heater to
bring the engine up to a satisfactory starting temperature.
Field tests indicate that this type heater, if it operates
properly, gives very satisfactory results. In a test at Fort
Churchill, a Caterpillar D7 tractor was started in slightly over
1 minute in a temperature of −38°F. However, numerous operational
difficulties sometimes arise, and in this same test it was report–
ed that the operators were somewhat discouraged by the heater fuel
lines freezing up, snow being blown into the heater, and the un–
certainty that proper circulation was taking place, due to the
formation of vapor locks.
Development work is still progressing and undoubtedly most
of these operational problems will eventually be overcome. If
so, this type heater will undoubtedly become very popular for

EA-I. Caterpillar Tractor Co: Tractor-T G ype Units

will undoubtedly become very popular for cold-weather operation, especially
on engines that rely on storage batteries or hand cranking for starting. It
was the opinion of test officers at Fort Churchill that engines should be
equipped with a coolant-type heater that would function as either a stand-by
or a fast heater, and could be considered to be dependable and not a fire
hazard. Heater capacity should be at least 50,000 B.t.u. per hour.
Open-Flame-Type Heaters. Gasoline-burning blowtorches, acetylene-gas
torches, and the like are not, in themselves, capable of heating large engines
to starting temperatures in conditions of extreme cold, although they are
useful for applying heat to local areas, such as the intake manifold. However,
where the diesel engine is equipped with an independent gasoline-starting
engine (Caterpillar), this is oftentimes the only external heating device
required to make a cold start, even in temperatures of −40°F. or lower.
The open flame is applied to the crankcase and intake manifold of the
starting engine and, if the starting engine is in good condition, it will
usually start readily . (See Fig. 5). The starting engine is tied in with the diesel engine
in such a way that the starting-engine heat is added to the common cooling
system and to the intake air of the diesel engine. Motoring the diesel
engine with the starting engine from 5 to 8 minutes is usually sufficient
to start the diesel.
The use of an open flame on the starting engine is not especially
desirable, because of the fire hazard, and the danger of the localized heat
causing unequal expansion with resulting cracking of the metal parts. In
general, however, the method is successful, and has led some operators to
comment that, with the Caterpillar diesel starting system, the only heating
aid required for cold starts in the lowest temperatures is a bottle of acetylene
gas and a torch. FIG. 155 - Using an open flame type heater on Caterpillar D7 tractor
starting engine. cold weather operation, especially on engines that rely on storage
batteries or hand cranking for starting. It was the opinion of
test officers at Fort Churchill that engines should be equipped
with a coolant type heater that would function as either a stand–
by or a fast heater,, and could be considered to be dependable and
not a fire hazard. Heater capacity should be at least 50,000 B.T.U.,
hr.
Open Flame Type Heaters
Gasoline burning blow-torches, acetylene gas torches and the
like are not, in themselves, capable of heating large engines to
starting temperatures in conditions of extreme cold, although they
are useful for applying heat to local areas, such as the intake
manifold. However, where the Diesel engine is equipped with an
independent gasoline starting engine (Caterpillar), this is often–
times the only external heating device required to make a cold
start, even in temperatures of −40°F. or lower. The open flame
is applied to the crankcase and intake manifold of the starting
engine, and if the starting engine is in good condition it will
usually start readily. The starting engine is tied in with the
Diesel engine in such a way that the starting engine heat is add–
ed to the common cooling system and to the intake air of the
Diesel engine. Motoring the Diesel engine with the starting
engine from 5 to 8 minutes is usually sufficient to start the
Diesel.
The use of an open flame on the starting engine is not es–
pecially desirable, because of the fire hazard, and the danger
of the localized heat causing unequal expansion with resulting
cracking of the metal parts. In general, however, the method is

EA-I. Caterpillar Tractor Co: Tractor-T G ype Units

Utilizing the same principle and procedure, but in a more acceptable
manner, is a hand-cranked gasoline-fired blower that throws a blast of hot
air on the entire starting engine, including the magneto. When tested at
Fort Churchill, this attachment made it possible to consistently start the
starting engine in from 5 to 9 minutes after the heater was started, in
temperatures ranging from −27° to −38°F. This heater was developed by the
Caterpillar Tractor Co. in conjunction with the U.S. Engineer Corps.
While discussing cold-weather starting, mention should be made of
investigations now going on of the use of other as an aid in low-temperature
starting of diesel engines. Ether in liquid form is squirted into the intake
manifold by a special device, and has the effect of promoting immediate firing
of the diesel engine. This new development is past the experimental stage,
and should soon be commercially available as an attachment for diesel engines.
OPERATION AND MAINTENANCE
The usual means of utilizing track-type tractors as transportation units
in the Arctic is the so-called “tractor train.” The material to be moved is
loaded on sled platforms, which are towed in tandem by the tractor. Ordinarily,
each tractor pulls three sled units, and this combination is termed a “swing.”
The train may consist of one or a number of swings, depending upon circumstances
and the nature of the operation. The load-moving capacity of each swing, or
tractor, depends upon the condition of the trail and the size of tractor used . (see
Figs. 6 and 7).
Over an established but infrequently used trail, the tonnage figures given in
Table IV are considered a close working estimate.
Fig. 6. Caterpillar D-7 tractor pulling 24 sleighs (each carrying 4 cords) of pulpwood logs. [Figure] Fig. 7. Caterpillar D-6 diesel tractors and 32
sleighs carrying approximately 300 tons
of supplies. [Figure]

EA-I. Caterpillar Tractor Co: Tractor-Type Units

Table IV.
Tractor Gross weight of tractor s
,
tons
Gross weight load of
cargo and sleds, tons
Caterpillar D-4 5.75 12
International TD-14 8.5 20
Caterpillar D-6 9 25
International TD-18 15 40
Caterpillar D-7 13 40
Caterpillar D-8 18.4 50
The sled units towed by the tractor may be of various sizes and designs.
Cargo-carrying sleds usually have two sets of runners, joined by cross-chains
so that the rear set track with the front set when negotiating a curve. Both
sets of runners pivot with respect to the sled platforms. All parts are ex–
tremely rugged and reinforced with steel.
Tractor trains ordinarily include one or more utility sleds, known as
“wanigans”. These are small buildings mounted on sled runners and provide
quarters, cooking facilities, and a repair shop for the train crew. They are
constructed of ply - wood or sheet metal on a strong metal frame, with the
interior insulated with Celotex or some similar material. Inside height is
a minimum of 7 feet, and the width is usually about 8 feet, but cannot exceed
the width of the tractor. Length is usually from 16 to 24 feet.
Table V gives brief specifications of some of the better known commer–
cially available sleds and wanigans.

EA-I. Caterpillar Tractor Co: Tractor-Type Units

Table V.
Manufacturer Weight, lb. Size, ft. Pay - load capacity, tons
McLaren 5,000 8½ × 20½ 10
Otaco 6,000 8½ × 20½ 10
Michler (large) 10,000 8 × 24 10
Michler (small) 6,000 8 × 16 10
Otaco sled
( W w anigan equipped)
10,000 8 × 16 4 men
Michler (large) sled
( W w anigan equipped)
18,000 8 × 24 6 men
Another commonly used cargo carrier, known as a “go-devil” sled, con–
sists of a heavy platform rigidly mounted on a single pair of heavy runners.
They are simple and easy to construct, and provide great load capacity with
a low center of gravity, reducing the possibility of tipping. However, more
power is generally required to pull a “go-devil” than a bobsled, which limits
their use to hauling such items as heavy pieces of machinery, etc., than
cannot be safely loaded on a bobsled.
Sled Loading. Proper sled loading requires experience and knowledge of
the condition of the trail. The height of the load is generally governed by
its tipping tendency rather than its weight. For any but old, smooth trails
the height from the ground to the top of the load should not exceed the width.
Loads should be secured before the train starts. A shifting load not only
wastes precious time on the trail, but it distracts the operator when he
should be concentrating on running the tractor. Loose loads should be boxed
in with lumber, and larger items should be spiked to the sled platform, or

EA-I. Caterpillar Tractor Co: Tractor-Type Units

otherwise secured. At each stop along the route every load should be checked
for shifting.
Selecting the Route. A straight-line route is the most desirable but
very seldom the most practical. In those areas of the North covered with
rivers and lakes, the usual practice is to take full advantage of them by
laying out the route to follow the relatively smooth the flat ice surface pro–
vided. Ascending grades exceeding 10% is slow and difficult, requiring
considerable winch work. Zigzagging up steep grades is dangerous, because
of the possibility of the sleds tipping.
Obviously, selection of the route is about the most important step in
assuring the success of a tractor-train operation. Careless or hasty
selection can result in delays and even loss of equipment and men. All
available means, such as serial reconnaissance, maps, and photographs
should be utilized, as well as experienced guides.
The usual practice in establishing new trails is to send out an advance,
or trail-breaking, party. The usual outfit for trail-breaking consists of
two tractors, equipped with bulldozers, and a utility wanigan, and operating
about a day in advance of the train. Usually, it is advisable to break trail
only in daylight, except in open country.
Trail-breaking in deep snow simply requires that the tractor move along
the selected route, with dozer blade raised, compacting the snow . (see Fig. 8). Where the
surface is uneven, or blocked by trees or rocks, the bulldozer blade is used to
clear and level the T t rail.
Assembling the Train. All the sleds pulled by each tractor should have
the same gauge, or distance between the runners, so that all runners follow
in the same track. The sleds will pull more easily if the heaviest loaded sleds Fig. 8. A Caterpillar D-7 diesel tractor opening a road for spring traffic. [Figure]

EA-I. Caterpillar Tractor Co: Tractor-Type Units

are to the front. Wanigans and “go-devil” type sleds should always follow
the loaded conventional-type sleds. If the sleds stand in the open for any
length of time, the runners may freeze to the ice or snow. They should be
broken free with a sledge or mallet, to reduce the starting strain on the
runners.
On the Trail. Tractor trains usually travel at the highest speed pro–
vided by the tractor, if trail conditions permit. Counting routine stops,
delays for minor repairs, time lost in negotiating bad spots, etc., the
average speed, figured on the basis of total elapsed time between two points
connected by an established trail, is from two to three miles per hour.
Operation is around the clock, to permit greater distances to be covered
and to avoid restarting cold engines.
During arctic winters, the limited amount of daylight means that most
of the time the train is operating in darkness, when the driver can see only
the sled immediately following the tractor. For obvious reasons, the most
experienced men should have the night duty, where possible. Each tractor
should carry an extra gasoline lantern, and there should be an ample supply
of flashlights in the wanigan for night emergencies. Kerosene flares should
also be available for marking the rear sled when the train stops, or disabled
equipment left along the trail.
Stops for refueling and maintenance are usually made at noon, when light
and temperature are at a maximum. Tractor maintenance consists of lubrication,
inspection and adjustment, and general tightening of nuts, bolts, and fittings.
On hauls of less than 100 miles, or over new trails, the tractor train usually
carries its fuel with it. On long hauls over established trails, it may be
more economical to establish fuel caches along the route. Fuel requirements

EA-I. Caterpillar Tractor Co: Tractor-Type Units

per tractor range from 2 to 4 gallons per hour, depending upon travel condi–
tions, load, and size of tractor used. On one typical test it was found that
a Caterpillar D-8 tractor consumed 53 gallons, or 500 pounds of fuel in 15
hours running time. Obviously, for a long trip the fuel carried will account
for an appreciable part of the starting load unless there is provision
for refueling along the route.
The six basic rules of tractor-train operation established by the
Canadian Army at Fort Churchill are as follows:
2. Tractors must follow the prepared trail at all times unless otherwise
ordered. If this is not done the object of trail-breaking, which is to facili–
tate floatation, is nullified and, in effect, each tractor cuts its own trail
with consequent loss of tractive effort. Additionally, more than one trail
can be extremely confusing on return journeys, especially at night or in
conditions of poor visibility.
4. As in every other transport operation, the speed of the column is
dictated by the speed of the slowest vehicle. Thus in conformity with accepted
practice the slowest tractor should lead the column.
6. When travelling in swings, the operator of the first tractor must keep
the tractor following in sight in order to provide mutual assistance. Thus the
two operators of a swing work as a team.
8. When crossing thin ice, tractors should be in the highest gear possible
and operate with reduced throttle. Sleights should be connected to the hook
of the winch cable in order that they may be released and the load spread if
cracks in ice appear.
10. To minimize strain, intervals of 100 yards should be maintained on
ice at all times . (see Fig. 9).
Fig. 9. Caterpillar D-8 diesel tractor, pulling 3 sleds, each
loaded with approximately 25 tons of lumber and other
building materials, went through the ice.
[Figure]

EA-I. Caterpillar Tractor Co: Tractor-Type Units

4. There should be no closing up of tractors when halted on ice.
Intervals must be maintained.
FUELS, COOLANTS, AND LUBRICANTS
Fuels for cold-weather operation of engines do not present much of
a problem, as satisfactory fuels are commercially available. Diesel fuels
conforming to U.S. Specification 2-102C - Grade C (Arctic) have been found
to give good performance in extremely low temperatures (Table VI).
Table VI. Diesel fuel, U.S. Specification 2-102C - Grade C (Arctic).
Test Requirement
Cetane No., min. 40
Flash point, °F. 110
Pour point, °F. −50
Cloud point, °F. −40
Distillation:
90% recovery temperature, °F. 600
End point temperature, °F. 650
Carbon residue (10% bottoms), %, max. 0.15
Sulfur, % by weight, max.
(preferably not more than 0.5%)
1
Kinematic viscosity at 100°F., centistokes 1.5-4.28
Water and sediment Nil
Corrosion Pass
In selecting a diesel fuel for extremely cold weather operation, the
specifications of greatest importance are cetane number, pour point, and water.

EA-I. Caterpillar Tractor Co: Tractor-Type Units

Cetane number correlates directly with ignition quality, or the ability of
the fuel to ignite and continue to fire. In general, the higher the Cetane
number, the more readily the engine will start. Pour point is important,
as the fuel must obviously be in a fluid state at the operating temperatures
encountered, so that it can flow freely from the fuel tank to the engine.
If the fuel contains water, the water will freeze in the fuel lines and
cause difficulty.
Even if the fuel is free of water to begin with, it is rather difficult
to prevent entirely the entrance of snow and ice when refueling, or condensa–
tion from adding water to the fuel. It is common practice to add denatured
alcohol (½ pint to each 20 gallons of fuel) to the fuel, as the al d c ohol will
mix with any water present and keep it from freezing in the lines. The alcohol
should always be added after the fuel is in the engine tan i k . If added in the
storage drums or containers, it will dissolve ice and water in the container
and carry it to the fuel tan i k .
The first time alcohol is added, run the engine long enough to clean all
nontreated fuel out of the fuel lines, and clean any sediment bowls or settling
compartments.
Servicing the fuel tank at the end of the day’s run will also help keep
water out of the fuel, as filling the tank drives out any moisture-laden air.
Never let a partially filled tank stand overnight or during a long halt on
the trail.
Gasolines conforming to U.S. Specification 2-103C - Type C are recommended
for operations below 0°F., and have been found satisfactory for extremely low
temperatures (Table VII).

EA-I. Caterpillar Tractor Co: Tractor-Type Units

Table VII. Gasoline, U.S. Specification 2-103C - Type C.
Test Requirement
Octane No. (A.S.T.M.), min. 80
90% distillation temperature, °F. 302
Distillation residue, %, max. 2
Reid vapor pressure, lb./sq.in., max. 12
Gum, mg./100 ml., max. 4
Sulfur, %, max. 4
Corrosion None
Tetraethyllead content, ml./gal., max. 3
Oxidation stability, minutes 430
Water and sediment None
Precautions for avoiding difficulty due to water in the fuel are the
same as those given above for diesel fuel.
Development work is continuing on improving motor fuels for arctic
service, and significant discoveries have been reported. There are indi–
cations that the use of additives such as ethyl ether to diesel fuel will
greatly improve ignition quality. Other investigations now in progress
show promise of providing improved fuels for subzero work as time goes on.
Engine Coolants . An antifreeze mixture containing 60% ethylene glycol
glycol (Prestone, Peak, Zerex, etc.) and 40% water will give protection down
to −62° E F . The solution should be mixed thoroughly before being poured into
the radiator. Check periodically with a hydrometer, and if additional coolant
is required always add thoroughly mixed 60% solution.
Ethyl alcohol can also be used, but because of its relatively low boiling
point (173°F.) an appreciable amount may be lost due to evaporation. For this

EA-I. Caterpillar Tractor Co: Tractor-Type Units

reason the more permanent type antifreezes are universally preferred.
Lubricating Oils . Not too satisfactory an answer has yet been found to
the problem of lubricating machines at low temperatures. The principal
difficulty is in providing lubricants that are viscous enough to protect
working parts, yet fluid enough to afford reasonable ease in starting cold
engines, shifting gears in transmissions, and operating clutches.
For example, good engine performances with maximum life and minimum
maintenance requires the use of a lubricating oil conforming to U.S. Speci–
fications 2-104B, which can be obtained in S.A.E. 10, 30, and 50 viscosity
grades. S.A.E. 10, the lightest, has a pour point of −10° to 20°F. This
means that for lower temperatures this oil must be dilute s d (preferably with
kerosene) to achieve the required fluidity for starting. As the engine warms
up, most of the diluent is burned off, requiring the addition of fresh oil.
Before the engine is shut down, additional diluent must be added while the
oil is still hot in order that the engine can be started on the next occasion.
At best, this is an uncertain, rule-of-thumb pr e o cedure, but lacking a better
solution, it gives fairly satisfactory results. The problem would be con–
siderably simplified by the availability of reliable heaters to warm the
crankcase oil, but the best answer would be engine oils that would remain
fluid at −60°F. and yet provide the required lubrication characteristics at
engine operating temperatures.
A very thin oil has been developed for arctic service, designated S.A.E. 5
viscosity grade, which has a pour point of about −50°F., but this is a straight
mineral oil without the additives required for peak performance of heavy-duty
engines.

EA-I. Caterpillar Tractor Co: Tractor-Type Units

The current recommendations of one tractor manufacturer for engine
lubrication are: For operating temperatures above 30°F., use S.A.E. 30
(U.S. Specification 2-104B oil in the crankcase); 0° to 32°F., use S.A.E. 10;
−20° to 0°F., use S.A.E. 10 diluted with 25% kerosene; below −20°F., use S.A.E.
10 diluted with 40% kerosene.
These recommendations apply to all engine compartments where engine
lubricating oil is ordinarily used. In the case of oil bath air cleaners,
dilution is not recommended, as it is preferable to leave the oil cups empty
for temperatures below the pour point of S.A.E. 10 be oil. S
The same difficulties which affect engine oils at low temperatures
apply to transmission oils and greases used in other parts of the tractor.
The general practice is to use S.A.E. 10 engine oil or S.A.E. 90 transmission
oil in transmissions, final drives, track rollers, etc., diluting as required
to establish fluidity or permit the shifting of gears.
The individual manufacturer’s recommendations for oil change periods,
lubrication intervals, etc., should be followed.
MAINTENANCE
Machine maintenance, of great importance on heavy machinery under any
operating conditions, takes on additional significance in the Arctic. Taking
a machine that is not in tiptop condition out on the trail in subzero weather
is taking a chance on not getting back home with it. Rigid adherence to
schedules is of extreme importance, and the extent of emergency repairs or
adjustments that have to be made in bitter cold, without shelter or established
repair facilities, is very limited. It must also be remembered that, should
failure of a critical part occur due to lack of maintenance or advance planning,
it might be weeks or months before a replacement can be secured.

EA-I. Caterpillar Tractor Co: Tractor-Type Units

Maintenance for individual machines is thoroughly covered in the published
literature of the various manufacturers, and with some elaboration these
recommendations hold true for arctic operations.
Operators and mechanics should school themselves thoroughly in the
manufacturer’s recommendations, remembering the extraordinary need for
adhering to the letter to the specific instructions given. The following
suggestions supplement the manufacturer’s instruction books, to cover abnormal
maintenance required by the climate and trail conditions.
Engine . Set up a service schedule to insure that the engine is properly
lubricated at all times with the correct lubricant for existing conditions.
Make sure the radiator is filled with the right antifreeze mixture, and
check the entire cooling system for leaks.
Check periodically for loose or missing cap screws, bolts, fittings, and
wires, and make all required adjustments regularly. Replace immediately any
parts that show damage or deterioration, such as frayed fan belts and hose
connections. Remember that extreme cold shortens the service life of parts
made from rubber and fabric. It causes copper wire to become brittle, and
may have the same effect on iron and steel parts. Take care to avoid rough
handling.
In general, ignition and electrical systems perform satisfactorily down
to −30°F. Below this temperature, cracking of the insulation on ignition
wires, excessive burning of distributor points, failure of condensers, and
the fouling of spark plugs occur and become maintenance problems. Check,
clean, and tighten all wiring connections, especially battery and starter
terminals. Check for breaks and shorts in high-tension ignition wiring.
Clean distributor thoroughly, and adjust or replace breaker points.
It may be necessary to remove practically all lubricant from the breaker

EA-I. Caterpillar Tractor Co: Tractor-Type Units

arm, to make sure that the points will close properly. Sluggish action
will cause pitting and failure to start at low temperatures.
Clean and replace spark plugs, making sure that the porcelain is not
chipped or cracked and the point gap is correct. Setting the points about
0.005 inch closer than normally recommended seems to promote easier starting
under conditions of extreme cold. Check the battery, if one is required,
and make sure it is fully charged to a hydrometer reading of 1.275 to 1.300.
a battery with a reading less than 1.125 will freeze and crack at 0°F.
Check the generator and starting motor to see that the commutator is clean
and the brushes make good contact. Make sure the voltage regulator is
functioning properly.
Remove and clean all fuel sediment bowls and water traps, and clean the
strainers. Drain any settling compartments in the fuel filters. Drain the
fuel tank periodically, and blow out the fuel lines.
Tractor transmission and Final Drive . Except for the dilution of
lubricants at low temperatures, as already covered, transmissions and final
drives usually require only the regular maintenance and adjustments recommended
for ordinary operation in more temperate regions.
Care should be taken to see that the drain plugs provided in dry clutch
compartments are in place. Keep clutches and brakes in proper adjustment at
all times.
Tracks and Rollers . Tracks should be kept in proper adjustment. Too
tight adjustment causes rapid wear, absorbes additional engine power, and
places excessive loads on track parts should rock or chunks of ice get caught
in the tracks. When mud or deep snow is encountered, the track chains will
usually increase their tension and should be slackened to avoid damage.

EA-I. Caterpillar Tractor Co: Tractor-Type Units

Track carrier rollers may fail to turn due to a comb us ina tion of snow
or mud packing around the rollers, and the stiffness of the lubricant.
When this happens, the heavy track chain drags over the immobile roller
and rapidly cuts a flat spot. A common remedy is to replace the carrier
rollers with a hard wood skid block.
To simplify the lubrication of track rollers and idlers while on the
trail, it is customary to carry the lubricant pump in the heated wanigan to
keep the lubricant warm.
Sleds and Wanigan s . Sled and wanigan running gear must be checked regu–
larly, and adjustments and repairs made as required. When traversing rough
terrain, constant attention should be given to bolts and chains, and to
adjustments, to reduce repairs and insure minimum drag on the tractors.
CONCLUSIONS
While numerous improvements remain to be made in both equipment and
technique, the use of tractors and sleds for transportation and freight–
carrying in arctic regions will probably be for some time to come the most
dependable and economical solution to the supply problem for remote, inland
points. It is interesting to note the increases in tractor-train hauling
accomplished by the U.S. Navy in conjunction with their operations surround–
ing their petroleum reserve in the vicinity of Point Barrow. The net tons
transported by tractor train (per winter freighting season) increased from
4,676 tons in 1946 to 10,288 tons in 1949. The net ton-miles traversed
during the same period increased from 826,222 in 1946 to 1,265,884 in 1949.
In this period, one of the largest single freighting operations was accomplished.
In the winter of 1946-47, three trains, totaling 13 miles in length, traveled

EA-I. Caterpillar Tractor Co: Tractor-Type Units

In the winter of 1946-47, one of the largest single freighting operations
was accomplished, when three trains traveled from Point Barrow, along the
Arctic Sea and up the Colville River to Umiat, a distance of 280 miles.
The three tractor trains, each made up of a series of units and each unit
consisting of a tractor towing five to seven sleds, with a track-laying
personnel carrier preceding the first train, stretched out for a distance
of 13 miles while in operation. Each train when closed up for refueling or
other purposes had a length of about 1,500 feet, while the closed-up length
of the three trains was possibly one mile.
Basically, problems of operation and maintenance are not radically
different than those encountered in more temperate areas. Although the
employment of skilled and experienced operators would doubtlessly reduce these
problems, it should be noted than an entire tractor train was manned by
Eskimos (operators, trail scouts, and crew members) in the movement of material
over roughly 50 miles of sea ice from Point Barrow to a site east of Cape
Simpson, during the winter of 1947-48. Special equipment is available to
overcome, to a reasonable degree, the effect of extreme cold, deep snow, ice,
and muskeg. Machine maintenance is higher, principally for the reason that
for safety’s sake machines must be kept in tiptop condition at all times. The
maintenance problem is further complicated by the lack of access to complete
stocks of replacement parts and organized repair shops.
When the investigations now in progress are completed, they will undoubtedly
bring into being new lubricants, improved fuels, and better designed machines
to cope with the unusual problems of the Arctic. This will mean additional
reliability and a simplification of the operational problems of using tractors
for transportation in the Far North.
Caterpillar Tractor Co.
HomeTractor-Type Transportation Units for Arctic Operation : Encyclopedia Arctica 2b: Electrical and Mechanical Engineering
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