D 1, 3
Forms of energy
a great computer tried to develop a better dogsled than the ones oldtimers
made, it would fail. Dogsleds are an engineering masterpiece. New
materials have opened up new possibilities, but the factors involved
are the same.
Dogs are available as an energy source in other parts of the world,
but arent used because more powerful animals are available,
like horses, donkeys, and oxen. Since those animals arent
practical in the arctic, dogs were the best sou rce of power until
the advent of the snowmachine. Each dog can get himself from point
A to point B, but pulling a load greatly reduces the distance that
each dog can go. Sled design and dog mushing has to be a science
to maximize the limited energy available from a team of dogs.
Dog mushing is a constant study in energy conservation.
Snowmachines seem to have power to waste, but the same scientific
principles that apply to dogsled design also apply to snowmachine
The dogs are pulling against several forces.
- Friction of the runners against the surface of the snow.
- Lifting the sled and load up banks and hills, although every
round trip, or trip from sea level to sea level averages out to
- Inertia of the load as the sled accelerates and decelerates
with the uneven surface of the snow.
- Steering to keep the sled on the trail.
- A very small amount of wind resistance.
Runners and Friction
High friction runners tire the dogs very rapidly. Of course, the
bigger the load is, the higher the friction will be.
Before plastic we used hard steel runners in warm weather and
wooden runners in cold weather.
Steel runners were very good for spring travel, swimming creeks
and crossing thawed lakes, but came to a halt on bare tundra. Megafriction!
In the spring we traveled for miles and miles on tundra, trying
to avoid bare ground, going from patches of snow to glaciered creeks
back to patches of snow. The difference in friction between snow
and tundra is tremendous!
Steel runners were also very high friction in cold weather. They
groaned like an old fishwheel. And woe unto the musher in cold weather
who didnt avoid fresh dog excrement on the trail. It froze
to the steel runners and was the equivalent of setting an anchor.
The hard ironwood runners used in cold weather were imported from
the lower 48 then to Alaska. They were fairly low friction in very
cold weather once they got a glaze on them. Some people used pine
tar to make them run smoother, but it soon wore off.
ironwood, many oldtimers split a green spruce tree in half, peeled
it, and used that for runners. The icy outside of the tree had very
low friction with the trails surface. However, the rounded
runners sank a little deeper in the trail than flat ones would.
The icy runners also dried out on cold nights, so we had to push
the sled into deep fresh snow to protect the runners from drying.
The oldtimers also knew that spruce trees that grow on hillsides
have a streak of hardwood on the downhill side that forces the tree
to grow straight up rather than straight out from the hillside (geotropism).
That hardwood is also good for sled runners.
Often we tipped our sled over in the morning and iced the runners
with a rag and a can of warm water. There was speculation whether
sugar made the icy film more durable. Long ago, urine was used,
but it isnt good for hunters and trappers who try to minimize
the impact of their presence on the country.
above wood runners worked well in cold weather, but woe unto the
musher who traveled far with wood runners and the weather turned
warm! Wood runners are very high friction in wet snow. Bolts, inset
one-half inch, hung down like a dozen thin brakes as the wood wore
away in the mild temperatures.
This is a part of the good old days we would just as soon forget.
The only solution was to put wood runners over steel runners preparing
for all types of weather. This worked, but made the sled heavier.
We spent many hours changing runners as the weather changed.
Very long ago, oldtimers used bone for runners. I understand that
bone provided low friction, but was very difficult to attach to
Today we have the choice of many plastics. While some are better
than others for low friction and durability, plastic has low friction
at all temperatures; it is strong, light, and dog excrement doesnt
adhere. It is easy to attach and fairly durable. (Be certain to
put plastic on when it is warm. Plastics expand greatly when heated.
If you put runners on cold, they will expand in warm temperatures,
creating bulges that fill with snow.)
Exposed mountain rocks destroy a pair of plastic runners quickly
as the sharp rocks havent been smoothed and tumbled like river
rocks. If the musher avoids exposed rocks, plastic lasts for a long
Plastic runners have more friction on the tundra than they do
on snow, but they are a hundred times better than steel or wood!
We have traveled many miles on bare ground with plastic runners
and a considerable load with only a few dogs. Plastic runners are
unaffected by water and give considerable strength to the sleds
frame as they are flexible and durable.
Traveling in the mountains can be dangerous. It is hard to climb
hills and mountains with a dogsled. Dogs get discouraged, and are
occasionally injured pulling on the hard-packed, windswept snow.
Going down a mountain pass is another story, particularly if traveling
on a sidehill.
There are several techniques to use. The main thing is to:
- Reduce the pulling power of the dogs.
- Increase the friction of the sled as much as possible.
Reducing Pulling Power
Dogs are afraid of being run over by the sled on a steep hill
- Attach a dogchain between the sled and the wheel dogs. This
puts a distance between them and the sled. They dont feel
threatened by the sled and dont pull too hard trying to
- Unhook the towline from the dogs harness and hook it to their
neckline. They cant pull as hard with their collar as they
can their harness.
- Sometimes we turned a few dogs loose if we could trust them
not to run away. Minimize power!
- To prepare the sled, we wrapped chains loosely, spiraling down
the sled runners. This greatly increased the friction.
- On steeper mountains, we wrapped them as shown on the left,
in front of the rear stanchion on both sides of the sled. This
usually slows the sled enough to make a safe descent.
You could imagine what would happen if we put the roughlocked
chain on the front of the sled. The inertia of the back end of the
sled would cause it to pass the front, like jamming the front brake
of a bicycle.
The snow on the mountains isnt consistent. There are places
where it seems as hard as concrete from the wind, and places where
it is soft. It is easy to run over the dogs or tip over and start
If the trail involves going down the side of a mountain, it can
be complicated. The sled will tend to slide sideways down the slope.
When traveling on a sidehill, we put more roughlocking on the uphill
side of the sled. As the dogs pull, the sled pulls unevenly, holding
it on the sidehill angle.
Once the sled gets out of control and starts tumbling down the
mountain, tremendous injury and damage to your sled and dogs is
you were to jump around wildly, you would tire quickly. Overcoming
the inertia of the erratic movements would require much energy.
If you were to dance for hours, you wouldnt get as tired because
the rhythmic motion is smooth, coordinated, and very energy efficient.
The same principle works with dogs. If they can get and keep a
rhythm, they can travel for many miles. If the sled is jerking,
it throws them out of stride, causing them to tire quickly. Overcoming
the inertia of the erratic sled is exhausting for them. The main
job of the musher is to kick, push and steer in a way that the sled
goes as smoothly as possible, without jerking, tugging, and breaking
the dogs rhythm. An inexperienced musher kicking out of rhythm
with the dogs can actually slow the sled. He thinks he is helping
to propel the sled, adding his force to the dogs efforts, but he
is being counter productive by breaking their rhythm.
Mushers have noticed, like cross country skiers and runners, that
their kick has far more power if they follow through on their kick
backwards, even after their foot has left the ground. Action equals
reaction. When the leg is forced quickly backward in the air, the
opposite reaction is the sled going forward. Cross country coaches
often instruct their runners, kick, kick. They are using
the same science principle.
mushers today put a shock cord in the towline. This helps to absorb
some of the impact of the bumps and jerking of the sled. Maintaining
the dogs rhythm is the secret to endurance. Violating physics
principles results in tired dogs.
Turning the sled takes energy from the dogs. This is why the musher
usually puts his/her strongest dogs nearest to the sled. Once the
sled gets off the trail, particularly with a big load, it takes
considerable energy to get it back on. The most efficient way is
to stay on the trail. It is important to rig and build the sled
so that it steers well.
the bridle were attached to the very front of the sled, it would
steer easily, but some of the dogs energy would be pulling
the sled downward, greatly increasing friction.
If the bridle were attached in the middle of the sled, it wouldnt
have the leverage to steer as the sled weaves from side to side
on the trail, or navigates trees in a portage.
The secret is to have the bridle attached as near to the front
as possible to facilitate steering, but have it back enough that
the towline is pulling slightly upward. It is also very important
to have the ring of the bridle perfectly centered. If it gets off
center, even a little bit, the sled will always tend to pull to
one side, tiring dogs and driver.
When traveling on a sidehill, the sled tends to slide downhill,
exhausting and frustrating the musher and dogs and complicating
travel, especially with a load. Oldtimers overcame this by putting
a stick in the loop of the bridle on the downhill side, thus shortening
that side of the bridle. This caused uneven pulling from the downhill
side of the bridle, helping it follow the dogs. When travel returned
to flat ground, the stick was removed, and the centered bridle pulled
One of the most important things in a longer sled (over eight
feet) is having a little rocker in the runners. One-fourth
to three-eights of an inch is all thats necessary.
If the runners are perfectly straight, or worse yet, high in the
middle and low on the ends, it will be very hard to steer. It will
always tend to go straight.
If there is too much rocker, the sled will continually swing back
and forth, requiring constant energy to steer. It will have no ability
to head straight and stay that way.
I have made both of these mistakes.
The sled with too much rocker had a twelve-foot runner, and it
was still hard to keep on the trail. The sled that had no rocker
was a ten-foot nightmare that couldnt follow the dogs around
the slightest corner.
Ninety Years Ago
Before the fishwheel made feeding larger dog teams possible, men
often traveled with only two or three dogs. The men had to pull
too. The backs of the sleds had no place for a person to stand.
The individual took his place in harness in front of the sled, behind
From this position, steering was a problem so they bolted and
lashed a long pole on the right side that could lever the sled onto
the trail. Braking from that position was very difficult, as might
skinners and farmers in the Lower 48 used the terms, gee
and haw in commanding their animals to go right or left.
They brought the terms to Alaska. The pole on the right side was
called a gee pole. From this we get the Alaskan term
gee pole spruce. They were the toughest trees to use
to lever the sled from side to side onto the trail.
When the trail was good, the man rode a single or double ski in
front of the sled instead of walking with snowshoes. It wasnt
until fairly recently that men rode on the back of the sled. The
single ski was similar to todays snowboard. Care was taken
to wax or oil the wooden skis and snow board to reduce friction
as much as possible.
Keeping in mind the need to save dogs energy in steering,
most of the load in a sled should be in the very back. This keeps
the front of the sled light, so the dogs can lever it onto the trail.
In March and April, when the packed trail becomes higher than
the soft surrounding snow, steering becomes very difficult with
Moving a Big Load
Nowadays most mushers run around with empty or nearly empty sleds.
We used to load a whole bull moose or three caribou in a sled and
make it home with four dogs. That involved science principles, particularly
when the sled got stuck. Static friction, the friction of something
not yet moving, is much greater than kinetic friction, the friction
of something that is already moving. Once the inertia of the stationary
sled has been overcome, and static friction has been replaced by
kinetic friction, the dogs can keep a big load moving without much
effort. Once the sled is stuck, either from bumping a tree or sliding
off the trail, three things must be overcome:
- Static friction
- The weight of the sled back onto the trail.
All of this amounts to an energy drain on the dogs and driver.
To get going after sliding off the trail with a big load, pull
about a foot of slack in the towline and let go while yelling at
the dogs. When they hit the end of that foot of slack, the force
of their weight and startup speed jerks the sled, overcoming inertia
and static friction.
We had to be careful using this trick with the dogs. They can
exert tremendous force, sometimes breaking snaps and towlines. That
meant a long walk home as the dogs took off alone.
This same principle is used today in snowmachines where there
is a spring in the sled hitch. The force of the machine hitting
the end of the spring jerks the sled loose. Without the six inch
spring, the snowmachine would spin out before it overcame the inertia
and friction of the sled.
A longer sled is heavier and harder to steer, but on a rough trail
it glides over the bumps that a smaller sled would dip into.
This saves tremendous energy for the dogs, as an erratic small
sled breaks the dogs rhythm and quickly tires them.
A longer sled has more surface area on the runners than a shorter
one. On a hard trail, this produces more friction. On a soft trail,
it means more surface to keep the sled up. It takes a lot of energy
to compress snow, and there is no return on the energy expended.
Longer sleds sink far less than short ones. As a longer sled is
harder to steer, it needs a little more rocker in the runners.
Once the sled sinks up to the crosspieces, the resistance is so
great that travel is almost impossible. Modern sleds that have a
plastic belly arent affected this way, but long ago, this
was the cutoff point for travel. Once the crosspieces were dragging,
we had to walk ahead with snowshoes.
A sled that has too abrupt a bend will constantly jerk the dogs
backward. The forces from hitting a bump with a sled of this design
are very negative.
The amount of upturn and degree of bend depend on the country
used to think of the brake as negative dog feed. The
chemical energy of dog feed converts to the energy of motion on
the trail. The motion and inertia of the moving sled must be preserved.
A brake is a friction devise to overcome that motion.
We made brakes from iron similar to the ones today. Tools and
materials were at a minimum, and brake manufacture was an art form.
The problem is to have a brake that will work equally well on
clear ice and soft snow.
To stop on clear ice, sharp points must dig in at the proper angle.
If the angle is too gradual, it will slide over the surface. If
the angle is too sharp, it can hook logs and stumps, rip off the
sled, and endanger the musher.
Stopping on a hard packed trail is fairly easy, but fall time
on clear ice, or traveling in the windswept mountains, the challenges
are far greater.
To stop in powder snow, there has to be enough surface area to
provide the resistance to slow the sled.
Some people now use pieces of cleated snowmachine tracks for a
There is no perfect sled. How you design a sled depends on your
purpose and conditions. Every adjustment is a tradeoff.
There is a limited amount of energy available from a dog team.
That energy must be conserved as much as possible if the musher
is going to haul a load or travel the distance. Sled design and
operator skills make all the difference. With the same dogs and
an efficient sled, a good musher can go two or three times farther
than an inexperienced one.
- If there are any dog teams in your area, study the sleds. What
is the length? Is there rocker in the runners? What are the sleds
used for: racing, cross country, hauling loads?
- Study the snowmachine sleds and hitches in your area. What
are the features people look for? What materials are best?
- What did people there use for runners before plastic became
available? Before that, what did they use? Ask about different
weather conditions. Does their experience compare with the above
- Ask the oldtimers how they determined where to put the bridle
of the sled and why they did it that way.
- What is the load most often hauled now by sleds in your village?
What used to be the main load?
- Ask people in your area why they switched from dogs to snowmachines.
What are the advantages and disadvantages of each?
- Watch dogs as they train. What rhythms do you see? Do all the
dogs in the team go from a walk to a trot to a full run at the
same speed? Watch the team on uneven ground. Why is the musher
- Try pushing the different sleds in your village. Which runners
are best and why?
- Roughlock the runners of a sled. Try to push or pull it.
- Try roughlocking a sleds runners and going down a small
hill. Roughlock only one side. Try again.
- Ask the oldtimers in your area how they traveled in the mountains
- Push an empty sled. Load it and push it again. Is there a difference
in getting it going? Is there a difference once it is going?
- Put most of the load in the sled on the front. Try to pull
it around corners. Now put the same load in the back of the sled.
Pull it around the same course. What is the difference?
- Put a temporary bridle on a sled. Move it from center. Pull
the sled. Is the difference obvious?
- If possible, try a long, short, and medium sled (eight, ten,
and twelve foot) on a rough trail. What differences do you observe?
- Get a big load in a sled and hook up a few dogs. Let them try
to get the load going. Stop. Pull slack in the towline, and command
the dogs to pull. When they hit the end of the slack, there is
a jerk (as in the chapter Moving a Big Load.) Is there
an easier way you know of to get the sled going with a big load?
- Put a fishermans scale on the end of a line from a small
sled. How many pounds do you have to pull to break the sled free
from static friction? How many pounds is the sled pulling once
it is moving? Of course, some of the resistance while the sled
is stopped is from inertia, but much is static friction.
- Look at the sled brakes in the village or ask the oldtimers
what they used for a brake. Were the conditions mostly powder
snow or clear ice?
- What five things are dogs pulling against when they pull a
- What kind of runners did the oldtimers have for warm and cold
- What were some of the local alternatives to ironwood runners
imported from the lower 48?
- Why have we changed to plastic?
- Draw a picture of roughlocking.
- Describe inertia as it relates to driving a dogsled.
- Why is rhythm important?
- What happens if a long sled doesnt have any rocker in
- What happens if the sled has too much rocker?
- What happens if the bridle on the sled isnt centered?
Explain or draw the result.
- Draw a picture that illustrates the advantages of a long sled
on a rough trail.
- Thinking of the five things that a dog is working against,
tell as much as you can about making the dogs job easier
and increasing the miles traveled in a day.
- Draw the top view of a sled that would be pulled by a man and
two dogs. Include the method by which he would steer.
- Why is traveling in March or April difficult?
- What two forces have to be overcome to get a sled moving?
- Draw a picture showing the disadvantage of a sled with a bend
in the runner that is too abrupt.
- What is the purpose of a sled brake?
- A sled has a runner that is in contact with the snow for 8.5
feet. Each runner is 2 wide. (Remember, there are two runners.)
The sled, including driver and load, weigh 275 lbs. What is the
pressure in psi of the runners? What would it be if the runners
were 1.75 wide? 3 wide?