The Art of Building Wood and Rawhide Dog Sleds

Standards A six, 15 B three C three D 1, 3 Concepts A = R Inertia Leverage Suface surface area Friction Forms of energy	If a corking figurer tried to develop a better dogsled than the ones oldtimers made, information technology 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, simply aren't used because more powerful animals are bachelor, like horses, donkeys, and oxen. Since those animals aren't applied in the arctic, dogs were the best sou rce of ability until the advent of the snowmachine. Each domestic dog can get himself from indicate 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 bachelor from a team of dogs. Dog mushing is a constant written report in energy conservation. Snowmachines seem to accept power to waste matter, but the same scientific principles that apply to dogsled design also apply to snowmachine sleds.
	Energy Considerations The dogs are pulling confronting several forces. Friction of the runners confronting the surface of the snowfall. Lifting the sled and load up banks and hills, although every round trip, or trip from sea level to sea level averages out to level ground. 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 pocket-sized amount of air current 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 Earlier plastic we used hard steel runners in warm weather condition and wooden runners in cold weather. Steel runners were very good for spring travel, pond creeks and crossing thawed lakes, only came to a halt on bare tundra. Megafriction! In the spring we traveled for miles and miles on tundra, trying to avert bare basis, going from patches of snowfall to glaciered creeks dorsum to patches of snow. The divergence in friction between snowfall and tundra is tremendous! Steel runners were also very high friction in common cold weather. They groaned like an old fishwheel. And woe unto the musher in cold atmospheric condition who didn't avert fresh dog excrement on the trail. It froze to the steel runners and was the equivalent of setting an ballast. The hard ironwood runners used in cold weather were imported from the lower 48 then to Alaska. They were adequately low friction in very cold weather condition once they got a glaze on them. Some people used pino tar to brand them run smoother, but it soon wore off. Lacking ironwood, many oldtimers split a green spruce tree in half, peeled it, and used that for runners. The icy exterior of the tree had very low friction with the trail's surface. Notwithstanding, the rounded runners sank a fiddling deeper in the trail than flat ones would. The icy runners also dried out on cold nights, then nosotros 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 direct up rather than straight out from the hillside (geotropism). That hardwood is too good for sled runners. Often we tipped our sled over in the morn and iced the runners with a rag and a can of warm water. In that location was speculation whether saccharide made the icy pic more durable. Long agone, urine was used, but it isn't expert for hunters and trappers who try to minimize the bear on of their presence on the country. Changing Weather The above woods runners worked well in cold atmospheric condition, just woe unto the musher who traveled far with wood runners and the weather turned warm! Wood runners are very loftier friction in moisture snow. Bolts, inset one-half inch, hung downwards similar a dozen thin brakes as the woods wore away in the balmy temperatures. This is a part of the good one-time days we would just as soon forget. The only solution was to put wood runners over steel runners preparing for all types of conditions. This worked, merely made the sled heavier. We spent many hours irresolute runners as the weather changed. Very long ago, oldtimers used os for runners. I empathize that bone provided low friction, but was very difficult to attach to the sled. Modern Materials 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 potent, light, and dog excrement doesn't adhere. It is like shooting fish in a barrel to attach and fairly durable. (Be certain to put plastic on when information technology is warm. Plastics aggrandize profoundly when heated. If you lot put runners on common cold, they volition expand in warm temperatures, creating bulges that fill with snow.) Exposed mountain rocks destroy a pair of plastic runners quickly as the sharp rocks haven't been smoothed and tumbled similar river rocks. If the musher avoids exposed rocks, plastic lasts for a long time. Plastic runners accept more friction on the tundra than they do on snow, but they are a hundred times ameliorate than steel or forest! 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 forcefulness to the sled's frame as they are flexible and durable.
	Mountain Travel Traveling in the mountains can be dangerous. It is difficult to climb hills and mountains with a dogsled. Dogs get discouraged, and are occasionally injured pulling on the hard-packed, windswept snow. Going downwardly a mountain pass is another story, peculiarly if traveling on a sidehill. There are several techniques to use. The main thing is to: Reduce the pulling ability of the dogs. Increase the friction of the sled equally much equally possible. Reducing Pulling Power Dogs are afraid of being run over by the sled on a steep hill or mountain. Attach a dogchain betwixt the sled and the wheel dogs. This puts a altitude betwixt them and the sled. They don't feel threatened by the sled and don't pull too hard trying to become abroad. Unhook the towline from the dogs harness and hook information technology to their neckline. They can't pull as hard with their collar equally they can their harness. Sometimes nosotros turned a few dogs loose if nosotros could trust them not to run abroad. Minimize power! Increment Friction To ready the sled, nosotros wrapped bondage 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 ordinarily slows the sled enough to make a prophylactic descent. You lot could imagine what would happen if we put the roughlocked chain on the front of the sled. The inertia of the dorsum finish of the sled would cause it to pass the forepart, similar jamming the forepart brake of a bicycle. The snow on the mountains isn't consequent. At that place are places where information technology seems equally 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 tumbling. Sidehill If the trail involves going down the side of a mount, it tin be complicated. The sled will tend to slide sideways downwardly the slope. When traveling on a sidehill, we put more than roughlocking on the uphill side of the sled. Every bit the dogs pull, the sled pulls unevenly, holding information technology on the sidehill angle. Once the sled gets out of control and starts tumbling downwardly the mountain, tremendous injury and damage to your sled and dogs is likely.
	Rhythm If you were to spring around wildly, y'all would tire apace. Overcoming the inertia of the erratic movements would require much energy. If you were to trip the light fantastic toe for hours, you wouldn't get as tired because the rhythmic motion is smooth, coordinated, and very energy efficient. The same principle works with dogs. If they tin can get and keep a rhythm, they can travel for many miles. If the sled is jerking, information technology throws them out of pace, causing them to tire chop-chop. Overcoming the inertia of the erratic sled is exhausting for them. The main job of the musher is to kick, button and steer in a mode that the sled goes as smoothly as possible, without jerking, tugging, and breaking the dogs' rhythm. An inexperienced musher kick out of rhythm with the dogs can actually irksome the sled. He thinks he is helping to propel the sled, adding his forcefulness to the dogs efforts, just he is being counter productive by breaking their rhythm. Mushers have noticed, similar cross country skiers and runners, that their kick has far more power if they follow through on their boot 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 forrad. Cross country coaches often instruct their runners, "kick, kick." They are using the aforementioned scientific discipline principle. Most mushers today put a daze 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 undercover to endurance. Violating physics principles results in tired dogs.
	Turning 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 free energy to get it dorsum on. The virtually efficient style is to stay on the trail. It is of import to rig and build the sled then that it steers well. Bridle If the bridle were attached to the very front of the sled, it would steer easily, only some of the dog'southward energy would exist pulling the sled downwardly, greatly increasing friction. If the bridle were fastened in the middle of the sled, it wouldn't have the leverage to steer as the sled weaves from side to side on the trail, or navigates trees in a portage. The clandestine is to take the bridle fastened as near to the front as possible to facilitate steering, but have information technology back enough that the towline is pulling slightly upward. Information technology is likewise very important to accept the ring of the determent perfectly centered. If it gets off center, even a petty bit, the sled volition always tend to pull to one side, tiring dogs and driver. Sidehill Undercover When traveling on a sidehill, the sled tends to slide downhill, exhausting and frustrating the musher and dogs and complicating travel, specially with a load. Oldtimers overcame this past putting a stick in the loop of the bridle on the downhill side, thus shortening that side of the determent. This caused uneven pulling from the downhill side of the bridle, helping it follow the dogs. When travel returned to apartment basis, the stick was removed, and the centered determent pulled direct again. Rocker One of the most of import things in a longer sled (over eight feet) is having a little "rocker" in the runners. One-4th to three-eights of an inch is all that'due south necessary. If the runners are perfectly straight, or worse yet, high in the centre and depression on the ends, information technology will be very hard to steer. Information technology volition ever tend to go directly. If there is besides much rocker, the sled will continually swing back and along, requiring abiding free energy to steer. It will have no power to head straight and stay that way. I accept fabricated 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 x-foot nightmare that couldn't follow the dogs around the slightest corner.
	90 Years Agone Before the fishwheel made feeding larger dog teams possible, men often traveled with simply two or three dogs. The men had to pull too. The backs of the sleds had no identify for a person to stand. The private took his place in harness in front end of the sled, backside the dogs. From this position, steering was a problem and then 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, every bit might be imagined. Mule skinners and farmers in the Lower 48 used the terms, "gee" and "haw" in commanding their animals to get right or left. They brought the terms to Alaska. The pole on the correct side was called a "gee pole." From this we get the Alaskan term "gee pole spruce." They were the toughest copse 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 wasn't until fairly recently that men rode on the dorsum of the sled. The unmarried ski was similar to today's snowboard. Intendance was taken to wax or oil the wooden skis and snow board to reduce friction every bit much as possible.
	Loading the Sled Keeping in listen the need to save canis familiaris'south energy in steering, most of the load in a sled should be in the very back. This keeps the front of the sled light, and so the dogs tin 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 a load.
	Moving a Large Load Nowadays most mushers run around with empty or nearly empty sleds. We used to load a whole balderdash moose or iii caribou in a sled and make it habitation with four dogs. That involved science principles, peculiarly when the sled got stuck. Static friction, the friction of something non nonetheless 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 large load moving without much attempt. Once the sled is stuck, either from bumping a tree or sliding off the trail, three things must exist overcome: Inertia Static friction The weight of the sled back onto the trail. All of this amounts to an free energy drain on the dogs and driver. To get going afterward sliding off the trail with a big load, pull nearly a pes of slack in the towline and permit go while yelling at the dogs. When they hit the cease of that foot of slack, the force of their weight and startup speed jerks the sled, overcoming inertia and static friction. Nosotros had to be careful using this trick with the dogs. They tin can exert tremendous force, sometimes breaking snaps and towlines. That meant a long walk home as the dogs took off solitary. This aforementioned principle is used today in snowmachines where at that place is a jump in the sled hitch. The force of the machine hitting the terminate of the spring jerks the sled loose. Without the six inch bound, the snowmachine would spin out earlier it overcame the inertia and friction of the sled.
	Sled Length A longer sled is heavier and harder to steer, merely on a crude 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 canis familiaris's rhythm and quickly tires them. A longer sled has more surface area on the runners than a shorter ane. On a difficult trail, this produces more friction. On a soft trail, information technology means more than surface to keep the sled up. Information technology takes a lot of energy to compress snow, and there is no render on the free energy expended. Longer sleds sink far less than brusque ones. As a longer sled is harder to steer, information technology needs a little more than rocker in the runners. Once the sled sinks upwardly to the crosspieces, the resistance is and so great that travel is near impossible. Modern sleds that have a plastic belly aren't affected this way, but long ago, this was the cutoff point for travel. One time the crosspieces were dragging, nosotros had to walk ahead with snowshoes.
	The Bend A sled that has too abrupt a bend will constantly jerk the dogs backward. The forces from hit a bump with a sled of this design are very negative. The amount of upturn and degree of bend depend on the state being traveled.
	Brakes I used to retrieve of the brake as "negative dog feed". The chemical free energy of dog feed converts to the energy of motion on the trail. The motion and inertia of the moving sled must exist preserved. A restriction is a friction devise to overcome that move. Nosotros fabricated brakes from fe similar to the ones today. Tools and materials were at a minimum, and brake industry was an art course. The trouble is to have a brake that will piece of work equally well on clear water ice and soft snow. To stop on clear ice, precipitous points must dig in at the proper angle. If the bending is too gradual, information technology volition 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 autumn time on clear ice, or traveling in the windswept mountains, the challenges are far greater. To stop in pulverization snow, there has to be plenty surface surface area to provide the resistance to dull the sled. Some people now use pieces of cleated snowmachine tracks for a brake.
	Summary In that location is no perfect sled. How you blueprint a sled depends on your purpose and conditions. Every adjustment is a tradeoff. There is a limited amount of free energy bachelor from a dog team. That free energy must be conserved every bit much every bit possible if the musher is going to haul a load or travel the altitude. Sled blueprint and operator skills make all the difference. With the same dogs and an efficient sled, a proficient musher can go two or three times farther than an inexperienced ane.
	Activities If there are whatsoever dog teams in your area, report 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 all-time? What did people there employ for runners before plastic became available? Before that, what did they use? Ask about different weather conditions. Does their experience compare with the above text? Ask the oldtimers how they determined where to put the determent of the sled and why they did information technology that mode. What is the load near oft hauled now past sleds in your village? What used to be the principal 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? Practise all the dogs in the squad go from a walk to a trot to a full run at the aforementioned speed? Watch the squad on uneven ground. Why is the musher pushing? Try pushing the dissimilar sleds in your village. Which runners are best and why? Roughlock the runners of a sled. Endeavor to push or pull it. Effort roughlocking a sled's runners and going down a small loma. Roughlock only one side. Try again. Ask the oldtimers in your area how they traveled in the mountains with dogs. Push an empty sled. Load information technology and push it again. Is there a difference in getting it going? Is there a difference in one case it is going? Put near of the load in the sled on the front. Attempt to pull information technology around corners. Now put the same load in the dorsum of the sled. Pull it effectually the same course. What is the difference? Put a temporary determent on a sled. Move it from center. Pull the sled. Is the difference obvious? If possible, try a long, short, and medium sled (eight, 10, and twelve pes) on a crude trail. What differences do y'all find? Get a big load in a sled and hook upwardly a few dogs. Allow them try to get the load going. Stop. Pull slack in the towline, and command the dogs to pull. When they striking the end of the slack, there is a jerk (as in the affiliate "Moving a Big Load".) Is at that place an easier way you know of to get the sled going with a big load? Put a fisherman's scale on the end of a line from a modest sled. How many pounds do y'all have to pull to break the sled free from static friction? How many pounds is the sled pulling once information technology is moving? Of course, some of the resistance while the sled is stopped is from inertia, just much is static friction. Wait at the sled brakes in the village or enquire the oldtimers what they used for a brake. Were the weather condition mostly pulverization snow or clear ice?
	Student Response What five things are dogs pulling confronting when they pull a sled? What kind of runners did the oldtimers have for warm and cold conditions? What were some of the local alternatives to ironwood runners imported from the lower 48? Why have we changed to plastic? Draw a moving-picture show of roughlocking. Draw inertia as it relates to driving a dogsled. Why is rhythm important? What happens if a long sled doesn't have any rocker in the runners? What happens if the sled has too much rocker? What happens if the bridle on the sled isn't centered? Explain or describe the result. Draw a moving-picture show that illustrates the advantages of a long sled on a crude trail. Thinking of the five things that a dog is working against, tell as much as you can about making the canis familiaris's task 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 past which he would steer. Why is traveling in March or April hard? What two forces have to be overcome to get a sled moving? Describe a picture showing the disadvantage of a sled with a bend in the runner that is too sharp. What is the purpose of a sled restriction?
	Math A sled has a runner that is in contact with the snowfall for 8.5 anxiety. Each runner is 2" wide. (Remember, in that location are two runners.) The sled, including commuter and load, counterbalance 275 lbs. What is the pressure in psi of the runners? What would it be if the runners were ane.75" wide? 3" wide?

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Source: http://ankn.uaf.edu/publications/vs/dogsleds.html