Snowmachines have come a long way in 40 years. One of the first snowmachines held 25 people! Back in those days, they were made out of miscellaneous tractor pieces and the engines were placed in the back of the snowmachine. The skis were made out of wood and were very heavy. The tracks were made out of rubber with no paddles at all. Boy have they have changed! Today, snowmachine chassis are made of aluminum and have plastic parts. The skis are also made out of light weight plastic. The track now is made out of a kevlar composite. With all these light weight upgrades, some snowmachines now weigh less than 400 pounds! Snowmachines, very complicated pieces of machinery, can be ridden by any one of any age. Learning how the pistons, the clutch and the drive chain work will help you understand how the snowmachine works.
Snowmachines have two main types of engines. The two types of engines are four strokes and two strokes. A four stroke engine fires once every other revolution. Unlike the four stroke, the two stroke engine fires every revolution. Snowmachine engines have two or three pistons. Since the two stroke fires every revolution, it has the best power to weight ratio out of either of the snowmachine engines. This makes the snowmachine with the two-stroke engine have more horsepower and makes it go faster. But before learning about the engine, learning how snowmachines start is also interesting. (Brian)
Snowmachines can start with the pull start or, an easier way, with electric start. When you pull the pull start the recoil starts spinning the crank shaft. The crank shaft is connected to the pistons. When the pistons go up and down it gets a fuel and air mixture in the combustion chamber, then enough pressure and it gets the spark plug firing. There is a sensor on the snowmachine that tells the snowmachine pistons when to fire. The electric start works basically the same way except its electric. When you turn the key it activates the starter, the starter turns the fly wheel which in turn turns the crank shaft. When the crank shaft turns, it makes the pistons go up and down. The pistons are the main part of the engine. (Delequato.)
Since the pistons are the main part of the engine, they are where the horse power comes from. The pistons go up and down inside the combustion chamber (cylinder). The combustion chamber sits inside of the crank case. The piston is made out of aluminum and can take a bad beating. When the piston goes up, a fuel and air mixture is let in the combustion chamber. The piston compresses the spark plug until it sparks, and an explosion happens in the cylinder and then forces the piston down. When the piston goes down it turns the crank shaft and forces the exhaust fumes out of the cylinder. The way that the piston gets the gas is from the carburetor. (Brian.)
The main process of the carburetor is to get the fuel and air to the pistons. Inside the carburetor there are jets. Jets are what regulate the amount of fuel through the carburetor to the pistons. The jets are placed inside the carburetor, and have a hole in the center and the gas shoots through it. Some snowmachines are fuel injected. Fuel injected snowmachines regulate the amount of fuel going through the carburetor and to the piston automatically. The other type of snowmachine is carbureted, and this is when the snowmachine doesn’t adjust the amount of gas itself so changing the jets has to be done manually. When the carburetor gives gas to the piston the piston turns the crank shaft, which turns the primary sheave. (Delequato.)
The primary sheave is made up of two main parts: a sliding sheave and a fixed sheave. The primary sheave has the clutch spring connected to it and a belt connected to it. As the crank shaft spins it spins the primary sheave. As the engine revs up, the spring pushes the sliding sheave towards the fixed sheave. As it gets closer to the fixed sheave it squeezes the belt and that is what turns the secondary sheave. The clutch also plays a major role in letting the snowmachine move. (Delequato, John.)
The main function of the clutch is to switch the gears. Unlike dirt bikes where they shift manually, it shifts the snowmachine on its own. Changing the gears is done by centrifugal force. The clutch is located on the primary sheave on the opposite side of where the crank shaft goes into. (Delequato.) To shift gears there is about 2000 pounds of force acting on the clutch. As the clutch makes the sliding sheave pinch the belt and move it, the belt moves another sheave called the secondary sheave. (Brian.)
The secondary sheave is the bigger of the two sheaves. The secondary sheave is spun by a belt coming from the primary sheave. The primary sheave is made out of metal. The secondary sheave has a helix. The helix helps it switch gears also, and helps the secondary sheave spin. The main function of the secondary sheave is to spin another shaft to the chain case. (Delequato.)
How does the chain in the chain case spin? The chain spins because of the secondary sheave spinning a shaft leading to the chain. The chain case is located on the other side of the snowmachine. You can change the top speed of the snowmachine by adjusting the chain. The chain spins the sprockets located on a jack shaft, and in turn this causes the sprockets to turn the track. Since the snowmachine moves it needs to find a way to stop. This is done by the brake which is located in between the chain case and the sprockets. (Delequato.)
The brake, sits around the jack shaft, and is welded on to it. When you press the brake lever located on the handle bars, a hydraulic fluid forces the brake pad to press against the brake disk. The main reason why the snowmachine stops is by friction. Now move on to another part of the snowmachine, the reeds. (Delequato.)
There are two reeds on every snowmachine. There is one in each of the combustion chambers. Reeds are what spit in the gas and fuel mixture into the combustion chamber. The gas gets sucked in to the combustion chamber because there is a vacuum that gets created in the crank case. Getting the right gas and getting the gas into the combustion chamber at the right time lets the engine run smooth. (Delequato.)
There are many types of gasoline. Gasoline is a mixture of liquid hydro carbon distilled from crude oil. Pump gas, which you buy at the gas station, is between 85 and 92 octane. Most racers use 110 octane which is aviation gas. The octane rating of gasoline tells you how much the fuel can be compressed before it ignites the spark plug. This is why racers use this kind of gas because it runs hotter, cleaner, and compresses faster so it makes the pistons move faster. Racers need it to burn hotter and cleaner because their snowmachines are modified. The average snowmachiner, like the trail riders and mountain riders run pump gas, they only use pump gas because there's no need for it to burn as hot. But if the mountain snowmachiners or trail riders have their snowmachines modified, they can use aviation gasoline. Not only does the snowmachine engine need gasoline it also need air. (Bookrags.com.)
Why does the engine need air? The main reason why the engine needs air is for the fuel and air mixture that happens in the combustion chamber. The engine gets air from the air box. The air box sucks in air through vents that are located on the snowmachine. Vents go to the air box filter; this filters the air through tubes. The tubes then send the air to the reeds and air gets sucked into the combustion chamber. Because of the engine burning so hot it needs a way to cool its self down. (Delequato.)
There are two ways a snowmachine can cool down. It can be fan cooled or liquid cooled. A fan cooled snowmachine has an axial fan located over the hot engine. It sucks air from out side the snowmachine and blows it over the hot engine. A liquid cooled snowmachine uses anti freeze that flows through tubes around the snowmachine. The anti freeze goes to the engine, but it can't just go straight to the engine because it’s not cold enough. The anti freeze goes to the back of the snowmachine where the heat exchanger is located. The anti freeze goes in a cycle from the engine to the heat exchanger, when it leaves the engine it is about 180 degrees, when it goes to the back, the heat exchanger gets hit with snow, the snow cools the anti freeze, and that this how it cools the engine down. Liquid cooled snowmachines have more horse power because they cool more consistently. The anti freeze goes through a tube and down the whole chassis, which is the body of the snowmachine.. (Delequato.)
What’s the main point of having a chassis? If there wasn't a chassis there would be no way to ride the snowmachine. The chassis is what the motor sits in. The chassis is made out of a light weight kind of metal called aluminum. It also has plastic which is what the cowling is made out of, and the front of the snowmachine. The chassis sits over the track, the track is what spins and makes the snowmachine move. (Salas. Pg. 14)
Why do snowmachines use tracks and not wheels? They use tracks because if they used wheels they would sink in the snow, and wheels don't have good traction on snow and ice. The track is made out of kevlar composite. They use kevlar instead of rubber like they used to because it is stronger. Snowmachines have lugs on the tracks. Lugs are the paddle like things that are on the tracks. Trail riders don’t need as much traction because they are not riding in deep snow. Racers need more traction than trail riders but not too much or else there is too much friction so they won’t go as fast. Mountain riders have big lugs because they normally ride in deeper snow so they need as much traction as possible. Lugs are what help the snowmachine go through the snow and give it traction, but what helps the snowmachine absorb the bumps for a smooth ride? The shocks are the key. (Emond.)
There are two places where shocks are located. There are shocks in the front and in the back of the snowmachine. The shocks are made out of aluminum on the out side and are filled with nitrogen. The shocks in the front have springs around them to help absorb bumps. But in the back of the snowmachine there is no spring around them. This is because they are not taking as much bumps in one certain area. Some shocks today don't have springs around them; they are filled with air and nitrogen. (Delequato.)
As you can see there are many mechanical parts to make the snowmachine go. So starting the snowmachine, you can either pull it or use a key. The pull and key start do the same thing; they spin the crank shaft and get the pistons going up and down. The crank shaft spins the primary sheave, the belt spins the secondary sheave. The secondary sheave spins another shaft to the chain case, the chain case then spins a jack shaft which has sprockets on it and the sprockets spin the track. Now that you have read this paper I hope you learned a lot about snowmachines, and when you jump on a snowmachine I hope you think about how they work.
Glossary
Anti freeze noun – I used anti freeze to cool down my engine.
Is Used for in internal combustion engines. Consist of methanol, ethylene glycol, and propylene glycol.
Axial fan noun – My axial fan blows the air at me and cooled me down.
Is a fan that blows air in a certain direction to cool things down.
Cowling noun – I just went and bought the lightest cowling.
The cowling is the hood that goes over the snowmachine engine and is made of fiber glass.
Crude oil noun – The crude oil was pumped out of the ground.
The term meaning unprocessed oil and is a fossil fuel
Heat exchanger noun – The heat exchanger cooled down my hot water.
An exchanger that turns hot things cold or cold things hot.
Helix noun – The helix sat at an angle inside the engine.
A curve that lies on the surface of a cylinder or cone, and cuts the element at a constant angle.
Horsepower noun – My new snowmachine has so much horsepower.
The engines torque times the engines rpm divided by 5252.
Hydro carbon noun – The hydrogen and carbon burn very easily
Organic compound consisting entirely of hydrogen and carbon.
Sheave noun – The sheave helped my rope grip onto it when I was pulling my car.
A wheel or disk with a grooved rim, especially one used as a pully.
Sprocket noun – The sprocket griped into the holes of my track and turned it.
A wheel with teeth that meshes with a chain or track.
Work Cited
Bookrags.com. World of chemistry. 2005e 23, Jan. 2008. <http://www.bookrags.com/research/gasoline- woc/>.
Marshal Brian. How Two-stroke Engines Work. How Stuff Works, Inc. Marshal Brian. 23, Jan. 2008. <science.howstuffworks.com/two-stroke/.htm>.
John Delequato Telephone interview. January 14
Emond, Patrick. How Snowmobiles work. How stuff works, inc.. 13, Jan. 2008. <http://auto.howstuffworks.com/snowmobile.htm>.
Joseph,James.
Snowmobiling.
Salas,Laure.
Snowmobiling.
Wikipedia.org. 18, Jan. 2008. 18, Jan. 2008. <http://en.wikipedia.org/wki/snowmobile>.