Hey everyone ! 
I just wrote a little text about the "snowmobile clutch" , in english. (I`m a 19 years old boy from norway).
I go to a veichle-mechanic-orientated school and our english teacher told us do a hand-in on a "technical" device, either from car/motorcycle etc.
I guess most will write about some boring car stuff but I chose to write about the snowmobile clutch system. I mostly wrench on bikes, so I`m not that into sleds, but I will post what I wrote here so that you can correct me, Ì guess there are some things that arent 100% right hehe
(please explain the secondary, I don`t know anything about it). I know that what I`ve written isn`t "enough" , but my teacher doesn`t know anything about this stuff so he wount think so.
Here`s what I wrote:
"The snowmobile clutch
Basics
Most engine driven veichles have a clutch and geargox unit in order to make the veichle move faster or make it stronger while moving slowly. The clutch/gearbox is also needed in order to decrease the engines rpm according to at what speed the veichle is moving at, the less rpm the less wear. Fast moving veichles without a transmisson would have an engine running at very high rpm and this would shorten the engines lifetime. A direct connection from the engines drive shaft (crankshaft) to the wheels of the veichle would be a simple but impossible way to transfer the engines torque, even at idle few engines has less then 600-700rpm. The veichle would move forward as soon as the engine was started, it would be impossible to get the veichle moving using a setup like that, a clutch is therefor needed to engage/disengage the rotating axels of the engine from the veichles wheels. Even if a clutch was fitted to this setup, the engine would stall imediately when the clutch was disengaged because the engine wouldn`t have enough torque to make the wheels move as fast as the engines driveshaft. It could have driven the veichle if you push started it, so that the veichle is already moving when the engine starts. This could work, but we need a system that is easier to use, a transmission system is therefor fitted to the setup. The rpm of the wheels can now be either higher or lower then the engines rpm, the veichle can now start to move easily by putting the transmission in a low gear (1st gear). When more speed is needed, we shift to a higher gear.
The less rpm, the less torque. The higher rpm, the more torque. The higher gear, the less torque, the lower gear, the more torque.
Snowmobiles are fitted with a variomatic system, this does not include a “normal” gearbox nor a clutch. The main components of the variomatic system is the primarytclutch, the secondary clutch and the variator belt. The variator belt is fitted between the primary / secondary clutch.
The primary sheave ia mounted on left side of the (onto the crankshaft) engine. The primary sheave consists of two sheaves, the one sitting on the outside is spring loaded. The springloaded sheave has three weights fitted, each weight moves against a roller that is mounted on a non moving bracket at inside the primary. When the engine rpm increases the rotation power forces the weights against the rollers and the outer sheave is now forced against the inner sheave. A belt is fitted between the primary and the secondary sheave. The belt is not moving at idle, but as soon as the engine rpm is increased and the sheaves of the primary moves closer against each other, the belt starts to rotate. The belt will not rotate at the same speed as the engine, the belt slips against the sheaves, the more rpm the more friction between the belt/sheaves.
The secondary sheave does not contain weights or rollers, the sheaves are springloaded. The closer the primary sheaves move together, the tighter the belt will be. When the sled is moving at it`s top speed, the sheaves of the primary are as close together as they can be. The sheaves of the secondary is as far away from each other that they can be.
"
I`m not finished yet, but I thought it would be funny to hear if atleast something makes sence to you.
Are there any websites explaining the clutch system of our sleds?
I just wrote a little text about the "snowmobile clutch" , in english. (I`m a 19 years old boy from norway).
I go to a veichle-mechanic-orientated school and our english teacher told us do a hand-in on a "technical" device, either from car/motorcycle etc.
I guess most will write about some boring car stuff but I chose to write about the snowmobile clutch system. I mostly wrench on bikes, so I`m not that into sleds, but I will post what I wrote here so that you can correct me, Ì guess there are some things that arent 100% right hehe
(please explain the secondary, I don`t know anything about it). I know that what I`ve written isn`t "enough" , but my teacher doesn`t know anything about this stuff so he wount think so.
Here`s what I wrote:
"The snowmobile clutch
Basics
Most engine driven veichles have a clutch and geargox unit in order to make the veichle move faster or make it stronger while moving slowly. The clutch/gearbox is also needed in order to decrease the engines rpm according to at what speed the veichle is moving at, the less rpm the less wear. Fast moving veichles without a transmisson would have an engine running at very high rpm and this would shorten the engines lifetime. A direct connection from the engines drive shaft (crankshaft) to the wheels of the veichle would be a simple but impossible way to transfer the engines torque, even at idle few engines has less then 600-700rpm. The veichle would move forward as soon as the engine was started, it would be impossible to get the veichle moving using a setup like that, a clutch is therefor needed to engage/disengage the rotating axels of the engine from the veichles wheels. Even if a clutch was fitted to this setup, the engine would stall imediately when the clutch was disengaged because the engine wouldn`t have enough torque to make the wheels move as fast as the engines driveshaft. It could have driven the veichle if you push started it, so that the veichle is already moving when the engine starts. This could work, but we need a system that is easier to use, a transmission system is therefor fitted to the setup. The rpm of the wheels can now be either higher or lower then the engines rpm, the veichle can now start to move easily by putting the transmission in a low gear (1st gear). When more speed is needed, we shift to a higher gear.
The less rpm, the less torque. The higher rpm, the more torque. The higher gear, the less torque, the lower gear, the more torque.
Snowmobiles are fitted with a variomatic system, this does not include a “normal” gearbox nor a clutch. The main components of the variomatic system is the primarytclutch, the secondary clutch and the variator belt. The variator belt is fitted between the primary / secondary clutch.
The primary sheave ia mounted on left side of the (onto the crankshaft) engine. The primary sheave consists of two sheaves, the one sitting on the outside is spring loaded. The springloaded sheave has three weights fitted, each weight moves against a roller that is mounted on a non moving bracket at inside the primary. When the engine rpm increases the rotation power forces the weights against the rollers and the outer sheave is now forced against the inner sheave. A belt is fitted between the primary and the secondary sheave. The belt is not moving at idle, but as soon as the engine rpm is increased and the sheaves of the primary moves closer against each other, the belt starts to rotate. The belt will not rotate at the same speed as the engine, the belt slips against the sheaves, the more rpm the more friction between the belt/sheaves.
The secondary sheave does not contain weights or rollers, the sheaves are springloaded. The closer the primary sheaves move together, the tighter the belt will be. When the sled is moving at it`s top speed, the sheaves of the primary are as close together as they can be. The sheaves of the secondary is as far away from each other that they can be.
"
I`m not finished yet, but I thought it would be funny to hear if atleast something makes sence to you
.Are there any websites explaining the clutch system of our sleds?
To be very basic the primary clutch is rpm sensing. The secondary clutch is torque sensing. RPM,s effect the way the primary shifts out. Torque is what causes the secondary to shift out.
"As the engine RPM's increase, the centrifugal force enacted upon the weights causes the outer shieve to move inward and grip the belt, propelling the snowmobile forward. At this time, the belt is riding low on the primary and high on the secondary. As Rpm's and torque increase, the belt moves higher up on the primary and is pulled lower (towards the center) into the secondary. By varying primary weights, secondary helix angles, and both primary and secondary spring tension, the mechanic aims to have the transmission shift out while the engine is at the peak of its power band."
Something like that!
Something like that!