| thanks to Sigma
So how does a Sigma slipper clutch work?
Diagram A
The following drawings (have another look at the pictures above for the detail of the internal ramps as well) show the basic idea; I would also suggest a nice cold towel for the head at this point.
When the engine power is driving the bike forwards in the normal direction the little ramps lock solid; the clutch acts completely normally. Diagram A shows the normal situation.
Under a slowing situation Diagram b shows what occurs when the engine is being turned over by the rear wheel; as gearshaft B is turned over by the rear wheel the clutch (attached to gearshaft turned over by the rear wheel the clutch (attached to gearshaft a) is forced to take the load in the opposite direction, this forces the centre of the clutch up the 45-degree ramps; so starting to force the clutch pack apart.
Diagram B
As soon as the clutch pack stops gripping (i.e. when the centre has risen slightly on its ramps) most of the force to hold the pack apart is lost and theoretically clutch grip is re-established as the pack tries to come back together. In practice the clutch establishes an equilibrium position where there is just enough force being transmitted to hold the clutch apart (i.e. to hold the centre partially up the ramps) yet just enough to stop the engine being revved up, this equilibrium point can be adjusted either by varying the spring rate or the effective preload on the springs holding the clutch together or by varying the height of the assembled clutch pack. This is why you will often see theoretically rich well-funded race teams sorting through endless piles of seemingly knackered clutch plates trying to get precise pack thicknesses they want to give their rider the feel he is used to.
Copyright Neil Spalding 2002- 2005
So how does a Sigma slipper clutch work?
Diagram A
The following drawings (have another look at the pictures above for the detail of the internal ramps as well) show the basic idea; I would also suggest a nice cold towel for the head at this point.
When the engine power is driving the bike forwards in the normal direction the little ramps lock solid; the clutch acts completely normally. Diagram A shows the normal situation.
Under a slowing situation Diagram b shows what occurs when the engine is being turned over by the rear wheel; as gearshaft B is turned over by the rear wheel the clutch (attached to gearshaft turned over by the rear wheel the clutch (attached to gearshaft a) is forced to take the load in the opposite direction, this forces the centre of the clutch up the 45-degree ramps; so starting to force the clutch pack apart.
Diagram B
As soon as the clutch pack stops gripping (i.e. when the centre has risen slightly on its ramps) most of the force to hold the pack apart is lost and theoretically clutch grip is re-established as the pack tries to come back together. In practice the clutch establishes an equilibrium position where there is just enough force being transmitted to hold the clutch apart (i.e. to hold the centre partially up the ramps) yet just enough to stop the engine being revved up, this equilibrium point can be adjusted either by varying the spring rate or the effective preload on the springs holding the clutch together or by varying the height of the assembled clutch pack. This is why you will often see theoretically rich well-funded race teams sorting through endless piles of seemingly knackered clutch plates trying to get precise pack thicknesses they want to give their rider the feel he is used to.
Copyright Neil Spalding 2002- 2005
So how does a Sigma slipper clutch work?
Diagram A
The following drawings (have another look at the pictures above for the detail of the internal ramps as well) show the basic idea; I would also suggest a nice cold towel for the head at this point.
When the engine power is driving the bike forwards in the normal direction the little ramps lock solid; the clutch acts completely normally. Diagram A shows the normal situation.
Under a slowing situation Diagram b shows what occurs when the engine is being turned over by the rear wheel; as gearshaft B is turned over by the rear wheel the clutch (attached to gearshaft turned over by the rear wheel the clutch (attached to gearshaft a) is forced to take the load in the opposite direction, this forces the centre of the clutch up the 45-degree ramps; so starting to force the clutch pack apart.
Diagram B
As soon as the clutch pack stops gripping (i.e. when the centre has risen slightly on its ramps) most of the force to hold the pack apart is lost and theoretically clutch grip is re-established as the pack tries to come back together. In practice the clutch establishes an equilibrium position where there is just enough force being transmitted to hold the clutch apart (i.e. to hold the centre partially up the ramps) yet just enough to stop the engine being revved up, this equilibrium point can be adjusted either by varying the spring rate or the effective preload on the springs holding the clutch together or by varying the height of the assembled clutch pack. This is why you will often see theoretically rich well-funded race teams sorting through endless piles of seemingly knackered clutch plates trying to get precise pack thicknesses they want to give their rider the feel he is used to.
Copyright Neil Spalding 2002- 2005
So how does a Sigma slipper clutch work?
Diagram A
The following drawings (have another look at the pictures above for the detail of the internal ramps as well) show the basic idea; I would also suggest a nice cold towel for the head at this point.
When the engine power is driving the bike forwards in the normal direction the little ramps lock solid; the clutch acts completely normally. Diagram A shows the normal situation.
Under a slowing situation Diagram b shows what occurs when the engine is being turned over by the rear wheel; as gearshaft B is turned over by the rear wheel the clutch (attached to gearshaft turned over by the rear wheel the clutch (attached to gearshaft a) is forced to take the load in the opposite direction, this forces the centre of the clutch up the 45-degree ramps; so starting to force the clutch pack apart.
Diagram B
As soon as the clutch pack stops gripping (i.e. when the centre has risen slightly on its ramps) most of the force to hold the pack apart is lost and theoretically clutch grip is re-established as the pack tries to come back together. In practice the clutch establishes an equilibrium position where there is just enough force being transmitted to hold the clutch apart (i.e. to hold the centre partially up the ramps) yet just enough to stop the engine being revved up, this equilibrium point can be adjusted either by varying the spring rate or the effective preload on the springs holding the clutch together or by varying the height of the assembled clutch pack. This is why you will often see theoretically rich well-funded race teams sorting through endless piles of seemingly knackered clutch plates trying to get precise pack thicknesses they want to give their rider the feel he is used to.
Copyright Neil Spalding 2002- 2005
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