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Discussion Starter #1
Been trying to read between the lines on some concerns users have had with the higher rpm (loud) 825i at low ground speed...does the clutch system operate like a sled and only engage and start turning the secondary on revving the engine?? I thought it would operate the same as my argo and most quads. On the argo, as soon as you start the engine the primary and secondary are spinning and will fully shift up according to engine RPM, in gear or not....Just curious, as to how it operates....my new 825i is at my dealer now awaiting pickup...Thanks
 

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It seems to operate similar to a sled. It's not that you won't move it's that the engine revs high for a given speed.....at 10mph I believe you're taching 3500+....It doesn't bother me in the least because I know OHV engines live happiest at higher rpms and that's where they develop their power. I feel my 825i stays in the powerband and personally I like that.
 

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Actually the 825i has a constantly tight belt, which is not like a snowmobile. A snowmobile has a loose belt and when the rpms hit a certain speed, the clutch starts to squeeze together, tightening up the belt and moving it forward.

The 825i with the tight belt system allows you to drive the machine like a car with no lurching. Yes it does operate at higher RPMS but think about if you are towing a trailer full of stuff plus the bed full of stuff....The higher RPMS give you more power to the wheels in order to keep it moving. And yes, the 825i belt will be constantly moving.
 

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Constantly engaged!! That’s what I was hoping to hear...way less belt wear on slow moves...and smooth....I agree with the power and such, I had a 2009 700 Rhino and it was so noisy in the cab....I'm just worried that the gator might be just as loud...hopefully not....thanks for the input guys....3 more weeks....She will be home...:) JD
 

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Actually the 825i has a constantly tight belt, which is not like a snowmobile. A snowmobile has a loose belt and when the rpms hit a certain speed, the clutch starts to squeeze together, tightening up the belt and moving it forward.

The 825i with the tight belt system allows you to drive the machine like a car with no lurching. Yes it does operate at higher RPMS but think about if you are towing a trailer full of stuff plus the bed full of stuff....The higher RPMS give you more power to the wheels in order to keep it moving. And yes, the 825i belt will be constantly moving.
If you have your Gator in gear and do not press the accelerator the Gator will not move it will roll backwards. How would that be possible without a loose belt?
 

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Theory of Operation:

The variable speed drive (VSD) clutch system is speed and load sensitive. The clutches work together, automatically up shifting or back shifting as load and engine or vehicle speed change. This shifting changes the ratio between the clutches, allowing the engine to operate at best efficiency or at the peak of its power curve, as required.

The drive clutch is engine speed sensitive, and operates on the principle of centrifugal force. The drive clutch is mounted to the engine crankshaft extension. The secondary clutch, mounted on the transaxle input shaft, is load sensitive to the rear drive wheels.

On machines so equipped, engine braking capability is incorporated in the clutch system. Engine braking provides supplemental braking on overrun, such as when decelerating or when descending a hill.


(1) Engine Idle Speed:

Drive clutch (A) incorporates a sleeve coupler (B) with a one way clutch. At engine idle speed, the sheave halves of the drive clutch are separated by a spring (C) so that the drive belt (D) is not gripped by the sheave halves. The belt runs only on the freely turning sleeve coupler, allowing a disconnection in the drive system.

An internal spring (E) in the driven clutch (F) positions the driven clutch sheave halves together for a low initial gear ratio.


(2) Transition from Low to Intermediate Ratio:

With an increase in engine speed, flyweights (G) rotate outward against rollers (H) at the outer ends of the central spider (I). The drive sheaves are moved closer together, moving the drive belt toward the outer pulley diameter. Forces are balanced between the centrifugal force of the flyweights and the clutch springs. As the belt moves further out on the drive sheave, it moves inward on the driven sheave, spreading the sheave halves further apart.

Rollers (J) on the internally splined dampener assembly (K) are contained within shaped apertures in the cam assembly (L). The dampener splines drive the transmission input shaft.

In operation at other than idle speed or high vehicle speed, most clutch operation occurs in this range. The clutch upshifts or backshifts to match load, terrain, or engine speed. Backshifting occurs when an increased load is encountered, such as soft terrain or a hill.


(3) High Engine Speed, Light Load, High Output Speed:

With high engine speed and a light load, the flyweights will rotate fully outward to overcome spring pressure and move the drive belt to the outer diameter of the sheave. The secondary clutch spring is compressed as well, moving the drive belt further toward the middle of the sheave. The higher gear ratio results in increased transmission input speed.


(4) Engine Braking with Low Engine RPM, High Output Speed

An engine braking clutch system, on machines so equipped, provides a means of connecting the clutch system to the engine for compression braking on overrun. The modified clutch includes a sleeve coupler (B) at the base of the drive clutch sheave and changes to the driven clutch cam follower (K) and cam profile (M). The sleeve coupler incorporates a one way clutch (N) which acts on the moveable portion of the drive clutch. The modified cam follower provides an increase in drive belt tension on overrun.

At low engine speed, when the drive clutch sheaves are farthest apart, the drive belt is allowed to slip in order to disconnect the engine from the driveline. In this condition, the inside surface of the drive belt runs on the outer surface of the sleeve coupler. In an overrun condition, when the driven clutch attempts to drive the belt faster than the drive clutch is rotating, the coupler’s one way clutch acts to narrow the drive sheave to grip the sides of the drive belt and prevent belt slippage. Drive force from the transmission forces the cam follower roller up the aperture ramp (M) to further increase driven clutch spring pressure, forcing the sheaves closer together and tightening the drive belt.

BASICALLY:
The tight belt runs on a sleeve on the driven clutch which does not allow the transmission to turn, therefore letting the machine be pushed back and forth while in gear. When the engine speed starts expanding the primary clutch, it moves the belt on the driven clutch up and down which gives you your motion.
 

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I guess this explains why my 825i when it is at idle and going downhill there is minimal engine breaking but if you give it some gas engine breaking kicks in and helps moderate downhill speed. I sure would like to see some video of it in action.

My 825i goes from idle to 3000 rpm very quickly at low ground speeds. The engine does not feel taxed at all. When I am going up hill, the rpms do not change dramatically. This sure helps me understand.
 

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Theory of Operation:

The variable speed drive (VSD) clutch system is speed and load sensitive. The clutches work together, automatically up shifting or back shifting as load and engine or vehicle speed change. This shifting changes the ratio between the clutches, allowing the engine to operate at best efficiency or at the peak of its power curve, as required.

The drive clutch is engine speed sensitive, and operates on the principle of centrifugal force. The drive clutch is mounted to the engine crankshaft extension. The secondary clutch, mounted on the transaxle input shaft, is load sensitive to the rear drive wheels.

On machines so equipped, engine braking capability is incorporated in the clutch system. Engine braking provides supplemental braking on overrun, such as when decelerating or when descending a hill.


(1) Engine Idle Speed:

Drive clutch (A) incorporates a sleeve coupler (B) with a one way clutch. At engine idle speed, the sheave halves of the drive clutch are separated by a spring (C) so that the drive belt (D) is not gripped by the sheave halves. The belt runs only on the freely turning sleeve coupler, allowing a disconnection in the drive system.

An internal spring (E) in the driven clutch (F) positions the driven clutch sheave halves together for a low initial gear ratio.


(2) Transition from Low to Intermediate Ratio:

With an increase in engine speed, flyweights (G) rotate outward against rollers (H) at the outer ends of the central spider (I). The drive sheaves are moved closer together, moving the drive belt toward the outer pulley diameter. Forces are balanced between the centrifugal force of the flyweights and the clutch springs. As the belt moves further out on the drive sheave, it moves inward on the driven sheave, spreading the sheave halves further apart.

Rollers (J) on the internally splined dampener assembly (K) are contained within shaped apertures in the cam assembly (L). The dampener splines drive the transmission input shaft.

In operation at other than idle speed or high vehicle speed, most clutch operation occurs in this range. The clutch upshifts or backshifts to match load, terrain, or engine speed. Backshifting occurs when an increased load is encountered, such as soft terrain or a hill.


(3) High Engine Speed, Light Load, High Output Speed:

With high engine speed and a light load, the flyweights will rotate fully outward to overcome spring pressure and move the drive belt to the outer diameter of the sheave. The secondary clutch spring is compressed as well, moving the drive belt further toward the middle of the sheave. The higher gear ratio results in increased transmission input speed.


(4) Engine Braking with Low Engine RPM, High Output Speed

An engine braking clutch system, on machines so equipped, provides a means of connecting the clutch system to the engine for compression braking on overrun. The modified clutch includes a sleeve coupler (B) at the base of the drive clutch sheave and changes to the driven clutch cam follower (K) and cam profile (M). The sleeve coupler incorporates a one way clutch (N) which acts on the moveable portion of the drive clutch. The modified cam follower provides an increase in drive belt tension on overrun.

At low engine speed, when the drive clutch sheaves are farthest apart, the drive belt is allowed to slip in order to disconnect the engine from the driveline. In this condition, the inside surface of the drive belt runs on the outer surface of the sleeve coupler. In an overrun condition, when the driven clutch attempts to drive the belt faster than the drive clutch is rotating, the coupler’s one way clutch acts to narrow the drive sheave to grip the sides of the drive belt and prevent belt slippage. Drive force from the transmission forces the cam follower roller up the aperture ramp (M) to further increase driven clutch spring pressure, forcing the sheaves closer together and tightening the drive belt.

BASICALLY:
The tight belt runs on a sleeve on the driven clutch which does not allow the transmission to turn, therefore letting the machine be pushed back and forth while in gear. When the engine speed starts expanding the primary clutch, it moves the belt on the driven clutch up and down which gives you your motion.

That is also how a snowmobile clutch works.....the big difference in rpms is because of the springs it has to overtake.
 
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