[BlackBart]

SECONDARY(driven) CLUTCH OVERVIEW

This discussion is geared ONLY toward the Team Roller Secondary clutch and not the Rapid Reaction Clutch.

The Secondary (Driven) Clutch is the one that attaches to the transmission and and accepts the power that is transferred by the Primary (Drive) Clutch thru the Drive Belt.
The unit consists of a stationary or fixed sheave,and a moveable sheave. The combination of these 2 pieces work against a cam and spring within the clutch. The cam is the tool which recognizes torque changes supplied by the rear wheels. These changes are transferred thru the cam by the angle of the ramp and in then coverted to side pressure on the belt. The belt force is governed by the Primary Clutch and the Engine. As the belt moves up in the Primary Clutch, it must be forced into sheaves of the Secondary Clutch. How quick this happens is controlled by the combination of the Helix(angle) and the Spring rate in Secondary. The amount of belt grip in the Secondary is is also controlled by the same 2 elements above. The unit as it exists today is torque sensitive or torque driven, which means in simple terms, if the torque requirement is greater, you get more side pressure applied to the belt AND if the torque requirement is lessen, you get less side pressure applied to the belt. This side pressure that is being applied to the belt in any given shift range is what keeps the belt from slipping.

I’ll now try to describe shift ratio and what it means with the Secondary Clutch.

HORSEPOWER = TORQUE X SPEED

The shifting is caused by the belt being moved with the Secondary Clutch, up/down between the sheaves in that clutch.

I believe that the shift ratio’s are:

Low – 3:1
Mid – 1:1
High - .75:1

And these ratio’s DON’t take into consideration any efficiency losses, which is really outside the scope of this overview.

The only time that the Torque SHOULD be the same is in the 1:1 ratio.

At the Low ratio, the Torque is 3 times greater than the engine Torque and
At the High ratio(overdrive) the Torque at the Secondary Clutch is only ¾
of the engine Torque. What this translates to is that in Low there must be much more side pressure applied to the belt than when in High(overdrive). Ok now here is what happens.
If you fail to stay within this range, you will either end up with BELT SLIP/Belt Wear or with Inefficencies due to TOO MUCH Pressure.

 

[BlackBart]

HELIX in SECONDARY Clutch


N O T E:---------------------------------------------------------------------------------------------
THE ANGLES being discussed below SHOULD NOT be confused with the Angle that the Secondary SHEAVES are cut on.(ie. the TAPER of the sheaves). This is a totally separate topic, but I’ll give it a VERY BRIEF description as as a highlighted entry below.


There are a number of different Helix setups:

1)Straight vs Multi/Angle

Straight Angle Helix simply means that there is ONLY 1 angle cut into the cam.
Multi Angle Helix means that there are different and varying angles cut in the cam.(these
are primarily to give a harder shiftout and not lose RPM on the top end.

2)Progressive vs Compound – Terminology Difference, the main distinction is how the
Angles are cut into the Helix.

To order to attempt to describe the different cuts, I am going to use the “S” helix angle of: 66 56 33

A true progressive angle cut would have the 66 degree angle at the top of the ramp and the 56 degree angle at the bottom of the ramp. The angles between the top and bottom are would then be equally divided down the ramp angle.

A compound angle cut would start with the 66 angle at the top of the ramp and stay at that angle for a specified distance down the ramp 33 %, then the degree of angle cut would move rapidly toward the bottom of the ramp ending with 56 degree angle.

There are MANY different variations and/or combinations of the above. Many can be purchased PRE-CUT or you could design your own and have someone like Team Industries(main supplier of springs/helix) make one for you.

Helix Ramp Angle (cut) Picture

GENERAL RULE OF THUMB FOR HELIX SELECTION

Trail Riding – TRUE Progressive – usually faster backshift(low & mid range), smoother upshift, due to the fact that it will stay in a steeper angle longer into the mid range

Drag Racing - COMPOUND Progressive – might accelerate faster, BUT Harder holeshot, normally slower backshift, not as responsive on/off acceleration after you are moving.

GENERAL RULE OF THUMB FOR HELIX ANGLES

The Steeper the angle at the beginning and end of the ramp cut would cause the clutch to Uphift and Accelerate FASTER, BUT, would have a SLOWER Backshift and not be as responsive to throttle changes.

The Smaller the angle would cause a SLOWER Upshift, BUT, should provide a FASTER Backshift

Another way to look at the Helix angles could be to compare them to Coarse or Fine threads on a bolt. If you have Coarse(meaning that the threads are at a LARGER angle) threads on your bolt, it would tighten up faster.
SO, LARGER angles would open the sheaves faster and would requireLESS force.
SMALLER angles would open the sheaves more slowly and would require MORE force.

IF YOU JUST LOOKING for a GENERAL all around riding setup, then probably the Smaller Helix angles would be the best choice.


SHEAVE ANGLE - B O T H….Primary and Secondary Clutches

Both the Primary & Secondary clutches contains 2 sheaves each. A fixed and a moveable sheave. The ANGLE or TAPER of these sheaves is Preset/Determined by Polaris. This determination MAY NOT be the BEST, since this clutch may be used in a wide variety of difference machines. THIS is what BEAN COUNTER’s call COST CONTAINMENT. Basicly we can’t do a thing about this(not entired TRUE statement), but we will not go into that topic in this discussion.
The Angle(taper)of the sheaves in the Primary Clutch is in theory the following:
With the smaller angle at the bottom of the sheave, this should increase the belt grip at
Lower gear ratios, when the clutch/belt contact area is the least. As the belt moves up
Sheaves, the angle is increasing and so is the belt contact area.
The Angle(taper) of the sheaves in the Secondary Clutch partially controls the belt
pressure as the Drive belt is being pulled into the sheaves.


In the RZR, the Secondary Clutch has 2 ramps spaced around a round surface, which I have pictured below.

Examples of 3 Different Helix
1)Top-Regular RZR Stock w/EBS Notch
2)Middle-RZR “S” w/EBS Notch
3)Bottom-RZR “S” Stock w/o EBS

Top View of a Helix

Normally if the Helix is an Off the Shelf variety, the ramp angles are stamped onto the top of the helix.

Closeup Top View Regular RZR Stock Helix

This is a multi-angled, progressive with angles of 65 62 60 58

Side View Regular RZR Stock Helix w/EBS

One will notice the Large Cut Out at the beginning of the ramp. This is the
EBS (engine braking system) Notch

Closeup Top View RZR “S” Helix

This is a compound,progressive with angles of 66 56 with transition point 33%

Side View RZR “S” Helix No EBS

You will notice that the “S” does not have the EBS notch, due to the fact that on this unit, the EBS was performed by a ONE-WAY bearing in the Primary Clutch


The torque is transferred thru these ramp angles and work against sliding buttons that are located in the moveable sheave. The type of angle as well as the degree slope of the angle influence the side pressure that is applied to the belt.
Smaller(shallow) Angles = MORE Side Force(less belt slip)good Backshift,SLOWS Upshift
Larger(steeper) Angles = LESS Side Force(some belt slip at Full Shiftout,MORE /faster Upshift
Now that’s the simple explanation, however if you get into the nuts/bolts of the equation, so to speak, you have to also consider the ramp radius in addition to the ramp angle.

The following link is to an article written by Randy Nouis regarding the theory behind Secondary Clutch. Technical YES, INFORMATIVE-YES, good pics and explanation of helix designs A good read, even though the end part of the article is pushing a particular brand of adjustable weights. Just never mind the sales pitch.


Theory & Mechanics of Radius applied to the driven clutch







PRESSURE SPRING in the SECONDARY Clutch

The pressure spring in the Secondary Clutch has 2 basis functions. The following is an example of how to determine the springs’ rating. The functioning of this spring is quite similar to the one in the Primary Clutch.
Ex. Spring is rated as a 105/185

The 1st number represents the ft/lbs at the Load Height. It is this side pressure that the Primary Clutch must overcome before the belt starts being drawn into the sheaves on Secondary clutch. This can also be called Pre-tension. So a Higher # means that MORE
force will have to be generated to open the sheaves AND more RPM’s are required to overcome the extra Tension.
The 2nd number represents the ft/lbs at the Compressed Height. This rating controls to some extent belt pressure, BUT, more specifically Backshift. In addition, the Secondary spring MAY have a higher rate if Unusually Tall or Heavy tires are being used on the machine. The reason being is that with the above you are already starting out in a Higher
gear and by increasing the spring pressure, you are in fact, HOLDing the Clutch back in a lower gear.

Normally springs are used with higher rates when higher horsepower mandates more pretension.

GENERAL RULE OF THUMB for Secondary Spring

HIGHER rate springs provide MORE belt squeeze and make Backshifting faster.

If you’re into Drag Racing or all out acceleration, then a LIGHTER rate spring should be used, for the opposite reason above.

If you want to increase the sideforce or pressure on the Drive belt, Use a spring with a Higher Pretension and a Higher rating.
However, one must be on guard, as mentioned earlier, that TOO much belt pressure leads to inefficiency and loss of performance/speed.



One should also check the cam buttons as well as the large bushing sliding on the shaft.
Both, if damaged or worn can cause addition friction, causing poor response as well as the amount of time it takes to slow down and accelerate out of a curve.

They can also be a build of Belt dust as well as the normal dust intrusion thru the air intake, so a periodic blowing out with a air hose and/or cleaning with aceotone is recommended.