Spring Plate: Why is it there?
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Stellar HDF Member
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Spring Plate: Why is it there?
Edit: Disregard my completely wrong theory, and refer to the post(s) by John_K. He includes a good analysis and some fantastic pictures as well.
Last edited by Scuba10jdl; Apr 3, 2013 at 08:57 PM.
Road Captain
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From: Windsor Ontario
That would make sense if the springs were arranged in a circular fashion like this
But the Sportster spring plate is designed to damp in an axial direction, and worse, presents a shearing force against the rivets in the rotational path. I believe the spring plate is there to expand the friction zone for rookies. It effectively begins clutch plate engagement before it normally would without a spring plate.
But the Sportster spring plate is designed to damp in an axial direction, and worse, presents a shearing force against the rivets in the rotational path. I believe the spring plate is there to expand the friction zone for rookies. It effectively begins clutch plate engagement before it normally would without a spring plate.
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It has some play in the axial direction, but not very much. It's not designed to extend/change the friction zone (that would be the job of the pressure plate and coefficient between the friction plates). There aren't really any oscillations axially to be dampened. Anything would be rider induced through the lever, which occurs at such a low frequency it really isn't an issue.
It acts like what some call a "judder spring", where when the clutch is first applied it absorbs some of the jolt and smooths out delivery. This reduces clutch shudder and noise. This is also why many refer to the spring plate as the noise reducing plate.
Also, the springs on the clutch you pictured are much more effective at this job, however they can only be fit in a single plate clutch due to size. Harley likes the multi-plate wet-clutch characteristics, which eliminate the ability to apply that design.
It acts like what some call a "judder spring", where when the clutch is first applied it absorbs some of the jolt and smooths out delivery. This reduces clutch shudder and noise. This is also why many refer to the spring plate as the noise reducing plate.
Also, the springs on the clutch you pictured are much more effective at this job, however they can only be fit in a single plate clutch due to size. Harley likes the multi-plate wet-clutch characteristics, which eliminate the ability to apply that design.
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I tried to find a good pic of one online, but it's all broken ones (go figure). And I'm not about to tear my clutch apart just to take a pic. haha
Essentially, you have two steel plates with holes around them. In the middle are a bunch of sandwhiched pieces of steel (the "spring" material) that is riveted from one piece to the other.
This gives you an idea of how it is setup. This one has broken. When the clutch is applied, the springs warp just a little bit and absorb the jolt and takes up the slight amount of space in the clutch pack (thousandths of an inch). These two actions make for a smoother clutch engagement.
Essentially, you have two steel plates with holes around them. In the middle are a bunch of sandwhiched pieces of steel (the "spring" material) that is riveted from one piece to the other.
This gives you an idea of how it is setup. This one has broken. When the clutch is applied, the springs warp just a little bit and absorb the jolt and takes up the slight amount of space in the clutch pack (thousandths of an inch). These two actions make for a smoother clutch engagement.
Tourer
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Making sure I get this right, they act as a stress dampner as the pistons fire off, tansferring torque to the tranny? So why remove the spring plate and put in an extra clutch plate? Or did we learn (because the brass rivets suck) that they are not necessary and we're just filling in the gap?
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Removing the spring plate is to prevent it from blowing up and destroying more expensive pieces. And like you said, you have to fill the gap in the clutch pack because that's how it was built.
It's not a necessary part at all. The bike will run perfectly fine without it. It's just there for a reason designed by the engineers: better clutch feel, less noise, and lower stress. There is a lot of **** on our bikes the engineers are forced to put on there (EPA anyone??) that we can do without.
It's been proven we can do without the spring plate, I was just attempting to explain why they chose to put it there in the first place.
It's not a necessary part at all. The bike will run perfectly fine without it. It's just there for a reason designed by the engineers: better clutch feel, less noise, and lower stress. There is a lot of **** on our bikes the engineers are forced to put on there (EPA anyone??) that we can do without.
It's been proven we can do without the spring plate, I was just attempting to explain why they chose to put it there in the first place.
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Road Captain
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From: Windsor Ontario
It has some play in the axial direction, but not very much. It's not designed to extend/change the friction zone (that would be the job of the pressure plate and coefficient between the friction plates). There aren't really any oscillations axially to be dampened. Anything would be rider induced through the lever, which occurs at such a low frequency it really isn't an issue.
in this shot you can see the gap (look at the shadow) as well as the 'wave' in the spring;
relaxed it measures in at .203 inch, was likely a little more when new
compressed it measures .187 inch, a difference of .016 (1/64th of an inch) a relatively large amount of 'springiness' compared to the compressibility of the friction material. Your effective friction zone is extended by 1/64th of an inch.
It acts like what some call a "judder spring", where when the clutch is first applied it absorbs some of the jolt and smooths out delivery. This reduces clutch shudder and noise. This is also why many refer to the spring plate as the noise reducing plate.
Also, the springs on the clutch you pictured are much more effective at this job, however they can only be fit in a single plate clutch due to size. Harley likes the multi-plate wet-clutch characteristics, which eliminate the ability to apply that design.
Here is the Barnett extra plate clutch pack that replaced the above components, notice the 2 rings at the top right, those are spring washers that do the same job as the original spring plate. One is concave in shape (Bellville washer)
Here are the Barnett instructions on assembling the pack, with the spring washers installed first
There is no way this type of spring, or the original spring plate would damp any torque forces.
Road Captain
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besides, there is a friction plate on each side of the spring plate, with the transmitted torque forces acting in the same direction. They would need to be in opposite directions to absorb pulses.