Difference between revisions of "Clutch tuning"

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This is a how-to on tuning a Puch E-50 clutch. This can be adapted to any other engine with a centrifugal clutch.
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This is a how-to on tuning a Puch [[E50]] clutch. This can be adapted to any other engine with a centrifugal clutch.
 
 
 
 
 
 
== What is it that makes a clutch good? ==
 
 
 
 
 
  
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==What is it that makes a clutch good?==
 
As most of you know one of the major problems when tuning a Puch is the clutch.  
 
As most of you know one of the major problems when tuning a Puch is the clutch.  
  
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==What to do?==
== What to do? ==
 
 
 
 
Shaving weight off of the shoes is a good idea in general. But there is a chance that you may make the shoes ''too'' light and that they start to slip instead of grab.
 
Shaving weight off of the shoes is a good idea in general. But there is a chance that you may make the shoes ''too'' light and that they start to slip instead of grab.
  
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The force of the shoe slinging outwards increases exponentially. This also explains why the weight of the shoe is the most important factor in the clutch.
 
The force of the shoe slinging outwards increases exponentially. This also explains why the weight of the shoe is the most important factor in the clutch.
 
 
  
 
Then we get to the bending of the pivot-points. If you've read the previous part, you'll know why they bend outwards. This is easy to fix by building a "rim" for the pivots.
 
Then we get to the bending of the pivot-points. If you've read the previous part, you'll know why they bend outwards. This is easy to fix by building a "rim" for the pivots.
 
  
 
And another thing to keep in mind: Old clutch lining can get hard and glassy. This causes a lot of slip and it can only be solved by replacing the shoes or lining.
 
And another thing to keep in mind: Old clutch lining can get hard and glassy. This causes a lot of slip and it can only be solved by replacing the shoes or lining.
  
== Tips ==
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==Tips==
 
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*Always use at least blue springs for your tuned clutch.
- Always use at least blue springs for your tuned clutch.
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*Never lighten the shoes under 55 grams.
 
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*Never turn the screws that hold the springs in too far. The springs need room to work.
- Never lighten the shoes under 55 grams.
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*Max spring tension can be found this way: Turn the screw all the way in and then 720 degrees out. This is the max tension.
 
 
- Never turn the screws that hold the springs in too far. The springs need room to work.
 
 
 
- Max spring tension can be found this way: Turn the screw all the way in and then 720 degrees out. This is the max tension.
 
  
 
== Solutions ==
 
== Solutions ==
 
 
Enough theory, lets get to solutions.
 
Enough theory, lets get to solutions.
  

Revision as of 13:35, 14 August 2008

This is a how-to on tuning a Puch E50 clutch. This can be adapted to any other engine with a centrifugal clutch.

What is it that makes a clutch good?

As most of you know one of the major problems when tuning a Puch is the clutch.

Specifically, the RPM when it grabs is normally too low.

Another problem is that the pivot-points bend when you have a high-rpm or high-torque setup.


What to do?

Shaving weight off of the shoes is a good idea in general. But there is a chance that you may make the shoes too light and that they start to slip instead of grab.

With shaving weight you can tune your clutch till it grabs at 5800 RPM (In combination with blue springs).

For moving the grab point above this RPM level, you will need even stiffer springs, so you can actually increase the weight of the shoes.

The springs only function is to stop the shoe till a certain RPM is reached and push the shoe back when it drops under a certain RPM.

The force of the shoe slinging outwards increases exponentially. This also explains why the weight of the shoe is the most important factor in the clutch.

Then we get to the bending of the pivot-points. If you've read the previous part, you'll know why they bend outwards. This is easy to fix by building a "rim" for the pivots.

And another thing to keep in mind: Old clutch lining can get hard and glassy. This causes a lot of slip and it can only be solved by replacing the shoes or lining.

Tips

  • Always use at least blue springs for your tuned clutch.
  • Never lighten the shoes under 55 grams.
  • Never turn the screws that hold the springs in too far. The springs need room to work.
  • Max spring tension can be found this way: Turn the screw all the way in and then 720 degrees out. This is the max tension.

Solutions

Enough theory, lets get to solutions.


The brace "rim"


Tclutch1.jpg


The modified baseplate with setup-bolts to adjust the play between the base and the shoe, and the weights on the shoe.


Tclutch2.jpg


Each shoe is weighed accurately.

You want to have the exact same weight on each shoe to limit vibrations and even the grab.


Tclutch3.jpg


Modified baseplate with tapped holes in the pivots to mount the rim.


Tclutch4.jpg


Lightened shoes.


Tclutch5.jpg


The shoes are numbered to identify them during the setup-phase (see advanced section) to see when they open.


Tclutch6.jpg


The clutch when finished.


Tclutch7.jpg

Tclutch8.jpg


We also investigated some new linings and some new springs.

These springs are super stiff to accommodate very heavy clutches that grab at high RPM.


Tclutch9.jpg

Tclutch10.jpg


1: Standard Puch

2: Self-made lining, comparable to stock.

3: Kind of fiber-lining for better grip and oil distribution.

4: Kevlar-lining with a profile for oil distribution.


Heavy springs on the right.


Tclutch11.jpg

Advanced

This is for very very advanced tuners only. This isn't meant as a how-to, more as information.


Setting up the clutch

Hank solved the setup problems by making a test-bench for clutches.

This way it's possible to see what you're clutch does at certain RPMs, without even having an engine to put it in.


Tclutch12.jpg


He used an old engine with max 2800 RPM and made a 3:1 drive-train to be able to reach 7500 RPM.

Then he installed a frequency selector, so he can change the RPM steplessly. It also boosts the max RPM of the engine, making it possible to reach 10500 RPM on the clutch-shaft. It also provides a read-out for the current shaft RPM.


Tclutch13.jpg

Tclutch14.jpg

RPM read-out during testing.


Besides the RPM read-out, we'll need a device to see how the clutch acts at those speeds. You'll need a steplessly adjustable strobe light for this. With the strobe, it'll look like the clutch is standing still and you can easily spot how it performs.


Tclutch15.jpg


Clutch mounted to the axle the same way the clutch normally mounts to the crank.


Tclutch16.jpg


The device isn't very big, so it's pretty mobile.


These are some pics from setting up a clutch. The pics were made with a spinning clutch.


Tclutch17.jpg


Here you can see the shoes coming outwards.


Tclutch18.jpg


Here you can see that the shoes are at rest.


Tclutch19.jpg


Here you can see the shoes coming outwards and the spring being compressed.


Tclutch20.jpg


The spring is compressed. Here you can also see what happens when the spring is too tight. The shoe can't go out enough, so the clutch would slip a lot.


Tclutch21.jpg


Here you can see that the shoe is completely out. There's room between the shoe and the adjustment bolt.


Tclutch22.jpg


Every shoe is numbered so we can see when each shoe comes out.

Experience indicates that this can differ a lot, so counting the strokes or measuring the depth of the clutch adjustment screws isn't as accurate as it looks.

Unfortunately, not everybody has a test-device. But setting up a clutch by hand & feeling can be pretty accurate too.

To set up a clutch perfectly, a device like this is a great tool.

Translated by SchijnHeilig

Written by Hank Kok from PuchForum.net