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http://atlanticgreen.com/ndnsclutch.htm
I'm re-reading this for the millionth time after trying to help my friend Mike with his heavy clutch. He bought some Barnett plates hoping it would help but it's still way too stiff. I tweaked some stuff and it's a little better but still not right.
I still haven't read a practical description of what is happening. Please correct this attempt.
I'll use outside (where the adjuster screws in) and inside (the side against the pressure plate) to describe the sides. If I understand correctly in its natural state the diaphragm spring is convex to the outside. The clutch spring compressor tool pulls the center out and flattens the plate until it's flat.
When installed the center of the spring center is trying to push in. When you pull on the clutch lever you are acting against the pushrod and pushing the center out.
If your stack is too short you are fighting agaist the full power (or most of it) with your hand.
If you're stack is too high the spring can't clamp down hard enough. The center is too far out, it's like you are partially pulling the lever. This is the problem I had with my slipping clutch, I had one too many plates.
On Mike's clutch it seems that the center is too far in. It's hard to tell how far in but when you compress the spring you just need to pull the spring flat to get it off.
There are a lot of numbers here and not enough reference. I'm not sure what Dave is saying about .68" and .58" and then .55" clutch pull of .1" and something about .03" inverted. I assume most of these measurements are being made at the clutch center with a dial indicator?
Here's my attempt at the various states:
Am I close?
Easy Pull, No Drag, No Slip, Commando Clutch
David Comeau 27 July 1997 Update Oct 2008
Introduction to the Commando Clutch
Diaphragm Description
The clutch spring in the Commando is a cupped piece of spring steel called a diaphragm. Its center has been cut into 18 radial fingers. A center carrier has 2 rows of slots, 9 per row, alternating HI-LO. These slots in the center carrier receive the ends of the diaphragm fingers. The diaphragm is pressed over the center carrier and 18 fingers get loaded into the 2 rows of slots. The center carrier also carries the clutch adjuster screw and lock nut.
To disengage the clutch the following observations can be made. The clutch carrier is pushed out .035" than the clutch starts to disengage. At this point the high fingers have been well lifted and the lo fingers are now just starting to lift off of the clutch pressure plate. By .050" lift both sets of fingers are free and clear of the clutch pressure plate and the clutch should have almost no engaging properties. The atlas actuator cam certainly has more than an adequate lifting range for a commando clutch, and in fact the commando actuator cam has more than double the lift needed to completely disengage the clutch. This makes the ROD/cam ball free play adjustment of little concern in actual use, with the commando actuator cam.
I'm re-reading this for the millionth time after trying to help my friend Mike with his heavy clutch. He bought some Barnett plates hoping it would help but it's still way too stiff. I tweaked some stuff and it's a little better but still not right.
I still haven't read a practical description of what is happening. Please correct this attempt.
I'll use outside (where the adjuster screws in) and inside (the side against the pressure plate) to describe the sides. If I understand correctly in its natural state the diaphragm spring is convex to the outside. The clutch spring compressor tool pulls the center out and flattens the plate until it's flat.
When installed the center of the spring center is trying to push in. When you pull on the clutch lever you are acting against the pushrod and pushing the center out.
If your stack is too short you are fighting agaist the full power (or most of it) with your hand.
If you're stack is too high the spring can't clamp down hard enough. The center is too far out, it's like you are partially pulling the lever. This is the problem I had with my slipping clutch, I had one too many plates.
On Mike's clutch it seems that the center is too far in. It's hard to tell how far in but when you compress the spring you just need to pull the spring flat to get it off.
Clutch Stack Height
Since the easiest clutch is when the clutch diaphragm spring is about .68” of deflection (175 lbs) and clutch pull is about .1”, the engaged position should be around .58” of diaphragm deflection to get the sweet spot. Therefore, the diaphragm appears to be about .03” inverted beyond flat (.55”) when engaged. The problem is how do you get the diaphragm to be at a certain position when assembled? You adjust the internal clutch stack height, the diaphragm is usually extended a bit to much. Therefore, you add thickness to a component in the clutch stack height. You could have a custom (thicker) backing plate made to be placed in the rear of the clutch basket, or you can add a clutch steel plate .080” thick. You can see using a straight edge on the diaphragm, if it is flat, extended or inverted. It is interesting to note that as the clutch wears, it always gets harder to pull until it finally gets to .40”extended. Then its up to 325lbs of pressure! I don't necessarily endorse this as a must do modification. But you should understand what is happening if you decide to go through with it. The lowered clamping pressure may cause slipping.
There are a lot of numbers here and not enough reference. I'm not sure what Dave is saying about .68" and .58" and then .55" clutch pull of .1" and something about .03" inverted. I assume most of these measurements are being made at the clutch center with a dial indicator?
Here's my attempt at the various states:
Am I close?