Clutch problem

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I cannot put the clip in the groove with the diaphragm flat, at least what I call flat, when the alternating springs are both up and down the same amount about .01". In order to get my clip in, I have to have the diaphragm already inverted, and when I let off the pressure, the diaphragm with the clutch fully engaged is still over flat, but not by much, it's hard to measure for me.

I checked the operating rod and my 68/70 one is the same number, 06.0715, as the MK3.

It's not that my clutch is working badly, it's just critical where I set the clutch adjuster stud (for proper engagement without slipping), and I don't have any slippage even though I've got a bit of oil on the plates. It's just not a 1 finger pull and I was trying to improve it to be lighter and maybe not so critical in adjustment. I would call it a 3 finger pull and with the lever all the way back it eases up quite a bit so it's easy to hold the clutch disengaged, that's what makes the adjuster so critical, if I don't keep it at about 1/4 turn off the rod, I never get the break over. What I call breaking over like a compound bow.

Dave
69S
 
john robert bould said:
Are all commando clutch's fussy?
Click to expand...

No, I think most Commando owners are probably happy with the pull from standard stack height arrangement-or they've just got used to it?
 
I've given up on it. The clutch was never bad, just not one finger. I dumped some moly oil down the cable today and couldn't tell the difference. The original pack I can pull with my pinky, ring and third finger. I'm just not going to worry about it any more. I'll install the rod seal, clean the little bit of oil off and let it go at that.

I need to start it up and see if the Taglieri head steady is going to work. Supposed to be nice weather next week, that means the brown marmorated stink bugs will be coming around trying to get inside and they've been breeding about 10 times this year from the heat. Hopefully I'm over this 3 week summer cold/cough I've had.

Dave
69S
 
I have the same sort of symptoms for my MK3 and have given up trying to run with an extra Barnett plate (slipping with that much stack height). I think even the OB 0.060 plate might be too much. What I have thought about is picking up some older style clutch plates (thicker) and using a mix to get a good stack height.

Conversely, it seems you might be able to pick up the newer style plates (thinner) and get the height low enough that an extra steel would work.

Since mine works as is, not sure I'll ever spend the money chasing a 1-finger clutch, but the idea sure sounds nice.
 
Wow, what a read.
L.A.B. is dead on about the need for a cross section (with pictures and circles and a paragraph on the back of each one).
I'm trying to get all this clear in my simple mind too.
Do I have the following captions correct or not?

Clutch problem


Clutch problem


Clutch problem


We're striving for the DIAPHRAGM INVERTED scenario, correct?
Thanks for any and all replies.
All the Best.
 
That's the way I read Dynodave's page. However, when I raise my clutch pack height to give a one finger pull, the pressure is not enough to keep the clutch from slipping. So I went back to my original, which starts of slightly inverted and with careful adjustment of the adjuster stud, I can make it a 3 finger pull, but is very easy to hold disengaged, and doesn't slip. Dynodave even told me that a too light a pull on my clutch would probably slip. I can live with it the way it is.

Dave
69S
 
you want in the EXTENDED position and to just go to the INVERTED position when you disengage the clutch.
 
bill said:
you want in the EXTENDED position and to just go to the INVERTED position when you disengage the clutch.
Click to expand...
I would say slightly inverted to flat leaning to the slightly inverted. That is how mine is and works great.
As the clutch wears it i will go to the extended position. I think when flat it is producing the most effective force but when over inverted it will be too relaxed and over extended too hear to pull. So slightly inverted to flat for easy to pull and most effective force.

Remember this spring is working as the force of a lever provided by the raise machined surface of the pressure plate. When a little too inverted I have machined this raised area down .020 or so to bring to the desired function.
 
you have backwards. if you look at the chart on dyno daves site it shows the closer to flat the less apply pressure and this trend continues well into the inverted position. like i stated the goal is to have it just go over flat in to inverted as the lever travel ends. the less it has for applied pressure the easier it is to slip the clutch, also the 4 plate 750 clutch is easier to slip the the 5 plate 850. maybe you need to take a closer look at his pressure chart!!!

pvisseriii said:
I would say slightly inverted to flat leaning to the slightly inverted. That is how mine is and works great.
As the clutch wears it i will go to the extended position. I think when flat it is producing the most effective force but when over inverted it will be too relaxed and over extended too hear to pull. So slightly inverted to flat for easy to pull and most effective force.

Remember this spring is working as the force of a lever provided by the raise machined surface of the pressure plate. When a little too inverted I have machined this raised area down .020 or so to bring to the desired function.
Click to expand...
 
Dave, is the stack, steel, friction and pressure plates flush with the top of the splines?
That is what you need to look for.
Maybe you have a different basket or pressure plate and things are just mismatched but using the "flush with the top of the splines" rule should give you what you need.
Weren't there 2 different thicknesses of pressure plates?
 
My stack puts the top of the pressure plate just under the top of the splines. Maybe .02 or so, hard to measure. Adding a .078 Barnett plain plate puts the pressure plate over the splines by a fair amount and the diaphragm is now pretty well inverted. Makes for a great one finger pull, but not good clutch engagement. Like I said, my diaphragm is already slightly over flat with my stock parts. I'm thinking even a .06 plate will be too much, so I'm living with it.

Dave
69S
 
bill said:
you have backwards. if you look at the chart on dyno daves site it shows the closer to flat the less apply pressure and this trend continues well into the inverted position. like i stated the goal is to have it just go over flat in to inverted as the lever travel ends. the less it has for applied pressure the easier it is to slip the clutch, also the 4 plate 750 clutch is easier to slip the the 5 plate 850. maybe you need to take a closer look at his pressure chart!!!

pvisseriii said:
I would say slightly inverted to flat leaning to the slightly inverted. That is how mine is and works great.
As the clutch wears it i will go to the extended position. I think when flat it is producing the most effective force but when over inverted it will be too relaxed and over extended too hear to pull. So slightly inverted to flat for easy to pull and most effective force.

Remember this spring is working as the force of a lever provided by the raise machined surface of the pressure plate. When a little too inverted I have machined this raised area down .020 or so to bring to the desired function.
Click to expand...
Click to expand...
Well from what i have read on Dyno dave site it would appear to totally validate what i said about the best set up. Maybe not the highest point of pressure like i said, but it is where it need to be.
From dyno dave text
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 I may not be right on, buposition 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.
Click to expand...
As you see on the chart the flat position is right at.58 deflection as I said, and the sweet spot at .68 or slightly inverted. OK? I may not be perfectly on the money, but pretty god damn close.
 
Thanks men.
I see all the info needed to grasp the concept is included throughout Dave Comeau's web page http://atlanticgreen.com/ndnsclutch.htm.
I sincerely appreciate his approach and willingness to make it all available. Good food for thought there.
The two curves plotted on the graph are labeled dc and sh, although not explained as such I'm suspecting these are averages compiled from two separate individuals at two separate times for validation.
A question for Dave Comeau: how many diaphragm springs were evaluated to arrive at the plotted curves and could one expect close similarity regardless of vintage?
Again, many thanks for making this data available to us. Without it I would have treated it as a dynamic belleville and avoided going inverted, your approach makes good sense.
All the Best.
 
the part that you left out.

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.
and this what dave is running in to. like I stated a 750 has 4 friction plates and THAT makes it easier to slip where an 850 with its 5 plate will work with less applie pressure. If you can get away with the stack height you are running than OK, but it is pushing the limits of the holding ability of the clutch
Click to expand...
Click to expand...
 
bill said:
the part that you left out.

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.
Click to expand...
Click to expand...

Yes bill, there is give and take here, and with the right balance an easy pull clutch is attainable without slippage.
Do you agree?
 
yes it is attainable and is a fine line along with several factors playing in to it. the # of plates and the type of plates are 2 more that will make a difference as to spring pressure and slipping.

pvisseriii said:
Yes bill, there is give and take here, and with the right balance an easy pull clutch is attainable without slippage.
Do you agree?
Click to expand...
 
Yes, Dynodave suggested that with my 750 clutch setup it would be unreasonable to expect it to stay engaged with the lighter pressure with the extra plain plate. My other option is to get 5 new friction plates, a new pressure plate, at a cost of around $200, and I have heard of the clutches not being as good with the not-cush drive rear end. So I think I'm going to live with it. It's not a big issue for me. It's not like I can't pull the clutch or it's even hard, just not like pv's one finger vid.

You pays your money and you takes your chances. I have more often than not, been dissapointed with after market fixes and at plenty expense, and then going back to the original at even more cost.

Dave
69S
 
1. I had unverified rumors there are 3 diaphragm pressings/variations. So they are potentially not all the same. I would suspect they are not radically different.
2. I have had in my possession for examination actuator cams with variations that easlily account for over 15% in mechanical advantage difference...it is a device I eventually converted to atlas style to eliminate the hard pull problem for a friend. His actual problem originated from using a QPD belt drive/clutch with little follow up support. That's why he came to me for help.

Sorry I'm so busy to not keep my articles updated I know they are not perfect, but I spent a big chunk of money for a building/property and construction on my to be new shop prevents large blocks of time for web site maintenance. Most people tell me to leave it up rather than take the web site down,,,,
 
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