throw out and Clutch Pedal linkage

AND...
would any body have the clutch arm measurement "C" WITHOUT the effort reduction toggle

ALSO, could someone provide the inches of clutch pedal stroke

I thought I would try to determine the mechanic advantage mathematically of the “effort reduction” toggle links. And before you ask me why… I just wanted to see if I can.

I have the toggle to get the measurements for my equations, but what I don’t have would be the normal clutch pedal travel.

So could someone provide me with how far down their clutch can be pushed.

Hmmm...that pic looks very familiar, like the one that I posted a while back from my car, including the orientation of the retaining clips and the scratches. Glad to see it's helping someone.

My clutch pedal travels 5.25" (a little hard to measure) as measured at the center of the foot pad.

From some old notes that I have, dimension "A" in your first post is 1.8125" (1-13/16").

Dimension "B" is 2.5".

John

YES thanks for the excellent pic. I was able to count pixels to verify some dimension. The video was also good.

THANKS for providing your clutch stroke. 5.25" is a little less than I was expecting to get full MC stroke of 1.25” (but I am using the arc and not straight line measurement)

Would you still have the old arm to provide that "C" dimension on my 2nd post. Without knowing what the original ratio was, I can’t tell how much better this is.

Using your angles, would have the clutch pedal adjusted to start about ½” on my graph. This would be a “fast” take up (with a harder to push pedal) before leveling out with a ~7:1 ratio. To get the full MC stroke, I calculated pedal needed to go to 7 ½ on graph (so about 7” pedal ARC)

Here are the measurements I used for calculations; I figured “to a tenth” was good enough just to get an ideal of how the toggle works
a 2.6
b 1.4
c 1.8
d 3.8
e -1.3
f 1.6
g 2.9

The calculations were to model the red links as a four bar crank-rocker and the blue as an offset slider crank mechanism.
Joe

Hi, just did measure "C" on my 4907 easy as all fully disassembled.
C = 65 mm = 2.55 inch

With out "knowing" the "C" length for a clutch WITHOUT effort reduction toggle, I can assume the 7" of pedal travel from my graph was needed to straight line stroke the MC 1.25", thus the ratio would be 5.6:1. this makes the effort reduction linkage(~ratio 7:1) about an 80% reduction in force.

I would think the "C" lenght WITHOUT to be about 2"

Hi
well you got "C" ref your request...
I cannot tell if on this "Car" any modifications happened, hence NO idea on "effort reduction".
my set up looks like someone did "modify the settings" per hammer foot prints..

if you need more pictures happy to do..just tell me..

Sorry If I change above post while you were replying. I convienced myself what I thought I was seeing

while I have never seen the early linkage, Yours does look like it has the effort reduction toggle.
the early linkage, from parts book drawings, shows "C" connecting directly to the MC pushrod.

I am thinking, the early linkage "C" should be shorter

Thanks for your measurement as it confirms the same on mine (also disassemble, but rusted )

Joe,

Yes, I would have expected the pedal stroke to have been closer to 6". The 5.25" is a cord of the arc.

My clutch pedal assy is using the original non-effort-reduction shaft and arm. That is what is used in your pic of my assy.

When I added the effort reduction kit to my pedal assy, the vendor that I bought the kit from said that the pedal shaft and arm were the same with and without the kit. I have not had the opportunity to verify this.

The clutch throwout fork is currently installed in the car. I will try to find another that I can measure next week.

I measured the stroke on an original Pantera clutch master cyl, and the stroke is 1.125". That is max stroke, with the piston bottomed in its bore. Bottoming the piston would not be good, so I would expect the acceptable in-service stroke to be no more than 1".

John

I got the MC stroke of 1.25" from a downloaded LARGE excel file of "all things Pantera".
Mine is frozen solid! Using the slightly less MC stroke would cut down my expected 7" pedal stroke.

the parts books and the TSB indicate differnt arm/shafts? I haven't written the equation to compensate for the large angle it actual goes through, I was just doing simple guestimating lever lenght on no angle. when I get a chance, I'll use the 2.6" arm in an offset slider-crank model and see what the results.

as for the throwout lever, I noticed I had my outer lever with the clutch slave, the inner arm is gone with the transaxle to Ron McC. looking at the scribbles on my pocket note pad, I think I measured the outer "B lever" at 2.5"
My desire with knowing this lever ratio is in setting the Throw out bearing pretravel. The instructions I have found (that make sense) is setting about 0.1" slave travel, but what would that be at the clutch fingers?

did you have to re drill and pin the clutch pedal to rod to set the clutch position when you installed the kit?

quote:

I got the MC stroke of 1.25" from a downloaded LARGE excel file of "all things Pantera".
Mine is frozen solid! Using the slightly less MC stroke would cut down my expected 7" pedal stroke.

Reducing the MC stroke to 1" would reduce the pedal stroke to ~5.6"

quote:

the parts books and the TSB indicate differnt arm/shafts?

Yes, the parts book shows different numbers, but I have not had the opportunity to have both in hand to compare / measure. I do know that if the MC pushrod is adjusted too long, the linkage bellcrank will not move "over-center" and the result is that the clutch pedal cannot be depressed.

quote:

I think I measured the outer "B lever" at 2.5"

Yes, 2.5" is correct.

quote:

My desire with knowing this lever ratio is in setting the Throw out bearing pretravel. The instructions I have found (that make sense) is setting about 0.1" slave travel, but what would that be at the clutch fingers?

Don't know until the clutch arm / clutch fork ratio is determined. With the measurements that are in my notes, the ratio would be 0.725:1. Using 0.1" at the slave would give 0.0725" at the PP fingers.

quote:

did you have to re drill and pin the clutch pedal to rod to set the clutch position when you installed the kit?

No, I did not.

John

quote:

Originally posted by jb1490:..
With the measurements that are in my notes, the ratio would be 0.725:1. Using 0.1" at the slave would give 0.0725" at the PP fingers...
John

my intuition was the other way on that! I recalled I had a photo of my ZF input shaft, counting pixels, I see that the ratio would be as you stated. so with your noted 0.725:1 ratio, the lever lenghts would be 1.8"/2.5"

Looking at the photo (and after studying parts drawings), Should I have return springs around the shaft to ensure the TOB fully disengages? or is just the spring at the slave sufficient?

quote:

Originally posted by jb1490:...I do know that if the MC pushrod is adjusted too long, the linkage bellcrank will not move "over-center" and the result is that the clutch pedal cannot be depressed....
John

my plot of the effort reduction linkage "0-0" is at that point where pressing the clutch is locked (and could go either pushing in or pulling out). the mark at MC stroke of 0.25" would the the "start" of the MC when I match the angles of your linkage.

the red line is the curve of the effective lever ratio between pedal and MC of the effort reduction and green is the line if "C" of 2.6" is connected to the MC pushrod directly. the straight connection stroke is actually a curve, just not that obvious on the scale shown.

this implies that the effort reduction does reduce original effort about 70%

The external Spring at your Slave Cylinder is sufficient. The Arm(Fork) that pushes the ToB forward is also pulling it away from the Clutch again when you release the Clutch Pedal by use of that same Spring. Check the play with the Spring disconnected and Engine/Trans warm. I believe the less play the better (from own experience) but some play is obviously required. If I remember correctly I have about 1,5mm (measured at Slave Cylinder)

I am not sure was your objective is by those calculations? (maybe I missed it somewhere in your text) Are you after a softer Clutch then you can also consider a Booster.
Booster
I was at an earlier point planning something like that, but just got used to the Pantera Clutch along the way I suppose.

quote:

Originally posted by goodroc:...
I am not sure was your objective is by those calculations?..

The point for me is just academic. I want to understand the design and document the components of the car. I still have several other aspects of the clutch and will be asking more questions so I can learn from all the experience here.

My Goal would be once enough information is gathered, to complie and condense into a technical discription and share

ok sorry, I get it now

You have a lot of work ahead

When one buys a new clutch, does the manufactor provide the travel and force needed to disengage?

Does any one has such info for varous clutches?

looking at the hydrualics,
the master cylinder having a 3/4" bore and a 1.125"(?) stroke, would stoke the 1" bore slave 0.633" out of its total 1.625" stroke
OEM MC volume (0.75/2)^2 X 3.147 X 1.125 = 0.498
OEM SC stroke 0.498/(1.00/2)^2 X 3.147 = 0.633

Force calculation
Pedal to Master cylinder 7:1
Master cylinder to slave 1.78:1 (ratio of areas)
Slave to TOB 1.38:1 (inverse of 0.725:1)
Therefore pedal to TOB 17.2:1
thus 10 pounds on clutch pedal gives 172 pounds at TOB

Does that sound right?

In theory yes. But I believe there will be both some Hydraulic pressure drop and some Mechanical friction that to some extend will influence the effect of the system. The way the ToB is rigged to the Fork means that it is not a direct Link and there will be some kind of friction during operation. I don't have the slightest idea how to incorporate those forces into your formula. It is however something to consider?

quote:

Originally posted by goodroc:..there will be both some Hydraulic pressure drop and some Mechanical friction that to some extend will influence the effect of the system....It is however something to consider?.

Of Course.

Sort of the work philosophy I had was to compare the actual responses of a system with the best simple model and the deviations will be the friction/losses you mentioned, then those are the maintenance items that need to be addressed. I would expect a few % error, probably less than the error due to “rounding” in my measurements of these small pieces so far

One thing that could be interesting to know is how various types of Fluid in the system will behave and/or influence the system and forces. Technically there is no reason (apart from type of Seals) to use Brake Fluid. You might as well use Hydraulic oil or maybe even ATF?

Just a thought ;-)

To sort-of answer the question on how much force to disengage: some clutch mfgrs or refurbishers will tell you their 11" pressure plate is an 1800 psi (stock), a 2200 psi (noticably stronger at the pedal for street use) or 2600-up (racing). They don't normally publish this info. Many years ago, I put a pressure gauge in the clutch line out of curiosity and got around 300 psi at full disengagement for my unique system.

If, that pressure plate clamping force is 1800 lbfs (not PSI), then assuming the diaphram spring arms are 6:1, that would be 300 pounds at the TOB.

using your observed 300 PSI applied to the 1" bore slave would give (300 X 0.787 =) 236 lbFs at the release leaver and (236/0.725 =) 325 lbFs at the TOB

using the 300PSI applied to the 3/4" MC bore would give (300 X 0.443 = 132; 132/7 =) 19 lpf at the pedal

Thanks Jack, it is begining to make sense to me!

What makes your clutch unique?

To me, it looks like the clutch mfgs would provide the release stroke (I would think it would vary some my mfg) since nearly all clutch linkage are a set amount and not too adjustable

quote:

What makes your clutch unique?

The clutch master is an aluminum Girling (I forget the bore size), the 'slave' is a Tilton hydraulic throwout (dirt track, adapted to the ZF) and all the lines are dash-4 Aeroquip. The clutch plate & disc are OEM from 1972- asbestos disc & all!

When you run an annular hydraulic throwout system, EVERYTHING stock is put on the shelf- 11 lbs of iron.

Thanks for all the information and education

I spent this AM searching/reading past post about this and became fearful of asking any more questions!