Does a mod using a ’39 clutch & brake pedal work correctly?

[Robert Dip]

George/Maine.....thanks, but we all know that the 11 - 1 o'clock position is the best scenario, and that is exactly where my lever on the '39 is at. And, NO, the shaft was not drilled....it is in an untouched condition. My pedals are also at max on the floorboard underside....cannot any closer unless I raise the floor. All said and being equal as before on clearance and parts, the mystery still seems to be with the PP. It is the only part that was changed.

[DICK SPADARO]

Robert there is nothing to be discussed except the missalignment angle of your contraption and the choice of brand of your Free Beer offer.

Increasing the length of the pedal lever is the same as installing the correct length clutch lever and leaving the pedal lever stock. By the time you junk rig some adjuster adapter up you could have unbolted the too short clutch arm and bolted the correct replacement arm back on and hardly got your hands dirty.

I thought about the reason the 9" worked and the 10" didn't work as well and came up with the conclusion the the pressure plate arm height is different between the two. The PP arms dont have to be exact matches because the pedal rod adjustment is used to take up minor differences in arm height. If you have your pedal adjusted all the way out and the pedal is bumping the bottom of the floor board but when depressed still not releasing completely you dont have enough throw in the clutch shaft arm( due to the short homemade arm) thus you need a longer arm on the clutch shaft.

[Robert Dip]

Dick..."I thought about the reason the 9" worked and the 10" didn't work as well and came up with the conclusion the the pressure plate arm height is different between the two."...yes, and that is the only thing left to do. I shall get from my stash, a '48 flywheel and 10" disc & PP assembly, have right beside it the '39 flywheel and 9" clutch assembly, and in my press, measure the travel required to release the disc.

As for your first paragraph, the beer is only going to be a chaser....a double scotch is in order....the clutch shaft still has to be shorter, not longer. We may have to empty the bar...it's going to be a long night. Cheers.

[Matt in Alameda]

OK guys, this may have nothing to do with nothing.....but in 39 the clutch (and Brake) pedal had a rather thick rubber bumper ( Mac's # 91A-2476/7527.....page 19 in my catalog) in place under the floor board. The pedal would be "down" farther initially with this bumper on it and it should be able to stroke the clutch arm farther forward since more adjustment is available on the threaded rod. In other words, you are shortening the relationship of the clutch pedal bracket to the clutch arm on the bell housing.....this should leave more threads available for adjustment and the adjustment is longer, which is what you want I think............or am I more confused than everyone else here today? ......Matt in Alameda

[Robert Dip]

Matt....a good one....the thick rubber bumpers.....however, I modified the wood floor board...they are now deep set in the wood for that added throw. How much more throw do I need with this clutch ?....Thanks...Robert

[V8COOPMAN]

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Mr. Dip...You seem like the type of guy that I would enjoy sitting and consuming a beer or three with, given the chance, but we're on opposite ends of this continent and we ain't likely to meet any time soon. Nevertheless, I would have thought Dick's recall of 10th grade geometry would have surfaced by now. Yup Robert, you've got a couple of oddball parts there, especially that short arm on the trans. You suspected it was short and Barn Junk confirmed that with his measurements for a '39 arm. You've shared some interesting circumstances here. Man, this is the stuff that ALL can learn something from while playing with these old cars, IF they'll just listen and think. Unfortunately, you've gotten 40+ replies so far, quite a few of which are quick shots from the hip, and a couple that don't agree with the laws of physics. Annnnnnnd, we still don't have an answer to your basic question which essentially was..."is there any difference in height between a 9" and a 10" PP assembly?". Obviously, you have a handle on the physics of what's actually goin' on here. I've enjoyed having the opportunity to kick this around with ya. Let us know when ya have it fine-tuned. DD

[Robert Dip]

DD.....I had you in mind to join in at the 'Bar' session.....needed back-up here....BUT, you never know, the world is getting smaller, and I have gathered friends form all over the US and Canada. We enjoy our pastime tinkering around with these ole Fords...and discussions like this are fun....it's part of us, even if we happen to agree to disagree. The passion lives on...Robert

PS....I am now committed to get back to this at one time or another...Las Vegas calls...wife's idea of a 45 year anniversary....Cheers.

[DICK SPADARO]

Good morning Friends, neighbors and countryman, Since I have been providing the entertainment for the past couple days on my math ability and I agree its not great because I was in shop class more than math. This is my latest attempt to solve Roberts clutch disengagement issue.

To back up my theory and allow my friends to follow I have provided a diagram of the issue. First the clutch will not completely release with the pedal at its highest travel and its lowest depress. The clutch arm has been converted to a shorter throw arm 3" than the stock 3.5" arm. The pedal travel is approximately 6" from top to bottom out and the pedal ratio is 6 x1 (approx) and 20* of rotation gives about 1/2" of pedal throw. The throw out fork is 3.5" long.

Now with this information we are changing rotary motion into lateral motion because we have to move the throw out bearing. When comparing the stroke range of the short arm Robert has installed on his car it shows that the pedal is bottoming out on the floor board before effectively disengaging the clutch disc as the movement is stopped by the floor board due to the short throw of the 3" arm( covers 20* quicker). The longer clutch stock arm has additional pedal travel because it has not reached the 20* rotation point where the pedal would bottom on the floor board. The distance differential between the throws is the distance necessary to disengage the clutch. Therefore the shorter arm does not allow the clutch to disengage because it needs a longer rotation and cant because the pedal is bottomed out. Reverting back to the original stock arm will give the necessary travel distance in the pedal to prevent bottoming out before the clutch disc is released. Making a longer pedal arm will increase the rotation but that not the best solution. Note the throw out fork leads the clutch arm by 10* so although the intersection points are similar the clutch pedal has not reached full depression with the stock clutch arm at point B and it is at this point the additional throw releases the clutch disc. Spacing of a-b is the distance the pedal must move to disengage. Its not real as big as the diagram but its easy to reference.

The main issue is to keep the pedal from bottoming on the floor to complete the required travel and that what is happening with the short arm. It worked before but probably really not at 100% and the thickness of the clutch disc or finger height is a variable with the 10" unit.

[bbrocksr]

Originally Posted by DICK SPADARO

Good morning Friends, neighbors and countryman, Since I have been providing the entertainment for the past couple days on my math ability and I agree its not great because I was in shop class more than math. This is my latest attempt to solve Roberts clutch disengagement issue.

To back up my theory and allow my friends to follow I have provided a diagram of the issue. First the clutch will not completely release with the pedal at its highest travel and its lowest depress. The clutch arm has been converted to a shorter throw arm 3" than the stock 3.5" arm. The pedal travel is approximately 6" from top to bottom out and the pedal ratio is 6 x1 (approx) and 20* of rotation gives about 1/2" of pedal throw. The throw out fork is 3.5" long.

Now with this information we are changing rotary motion into lateral motion because we have to move the throw out bearing. When comparing the stroke range of the short arm Robert has installed on his car it shows that the pedal is bottoming out on the floor board before effectively disengaging the clutch disc as the movement is stopped by the floor board due to the short throw of the 3" arm( covers 20* quicker). The longer clutch stock arm has additional pedal travel because it has not reached the 20* rotation point where the pedal would bottom on the floor board. The distance differential between the throws is the distance necessary to disengage the clutch. Therefore the shorter arm does not allow the clutch to disengage because it needs a longer rotation and cant because the pedal is bottomed out. Reverting back to the original stock arm will give the necessary travel distance in the pedal to prevent bottoming out before the clutch disc is released. Making a longer pedal arm will increase the rotation but that not the best solution. Note the throw out fork leads the clutch arm by 10* so although the intersection points are similar the clutch pedal has not reached full depression with the stock clutch arm at point B and it is at this point the additional throw releases the clutch disc. Spacing of a-b is the distance the pedal must move to disengage. Its not real as big as the diagram but its easy to reference.

The main issue is to keep the pedal from bottoming on the floor to complete the required travel and that what is happening with the short arm. It worked before but probably really not at 100% and the thickness of the clutch disc or finger height is a variable with the 10" unit.

With all due respect Dick You've still got it wrong. A shorter lever on the throwout shaft will move the throwout fork farther.
The longer the throwout shaft lever the less the travel of the throwout fork.
Bill

[George/Maine]

I,ll second that shorter more throw.
On my 39 I had a 32 trans and was having same problem about 4" and shorted it and worked better.
If the screws on the pp are not even could cause wobble,or not adjusted right.
It has a open drive trans best remove it,check loose pin on fork,shaft, and make sure you have a return spring and up tight to floor.You want it to just about touch the throw bears don,t go for 1" play.With 3" laver you should have plenty of travel.

[Mart]

This is kind of going around in circles.

The 10" and 9" clutch assemblies should be interchangeable. The release mechanism should work the same for both. One should not require more throw than the other.

If your 10" clutch is not releasing, and your 9" was, there is something wrong with your 10" clutch assembly. If the 10" does not release and neither did the 9" then there is something wrong with your lever ratios.

I repeat - in my car I have used both 9" and 10" clutches and have only had to make a minor adjustment to the push rod.

Mart.

[Robert Dip]

I'm afraid to comment....glad to see I have back-up. For the sake of the archives, I measured the clutch bearing fork arm, and the c/c is at 3 1/8". It can increase slightly as the fork moves forward, but now we may be splitting hairs. All this to say that I have practically a 1/1 ratio on the outer clutch shaft arm as to the actual inner bearing fork.
This bar bill is gonna cost me plenty....it's now triple scotch with multiple chasers and a very, very long night.
Are we having fun yet!

[Fordors]

I was going to stay out of this one, but here goes anyway. There are two different lever ratios commonly used on Long style PP's, the 5.1-1 and a 4.7-1. A PP using the 4.7-1 levers will require more force at the pedal but it will move the pressure ring faster and would release the disc where a lever ratio of 5.1-1 might not. With no change to the linkage lever ratios (with t/o bearing travel remaining constant) 4.7-1 levers would "help" the situation.
When Ford went to the 10" clutch did they at the same time increase the static load of the pressure plate by changing the springs, or at least setting them tighter? Greater friction surface alone would not help transfer the torque but more static spring pressure would. More spring pressure makes for a stiffer pedal and Ford may have felt that undesirable so the question is this- is there a difference in lever ratios between the 9" and 10" PP's? Throwing a value out there of .100 (the amount of pressure ring travel needed) the 4.7 lever needs a t/o travel (once the fingers are contacted) of .470 to release the disc and the 5.1 needs .040 more t/o travel. Can anyone compare levers on a 9" and 10" PP?

[Robert Dip]

Fordors.....glad you did not stay out of this one....what you are saying about the different PP levers could be a problem solver here on this forever question of is there a difference between the 9 and the 10. From all of the geometry lessons we have seen here, it does not take much to make a big enough of a difference. I will definitely have to make the comparison of throw from a 9 to a 10.....at least, with the ones that i have...and who knows what has been done in the past with the different PP levers. One may have thought that they are all the same. Your input may be quite valuable....thanks for sharing this.....Robert

[George/Maine]

I think if you bend the trans lever and make 1/4 shorter you will be ok.
I had a mercury 10" on mine fingers different and made the lever on mine shorter.
The 39 big trucks used a 10" but think the pedals are not the same but also had bigger frame and may have used another shaft end.
39 pedels work but need some tweeking for other cars.
If you add on the end of shaft would need about 1/2" would buy you about 1/4" travel.I had another car and used a11" truck clutch would snap the theet trying to get 2nd gear rubber. The good old days That trans in a 51 ford car.

[DICK SPADARO]

OK This is my almost last post on this science project, I'm going to have so much free beer that I'll have to purchase a cooler.. This is whats up.. All you guys that are telling me I'm wrong are assuming the pivot points for the pedal shaft and the clutch shaft rotation are on the same plain thus the reason you believe I'm wrong and you are correct, that is not the case.

With the pivot points at the level, the rotation is as you state it, the short lever moves the 10* while the long lever does not move that distance, only about 8* of rotation. You guys would be correct if the trans shaft/pedal shaft was aligned like that but it is NOT.

The pivot point for the transmission clutch shaft is approximately 1 1/2" below the pivot point of the pedal shaft. This offset of rotation centers almost reverses the math and the short arm travels about 8* while the longer arm travels the 10*. Thus making the longer arm necessary to disengage the clutch fully.

Time to pay up Robert, do Canadians have any good beer???

[bbrocksr]

Originally Posted by DICK SPADARO

OK This is my almost last post on this science project, I'm going to have so much free beer that I'll have to purchase a cooler.. This is whats up.. All you guys that are telling me I'm wrong are assuming the pivot points for the pedal shaft and the clutch shaft rotation are on the same plain thus the reason you believe I'm wrong and you are correct, that is not the case.

With the pivot points at the level, the rotation is as you state it, the short lever moves the 10* while the long lever does not move that distance, only about 8* of rotation. You guys would be correct if the trans shaft/pedal shaft was aligned like that but it is NOT.

The pivot point for the transmission clutch shaft is approximately 1 1/2" below the pivot point of the pedal shaft. This offset of rotation centers almost reverses the math and the short arm travels about 8* while the longer arm travels the 10*. Thus making the longer arm necessary to disengage the clutch fully.

Time to pay up Robert, do Canadians have any good beer???

Still wrong.
Longer arm = less throwout fork travel.
Shorter arm = more throwout fork travel.
Lowering the throwout shaft1 1/2 " is not going to change this.
Bill

[George/Maine]

The 39 first year for hyd brakes needed new setup.I was only made for 9" clutch.
In 40 remade different setup.I don,t have one to look at but clutch arm must have been down so not hit floor.pivit for trans level to frame also lecer down.
Down makes trans shaft turn forward on top.They did away with arm.
So bend arm shorter,go with 40 pedals,or put the 9 back.
I was going to do same setup,and went with Flatomatic c4 and realy like it.
Have fun.

[Robert Dip]

George/Maine....glade you brought up the '40 scenario.....I just happen to have an entire '40 rolling chassis....another project of mine...don't ask....and dug out the trans pivoting arms. Yes, this is a different, however, the clutch pedal arm and the trans clutch shaft arms act in the same manner. Well, now it gets interesting....the '39 pedals arm is 1 3/8" c/c. The '40 is 1 5/8" c/c....1/4" increase in arc. Now for the clutch shaft arm that pivots on the frame....well, well, it measures 2 5/8"...yes shorter than the one I have which is at 3"...shorter by 3/8".....SO....we have more distance on the pedal arm, and less distance on the clutch shaft arm. This means that we have gained stroke on both counts.....and that....is self explanatory. I certainly would not have any issue with this geometry. Also for the record, I measured the difference of pedals itself, and they are exactly the same. They arcs at
11-1/4" and throws at 6"...which, when triangulated, converts to 30 degrees arcing.

Dick....we have to be careful with Canadian beer, the alcohol content is very high, but we could go with the Coronas. My army ( geometry supporters ) is increasing every day....but, we need you still alive to take care of our Flathead needs. Your loyal supporter, no matter what.... Robert

[Robert Dip]

OPPs I goofed.....the '40 pedal arm is at 1 1/8"....shorter than the '39....shoot first, ask questions after....but the '40 arm is definitely shorter by 3/8"....back to the drawing board.