1962 Clutch - gorilla spring redux
My clutch is a modern bent finger style and I am restoring the car for top flight and my clutch pedal stays on the floor .... age old problem searching in the archives, I want to keep my Gorilla spring. Several folks have done that but I can't seem to adjust my clutch per ST 12 manual and get the pedal to return. I have the 6" travel and 1" free play, what else can I adjust without abandoning the configuration or replacing parts? Your help would be greatly appreciated. Does the fast clutch setting help this or hurt it? What direction can the swivel adjust to eliminate the problem without wearing the clutch prematurely? I have adjusted the over center spring adjustment both ways, no change? Which direction would help me? I have to say the pedal depresses very smoothly and with little effort compared to my C2.
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Dino Lanno -
Re: 1962 Clutch - gorilla spring redux
Dino, Yes age old problem. The fast clutch setting may make it worse, and will be noticed by the keen interior judges eye as it wasn't shipped in that configuration.
It sounds like the gorilla is going over center a tad too much so it won't release, and/or you have too much freeplay and the bent finger springs in the clutch are too flat and can't spring back. You are using the correct short throwout/release bearing and the correct fork? Sorry, have to ask.
Variations in frame brackets, springs, forks, rods, cross shafts and links make this miserable. I feel your pain. I've done many clutches like yours and some were more problems than others. I've been able to sometimes overcome the pedal stuck to floor syndrome by bringing the upper link on the cross shaft further back when the gorilla is over center. On others I had no luck and succumbed to a added pedal return spring, but I don't like doing that.
I'm wondering if on yours the link is at the max and can't go further. I'm thinking maybe open the slotted hole in that link a bit more. This might keep just enough tension on the spring to help return it. You don't have much though as the link will hit the bushing eventually. Maybe experiment before modifying it. Remove the top bolt and somehow clamp the link to the cross shaft(hose clamp?) and try it. Either way, be careful. You know those springs are monsters.
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Re: 1962 Clutch - gorilla spring redux
Rich is spot on as usual...
I would add that you need to make sure the configuration is assembled correctly....I have seen the upper gorilla spring attached without the upper link or missing the hairpin clip at the frame. You can read through the attached discussion for more insight...and the 'fast' position will not help...it sacrifices pedal effort for faster operation. Most that try it go back to the normal setting.Comment
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Re: 1962 Clutch - gorilla spring redux
Thank you Richard and Frank, i am assuming the adjustable bracket that is shown in the pics to help the pedal return would be adjusted back toward the rear of the car? Correct? DinoDino LannoComment
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Re: 1962 Clutch - gorilla spring redux
Check item #6 in the first column on this page;
http://chevy.oldcarmanualproject.com/shop/5362csg/5362csg06r03.html
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Re: 1962 Clutch - gorilla spring redux
Yes. I think I may have assumed you knew about the adjustment of the upper link arm as Frank pointed out in the ST-12. Loosen the lower pivot bolt, then the upper bolt which holds the slotted hole in the arm. Use the Crescent wrench to move the arm rearward, tighten the hardware and re-test pedal action.
If after readjusting and experimenting, the pedal still stays at the floor, then you may want to try opening the slot in the arm to gain more travel rearward. In most cases I've been able to fix the problem with more movement of the arm to the rear, but not always the case. It's really trial and error when adjusting the upper link arm.
The geometry of the spring arcing reaches a point in its travel after it stretches to its maximum length, it then begins to retract as it travels beyond the over center point. It's a very fine line where it becomes a problem.
When it goes past over center it is then beyond the arc and is now tensioning the linkage. This tension may be too much for the bent fingers in the clutch pressure plate to overcome the spring and total geometry to return the pedal. By limiting how far the spring stretches over center is the key. Some times very small adjustments on the adjustable upper link arm angle can make a difference in pedal return.
Try to view your mechanisms actual travel arc by having a helper slowly press the pedal. As the spring stretches, carefully observe when it reaches center, then overcenter as the spring retracts. Sometimes you can see the point where it changes.
Also, I often find it useful to test the pedal gorilla spring geometry without the fork rod connected to the inner cross shaft arm. Once the pedal rod is connected to the cross shaft arm pivot bushing bolt, the entire mechanism from pedal to cross shaft is testable. I test the pedal action and then use the adjustable clevis on the fork arm to get proper free-play adjustment. I slip the clevis into the inner cross shaft arm and use a cotter pin(unbent) in the clevis temporarily. I adjust freeplay with repeated clevis adjusting. The temporary cotter pin makes it easier for repeated testing. When I'm set, I then slip out the cotter pin and replace with the proper circlip. Just be careful as the rod is tensioned and clevis is under pressure in the arm.
Again, just to be sure, make sure you have the proper throwout/release bearing and fork as these will greatly affect operation. If the "tall" TO bearing is installed in a bent finger clutch, you'll never get the pedal to return.
RichComment
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Re: 1962 Clutch - gorilla spring redux
All of Rich's advise is always, as in this example, is spot on.
Just understand -- the gorilla spring is an over-center device providing "bi-stability" (yes, that's a real word). Just like the old household light switches...when you pushed that lever past the over-center point (in either direction) it was designed to ease completion of the engagement/disengagement with minimal effort on the user's part...
What Rich is describing above is the technique to strike the balance of how the over-center action 'kicks-in' between the two pedal directions...
This spring may well be the most misunderstood piece on the C1 cars...Comment
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Re: 1962 Clutch - gorilla spring redux
Can not offer anymore then what has been stated but if you have the parts installed as per every ones advice, it will work. Out of all the C1's I've worked on, they all worked. Some took a little more adjustment here and there but they will work. I just wish the C2's had that design. Makes pushing in a clutch a lot more easier..Comment
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Re: 1962 Clutch - gorilla spring redux
Chester, Yes but a effect of operation could also be the variation of bent finger clutch manufacturers' specs. I have had good results with LUK clutches, but I have read elsewhere that some other brands are troublesome. Someone did a detailed analysis bench test using a hydraulic press testing various brands. Surprising results and showed how some brands were way off spec.
In 1989 I installed a GM bent finger clutch in my '59. No problems ever with stuck-pedal syndrome.
Dino, what brand/part# clutch did you use?
RichComment
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Re: 1962 Clutch - gorilla spring redux
I installed a Sachs bent finger new assembly.Dino LannoComment
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Re: 1962 Clutch - gorilla spring redux
I had to find a measurement scale to measure the 6-9 pedal depress force to move the pedal from stop.Dino LannoComment
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Re: 1962 Clutch - gorilla spring redux
Dino, To get in the ballpark I use a postage scale.Comment
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Re: 1962 Clutch - gorilla spring redux
That's what I have, dated 1905.....a classic service tool on a vintage Corvette.....gotta love it. I am going to whip this baby this weekend, and have me a working clutch by Turkey day.Dino LannoComment
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Re: 1962 Clutch - gorilla spring redux
Problem solved, adjustments using the crescent wrench on the z bar and adjusting the position of the over center spring bracket, thanks everyone for your advice, happy thanksgiving.Dino LannoComment
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