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Hot Rods Clutch Linkage Help.

Discussion in 'The Hokey Ass Message Board' started by GordonC, Feb 24, 2017.

  1. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    I have done a search of the HAMB but haven't seen anything that addresses a couple questions/problems that I have come up with while installing my clutch linkage and maybe one of you guys has some experience in this area. First is that I am using a 66 mustang top loader 4 speed connected to a 50 ford flathead via a stamped steel bell housing. Only thing required to use the bell housing was to open up the registration hole 1/8" to match the top loader. It has a typical F1 truck flywheel on it, and I am using a mustang clutch disc, along with the 3 finger pressure plate that mates up to the flywheel. Using a stock flathead throw out bearing. All goes together without any interference or problems that I can see. I finally hooked up my clutch linkage today and when attempting to push the clutch pedal down I couldn't move it at all! Now I built my own pedal box (think F1 pedals here) so that the clutch pulls against the throw out arm instead of pushing on it. When it wouldn't move I pulled the tranny out and everything looked ok so I put a ratchet strap on the clutch arm and pulled with that and it moved 2 to 3 inches all told. I had inserted a disc alignment tool before doing this and I could then turn the clutch disc by hand so it is moving enough to release the clutch. Hooked up the linkage again and I can get it to move but I really have to stomp the hell out of the clutch pedal, so much so you couldn't drive it this way. What am I missing or overlooking? Is the pressure plate the problem here? The fact I am pulling on the arm instead of pushing on it? I can shoot a couple pics of the temporary set up if that would help. Any help appreciated! Thanks.
     
  2. Fordors
    Joined: Sep 22, 2016
    Posts: 5,372

    Fordors
    Member

    Just a guess here, because I'm trying to visualize what your clutch linkage looks like. The F1 pedal action did push on the linkage like you say and you have designed linkage that pulls instead. The original linkage had a lever on the clutch release shaft (the shaft that rotates to move the throw out bearing) and if you have changed that lever you may have also reduced the mechanical advantage built into the factory linkage. It sounds like you have a ratio problem built into your new linkage.
     
  3. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    Fordors maybe I should post up some pics with the temporary set up in place so folks can see what I am describing. I would think if the force is equal and along the same plane as when it is pushed then the force to move it would be the same regardless of if you are pushing the throw out arm or pulling it. I could be full of crap about that so I hope someone will enlighten me. Pics to follow!
     
  4. AVater
    Joined: Dec 9, 2008
    Posts: 3,147

    AVater
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    1. Connecticut HAMB'ers

    Gordon, Pics helpful. I think what Fordors is saying goes something like this: If the length of the clevis set up on the pedal is different than the length of the original set up, you will be changing the leverage and therefore affecting the effort needed to disengage the clutch. It's like changing the length of a lever relative to the work needed to be done.

    Hope this helps.
     

  5. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    Here are some pictures of my temporary set up. I used 2 47 ford brake pedals and had a keyed shaft machined. The clutch uses the key to actuate the arm which is on the right end of the shaft in the first picture. The brake pedal just pivots on the shaft without a key in that area. I have tried 2 different length arms, one 6 3/4" and one 8 3/4". The 8 3/4" one is the one showing in the picture and is the one I can move the clutch arm with but the effort to do this is crazy!

    First picture is from inside the car looking down at the pedals box. The Clutch is on a keyed shaft on the left and the clutch activation arm is on the right hand end of the shaft. You can see the althread underneath the clutch arm running to the throw out arm.

    Second is a side view taken from the driver side looking under the frame rail below the drivers side door at the clutch linkage.

    Third picture is the connection at the throw out arm.

    20170224_204632.jpg 20170224_204710.jpg 20170224_204717.jpg
     
  6. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    AVater I just added some pics, thanks. I understand about the length of the lever effecting the amount of effort to push/pull the clutch arm, but I don't recall stock Fords needing a clutch arm 8 or 10 inches long to push the clutch throw out arm in on the old Fords I have driven. Again, the setup in the pics is temporary as I am working this out. I plan on standard rod threaded at each end with spherical rod ends where appropriate.
     
  7. Jimmy2car
    Joined: Nov 26, 2003
    Posts: 1,707

    Jimmy2car
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    from No. Cal

    Gordon,
    I also think it has to be a ratio issue. I have a Toploader in my 32 behind a flathead, and am using the stock 32 pedals. No issues, other than a stiffer pedal, and I use a diaphram pressure plate from a 85 Mustang GT
     
  8. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    Jimmy2 car thanks. I wondered if the 3 finger pressure plate was too much for what I have and if I should use the diaphragm type instead? Did that pressure plate bolt up to your flywheel or did you have it re-drilled to match the pressure plate? Also what throw out bearing are you running?
     
  9. AVater
    Joined: Dec 9, 2008
    Posts: 3,147

    AVater
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    1. Connecticut HAMB'ers

    You note the length of the pedal arm. Quick question: what is the length of the arm where the all thread is attached below the pedal? While I can't be sure, it looks to me that this arm is much longer than stock affecting the ratio and thereby making the effort needed to disengage the clutch greater. Compare the relative difference on a stock pedal to what you have made. Just a suggestion and hope this helps.
     
  10. Barn Find
    Joined: Feb 2, 2013
    Posts: 2,312

    Barn Find
    Member
    from Missouri

    I'm anticipating a similar problem on my next build. Because of the odd combination of engine and trans that I am using, I am fitting them together using the pressure plate from a big truck. I won't have room for the long pedal arm as in the big truck. So, my plan is to have a local shop change the spring pressure in the pressure plate so I have a normal clutch feel. It will reduce the maximum rating of the clutch, but I won't be loading it as much as the heavy truck.
     
  11. I agree with AVater,the length of the arm looks much longer that stock throwing out the ratio. If you want it to work the same you can't change those dimensions.Plus,it will alter the travel of your throw out bearing giving it way more travel than it needs to disengage your clutch .
     
    Last edited: Feb 24, 2017
  12. Fordors
    Joined: Sep 22, 2016
    Posts: 5,372

    Fordors
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    I will use the length of a '32 pedal because that is the only early Ford pedal I have to measure. With an effective length (perpendicular to the line of the applied force) of 14 1/2" and on your design the next, and only, lever is 8 3/4" giving a ratio of 1.65-1 working against the clutch fork which we'll estimate to have a ratio of 2.5-1. 1.65 + 2.5 = 4.15 to 1, so 50# pushing on the pedal is applying 207# to the throw out bearing.
    I think you need a mechanical advantage built into the pedal to make it a 6-1 ratio, or so. Then the pedal needs to work on a bellcrank (or z-bar, cross shaft, whatever you call it) with some more mechanical advantage (ratio) built in to that.
     
    Last edited: Feb 25, 2017
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  13. GordonC
    Joined: Mar 6, 2006
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    GordonC
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    AVater, so if I had a shorter arm, which I did, (2 inches shorter) and I couldn't push the clutch in at all with that, I know it would be closer to what an original would be like but I doubt I could move the clutch at all. Unless I don't understand, doesn't a longer lever require less force to move a given object? I don't want to sound argumentative but I am just not seeing what is making this take so much force to push the pedal down. Is it less force on the shorter arm because it is so close to the center line/shaft of the clutch pedal as opposed to a longer arm which is further away from center line, say at 8 inches? Either way a short stock type arm puts the rod at such an angle with this setup I suspect it will bind the throw out bearing on the front shaft of the tranny. It will be easy enough to try though as I can just drill a hole up closer to the center line of the clutch pivot shaft.

    Barrelnose I think your on the right path when you note there is a ratio that the stock stuff has and it works. Unfortunately these are the pedals installed on the crossmember in the car and Im trying to make them work, not go to a stock set up as it won't fit with what I have in place currently. I may have to change that however!

    I appreciate the help guys!
     
  14. Jimmy2car
    Joined: Nov 26, 2003
    Posts: 1,707

    Jimmy2car
    Member
    from No. Cal

    Gordon
    I used a Long Pressure Plate before and it worked fine, but was an import and chattered a bunch.
    I'm running an early 59 type block and the Mustang Pressure Plate bolted up just fine to the early flywheel.
    I use a stock Ford throwout bearing. I have a sleeve installed on the input shaft housing of the 4 speed
     
  15. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    Fordors I like it! I am not familiar with how to calculate those ratios but if you are and feel therein lies the problem I am more than happy to make adjustments to try out your theory. Can you educate me as to where you took your measurements from for the pedal length? I just tried doing this and I measured mine straight up off the centerline of the shaft the pedals are mounted on I get a pedal height of 12" with the pedal directly above the pivot. My arm is 8.75" long. So that gives me a ratio of 1.37 - 1, plus the agreed upon estimate of 2.5-1 for the throw out arm, which gives me 3.87 to 1. Which at 50 lbs push comes out to 193.5 lbs of pressure at the throw out arm. Did I figure this correctly? As I said I'm not familiar with this part.
     
  16. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    Jimmy2car I feel like Fordors is on to something with me screwing up the ratio on the pedal and arm length. I am going to have to give this some serious thought on how to correct this. When I checked the throw out bearing on the input shaft it looked to me to slide right on. Not tight but not loose either. I may need to look at that too. Where did you get the sleeve in case I need one? I appreciate the additional info tho! Thanks.
     
  17. Jimmy2car
    Joined: Nov 26, 2003
    Posts: 1,707

    Jimmy2car
    Member
    from No. Cal

    A friend of mine made it. Just a piece of tubing turned on a lathe to fit, with an allen head screw to hold it secure
     
  18. GordonC,
    A longer lever does make it easier to shift an object but,the longer lever has to be on the upper side of the pivot point,not the end work the work is done.That is where the mechanical advantage is gained.
    In your setup,the longer lever below your pivot point means less advantage but more unrequired travel of the clutch arm.
    Your trouble with linkage angle is because on a standard ford setup there is another lever on the cross shaft connected to the throw out bearing about 3" long pointing up that gives more mechanical advantage and lines up the linkage shaft.
    I hope this makes sense.
     
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  19. Fordors
    Joined: Sep 22, 2016
    Posts: 5,372

    Fordors
    Member

    Yes GordonC, you are correct with the way you are figuring the ratio and the applied force. That '32 pedal I mentioned has a lever on it that is connected with a clevis and adjustment rod to the lever on the end of the cross shaft. The 14 1/2 pedal and a lever with an effective length of 2 5/8 gives an rounded off ratio of 5.5, (14.5/2.625 = 5.5). This 5.5-1 pedal is working a lever on the cross shaft that is 4 3/4 (from a dimension I found on line) so now that ratio using the 4.75 / 2.625 = 1.80 and the cross shaft has a ratio of 1.52 (4.375 / 3.125 = 1.52). Total them up and the overall ratio is 8.82.
    I'm not much of a draftsman but here's a sketch. You used a different style throw out fork but the ratio still factors in the same way. Scan0037.jpg
     
    Last edited: Feb 25, 2017
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  20. Fordors
    Joined: Sep 22, 2016
    Posts: 5,372

    Fordors
    Member

    Next think about what is needed. Stock clutch? Maybe a 10" with 2000# and Long style PP levers are 4.7-1, again using a number found on line. 2000/4.7 = 425 lbs. and through dumb luck we arrived at 50# force x 8.8 ratio = 440#.
    For a clean release you need an air gap of .080 at the disc so using the ratio you eventually arrive at for your linkage you can know the throw of the pedal. .080 x 4.7 = .375 throw out travel x the 8.8 linkage ratio gives a pedal throw of 3.3 inches and don't forget an inch of free play.
    I went through this exercise back in 1979 when I modified a Neal Products hanging pedal hydraulic clutch and brake set to floor pedals in the coupe in my avatar. Flipped the bracket, added tabs to the bottom of the pedals, used an Airheart master for the brakes and a modified '67 Corvette z-bar to work a GM L88 diaphragm PP. Took a bit of work, and I had to dust off some old brain cells and I think this might get you on the right path.
     
  21. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,966

    V8 Bob
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    As GordonC and others have stated, your linkage ratio is wrong. Based on a clutch design/operation book (HP Books Clutch and Flywheel Handbook by Tom Monroe 1977) I have, the overall ratio should be around 10 - 11:1. This will result in a pedal free-play under 1 1/2" with around .100" (tenth of an inch) T/O bearing to clutch finger clearance. The two linkage setups I've built for my '32 and '40 work very well using guidelines from the book. I am using diaphragm pressure plates (10.4" with a flathead, and 11" with a BBF) which require less pedal effort during actual disc disengagement, compared to same-sized Ford Long PPs.
    The book mentioned above is still available from Amazon and Ebay, JFYI.
     
    Last edited: Feb 25, 2017
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  22. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    Fordors thanks for the additional info. I think I understand now and will work at getting my configuration changed around to generate force closer to the numbers you show above. And I said what the hell will I ever use ratios for in real life when I was in high school! Nice art work too! :D

    Barrelnose I think your correct on the lever on the side of the bell housing adding a mechanical advantage. I hadn't considered that on the stock setup. Thanks.

    Jimmy2car thanks for the info.

    I am going to spend the day looking at this and thinking about the best solution. I have the body mounted and its all painted so I have to keep my fab work at a minimum if I can. I may look at a cable setup like D-Russ did on his. I happened to find that post last night while researching this further. Not sure I want to add a z bar and all that entails but if I have to I'll figure out something. Either way I will come back here with what the solution was and how it works. I appreciate all the help guys!
     
  23. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    V8 Bob. I am going to work on correcting my setup as I obviously have it screwed up. Ill be back with what the solution is. Thanks for adding that info! I appreciate it.
     
  24. AVater
    Joined: Dec 9, 2008
    Posts: 3,147

    AVater
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    GordonC, Looks like the rest of the HAMB team provided the needed insight. Sorry for the late reply on my part as I was out of town most of today. You can make this work!
     
  25. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    So I spent the day looking at this clutch stuff and considering what I can do to solve this. I scrounged around in my parts stash and came up with a stock 47 clutch pedal, brake pedal, 2 pedal boxes, and 3 throw out cross shafts with a 3 inch arm on one end and a slot on the other end. The type that rest on a ball on the frame and go into a keyed slot on the end of the throw out arm in the side of the 47 bell housing. Also, two pivot balls. I am considering making a z bar set up by cutting two of the cross shafts in half and welding them together so I now have a socket at each end. If I weld the two pieces together 180 degrees opposite each other I have essentially made a z bar. This started me wondering how does this figure into the calculations we were doing last evening Fordor? If the length of the arm on top of the cross shaft and the length of the arm below it are the same length, and 180 degrees opposite from each other, do they simply cancel each other out and are not a part of the calculation? Here are some numbers I got with the new stuff I am thinking of using.

    Pedal 13" / Lever 1 1/2" = 8.66 to 1. Estimated throw out ratio = 2.5 to 1. Total of the two is 11.1 to 1, which is dead on V8 Bobs info from above. Now if I could just hook this straight up to the throw out arm like this I would be golden, but NOOOOO!!! I have to add in some kind of z bar setup to get the force of the pedal down to the level of the throw out arm. So how does the cross shaft with levers on it figure into this calculation?

    I'll include some pics tomorrow of what I am thinking of doing and you fine gents can tell me I am nuts! But do it gently!:D
     
  26. Fordors
    Joined: Sep 22, 2016
    Posts: 5,372

    Fordors
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    Yes Gordon, that z-bar would have no effect on the overall ratio, it is just transferring the direction of the force.
    When I modified my Corvette z-bar I put a tube inside rather than just butt welding it even though I trusted my welding ability. Sometimes a little "belt and suspenders" doesn't hurt.
    You are on the right track for sure, we just gave you a little nudge.
     
  27. Marty Strode
    Joined: Apr 28, 2011
    Posts: 8,796

    Marty Strode
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    Here is an 8BA with 49-51 bellhousing, with the 3 speed version of your trans. Different pedal setup than yours, but maybe I have notes on the pedal ratio, I'll look tomorrow. IMG_0672.JPG IMG_0892.JPG
     
  28. V8 Bob
    Joined: Feb 6, 2007
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    Keep in mind that a direct acting clutch linkage will try and move the engine/trans during disengagement through the forces going directly to the clutch arm, and is the reason Ford used "steady" or "anti-chatter" rods on V8s up to '40, the first year for a clutch linkage equalizer. I had to add steady rods on my '32 to keep the engine from moving forward because of tight engine/radiator clearances.
    A properly designed "Z" or equalizer bar will eliminate or minimize any engine movement during clutch disengagement, along with helping ratio stack-up. I did this with the '40 linkage, but have no good pictures at this time.
    [​IMG]
     
    Last edited: Feb 26, 2017
  29. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    Fordors thanks! I just need to figure out how to squeeze it into the space allowed. I was going to cut two of them in half, shorten them to the length needed, center drill them, insert a rod and pin it or rosette weld it, and then weld the joint between the two pieces. I dislike doing rework!

    V8 Bob thanks for the pics. I see what your saying. I hadn't considered the amount of force pushing on the throw out arm! I guess with a z bar and the linkage down low near the side of the block and on plane with the throw out arm it generates less side ways twist when the clutch is pushed in. I guess I should have paid more attention to the way Henry originally designed them to work! :(
     
    Last edited: Feb 26, 2017
  30. GordonC
    Joined: Mar 6, 2006
    Posts: 3,140

    GordonC
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    Marty thanks for your shots as well! All these pics help me to visualize what I am going to need to do.
     

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