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Here's an odd question-please read

Discussion in 'Technical Q&A' started by FamilyCar, Jan 20, 2011.

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  1. FamilyCar

    FamilyCar Formula Junior
    Rossa Subscribed

    Sep 26, 2007
    790
    Seattle, Wa
    Full Name:
    Peter Goodall
    #1 FamilyCar, Jan 20, 2011
    Last edited by a moderator: Sep 7, 2017
    While working on the clutch slave cylinder of my '87 Mondial, I've had to replace the Q-Ball bearing-part 34 on the attached diagram. It was exceptionally difficult to remove--partly because of access to it, but also because it was in very tightly. I ended up using a pneumatic hammer to break it out. I then cleaned the bore that it pressed into out with an abrasive cylinder and a wire brush on a dremel tool.

    To my horror, the new bearing easily pushes in by hand. While it doesn't have up and down play, there is clearly not enough friction to keep it from vibrating off to one side or the other. The bearing won't fall out since the forked pushrod (part 38) will hold it in place, although I suspect it could get about half-way out to one side. As a note, the bearing is 18mm in diameter, and maybe 4mm thick. It has a groove machined in the center, such that the bearing will occur only on the outer 3rds. I think it probably has enough room to move that it could move sideways to the point where only 1/3rd of it was bearing inside the clutch arm.

    So I'd like to do something to keep it from moving around. There shouldn't be lateral forces on it from the clutch, but I'm fairly certain it should be at least somewhat stuck in the bore. Sound good?

    Here are my potential solutions, please tell me your thoughts on these or suggest something better:
    1. Use red thread lock
    2. Epoxy it in
    3. Use some fairly generic, flexible adhesive.

    I've been told that the thread lock won't act as a glue, although it is appealing because it can be defeated with heat and will wick into the very small gap. I'm not sure if epoxy would go in, for example JB Weld would most likely just get pushed off. Also, I'm assuming a bit of flex would be good to keep it from cracking. Some flexible adhesive/sealant could probably get a skin in there, but may not stand up to the heat and general pollutants.

    Any good ideas here? Thanks in advance...
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  2. Cribbj

    Cribbj Formula 3
    BANNED

    Jan 1, 2011
    2,316
    Cooke City MT, The Coolest Small Town in America
    Full Name:
    John
    #2 Cribbj, Jan 20, 2011
    What about making your own bronze bushing which would have a better fit, and more load bearing surface?

    It looks like a similar situation to one I had around 10 years ago for a sloppy shifter linkage, and I made my own bush with teflon, and it's still going strong. Mine doesn't have near as much force on it in shear as your application, so teflon probably isn't a good choice for you, but maybe bronze would be.
     
  3. solofast

    solofast Formula 3

    Oct 8, 2007
    1,773
    Indianapolis
    #3 solofast, Jan 20, 2011
    Last edited: Jan 20, 2011
    You are correct in that normal thread lock won't act as a glue, but Locktite Retaining compound will work if the fit is tight enough. It is made for this kind of thing and, like regular Locktite, it can be softened by heating. Most all of these thread compounds are anerobic curing materials. So long as there isn't air in there the Locktite will cure. Also you can use some of their accelerator and that will promote the curing. If it is a slip fit and relatively tight that will do it. If it is sloppy you are SOL and it won't cure, but that's probably the best thing since you can get it back out with a heat gun.

    Here is a blurb from the Locktite site...

    Retaining compound is used when press or slip fitting cylindrical components that are not threaded. It fills the gaps between parts, creating a rock solid connection. 609 formula is an all purpose, quick curing compound that is perfect for general press fit applications for gaps up to .005" that will not be exposed to excessive heat. 620 is a high heat slip fit formula that will withstand temperatures of up to 450 F and fill gaps up to .015" while sealing the metal and preventing corrosion. 638 is a super heavy duty compound for use in high stress applications, for slip fit applications of up to .010".
     
  4. BigTex

    BigTex Seven Time F1 World Champ
    Owner Rossa Subscribed

    Dec 6, 2002
    79,406
    Houston, Texas
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    Bubba
    #4 BigTex, Jan 20, 2011
    Use shim stock to tighten the fit on the outer race???

    Once assembled I don't see where it's gonna go....but maybe I'm not seeing it all...
     
  5. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    37,288
    Cowboy Capitol of the World
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    Brian Crall
    #5 Rifledriver, Jan 20, 2011
    Next time don't use an air hammer.

    In fact, lose that thing.


    I bought one when I was young and dumb and it hasn't been out of my tool box in 30 years.
     
  6. NW328GTS

    NW328GTS Formula 3

    Nov 16, 2009
    2,191
    Washington
    Full Name:
    Hal
    #6 NW328GTS, Jan 20, 2011
    Last edited by a moderator: Sep 7, 2017
    I'd go old school and stake it in place. With the bearing in place, support the opposite side so that it is located correctly and then use a center punch to stake it in place in the arm in 4-6 places around the perimeter. The punch mark slightly swells the material towards the hole to tighten it up and lock it in place.

    here is a photo.
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  7. finnerty

    finnerty F1 World Champ

    May 18, 2004
    10,406
    #7 finnerty, Jan 20, 2011
    Good for you! They definitely do more harm than good (and, can do it in a hurry, before you realize it).

    I cringe whenever I see any mechanic with one of those nearby --- other than the body repair technician, who needs to remove parts that have already been destroyed. No skilled mechanic has any need for that tool.
     
  8. finnerty

    finnerty F1 World Champ

    May 18, 2004
    10,406
    #8 finnerty, Jan 20, 2011
    Last edited: Jan 20, 2011
    4. Source a slightly larger OD bearing (generic, non-Ferrari supplier), and over-bore the hole to accept the larger size with proper fit.
     
  9. finnerty

    finnerty F1 World Champ

    May 18, 2004
    10,406
    #9 finnerty, Jan 20, 2011
    Last edited: Jan 20, 2011
  10. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    37,288
    Cowboy Capitol of the World
    Full Name:
    Brian Crall
    #10 Rifledriver, Jan 20, 2011
    That would be best but if it is near a zero fit bushing/bearing mount Locktite should work.
     

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