Time for some Sphere Reassembly
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  1. #1
    1000+ Posts pottsy's Avatar
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    Default Time for some Sphere Reassembly

    As detailed elsewhere, I managed to dismantle a couple of spheres and have sourced some diaphragms from Roger Parker (thanks Rog).

    I now look to the brains trust for a couple of bits of advice and a critique of the process I plan to follow for reassembly.

    Firstly though, a question that concerns the matching front sphere of the set I bought in 2005. While showing no signs of decay as yet, and holding pressure nicely, I wonder if I should dismantle and replace this one and replace the diaphragm as well? Part of me says "if it ain't broke, don't fix it" while the other part of me (anyone remember the devils on Donald Duck's shoulders?) says that if one diaphragm has failed then the other will follow suit when the time is the most inopportune. Thoughts People?

    As far as reassembly is concerned, I believe that I need to observe the following:

    Ensure everything is clean as a whistle, then clean it again. (I plan to use isopropyl alcohol to clean the metal bits. Is this OK?)

    Lubricate the rim of the new diaphragm with LHM. (Should I also use anti-seize on the threads?)

    Assemble with as much rotational force that I can muster by hand, then add maybe a bit more with the machinery. (How much should the bit more be? a half turn, a quarter turn, a fixed distance, a fixed number of degrees?)

    Is the best plan to dry assemble to the point where it just touches and mark that on the rim, then see how much is left with the diaphragm in position? I suppose this will partly determine the "bit more"?

    Once they're assembled and successfully pressurised I'll give them a flash new coat of British Racing Green (or the Cit equivalent. I'm not a purist so the blue stripe is not happening).

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    Hopefully all this will be achieved before I visit Peter for some regassing on Thursday.

    As far as spares go for the rally I'm preparing for in November, I figure if I've got freshly re-gassed units front and rear, plaus a fresh acculumulator and a spare front and rear shpere, I should be fine. The last time I went bouncing through the bush I didn't need any of the spares I took, but I don't plan to tempt Murphy that much!

    Lastly, here's couple of piccies of the freshly cleaned front sphere ready for assembly, and the failed diaphragm. The machining on these units is stunning.

    Cheers for now, Pottsy.
    Attached Thumbnails Attached Thumbnails Time for some Sphere Reassembly-failed-inside.jpg   Time for some Sphere Reassembly-failed-outside.jpg   Time for some Sphere Reassembly-squeaky-clean.jpg  
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  2. #2
    Fellow Frogger! Balki's Avatar
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    i put lhm on the edges of the diaphragm and a little anti seize on the threads so moisture can't get in the clean threads and rust it solid for next time
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  3. #3
    Fellow Frogger!
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    As Balki mentioned - cover the upper and lower edges of the new diaphragm with lots of lhm. And grease the sphere threads well. No real need to use anti-seize, a good quality wheel bearing grease works a treat. The grease helps prevent moisture intrusion and rust formation on the threads. Hand tighten until firm contact and then give the upper half about 1/2 more turn (or a bit more) to ensure a good gas/lhm seal. Depending on sphere design (they do vary to some extent) you may only be able to give it 1/2+ turn before you get metal to metal contact between the two halves. Once assembled, and re-pressurized, place the sphere in a can with sufficient water to cover well the joint. Leave it there for at least a couple of minutes and look for any signs of gas leakage.

    As for the other sphere. Given that what is in there is most likely a rubber diaphragm I would replace it with a new Desmopan one. They are far more rugged, mechanically. The only downside is that they are more gas permeable compared to the rubber units. So need to be check for pressure a bit more often. The one that failed shows signs of rubber deterioration and bubbling. By chance would that sphere (if a front) have been on the exhaust side of the engine?

    Steve

  4. #4
    1000+ Posts pottsy's Avatar
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    Thanks Steve.

    Yes, the sphere that failed did spend a deal of time on the exhaust side, albeit wrapped in a silver reflective tape in an obviously vain attempt to minimise heat effects. After I had them regassed, I swapped sides to try to balance it out so to speak.

    I'm thinking you're right, that I'd be better off to have two completely re-conditioned units in the front rather than assume the other one will stay intact.

    Cheers, Pottsy.
    Buvito Ergo Sum!

    The Fleet:

    2018 C3 Shine ("Oscar" Mrs P's)
    1974 D Special Manual Sedan ("Moby Dick")
    2006 C5 HDI Wagon Auto ("Mephistopheles")
    1982 2CV6 ("Gaston") Seasoned traveller
    1975 GS Pallas ("GiSelle") Next project
    And for Fun, 1968 Mini Deluxe ("The R & D'luxe" 1078cc, Grin Factor 100!)

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