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Paging Chemical Expert !

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  • Paging Chemical Expert !

    In my random cleaning of the garage today I ran across some Silicon oils that I used to use in the shock absorbers of my 1/8th scale off road vehicles.

    One of these "weights" was 7,000wt which was thicker than honey, and one was 50,000wt that was thicker than tar, but both were still viscus. Now, since these are in fact lubricants, what is stopping anyone from using the 600wt in and about the Model A where appropriate?

    Oh, forgot to mention, they were also used in the drive gear assemblies.

    Are we banned from using pure Silicon lubricants in the Model A?
    Last edited by DaWizard; 11-06-2017, 07:02 PM.
    You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

  • #2
    Silicone oils and greases are a voodoo mix of various length polydimethylsiloxane chains and fumed silica, added as a thickening or viscosity modifying agent. At low static and shear pressures fumed silica acts as a lube but actually becomes abrasive in EP situations. Good for sliding apps with little pressure, like elastic O rings and hydraulic cylinder seals, but bad for differential and tranny gears under heavy, hard metal to hard metal load. Also terrible for highly loaded ball and roller bearings.

    You would think something that slippery would be a great all-around lube, but no. To complicate matters the "weight" is very subjective due to the bizarre flow properties of the polysiloxane-fumed silica mix. PDMS tends to be thixotropic, fumed silica is often rheopectic, just the opposite. How it behaves in a mechanical situation is not directly related to viscosity, flow, or 'weight'.

    If you get a drop of it on your brake linings they are trash. If you get a fingerprint of it on your paint and then wash the car 100 times any attempt to respray a panel will result in fisheyes.
    Mechanical engineering 101: If you put an adjustment knob, screw, bolt, or tolerance specs on something, some people will immediately fiddle with it. If you mark it DO NOT TOUCH everyone will mess with it.

    Comment


    • #3
      Thanks Mike
      You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

      Comment


      • BILL WILLIAMSON
        BILL WILLIAMSON commented
        Editing a comment
        Hold up a second, the Dog is STILL lookin' up some terms you used???
        Slow Dad

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