Repair for Air Ministry Bakelite Instrument broken mounting lugs.

Discussion in 'Other Electrical Systems Tech.' started by abaddon1, Mar 27, 2014.

  1. abaddon1

    abaddon1 Member

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    This also applies to fuse boxes, connector blocks, etc.
    I developed this procedure when I was with the Cotswold Aircraft restoration Group. It is effective, provided the component in question is not an "in the bin" candidate!

    Broken mounting lugs are the normal damage found on these components and can be rectified by the following repair procedure.

    Plasticine is used to make a mould, using a good corner of the damaged component as the master pattern.

    This good corner is pressed into the Plasticine block to leave a master impression for moulding the damaged area.

    The component is then carefully removed and small angled holes are drilled laterally into the damaged lug area, into which, fine copper or steel rods are inserted to reinforce the area to be moulded from the master impression. Position these reinforcing rods so that the ends do not encroach any component mounting holes.
    The drill size is usually 1.5 - 2 mm, depending on the thickness of the damaged lug.

    The component is then fitted into the plasticine mould with the broken section located into the master impression.

    Slow-setting Araldite... (Araldite ARA400001 Precision grade is preferred)... is mixed with bakelite filings from a similarly coloured scrap piece of Bakelite, and introduced into the mould void, slightly overfilling to allow for final shaping and finishing.

    The epoxy/Bakelite mix will flow more successfully if gentle heat is applied as the void is filled.

    When set... allow at least 24 hours undisturbed; carefully peel the Plasticine mould away, and trim up and shape with scalpel and fine files.

    Finish with a fine-grade wet and dry paper.

    Bakelite repair procedure.jpg
     
  2. T Bolt

    T Bolt Well-Known Member

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    That's a very useful technique. I have several old instruments that I can use it on. Thanks for posting, and welcome to the Forum.
     
  3. vikingBerserker

    vikingBerserker Well-Known Member

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    Great info, and welcome aboard!
     
  4. Capt. Vick

    Capt. Vick Well-Known Member

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    Interesting
     
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