Restoring 1920's crankcases and gearboxes

[Alan]

Looking at a 1960's Triumph as supplied from a reputable dealer ! with a well burnished and smooth crankcase ( they were never like this originally and even worse the frame number had been visibly "altered !" ), I was wondering what blasting techniques  Duggie owners prefer these days when restoring circa 1920's  muck encrusted crankcases and gearbox casings.....sand, fine glass beads, walnut shells,vapour ??...

[Dave@NZ]

Hi,
   with the alloy parts I have done which i must say are mostly car engine related.
Vapour blasting and wet blasting leaves it quite grey and dull.
Sand is too abrasive and would do more damage than good.
I havent tried walnut shells.

My first choice is blast with glass bead then a good wash and light rub up with medium grade
scotch brite, not rubbing hard enough to cause visible scratches.

 If I was after a shinier finish I would use metal polish with the scotch brite then a good wash,
the thing is not to rub too hard
and remove the original texture of the alloy.






David.

[eddie]

Hi,
     For those who are still prepared to get their hands dirty, here is the method I use. On alloy castings that have white corrosion, use an acetylene torch with a small nozzle and an oxygen rich flame. Pass this back and forward over the corroded areas - most of the corrosion gets loosened by the heat and can be brushed away (be careful not to get the casting too hot!, rubbing on white soap is a good temperature indicator - when it starts to turn brown, that's hot enough). When the casting has cooled, apply some rust remover with a stiff brush, wire brush or scouring pad, depending on the preferred final finish (a couple of applications may be necessary). Finally, wash the casting with plenty of hot water and spray on some WD40 to give protection against further corrosion. The rust remover does a great job of restoring the 'white' look of a new casting, and the whole process is relatively abrasion free, so does not affect the original texture of the casting.
    Good luck - Oh, and wear the recommended eye and skin protection when working with chemicals like rust remover!

   Regards,
                   Eddie.