hi guys,
this is what we do to prevent screws from loosening. learned this from another hobby of mine, R/C helicopters and airplanes.
for metal-to-metal contact (i.e., metal screws screwed on to metal parts), use a threadlock solution. just dab a few drops on the thread and tighten as usual.
this will prevent the screws from backing out. the good thing is, this is not permanent. when you need to remove the screw again from maintenance, apply a little heat to soften up the threadlock and loosen the screw normally. you can use the tip of a soldering iron, touch the tip to the head of the screw to heat it up.
this can be found in some hardwares, but moslty they are abundant in R/C hobby shops. there's one in parksquare 1 makati, Lils hobby shop. there are also a couple of hobby shops in the Hobby of Asia Mall Macapagal. it usually costs around Php200-600.
hope this helps.