Banging brakes

[Murphy]

For many years I have experienced similar problems with brakes, often dismantling, fitting new cams, bushes etc with in reality little effect.  Some 5 or so years ago, there was an article by Ian Moorcraft in the Association magazine,describing how to make a tool from a scrap brake drum to check the positioning of the brake shoes. In brief, the brake drum was cut down to leave a flat disc which could be attached to the hub using the three set screws. This enabled an arm to be attached which accurately described the same circle as the surface of the brake drum. (have just found the article 2011A)
Using this tool I found that in many cases the the brake shoes were not reaching the brake drum evenly and worse the face of the brake linings were not parallel with the drum. I think the rather nasty noise you describe on applying the brakes, is the moment when an offending brake shoe suddenly squares up to the drum.
Having checked the operation of the shoes, a way to rectify any anomalies is make up some 'over shoes'  for the shoe pads (which must be in good condition to start with) to ensure that the shoes evenly approach the brake drum. Additionally, if the shoes are not parallel to the brake drum, a very light filing of the shoe pads can correct this but be careful as adjustment of the angle of the pad will be magnified at the lining face.

Hope this helps.