Straightening out brass instruments
That's how dented tubas or the like can be whipped into shape again
Project 8 - Online since: 24/03/2008, Number of visits: 202725
Then he let a steel ball, somewhat smaller than the dent, roll into the instrument. The steel ball naturally "attached itself" through the instrument to the magnet. He then moved the magnet back and forth over the brass where the instrument was dented, and with time the steel ball pushed the dent outwards.
To ensure that the instrument would not be scratched, he placed a drumskin between the instrument and the magnet and applied some oil on both the drumskin and the instrument.
To remove the dents on the hard parts of the instrument, Roberto developed a "reverse hammer". It is made of a non-magnetic rod (e.g. copper) with a movable heavy metal block on it's axis (e.g. the head of a normal hammer), a magnet on one end of the rod and a stopper on the other end (see drawing). When the hammerhead hits the stopper, a part of the resulting energy is transported through the magnet to the steel ball within the instrument, which "hammers" the dent from the inside.
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