While everyone is barking on about what fluid to use in a compass, there was
not sufficient good advice given to Bob R. on which Nico Press sleeves to use,
far more critical and important.
Bob, there is only one Nico press sleeve material you can use. They have to be
made of copper end of... Some are pure copper others are Zinc plated copper.
You can not use the Aluminium sleeves, they are not strong enough.
The reason for the pure copper or zinc platted copper sleeves are because there
are two different materials used for cable. The two types of cable are
Stainless steel cable or Galvanised steel cable. Stainless steel cable is
obviously better for external flying wires and so on for its anti corrosion
properties, but it does not flex and go around pulleys as well as the more
usual Galvanised cable which is more flexible and less brittle than Stainless.
So IT IS IMPORTANT not to get the two mixed up. You have to use the pure copper
sleeves with Galvanised cable and the zinc or tin plated copper sleeves with
the Stainless cable, otherwise you get internal corrosion of the cables due to
electrolysis caused by the different materials.
Below is a quick write up by our BGA governing body.
a) Only aircraft quality, `extra flexible' 7 x 19 cable is to be used for
glider control
circuits (including the release system). Either galvanised carbon steel cable
to American Mil Spec MIL-W-83420 type A or British Standard BS-W9 or ñW12, or
corrosion resisting steel cable to American MIL-W-83420 type B or BS-W11or W13,
may be used, which are approved alternatives for the DIN specification cables
used on many European gliders. However to avoid corrosion problems, only use
the correct combination of swages and cable types. The BGA do not recommend
using Stainless Steel cable due to poor fatigue and rapid wear properties
b)Nicopress system: American manufactured cables with wide applications.
Ferrules are all made from copper. Plain copper ferrules are used for
galvanised cable and plated copper ferrules are used with stainless steel
cables due to electrolysis caused by different materials. The Nicopress system
used 3 operations of the swaging tool. The first is in the centre position of
the ferrule, second at the thimble end and the third at the cable end.
Nicopress do not specify free of thimble cable dimensions but on completion,
the free cable must protrude from the ferrule by at least 1D and it is
permissible for the thimble ends to just enter the ferrule.
Regards,
Colin H.
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