Tonna Driven Elements why they fail

 

The picture below shows a 2m driven element that has been in use for a few years, you can see that the plastic moulding has fractured in numerous places allowing water to get in and corrode the connections.

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Once the plastic moulding is stripped away to reveal the method of construction it becomes clear why these things fail. The Hairpin is connected to the Aluminium driven element tube by two steel self tapping screws. A dissimilar corrosion point is created here

 

 

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The N connector centre Pin is made of Brass, it is riveted to the Aluminium Driven element creating another point where dissimilar metal corrosion will take place.

 

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The outer body of the N socket is once again riveted to the Aluminium Dipole creating another point for corrosion to take place.

 

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The entire structure has no mechanical rigidity on its own, and relies on the plastic moulding to ensure the connections are not compromised. The idea falls apart as soon as the plastic moulding starts to crack.