SBD/CSX Nathan K5LA Repair and Bare to Painted

[NickN]

Quite a while back now, on the original H&W Board (RIP), I bought my very first chime horn from the USA, which was a sandblasted tagless wide font K5LA from a Dash 7 (B36-7), and given the manufacturing date of around 1982, would have started life with Seaboard System Railroad (possibly Seaboard Coast Line) which then became part of CSX in 1986. The date can be narrowed down by the fact that the 'A' is not marked on the 3A and 4A bells, and the manifold casting number 30115L, is turned upside down.

It's been left as was for a time, but I always thought it would look a lot nicer painted than the very rough textured sandblasted finish (by the way, not a finish recommended for aluminium, media blasting with plastic is much better).

So I thought I'd take you through the process of doing this - it also included reparing a small chip out of the flare on one of the bells.

[NickN]

The very first thing was to set about repairing the missing small piece out of the flare of one of the bells. There are not all that many optimum materials to use for this - and as I can't weld - it needed to be an epoxy filler and preferably one with aluminium in its makeup. So I found a fairly local company selling just what I needed.
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Very easy to use, just cut a slice off, knead it for two minutes, and press into place. It sets hard quickly, and can then be sanded and shaped (even drilled or tapped if necessary).
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[NickN]

Onto the sanding and careful profiling to match the bell flare... I thought the result was not too bad.
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While doing this I also discovered a tiny piece of evidence that this was indeed a CSX horn - a fragment of dark blue on the rim of the flare.
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[NickN]

The next step: clean the bells and manifold with degreaser (I used sugar soap solution) to make sure than any grease or oil picked up since it was sandblasted were removed.
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Then it was time to prime the whole lot with an etching primer. I opted to use a brush for this part so that I could control exactly where it went and avoid any getting into threads or orifices.
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[NickN]

I had spent quite some time researching and comparing the colours used by CSX on their horns on the B36-7, which was the YN2 scheme or "Bright Future", and after many checks and double-checks, I decided that the closest match for a paint here in the UK would be one called "Sapphire Blue" or RAL 5003. WHile the horn would normally have been painted blue both inside and out, as this wasn't original now anyway, I decided to upgrade the paint job and give it a 'front-end' yellow inside the bells.

As I wanted a high quality finish more typical of that used, and not just a rattle-can cheap special, I went for a 2k ADC (Air Dry Converter - non-isocyanate) spray paint, not cheap but excellent quality.

I needed to remove the rubber o-rings from the bell feet first, then I placed small pieces of masking tape over the orifices, as well as placing some old bolts into the bolt holes to prevent too much spray paint entering. I also replaced the o-rings with newer ones while at it.
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[NickN]

Spraying took more coats than I had thought, because of the very rough textured sandblast finish. Even the completed horn doesn't have a completely smooth surface all over, but I did pay special attention to getting the inside of the bells smooth, at least.
The yellow didn't quite come out as I expected, either, was a little too green in hue for my liking, but the overall effect still looks good.
I installed stainless steel new manifold bolts throughout, and re-used the stainless backcap bolts as they were in perfect condition. Not forgetting the anti-seize, just for reassurance.
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[NickN]

So, the moment of truth arrived... I think it turned out ok, and definitely better than it looked before. If I ever have to repaint inside the bells I'll use a slightly oranger yellow, but otherwise the blue was an almost perfect match.

This is what the horn would have looked like when in use:
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And this is what it looks like now:
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[epederson]

Wow, very nice. And the repair job was awesome.

[Airchime]

That paint color is a great match! Nice work!

[Nathan_P5A]

I love how you did that repair to the flare like that. Job very well done!