Friday, August 12, 2016

Sounding Off

I know the car doesn't go, or stop, or anything yet, but it will be nice to let others know I'm coming.  So it's time to clean the horn.

Thankfully, the horn works when I apply 12 volts, so it's a matter of making the outside look pretty.  So far, I'm up to this:


You guessed it... I used the blasting cabinet.  How could I do that without mucking up the insides?  By stuffing a paper towel in the sound hole.  The horn still works after the cleaning (and removal of the towel), and is nice, loud and mellow..

The horn I have is a Lucas Windtone 9H, high tone (H).  These horns were used on all sorts of British road machines; MG, Triumph, Austin, and Jaguar cars, and (at least) Norton motorcycles.  They actually come in two tones (high and low).  I've always wanted a low tone horn to match my high tone horn for that nice sound and extra sound output.  So I found one on eBay for $10.  It was untested, and when I tested it... it didn't work.

You don't think that stopped me, do you?

I cleaned it up in the blasting cabinet and decided to take it apart.  What the heck, it's only $10.  There are actually lots of sites that discuss how to disassemble and repair these horns on the Internets ( is the one I referenced).  

The first step is to drill out the rivets that hold the thing together.  

I figured, why not give it one more go to see if there's anything happening?  Well, guess what.  The horn works!  It's a very pleasing tone, a third down from the high tone at concert F# (the high tone is concert B natural).  Except now I've drilled out the rivets... so I might as well take it apart.  $10, right?

Ugh.  I'm glad I did.


Separating the components was delicate work, but I managed to get everything apart without splitting any gaskets or ruining anything inside.

There's not much to this thing.  A set of points starts closed and energizes a coil.  The coil moves a plate that moves a diaphragm.  When the coil moves the plate enough, it breaks the points' contact and the whole thing collapses, closing the points, and starting the process again.  The sound comes out the sound hole and is amplified; the tone results from the shape of the cavity.  I'm guessing the points were stuck and all the vibration freed them up.  I ran 1000 grit sandpaper over the surfaces and I think they'll be fine.

Once it's all clean, it looks like this:

Now I have to find some rivets that look like what I drilled out, reassemble, adjust, and paint.  Oh, and make a bracket for the second horn.  Then I'll have a nice set that will get people's attention going down the road... someday.

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