Lucas horns

Crikey. Just about every 50s car had those. Morris Oxford etc. Painted black, though. Chroming the whole thing used might not be easy as much of it is a casting.

I've got a pair on my SD1.

It's the dome and the trumpet that are normally chromed. I also have a pair, and I have a source for them for my otherwise functional but non-chromed units.

My 3-Litre Rover I owned in the 1970s had a tuned pair (Doh and Soh, I think) You didn't really hoot, just played a chord. :-)

Jim

Yes. Somewhere round the 60s, they were replaced with much smaller units which didn't need a relay. Higher pitched sound.

Any idea what current the big ones draw? I have seen a car with them, and no relay. If you don't keep your hand on the horn button for a full minute, it might not be so bad.

It's something like 20 amps. Cheaper to use a relay than a meaty horn push.

Yikes! 20A each? My DMM won't even measure that high!

Do you remember those 'Town and Country' selector switches?

I can't remember a horn relay on my Rover (but I didn't look for the presence or absence of one either), but I do remember that the internals of a horn are configured like an old-fashioned bell or buzzer. The electromagnet attracted an arm connected to the diaphragm, and as the diaphragm moved it broke the electrical contact so that the diaphragm returned to its resting position which made the circuit again and the electromagnet was energised again. The cycle repeated while the horn was pushed. The diameter of each diaphragm and the length of the (coiled) sound trumpet determined the note of the horn.

The wire to the horn was reasonably thick, and would probably carry 20A if necessary, but because of the intermittent use of the power, it would only need to do so for half of the time the horn was sounding. Averaging current over time, you are probably looking at 20A the pair, with a few instantaneous higher readings. Also, given that the wiring used in the 1960s tended to be over-engineered, a wire looking capable of passing 20A was probably only be required to pass 15A max because the manufacturer wouldn't want the wiring loom to carry a warm wire.

Jim

No - about 20 amp total for two. Most common car relays are 30 amp.

To switch off one of the horns?

Excellent points, indeed.

Yes.

There is a wonderful cartoon by Brockbank, the title is 'Citroen Pressé'. Hopefully this will get to it.

DVMs ain't ideal for current measuring on cars where current can be high - and maybe a switch on surge too. The fuse in my Fluke costs a fortune to replace. ;-)

An old fashioned meter type ammeter is more robust.

Using a too thin wire would cause voltage drop and reduce the output from the horn.

Remember older cable had much thicker insulation than modern stuff, so not so easy to guess the size.

But in the old days, cars had often only two fuses. And since the fuse protects the wiring, all the wiring downstream of the fuse had to be capable of carrying that current. So could be much larger than with individual fuses. The days when copper was cheap. ;-)

Ended, with 0 bids, I see. What a surprise.

Perhaps now they will list them with a decimal point in the price :-)

Jim

That would be a bargain. One can live in hope...

They're back, at £300 this time. I sense a problem here...