LOUD diesel horns?

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BudBudzien
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Re: LOUD diesel horns?

Post by BudBudzien » Tue Aug 21, 2018 8:28 am

Wolo makes 12 volt compressor/horn sets and their largest is touted as a locomotive horn. They are loud. Auto parts stores may have them cheaper than buying from Wolo themselves

hoppercar
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Re: LOUD diesel horns?

Post by hoppercar » Tue Sep 18, 2018 12:33 pm

The best air horn I found comes from an unlikely place...lol.....get on of these little compressed gas bottles, with the horn that people take to a ball game...if you use one of these cheap 12 volt compressors to supply the air....they don't sound to bad

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ccvstmr
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Re: LOUD diesel horns?

Post by ccvstmr » Tue Sep 18, 2018 2:18 pm

Just purchased a 12 volt horn on Ebay...includes horn, mount and compressor. Something like $17. Before the purchase, inquired about the pitch. Not the volume...the horn was advertised at 150 dB. The response was 105 to 110Hz. Haven't seen anything lower advertised on-line. As BDD eluded to, 1st gen diesels usually had (2) horns...(1) facing fore, the other aft...but low tones. Figured I'd try to hide this horn inside the body of my NYC F unit. For the price...couldn't hardly go wrong. Carl B.
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BigDumbDinosaur
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Re: LOUD diesel horns?

Post by BigDumbDinosaur » Tue Sep 18, 2018 2:43 pm

ccvstmr wrote:
Tue Sep 18, 2018 2:18 pm
Just purchased a 12 volt horn on Ebay...inquired about the pitch...The response was 105 to 110Hz.
105 to 110 Hz seems unlikely—110 Hz is A2 on the piano.

A locomotive air horn (aka "air trumpet") is acoustically modeled as a stopped pipe. The fundamental frequency of a stopped pipe corresponds to a wavelength that is twice the pipe's length. In the case of an air horn, the acoustic length is measured from the vibrator, which is the part that is excited by air flow, to the end bell. That length would have to be 60 inches in order to resonate at 110 Hz at sea level and in standard atmospheric conditions.

The "honkers" used on the E- and F-units, as well as the GG1 and others, emitted a pitch that was approximately D3 to E3. Assuming D3, which is ~150 Hz, the theoretical pipe length would be 3.67 feet, assuming the horn was at sea level and in standard atmospheric conditions.
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rkcarguy
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Re: LOUD diesel horns?

Post by rkcarguy » Tue Sep 18, 2018 4:22 pm

Some of the Baldwin S-12's have a long single tone horn on them that was reported to be 190hz. Measuring off of the Athearn model, it would be about 30" long in full scale, it's 5" long for my model at 1/6th scale.
I have found a bicycle horn I'm going to cut up and use for the cosmetic side, but have had no luck finding a horn with a low enough tone. I may have to experiment with mounting one in an ABS tube to see if it deepens the tone.

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BigDumbDinosaur
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Re: LOUD diesel horns?

Post by BigDumbDinosaur » Wed Sep 19, 2018 5:29 pm

rkcarguy wrote:
Tue Sep 18, 2018 4:22 pm
Some of the Baldwin S-12's have a long single tone horn on them that was reported to be 190hz. Measuring off of the Athearn model, it would be about 30" long in full scale, it's 5" long for my model at 1/6th scale.
The theoretical pipe length for 190 Hz would be about 34.74 inches at sea level and in standard atmospheric conditions.
I have found a bicycle horn I'm going to cut up and use for the cosmetic side, but have had no luck finding a horn with a low enough tone. I may have to experiment with mounting one in an ABS tube to see if it deepens the tone.
If you are going to experiment with length in order to lower the frequency you have to splice in the extra pipe between the vibrator and the end bell. You also have to maintain a reasonable "scale" for the pipe. In acoustics, "scale" refers to the ratio of pipe length to pipe diameter as measured at any given point along the pipe. Scale has a significant effect on the tone. A trumpet-like instrument can have a straight (cylindrical) bore or a conical bore. A straight bore produces a strong spectrum of even- and odd-order harmonics, which tends to make the tone "bright" and "brassy." A conical bore favors even-order harmonics, making the tone somewhat "dark" and "mellower" in comparison to a straight bore horn. Locomotive air horns are conical bore, which causes the sound to be more penetrating over a distance.
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Re: LOUD diesel horns?

Post by rkcarguy » Thu Oct 04, 2018 3:46 pm

That's interesting BDD, I found an image online of the single horn I had referenced earlier, and behind it in the picture is a chair and I'd say the flare is a good 14" in diameter and its about 3' long if not more.
I have actually heard one of these, there is a 4-some of repainted GP's that run our subdivision and one of them has this lower frequency mono-tone horn on it I've never heard before.
I still need to figure out a way to make this noise, maybe a boat speaker setup and something to product the frequency, I don't know. I don't want a really loud horn it will be more of a novelty for my son to play with.
horn_a-200.jpg

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