I have been watching a lot of videos of K3LA and K5LA horns. Where I am in Georgia, there are a lot of CSX and BNSF trains, and most of them have a K3 or K5 that pitch up a little at the end of the honk. The attack and sustain all sound fairly similar, but there are a bunch of videos where the note doesn’t pitch up in the decay. What causes this? Is it the manifold, air lines, or just a different sound for different models? If there is a thread explaining any of this, could someone point me toward it?
The diaphragms tend to squeak as air pressure drops below what they need to resonate. Could just be some of that when trailing off through a metered valve.
This sort of thing might happen if there is a lot of air line between the valve and the horns, since the air line can act as a small reservoir that continues to empty after the valve is closed.
The effect happens only when the horn is moving and only after it has passed. I noticed this in several videos. I would surmise that once the horn has passed, you’re hearing a lower frequency because of the Doppler effect, and if the sound echoes off something ahead of the horn, it’s going to echo back to the observer and be at a higher frequency than the horn’s note. Or so my theory goes.
Yeah, what you’re referring to in that video is definitely doppler, although the effect is a higher frequency on approach, not the departure. Good 'ol ED is running a manual valve on the beauty as well.
Approach: higher frequency
Departure: lower frequency
Departure + echo off stationary object ahead and back behind: delay + higher frequency
It sounds symphonic. Hence why I’m in Solidworks right now designing some brackets to mount the K3LA components individually under my car. Got to put that plasma cutter to use sometime…
Ah the video helps me understand what you mean. So what’s happening here is that the vehicle moving away is hitting you first with the doppler-shifted sound, and then the reflections from the surrounding hills are hitting you but they are not doppler shifted because the hills are not moving. Obviously the reflections are fainter and more delayed because the hills are farther away than the vehicle was.
You would also get the same effect as the vehicle is driving towards you, except that it is harder to hear since the horns are facing you and are much louder that way. In that case, the doppler shift would be higher than the reflection off the hills, instead of lower.
^^ Yes please.
Any pics of plasma table / drawings / brackets would be great.
How thick of material are you using and I assume you plan to tap the brackets for an air fitting?
A little tip - we never plasma cut pilot holes that are to be tapped. They’re just too hard on tooling. Plasma cut the perimeter and all your mounting holes, but drill the pilot hole for the NPT tap on a drill press. Your tap will thank you. Maybe you already know this…
I took a video a few hours ago of cutting some corner brackets for something else. I will post it when I get a chance. I was a little busy at the surface grinder for an entirely different project today, but I should get around to the K3LA brackets soon.
Cool stuff. Is it a commercial table or a home-built?
Year ago I designed and built my own CNC router table (just out of alloy), and when I got my plasma torch I tried to adapt it for the cutter instead of a router. Much to my dismay I ended up blowing up one of the X-Axis controllers due to the high frequency start of the plasma torch. DOH! I would love to get a proper one but can’t really justify it.
We know about punching holes with the plasma table. Thanks for mentioning that, ear2ear. My buddy got the idea to add a center punch head to the table but hasn’t gotten around to doing that yet. It’s definitely home-built. There have been a lot of advances in the past decade, so you might want to revisit it. LinuxCNC can do a lot.
