Hi,
Here’s a picture of my self-made train horn kit.
The air is coming from the bottom, from the center plug (there’s no tubing for the input at the moment where the picture was taken).
My question is : does the four lines must have the same length ?
On the picture, there are 2 short and 2 long.
Many thanks for your thoughts and again, please excuse the misspellings , as it’s not my mother tongue 
The ones with the shorter lines will sound first. If you are using a solenoid, this probably will not matter. If you are using a manual handle valve, you might want to make them even lengths.
I would also make sure that the tube you are using is rated for the correct pressure.
I agree with rjk - Make sure the tubing is rated for pressure.
It looks like vinyl tubing to me.
Hi,
Thanks for your answers.
Yes, it’s a solenoid valve.
What’s the problem if the tubing is not rated for pressure ?
As it’s an output, it’s never “under pressure”, its just an exhaust output through the horns.
Am i wrong ?
Well, it’s under pressure as soon as you hit the button soooo …
I would swap it out with something rated for dealing with pressure. Vinyl won’t handle those pressures for long, and it’s easier to do it now versus trying to replace it once you have it installed.
-Kris
There is pressure even though the horns are releasing air.
There is a chart floating around for loudness of Nathans. One of the measurements is pressure in the manifold while the horn is blowing.
What air pressure are you sending to the horns anyway? By looks of them they won’t need much air so you shouldn’t have any issues. Those fittings are just push on barbs onto the horns?. If they over-pressurise they should just pop off so no big danger
I can’t see the pics 