Hi, I just got into this hobby and unfortunately bought plans on the web that were less than stellar. I only learned about dozerboymiller after I started my build, as I’ve heard his plans are very good. So I built my own version of the PVC horns anyway. Some of the design elements are good and some, which i got from my online plans, suck.
Check out the pics, I have a full CNC machine shop so nothing is out of realm of possibilities.
The plans I bought talk about tuning the horns by moving the main exit tube in and out until the sound is correct and then super gluing it in place. Well this works on some and not on others, on others the fit is not tight enough and air escapes or pulls the tube down allowing it to not make any sound.
It also talks about, in the plans, using aluminum flashing, which is very thin and didn’t work well as a diaphragm. I ended up using 22 gauge steel, .026" thick. This makes a good sound.
For dimension I ended up drawing out what the inside a Nathan air horn is and then scaling it down to the size PVC I am using. I’m using 4" PVC caps.
So here’s my question:
- On the inside I have the exit tube with a reducing bushing that is 2" in diameter, this is what the diaphragm vibrates against. I want to know how to set the exit tube permanently so it won’t move and then I can use shims to move the diaphragm in and out to tune it more accurately.
So what I need to know is where do I start as a position with that inside part that hits the diaphragm? Should it be touching the diaphragm, pressed against it tight or loosely touching it?
Thanks for the help.