ORIGINAL: G-Pete
Yeah Leo, I have one of them too. Years ago the propeller broke off the I4C made a halfway fix. Anyhow these are as loud as a firetruck or louder
The inner parts don't need to be alu a good plastic would do the job.
My suggestion would be a small electric motor (RC) to drive the siren - this eliminates the prop and the brake servo. I'm the first to order when you get that done!
G-Pete, Yes, My I4C prop broke off the front too after the second time I used it. I then tried it without the driving prop and it wasn't very loud. I was able to fix it by mounting a very low pitch APC prop on the front. I found a 6 X 3 and it is fantastic. If you think about it you have to go down on the pitch to get the RPM. I figure that I get about 20,000 RPM out of that siren in a 90 mph dive. People have heard it for over 1.5 miles when I do it. That is some noise!
You have to really respect the I4C guys as they did so much right. It was a fantastic product. But with as much as they did right they sure missed when it came to the propeller an the price. The CNC cut propeller with all the stress risers in is was doomed to failure from the start. Too bad they didn't stick with it long enough to create greater durability and cut cost with alternative materials.
Aluminum is out. Too costly. Yes, plastic is the direction. You and I see it the same way. But I cannot give away all my ideas or secrets on how I am going to develop this siren. If I do that then somebody else will beat me to the punch and I will have nothing. My goal is to work it up through some prototypes this spring and then introduce it if I have success. If the whole thing flies apart at 20,000 rpm, then I will have nothing. So we will see. Leo