Amateur Mini Siren Help

[StonedChipmunk]

I have no idea what I'm doing, just bear with me here.

I'm trying to make a very amateur siren that will most likely not work at all. I've gotten a mini vacuum cleaner motor (just a motor with a vacuum spinner thing on it) and some tape. Unfortunately I need more materials to complete it, but I hope to get it finished soon. I'll also get some pics later.
My question is, will a 4-port siren actually produce an audible tone? And is it possible to construct the ports out of tape? (I'm too broke and lazy to get a piece of metal).

[StonedChipmunk]

Here are some pics (sorry for terrible quality):


Overhead view. Look for the slight curve in the openings to force air in that direction.


Side view. Shows more of the motor than the actual rotor.


Back view. Shows the terminals. The motor is rated at 6V AC. (Think 4 AA batteries.)


Another side view. This time more rotor than motor.


Rotor view. A more detailed picture on what the rotor looks like. Shows the 4-port setup.


Just another view. Nothing special here.

Now, I know chances are that it wont work for crap, but any suggestions?

[Blasty]

A four port rotor can still produce good sound. The model 2T uses a dual-tone rotor with a row of 4 ports and one of 5. Also, there is a WWII-era German siren called the Elektror S3B that uses only three ports and produces a very low tone still at high volume.

[Robert Gift]

Nice, Chip.

Years ago I made a siren using a 4 inch PVC pipe and an electrolux vacuum motor.

You can easily cut and file the stator ports in the PVC.
Any imperfections can be filed to be perfect.
I was able to file the edges sharp beveled in from the outside.
(Wish I had tried blunt edges and then filed them to hear any difference.)

I found a rigid cardboard (carpet?) tube with 1/4 inch wall which very closely fit the PVC interior.
I cut the tube wall three ways to make a "tab" and bent the tabs in and glued them to a disk cut from a cardbord box.

The biggest problem was attaching the motor shaft to the disk and aligning the asssembly to not rub againsthe stator.
Getting the rotor balanced never happened.
I used pencil graphite to lubricate the rotor where it hit the stator.

Still, was amazed how well it spoke?

Unfortunately the siren got soaked and the rotor was ruined.
But I had planned to make a PVC or something rotor, but never did.

All kinds of appliance motors will work, but I most wanted to make a crank/pully system - but never did. Motor was easier.

Wear safety glasses and gloves when you operate it.

Good luck.

Robert -XVII

[Daniel]

The good news: if you motor can do 7,800 RPM like a Model 2, you will get a nice tone from four ports.

The bad news: at that speed, it will probably blow itself apart.

[loudmouth]

maybe cut out a coffiee can with ports.

[Robert Gift]

I thought of coffee can but it'sides are too flexible.
Also PVC is much easier to file into the exact shape.

Model 2 spins at 7,200 rpm?!!

That sounds dangerous.

Do the Chinese air raid sirens have a bigger diameter and more ports
so they can be lowerpm?
(Still displeased that I failed to counthe stator ports on the one I molested.)

Wouldn't it be fun and a great workouto pedal their bicycle siren?!
http://www.lksos.com

Now I'll have to start looking at PVC pipes and see if I can find something
to be a rotor.

[Robert Gift]

maybe cut out a coffiee can with ports.

Hey, Loud.

I'll try your advice and try to find a coffee can from which to cut out
a ROTOR.

Cuthe rotor openings on three sides. Bend the "tabs" inwards to act as fins.

The biggest problem is finding something which is only slightly smaller
than the 4 inch PVC Stator inside diameter. Otherwise too much air leaks
around the rotor "vanes"(?).

Thanks,