The Siren Board

Hello,

I have an early version of the Federal-5 siren. It's called the model AV37X. I think it was made in 1937. It has a three phase 7.5/hp motor which is housed in a cast iron frame with a large circular base ring. It's identical to the pictures of the Federal siren which was posted here by 'Siren_Dude' in the following URL.

https://airraidsirens.com/forums/viewtopic.php?t=10607

My siren is in better condition. The motor still runs. I think it was rebuilt (rewound) about twenty years ago. It has new bearings too.
The rotor seems to be cast aluminum. I think it may also have some magnesium in the alloy. A few of the blades which cover the holes in the stator frame have some damage. One blade has a semicircular chip on the edge which is about 10-mm in diameter. Another blade has a crack about one centimeter long through the aluminum material. A third blade has a dent on the edge which about 25-mm long and a few millimeters deep. The siren may have been mishandled when it was removed from service but it's also possible that it operated with the rotor damage for many years.
The rotor seems to be similar if not identical to later ones which were used on Model-5 sirens which do not have the cast iron motor frame with the circular base. My rotor measures 18" in diameter and 5-9/16" high. The center hole fits the 1.125" (1-1/8) motor shaft and is held in place with a gib key. The shaft is not drilled or tapped for a bolt to hold down the rotor.
I have attached a picture (below) of a rotor which seems to be identical to mine. It was posted here by group member idk6000 in 2011. It came from a real Model-5, not the AV37X.

My question for the group is what are the chances of finding another rotor like mine? I'm hesitant about using the rotor that came with the siren because of its age and the damage I described. Does anyone know what range of years Federal used this rotor for the Model-5?

On another topic, has anyone attempted to fabricate a large rotor like the Model-5 from aluminum material? I have some ideas for how it could be done, but I'll save that for another post.

Thanks for your replies

The 12 port rotor is the common rotor option for model 5s, so its not super rare but isn't super easy to find either. Holler can provide you with more insight on how risky is it to run it.

mixerbd699 wrote:The 12 port rotor is the common rotor option for model 5s, so its not super rare but isn't super easy to find either. Holler can provide you with more insight on how risky is it to run it.

How would I go about locating another 18" 12-port rotor from a Model-5 which uses a gib key on a 1-1/8" motor shaft? I assume their must have been a lot of Model-5s which were retired and hopefully kept for spare parts.

Thanks

federalfan wrote:

mixerbd699 wrote:The 12 port rotor is the common rotor option for model 5s, so its not super rare but isn't super easy to find either. Holler can provide you with more insight on how risky is it to run it.

How would I go about locating another 18" 12-port rotor from a Model-5 which uses a gib key on a 1-1/8" motor shaft? I assume their must have been a lot of Model-5s which were retired and hopefully kept for spare parts.

Thanks

I would start with placing a wanted add in the wanted section, and see if that turns up any leads. I'll keep my ears open for any model 5s being parted out.

Take it to a motor shop that does balancing. They will let you know what condition it is in, and if it can be salvaged or not.

mixerbd699 wrote:

federalfan wrote:How would I go about locating another 18" 12-port rotor from a Model-5 which uses a gib key on a 1-1/8" motor shaft? I assume their must have been a lot of Model-5s which were retired and hopefully kept for spare parts.Thanks

I would start with placing a wanted add in the wanted section, and see if that turns up any leads. I'll keep my ears open for any model 5s being parted out.

Thanks for offering to keep an eye out for a Model-5 12-port rotor like mine. You can contact me via the email address in my account profile. In the meantime, I'll post a request in the wanted section.

theroofable wrote:Take it to a motor shop that does balancing. They will let you know what condition it is in, and if it can be salvaged or not.

I assume the rotor can be rebalanced in its current condition but my concern is whether it's safe to use at all. I don't know if it's possible to safely repair cracks in these cast aluminum rotors using standard welding techniques, since the rotor is subjected to very high stress when rotating at about 3400-rpm. We also don't know much about the composition of the alloy. This would determine what kind of welding material to use. There are some new alloy brazing rod materials that will repair aluminum without having to heat the base metal to the melting point. This might work to repair small cracks or broken edges.
I've been thinking about how to make a new rotor using aluminum plate material, starting with a large aluminum disk about 1/4" thick which would be the base of the rotor. The center of this disk would have a piece of aluminum rod about 3"-dia. welded vertically to the base plate. A hole would be drilled in the rod to the size of the motor shaft. It could also be broached with a keyway slot. The base plate would be surrounded by a rolled plate of thinner aluminum having the circumference of the base. This would form a vertical wall around the base and become the ports of the rotor when the openings are cut in the outer wall. The rest of the fabrication would involve cutting and welding the upright sections which define the partitions between each port and finally the top ring which ties the port partions and outer wall together. I think it would be an interesting project for a welding school class.

I've seen sirens that had chunks missing out of the rotor and still ran. Yours doesn't look that bad to me. Most of those castings were not of the greatest quality either. Lots of voids and pockets.

Looks similar to a 12 port xT22 rotor too. How did they balance this one? I don't see any bolts like some of Federal's sirens are. Maybe that is what the lady bug is for...

Andys Live WX wrote:Looks similar to a 12 port xT22 rotor too. How did they balance this one? I don't see any bolts like some of Federal's sirens are. Maybe that is what the lady bug is for...

The rotor from my AV37X was balanced by drilling nineteen shallow holes about 3/4"-dia. in the bottom surface. The holes are arranged in three curved rows. The outer row near the edge has nine holes, the middle row has six holes and the inner row is four holes. The holes are close together and form a pattern about 8" long on the circumference and 3" wide radially.