The Siren Board

Hi everyone,

Yesterday I acquired an interesting siren. Some of you who read the Horn_Whistle Yahoo group might remember that I mentioned a siren near my home in the UK which was mounted on a building due to be demolished. Well yesterday I passed the building and noticed that demolition had started. The siren was still there. So I got chatting to the demolition crew about the siren. At first their attitude was "no, it's too dangerous to get it down, our boss will be annoyed, etc". Then I offered them some cash to get it down for me, and at about the same time they discovered that their boss was off site, so they agreed to do it.

About half an hour later I had the siren, cowl and mounting bracket, and we agreed a price of ?40. I didn't think this was too bad given that it took several guys quite a lot of effort to remove the siren, and that they risked the wrath of their boss if he turned up.

Here are some pictures of the siren:
http://pg.photos.yahoo.com/ph/cdtidy/al ... e2&.src=ph

Unfortunately galvanic corrosion has attacked the aluminium and the siren is seized, so it looks like a challenging restoration project. However, I've got a fairly well-equipped workshop and I've completed other restoration projects before, so I'm ready for the challenge. I think the aluminium part of the body will need to be repaired in one place, but I reckon I can get someone to TIG weld it for me. Also the terminal box will need to be replaced. My greatest concern is that the rotor is badly corroded and may need replacing, but I won't know for sure until I get inside the siren. If it does need replacing I'm hopeful that I may be able to get a new one cast or CNC milled by one of my metalworking friends.

Now I've got a few questions. Does anyone know the manufacturer and model of this siren? I haven't yet found a maker's name. If it's of any help, the building it was mounted on dates from 1931. It appears to be a two-tone siren. The front rotor has five lobes and the rear rotor six lobes. There are two rings of holes in the aluminium body, one with five holes and one with six. The motor looks to be a single phase induction motor and appears to be in good condition. The rear part of the body which houses the motor is thick cast iron. It bears a slight similarity to some Carters sirens I've seen, but not enough for me to be sure it's a Carters product.

I've also got a few restoration questions. Are there any chemicals which will strip aluminium oxide but leave solid aluminium untouched? Or perhaps there's an electrolytic process which can be used to clean the aluminium parts, similar to electrolytic de-rusting? Does anyone know? Also, do people have any hints about removing steel screws from aluminium? These screws really must come out. They aren't in the worst condition imaginable but I'm still cautious about removing them. I'm tempted to use a nut splitter on the nuts, but obviously this won't deal with screws.

Any other do's and don't's regarding siren restoration?

I know some people will no doubt think I bought a turkey of a siren at an exorbitant price, but so far it feels good!

Best wishes,

Chris

Wow, thst think is caked over in paint. As far as the type of siren, I have no idea, though its probably some type of Klaxon 50+ years old. The best advice I can give you on restoring it, is just take the thing apart and sandblast the crap out of it. As far as solvents for paint removal, I dont play with that stuff; thus, I cant help you on that one. Its just gonna take some elbow grease to get it running again.

~Jason

Even though my restoration only went as far as patching up a few holes in the (thin) metal and repainting it, go to it with an open mind.

That always helps.

Hi folks,

Thanks for the replies!

I got a bit further with the project tonight and did some disassembly. Here are some pictures:
http://pg.photos.yahoo.com/ph/cdtidy/al ... e2&.src=ph

I was relieved to see that the motor looks to be in good condition. There's no corrosion, dirt or flaky insulation in there. Interestingly, there is a date: 20/7/38. This makes me think it's quite likely that the siren was installed for wartime purposes.

Jason, I think blasting with a medium which isn't too aggressive is probably a good idea. Corrosion has already roughened the surface of the aluminium so there isn't a surface finish to spoil. I think I'll keep the iron base (with the brass inventory number plate on it) separate and de-rust this electrolytically. I think all the parts can be saved apart for the rotor, terminal box and a few screws and bolts. Making a new rotor is going to be fun!

I still haven't found any indication of the manufacturer. I'm doubtful that it's a Klaxon. I always understood a Klaxon to have a horn, like the grey one on the top page of this site, but this siren is omnidirectional.

I'll keep you informed.

Best wishes,

Chris

Hi folks,

Thanks for the replies!

I got a bit further with the project tonight and did some disassembly. Here are some pictures:
http://pg.photos.yahoo.com/ph/cdtidy/al ... e2&.src=ph

I was relieved to see that the motor looks to be in good condition. There's no corrosion, dirt or flaky insulation in there. Interestingly, there is a date: 20/7/38. This makes me think it's quite likely that the siren was installed for wartime purposes.

Jason, I think blasting with a medium which isn't too aggressive is probably a good idea. Corrosion has already roughened the surface of the aluminium so there isn't a surface finish to spoil. I think I'll keep the iron base (with the brass inventory number plate on it) separate and de-rust this electrolytically. I think all the parts can be saved apart for the rotor, terminal box and a few screws and bolts. Making a new rotor is going to be fun!

I still haven't found any indication of the manufacturer. I'm doubtful that it's a Klaxon. I always understood a Klaxon to have a horn, like the grey one on the top page of this site, but this siren is omnidirectional.

I'll keep you informed.

Best wishes,

Chris

The more and more I look at it, I could sware it looks like an ACA Sentry 95, but probably not.

Nelso90 wrote:The more and more I look at it, I could sware it looks like an ACA Sentry 95, but probably not.

Interesting. Does anyone have a picture of an ACA Sentry 95? I couldn't find one using Google.

Chris

Here is an old ACA ad showing the Sentry 95. Boy does that look like a close match.

quiksmith10 wrote:Here is an old ACA ad showing the Sentry 95. Boy does that look like a close match.

It does look really close. The only difference I can see is that in the ACA ad there's a slight narrowing of the siren body between the motor and siren stator, which isn't present on my siren. I wonder if mine might be a British variant made under licence from ACA, or just a slightly earlier/later Sentry 95 than the one in the ad?

Does anyone have a large photograph of an ACA Sentry 95? Perhaps someone has one in their collection? I'm also interested to know the scale. My siren is roughly 14 to 16 inches high.

Thanks for the help!

Best wishes,

Chris

Apparently ACA only started manufacturing in 1942:
http://en.wikipedia.org/wiki/Alerting_C ... of_America

Before that they were Biersach & Niedermeyer Company, so with the date of 1938 my siren would have to be a Biersach & Niedermeyer siren.

Chris