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Police sirens

Good day, everyone. Welcome back to another installment of Police Car Collecting. I hope you are enjoying the column so far. With that said, grab your seats and let's get started.

In the last column, we talked about lights and how they evolved. Sirens saw an evolution also. They came a long way from the hand crank models of the early 20th to the sophisticated electronic models of today.

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Before we get into the history and what you need to consider when installing one on your copcar, take a minute to check out the newest innovation in vehicular sirens, The Rumbler. This new device uses both sound and projected vibration to alert drivers. Newer vehicles have become insulated cocoons with high powered sound systems to isolate the occupants from the outside environment. This also isolates drivers from being able to hear the approach of emergency vehicles. The Rumbler might actually be the solution.

The biggest innovation in sirens came in the 1960s when several manufacturers perfected the electronic siren, which started to be developed in the 1950s. The advantages were less weight (the old growlers were heavy), a distinctive sound and the ability to vary the sounds, an available integral public address function, ability to rebroadcast the radio over the PA, and significantly less drain on the vehicle's electrical system.

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Today, for the most part, the only time we see mechanical sirens are on fire and rescue apparatus. The electronic siren is the mainstay of most emergency vehicles.

Now, since you have an older example of what patrolled the roads, you might well need a mechanical siren to do a correct restoration, even up through the 1970s. There are a few things you need to consider when installing one of these relics.

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First, if you are doing an exterior installation like the one pictured at right, make absolutely sure that you have a firm mounting surface. These units are very heavy and require a solid mounting area. You might have to reinforce the underside of the roof under the headliner to adequately support the weight. If it is a front fender install, the same holds true. Underhood installs have the advantage of having structurally heavier metal surfaces to mount the siren on. Either way, make quite sure that the unit is securely bolted to the mounting surface or it absolutely will loosen from vehicle shaking and vibration, as well as its own vibration from being used. If the mounting surface is not solid enough, the metal used to mount the siren on will fatigue from stress.

Another serious consideration is using the proper gauge wire and heavy duty switch to activate the siren. These units draw a lot of juice, especially on starting. These are little more than electric motors that have an attachment to move the air in a way that creates sound. Electric motors draw considerable juice, especially on starting. I would recommend checking with a dealer in fire apparatus for the proper switches to handle the load as they still sell modern mechanical sirens and have a clear understanding of the electrical demands. The wiring must be heavy enough to handle the load or you risk damaging the siren or worse, an electrical fire. Always fuse any electrical accessories you install to help prevent this risk. I recommend using a relay to activate the siren. These will allow you to more safely wire and activate the siren. The relay allows a more controlled draw of power whenever the siren is activated with less stress on the wiring and switch from the power demands of the siren. Standard relays are easily available from most any auto parts store. All holds true regardless of whether the car is an older 6 volt or 12volt model.

This is not to say that you shouldn't take the same care in installing electronic sirens. Proper and secure mounting is just as important. The siren drivers in the speakers are the heaviest component by far. This requires firm and secure mounting places whether exposed units or underhood.

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One issue that comes up with electronic siren speaker mounting is when weathered speakers require servicing or even just reuse of working old units. It is common for mounting bolts that secure the driver to the mounting bracket being frozen and unable to be removed. For those not certain, the driver is the sound reproducing portion of the siren speaker located at the rear of the unit. This problem happens due to corrosion that occurs with dissimilar metals being in contact and subjected to weather, road salt, etc. Speakers enclosed in lightbars are not immune from this problem. The metals that drivers are constructed with are different than the fastening bolts that secure them to the mounting brackets.

There's a bit of metallurgy and chemistry involved here that isn't necessary to get into. Bolts are made with hard, dense metals, which get harder as the rating grade of the bolt gets better, and are notoriously difficult to drill, and often even to cut. More often than we would like, they have to be drilled out as penetrating oil can be ineffective. If you do not have a high speed corded drill or drill press and sharp high strength metal bits of the correct size, do not attempt to do this. Cordless drills are poorly suited for this kind of job, even the newer higher voltage models. You will end up ruining the bits you have without accomplishing your task, at the very least, especially if you use lesser grade bits. At the very worst, you could ruin your drill or suffer injury when a bit breaks, something I know about intimately. This is a difficult task, and too often results in the entire unit being discarded despite the best efforts. The driver mounting holes will have to be retapped with new threading to accept new mounting bolts after the old ones are drilled out, if you are even successful at doing this. This means that you have to have a tap and die set available also.

If you try using penetrating oil, make sure you allow for sufficient time for the oil to creep into the threading before attempting removal. This is a common mistake when using oils. Applying heat carefully, and I emphasize carefully, from a torch can help with removal of the offending bolts, and is a common mechanic practice when repairing under car to break loose corroded fasteners from components, but be very cautious near rubber, paper, plastic or cast metal parts with high heat. They can be easily and permanently damaged with less heat than you might expect. A combination of heat and oil should be done with extreme caution. These oils are flammable. I would heat the unit than apply the oil as it starts to cool. There will be some evaporation, so use more.

It is a good idea when installing these parts to use an "anti seize" metal coating on all fasteners to keep this from happening on new components or reoccurring on reconditioned ones. Oils and other lubricants will not work as well or last as long. Keep this coating in mind for any fasteners you have to deal with especially ones that are subjected to direct weather and moisture. Every place that sells auto chemicals sells this valuable coating.

In short, if you don't have the proper equipment for properly drilling out bolts or to recondition these components at all, you may not want to bother. You might be successful still, but the odds aren't necessarily with you and it will be a lot more effort.

The same rules for using proper gauge wire, running the wires not allowing for metal chafing, installing fuses, using correct switches, and clean mounting hold the same for these as for any electronic or electrical item you mount in your car.

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Another feature of this column, by request I might add, is that I'll be featuring a noteworthy vintage Mopar police car from time to time. Whose is it today?

In this edition, it is the 1972 Dodge Polara, CHP, owned and restored by Mark Mroz of Colonie, NY. This car has a pedigree to show that it actually served in the CHP in the early '70s.

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Mark's Polara has seen a complete restoration accurate to '72 Mopar and CHP specs. The car has been at the All Chrysler Nationals at Carlisle, Pa. as well as numerous other events along the east coast. I've seen this car up close on more than one occasion and can attest that it is one beautiful copcar, and runs as fast as it looks. Mark's Polara is a staple at many events in upstate NY and is well known and respected.

Ok, guys, time to hit the streets. I'll be back with another new installment of Police Car Collecting soon. Until then, don't forget to send in those questions and comments through our interactive forum.

And keep saving those copcars!!!!!!!

Other columns

Introduction | The basics of police car collecting | Who are collectors? Why do we collect?

Emergency lighting | Sirens | Where to find retired police cars | Emergency vehicle shows | Investing in police cars

Restorations: Rules and regs for restorers | bodywork | Do-it-yourself mechanical work

Shows: Chicagoland Emergency Vehicles Show | Aquidneck Island Police Car Parade (2008 | 2009)

Also see the EVOOA home page

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