Wed Mar 29, 2017 4:17 pm
Here is the write up I did for Wikipedia, with all the information I have found regarding the Denver Siren. I have several photos of all models avalible, however the mobile browser is not very friendly for attaching them.
Hendrie and Bolthoff Manufacturing and Supply Co – A Denver, Colorado-based company that was famous for selling mining equipment through the early 20th century. They began supplying the local mines with tools and equipment, and later entered the business of producing municipal Supplies. They contracted Dillon Box Iron Works to produce the "Denver Siren", Pat. by William A. Box, as early as 1915 until the early 1920s.
These sirens used a centrifugal clutch connected to a 5 HP motor, usually General Electric or Westi house, with single and 3 phase motors avalible.
These distinctive sirens had one or two large, open-ended, double sided, 20-port rotors connected by a long shaft to the motor and mounted to a common horizontal frame. single head models were known as the "Duplex" and double head models were known as "Quadruplex". Two smaller models were also available, connected directly to a single phase motor, the small double 12 port Type A or the slightly larger double 20 port Type B.
Sometime in the early 1920s, Sterling Fire Alarm of Rochester NY. Sold a variant of the Denver siren under the name "Sterling Siren Fire Alarm", and produced them for a short while. Early Sterling models have a window-frame grill bolted to the stator, most likely to keep birds from nesting in the rotor. Sterling also produced a double head 12/12, and 15/15 port version, which was available with a coding mechanism on the stators.
Due to their weight, (the largest being nearly 6 feet long and 2 feet wide, made completely of iron with bronze or aluminum rotors on the Sterling models grossing near 2000 lbs) they were usually mounted on top of high buildings rather than poles.
An article from "Electrical Review and Western Electrician" once stated when tested, local official departments received calls from several miles away by people wondering what the cause of the noise was. Few of the sirens still exist and only a handful of these are still in use.
Resident Historian
Denver Siren Expert
Michigan