Early Harley-Davidson Police Motorcycles: Sirens, Radios and Patrol Equipment
Early police motorcycles did not leave Milwaukee looking much different from the machines sold to ordinary riders. The transformation happened a piece at a time: a department color, a POLICE plate, a siren squeezed beside a wheel, an extinguisher on the rear fender, and eventually a radio receiver large enough to occupy most of the back of the motorcycle. These photographs show that change taking place from the early 1930s through 1941.
The First Harley-Davidson Police Motorcycles
Harley-Davidson's connection with law enforcement is commonly traced to 1908, when Detroit reportedly became the first municipality to purchase a Harley-Davidson for police work. That early machine was not a purpose-built patrol motorcycle in the modern sense. It was a motorcycle placed into municipal service, with the specialized equipment associated with later patrol machines still to come.
For years, the badge and paint were often the main things separating a police Harley from a civilian one. Some departments used white or gray paint instead of the usual olive-drab finish. Local departments also chose their own tool boxes, signs and emergency equipment, so two police motorcycles of the same year could be outfitted quite differently.
That distinction matters when looking at old photographs. Equipment visible on a police motorcycle was not automatically installed by Harley-Davidson. Some pieces came through the factory or dealer network, some came from specialist accessory makers, and others were fabricated or mounted by a department shop. In a few cases, the officer himself reportedly bought the extras he wanted. By the late 1920s and early 1930s, however, Harley-Davidson was offering more specialized equipment for police motorcycles.
From Civilian Motorcycle to Police Machine
The first photograph already shows how far the equipment had progressed. The early-1930s Flathead carries a siren at the front and a fire extinguisher at the rear. Neither item changed the basic motorcycle, but together they gave the officer warning power and a small emergency-response capability that a civilian rider normally had no reason to carry.
Rear-mounted sirens became another common solution. On the 1934 machine above, the siren sits beside the rear wheel, where its drive wheel could contact the tire. The motorcycle is still spare compared with later police Harleys, yet the rider, POLICE marker and siren make its purpose obvious.
By 1936, the patrol motorcycle could carry much more. This Flathead sidecar outfit has department-marked luggage, a rear siren, a front police plate and the long floorboards and crash bars expected on a heavy service machine. It also demonstrates why there was no single universal police specification. Departments ordered what matched their work, budgets and maintenance practices.
Police agencies were experimenting with specialized motorcycles across several manufacturers. New York's unusual armored motorcycle built for bandit-chasing duty was an extreme example, while Harley's later purpose-equipped proposal for New York police work shows how seriously manufacturers pursued municipal contracts.
A sidecar offered another way to expand the motorcycle's usefulness. The open sidecar in this photograph has a fitted fabric cover over the passenger opening, with the spare wheel carried at the rear. The photograph does not establish exactly how this particular outfit was assigned, but the police plate confirms that it belonged to the same broad effort to adapt motorcycles to department needs rather than force every job onto a solo machine.
Police Radios Arrive in the 1930s
Sirens and lights helped an officer move through traffic, but radio changed how the motorcycle was dispatched. Before a receiver was fitted to the bike, a motor officer could be difficult to reach once he left the station. A one-way radio allowed headquarters to send calls directly to the rider, even though the officer still lacked the normal talk-back ability of a later two-way set.
The late-1930s Knucklehead above looks much closer to the police motorcycle most people picture today. It carries dual headlights, a prominent front speaker and large radio boxes behind the seat. Those boxes were not decorative luggage. The receiver, power supply and related hardware were heavy, and the installation had to survive vibration, weather and daily patrol use without making the motorcycle unmanageable.
The speaker mounted near the handlebar put dispatch traffic where the rider could hear it. This was a receiving system, not a full conversation between officer and dispatcher. Even so, the ability to redirect a motorcycle already on the street was a major step forward. An earlier Harley-Davidson VL fitted for police radio service shows how quickly the motorcycle became part of the developing communications network.
Mechanical Sirens and Emergency Equipment
The old mechanical siren was simple in theory and clever in practice. Instead of depending on a large electric motor, the siren borrowed motion from the motorcycle's tire. The rider operated a pedal or lever connected by cable, bringing a small drive wheel into contact with the rotating tire. Tire speed spun the siren, and lifting the control let the unit move away again.
This close-up makes the arrangement easier to understand. The contact wheel sits where it can be pressed against the tire, while the cable and linkage control engagement. Pressing the roller against the rotating tire drives the siren; releasing the control moves it away again.
The second detail view shows how tightly the siren and linkage were packed beside the wheel and frame. Installations varied, which is another reason to avoid assuming that every period photograph shows one factory-standard arrangement. What stayed consistent was the operating idea: use the moving tire as the siren's power source and give the rider a mechanical way to engage it only when needed.
The fire extinguisher visible on the early Flathead is another example of service equipment carried on a police motorcycle. Additional front lights also appeared as the machines became more specialized. By 1941, the motorcycle shown below had several lights facing forward in addition to its radio equipment and rear-mounted siren.
Mesh Antennas, Speakers and One-Way Communication
The 1936 Harley-Davidson-RCA police-radio flyer is unusually helpful because it explains what the manufacturer was trying to solve. It promoted an RCA receiver and power unit carried in saddlebag-style boxes designed to take hard use while keeping the weight low. The listed features included low current draw, a speaker designed for voice reproduction, a tank-mounted volume control, weather-resistant boxes and a tamper-resistant lock.
The flyer also claimed that more than 250 police departments were using Harley-Davidson radio equipment. That was advertising copy, but it shows that motorcycle radio was no longer being presented as a one-off experiment. Harley-Davidson was selling a coordinated package and emphasizing durability, electrical demand and weight placement—the same practical concerns that mattered to a department mechanic.
One of the most recognizable parts of the installation was the broad mesh, or screen, antenna over the rear fender. It spread across the back of the motorcycle and worked with the radio boxes mounted on either side. The arrangement was functional, but it took up space and gave the rear of the machine a complicated appearance.
By 1941, the State Patrol motorcycle above carries a conventional vertical whip antenna instead. It also has several lights facing forward, radio equipment behind the rider and a rear-mounted siren. In a single photograph, it brings together most of the changes that had accumulated during the previous decade.
The Prewar Police Motorcycle Takes Shape
Between the early municipal Harley and the radio-equipped machines of 1941, the police motorcycle stopped being merely a civilian model in department paint. Sirens, extinguishers, lights, luggage, radio boxes, speakers and antennas turned it into a specialized service vehicle. The work was incremental, and the exact equipment still varied from one agency to another, but the basic pattern had been established.
These motorcycles also demanded skill. A radio and a siren did not make a rigid-frame big twin any lighter, and motor officers still had to control the machine at low speed, work through traffic and operate added equipment at the same time. Period machine-control demonstrations by Washington motor officers make that part of the job especially clear.
What stands out in this group of photographs is not one breakthrough but the steady accumulation of equipment. Each new piece answered a specific problem: warn traffic, carry emergency gear, receive a dispatch, protect the radio, or keep an officer visible. By the start of the 1940s, those solutions had produced a police Harley that would have been instantly recognizable to later generations of motor officers.