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Vulcan's first venture into the vibratory market took place in the 1960's with the introduction of the Uraga electric vibratory hammer from Japan, which Vulcan marketed as the Vulcor Vibratory Hammer.

Vibratory pile driving technology had been developed in the Soviet Union. One of the first countries to pick up the technology was Japan. With its volcanic soils, it is an ideal place for a vibratory hammer to be used.

Most early Japanese vibratory hammers (which are described some here) followed the Soviet pattern of electric motor(s) driving eccentrics through a chain drive system. (An example of this kind of design is shown here.) This unimaginative application of the technology prompted one Soviet trade official to describe the Japanese as "not very good students."

The Uraga/Vulcor machine was a deparure in that Uraga reversed the rotor and stator on the electric motors and positioned one motor inside of each eccentric. This resulted in a vibrator with a more direct drive than has been seen before or since, making for an efficient construction and operation.

Right: the VHD-1 model, with only one "stack" of eccentrics.

Unfortunately the width of the machine clashed with the normal American practice of setting the sheets before driving, which requires either that the vibratory hammer be narrow enough (less than 355 mm) at the throat or use an extension (which adds to both the vibrating mass and hanging weight of the hammer.) Some Uraga machines also suffered from misalignment of the eccentric bearings, a function in part of the "modular" construction of the machines (to increase the number of eccentrics, it was simply necessary to add another "stack" to the unit.

All of these difficuties, combined with American contractors' aversion to electrics on the job, put the Vulcor at a disdavantage to other vibratories coming into the U.S. By the time Vulcan moved to West Palm Beach, the Vulcor programme was pretty much over and it would be another twenty years before Vulcan would attempt a vibratory hammer again.

Below: the VHD-2 (with two eccentric stacks) at a power plant project in California. The hydraulic clamp, although primitive by modern standards, was an advance over the "lever-style" clamps use by many other Soviet and Japanese units. Even Foster was still using lever-type clamps in their units in the early 1990's.

More on the Uraga/Vulcor Hammer:

Driven Pile Manual Volume 1a
Driven Pile Manual 1b
Driven Pile Manual 2