As the Nilens concern inched (or more accurately millimetred) its way to receivership, Vulcan embarked upon a project using one of their hammers that, had it succeeded, would have made an interesting addition to Vulcan's lineup: the Liquid Propane Gas (LPG) hammer.

As was the case with noise pollution, the 1970's were also the years when the U.S.'s commitment to clean up (well, in one sense) its air kicked into high gear. Diesel technology, although fuel efficient, tends to produce a great deal of particulate matter. This is true both with diesel engines and with the diesel hammers. With the latter, emission control is even more problematic than with diesel engines. As the combustion configuration (compression ratio, fuel mixture, position of the combustion chamber itself) varies with the hammer's varying interaction with the pile, controlling the particulate matter is more difficult than with diesel engines.

Vulcan's concept was to power internal combusion hammers using a fuel with no particulate matter at all, in this case liquid propane gas (LPG.) To do this they enlisted the help of John Kupka, who had earlier in the decade designed the linear vibrator. In 1974 plans were drawn up for an LPG hammer, and a Nilens diesel hammer was modified for the testing.

Below: the carburettor for the LPG hammer. It took the place of the diesel fuel pump, and was mounted directly adjacent to the combustion chamber.

Right: another view of the positioning of the pressure carburettor, showing its position relative to the old fuel pump.

Below: a close-up (left) and more general view (right) of the LPG hammer at the Special Products Division. The left view shows the relief valve on the left side of the hammer.

In spite of several design changes and the inclusion of another designer to the task (John Lerch, who later oversaw the designs of the 5150 and 6300 hammers,) the LPG hammer never got out of its prototype stage, and the project was ended in 1976.

Diesel hammers have had their environmental problems, and are banned in certain places. But they have also had their successes, with new and improved fuels to reduce particulate matter, biodiesels and environmentally friendly lubricants. But now we have the drive to reduce carbon emissions.

The end of internal combustion hammers? Or fuel cell hammer, anyone?