The use of a hydraulic excavator or backhoe-loader as a demolition machine with interchangeable tools is a relatively recent development in the 180-year history of mechanized excavating and construction equipment. But just as with so many other concepts of equipment design and application, it has roots in a machine from long ago.
The Keystone Portable Steam Driller Co. was founded in 1882 at Beaver Falls, Penn., to produce a line of then-revolutionary self-propelled drills for applications such as farm and residential water supply, blast holes, and mineral prospecting. The firm prospered, and in 1912, it diversified into the manufacture of excavating machinery.
The initial Keystone excavators were of a design patented by Leroy P. Clutter. The design was offered to Keystone, because Clutter saw the potential for building the new excavator on the Keystone drill chassis. Keystone’s executives agreed and signed a contract to build excavators to Clutter’s designs. The first Keystone excavators were failures, but problems were corrected and 100 or more machines were sold annually by 1916. The improved excavator was light, highly portable, and its hallmark “skimmer” was ideal for road and street repair.
The skimmer had a straight boom with a bucket that rolled along its underside, and it dug by drawing the bucket along the ground away from the machine. At the end of the digging pass, the boom was raised and swung left or right up to about 90 degrees with the bucket held in place. The bottom of the bucket fell away to dump the spoil, and a catch was released to allow the bucket to return to the base of the boom as the boom lowered and returned for another pass. The second Keystone excavator built was quite important historically. After its original sale as, apparently, the first skimmer, it was returned to the factory in 1914 and rebuilt as the world’s first cable backhoe.
Keystone offered its excavators primarily as skimmers or backhoes until 1940, and on the original half-swing machines, both fronts used the same boom. Indeed, the relatively few shovels and clamshell cranes Keystone built as half-swing machines also used the same basic straight boom.
Keystone developed its first full-revolving excavator in 1930 and went on to produce four models, rated from 3/4 to 1-1/4 cubic yards, as well as a fifth model that was apparently built only as a prototype. The excavators were discontinued in the mid- to late-1940s. Most, but not all, were offered as conventional shovels, and all but the last production model, the 19A introduced in 1941, could be equipped as skimmers.
It was one of these full-revolving excavators, the Model 18, produced from 1933 through 1937, that pioneered the concept of an excavator with interchangeable demolition tools. Along with a “plunger shovel” skimmer, “trench shovel” backhoe, and crane attachments, the Model 18 was offered for “hammer” service. Not a pile hammer, mind you, but Keystone’s unique Utility Demolition Hammer.
The Utility Demolition Hammer could be mounted to the end of the shovel boom in two hours and could be equipped with a 3,000-pound hammer (shown), pick, mattock (similar to a pick-axe), axe, hoe, or ball peen. It could cycle 20 times per minute with a drop of 5 to 10 feet, and the operator could increase force with a sharp pull on the hauling line at the top of the cycle. It packed a considerable wallop, but the damage it did to the excavator and its surroundings, along with its target, was its undoing. Despite its failure, the concept was decades ahead of its time.
The Historical Construction Equipment Association (HCEA) is a 501(c)3 nonprofit organization dedicated to preserving the history of the construction, dredging and surface mining equipment industries. With more than 4,000 members in 25 countries, activities include operation of National Construction Equipment Museum and archives in Bowling Green, Ohio; publication of a quarterly magazine, Equipment Echoes, from which this text is adapted, and hosting an annual working exhibition of restored construction equipment. Individual memberships are $32 within the U.S. and Canada, and $40 elsewhere. Information is available at www.hcea.net, 419.352.5616, or email@example.com.