Brown Hoisting catalog, 1919 photo
The Brown Hoisting Machinery Company of Cleveland, Ohio, offered this very typical steam-powered locomotive crane with lattice boom at the turn of the century.
We see them everywhere. They are ever evolving in technology, mobility, and size. They are a prominent part of every construction site, be it bridges, buildings, dams, reclamation, docks, road building and everything else. I’m talking about the mobile crane. Typically wheel or crawler mounted, they can dominate the skyscape in a way that is both wondrous and commonplace. Let’s take a look at the mobile crane’s humble beginnings.
The First Mobile Cranes
At the turn of the century, a mobile crane (a term not yet coined at the time) meant only one type of machine: a locomotive crane, a full-revolving crane mounted on railroad tracks. These machines were big and heavy, and commonly used one source of power: steam. And in that sentence I have described the inherent limitations of this early type of crane. It was limited in its mobility because it must be on rails, and its large size was necessary because of the weight of the boiler, water and coal.
There were other means of lifting on the construction site, but these machines were not mobile. The stiffleg derrick has roots that go back thousands of years, and the guy derrick represents lifting technology that is at least hundreds of years old. Even a machine looking somewhat like a modern, full-revolving tower crane was stabilized by guy cables. Even when the derrick concept was made mobile, as represented by the bridge builder’s derrick car, it was still doomed to containment by its rail mounting.
Getting Off the Rails
Manufacturers recognized the need to develop cranes that were truly mobile. The earliest efforts saw machines mounted on traction wheels. The John F. Byers Machine Company of Ravenna, Ohio, introduced its Auto-Crane in 1914, and by the early 1920s many manufacturers offered traction wheel mounted cranes, some with wide wheels good for flotation and some with narrow, hard rubber tires.
Wars always push hard on the envelope of innovation, and World War I played a big part in the evolution of crane mountings. The first evidence came from a problem that needed an immediate solution. Because of a need for a mobile crane to be used on the docks in France, the Quartermaster General of the American Expeditionary Forces put out a request for a truck-mounted crane. Although this type of a machine did not exist at the time and the void was filled by other means, the truck-mounted crane made its appearance immediately following the war. Cranes were now truly mobile, and moved down roads and around the job with a quickness and efficiency never before dreamed of. They were offered ready to mount on any commercial truck chassis, and most excavator manufacturers quickly jumped into the truck crane market.
The next crane mounting also found its roots in WWI. For the first time, the Army had used crawler tractors to pull wagons and cannon in the field. The “caterpillar” concept quickly showed its validity in the shell-torn and muddy terrain of the Western front, and before war’s end, the tank came on the scene and forever changed the battlefield. The crawler mounting concept was a complete success and, after the war, crane manufacturers decided to put it to use. The first crawler-mounted machine appeared before the war’s end, and locomotive crane manufacturers were some of the first to give it a try.
One manufacturer even tried the half-track concept, but to no fruition. Interestingly, the crawler mounting was even used successfully along with the truck crane mounting. It should be mentioned here that a wagon-mounted crane had also been offered over the years by some crane manufacturers. This un-powered mounting did see some success in special applications.
A Need for New Power Sees Many Advantages, But One Big Loss
Early alternatives to steam power were very limited. The use of one-, two-, and three-cylinder oil engines were tried with little success. It was the simultaneous development of the gasoline industrial engine in the 1920s that not only turned the mobile crane industry, but indeed the entire construction equipment industry, loose, thus leading to the “golden age” of construction equipment development. Such manufacturers as Hercules, Waukesha, Climax and Le Roi developed the four-cylinder and later the six-cylinder engine, which ranged in power from 20 to more than 100 horsepower. The small size and weight of these engines allowed for the development of small cranes that were truck- and crawler-mounted, and crane owners no longer had to deal with poor coal and bad water to keep their steamers going. By the early 1930s, a few larger cranes were even powered with diesel engines.
The problem with using internal combustion engines to power cranes was the loss of the infinite control the operator realized with the steam throttle. The steam crane operator could set a hoist clutch and then, by skillfully manipulating the throttle, could not only raise the load slowly and gently, but also lower it just as carefully. Trying to raise a load slowly with the gas-powered crane required the operator to keep the engine at a high enough rpm to not stall the engine when engaging the hoist clutch. The load either jumped off the ground, or the operator slipped the clutch trying for some kind of easy lift off, usually to no avail. And the gas engines were loud. It would take many years before this problem was resolved.
Mobile Craning Takes Off
The advent of the truck crane mounting very quickly led to a new type of business in the construction industry: Crane service. Today we know it as crane rental or taxi crane service, but little has changed since its inception in the 1920s. As touted in a mid-1920s Universal Crane Company truck crane brochure: “Three items are required of a unit to successfully serve the Crane Service field: (1) speedy mobility to get from job to job, (2) adaptability to all job conditions and, (3) reliable performance.” The same brochure asks, “How much territory can crane service cover? Traveling from job to job at truck speeds of 10 to 15 miles per hour, Universal truck cranes serve a territory within a 25 to 50 mile radius”. It also asks, “Is crane service profitable? On most jobs, a Universal will generally do the work of 20 to 30 men or the equivalent of $100 a day in hand labor. In return for such service, it is not difficult to obtain the usual Crane Service daily rentals of only $60 to $75, or $7.50 per hour.” As we will see, the truck crane industry would continue to develop and adapt.
A Few Creature Comforts and Addressing Operator Fatigue.
Early cranes required the crane operator to stand at the controls. At the turn of the century, one manufacturer offered a wooden plank for a seat. Although the metal tractor style seat became common in the 1920s, the plank seat was still evident, and this poor operator didn’t even get to face forward!
Operator fatigue was a logical result of manipulating the long, hard-to-engage control levers of the day. As machines grew in size, the effort it took to push or pull the controls took even more strength from the operator. Owners realized early on that they were losing money late in the shift as the operators gradually tired. Northwest Engineering Company offered an early successful method to lessen the amount of effort required to engage clutches when they introduced their “Feather touch” booster clutches in the late 1920s. When manipulating the control lever, the operator was merely engaging a small clutch which, in turn, did the work of engaging the main clutch, resulting in much less effort expended.
In the early 1930s, Michigan Power Shovel Company introduced air-controlled clutches on their early truck cranes. These controls represented the beginning of a series of control systems that required a minimum of exertion by the operator. In 1936, Link-Belt Company introduced the Speed-O-Matic system of clutch actuation that used low-pressure hydraulics, a system used successfully for more than 60 years. A much less successful control system was launched in 1937 by the Buckeye Traction Ditcher Company with their Clipper series of machines. Called MEVAC (metered vacuum), it used a vacuum system to actuate clutches. This system went the way of the automotive vacuum brake systems popular at the time. A further evolution of the low-pressure hydraulic control system was introduced after WWII by the Harnischfeger Corporation (P & H). Labeled “Cushion Control,” its hydraulic cylinders looked just like automotive brake cylinders. Air and low-pressure hydraulic clutch controls were the norm of the industry for more than 50 years.
Manufacturers Look for Stability
Cranes have always been limited in their capacity by two factors: Stability, and structural strength. Until the advent of computer-aided design in the 1970s, bigger and heavier was the answer to issues of structural strength. The problem of stability was addressed early on by the development of stabilizing extensions commonly referred to as outriggers. While the behemoth railroad shovels of the turn of the century commonly used outriggers, it was less common to see any railroad cranes use them, except for the large wrecking cranes. As time went on, however, railroad cranes were almost universally offered with outriggers. The early truck cranes also needed outriggers to counteract the flexing of the leaf springs used on the commercial trucks on which they were mounted. The most common arrangement was simply a structural box that housed sliding beams. These could be pulled out manually and supported by wooden blocking. This system was used into the 1950s, when hydraulically-powered outriggers were offered by most truck crane manufacturers. It is interesting to note that manual outriggers were sometimes still an option into the 1960s!
The Purpose-Built Crane Carrier Enters the Truck Crane Scene
Well into the 1940s, many crane manufacturers were still offering its machines for mounting on commercial truck chassis. In the mid-1930s, Michigan introduced a carrier for its small cranes that they manufactured themselves. This opened the floodgates, for in 1940 two of the largest truck crane manufacturers introduced its own carriers. Thew Shovel Company introduced its Thew Lorain Moto-Crane that used a crane carrier of its design. Later that same year, Bay City Shovels Inc. brought out its own version of the purpose-built carrier line, calling them CraneMobiles. Truck cranes were now not only much more stout and stable, they were able to grow quickly in capacity as ever-larger carriers were designed. One interesting development using special carriers in the early 1940s was the rebirth of the self-propelled wagon crane. Unit Crane & Shovel Company was a big proponent of these mountings. Osgood Company developed the Mobilcrane concept, and even built carriers that were wide gauge, thus requiring no outriggers.
Business Is “Booming”
The one mobile crane function that required special attention was that of controlling the raising and lowering of the boom. Early machines simply used a brake pedal and wrap-around brake band to lower the boom. This “live boom” system could get very exciting, especially when lowering with a load! These types of boom controls were eventually outlawed in the early 1950s. A common method of lowering a load on the hoist drum was to disengage the master clutch and engage the hoist clutch; then, by carefully feathering the brake, a load could be lowered against the machinery. The entire draw works would turn backward, aiding in controlling the descent of the load. This method raised two problems. If the load lowered too quickly, the braking system may not have the ability to stop both the weight of the load and the momentum of the turning machinery. Another problem was that, when using this method with some types of machinery and clutch systems, the backwards-turning deck machinery would raise the boom. If the boom was at a high enough angle, it could easily be boomed over backwards when lowering the load against the machinery. More often, the lowering load could not raise the boom, thus stalling the machinery, so nothing happened.
Thew Lorain introduced the precision boom hoist in the mid 1930s. Marketed to steel erectors, it allowed both power boom lowering and raising and the ability to disengage a clutch, thus allowing the operator to back down the hoist line. After WWII, P & H introduced a planetary boom hoist system that allowed full powering of the boom both up and down and independently permitting the load to be lowered against the machinery.
Clutches and Brakes
Very early cranes still used the jaw clutch for engaging various crane functions. This either had to be done very slowly and inefficiently, or the clutch could be jammed in, causing an instantaneous movement of the function. Friction clutches solved this problem in that they allowed some slipping during engagement. Early cone-type friction material was originally made of oak. Later, asbestos friction material was used for both clutches and brakes. Clutches were usually internally expanding, while brakes were usually externally contracting, all around the hoist drum. In the late 1930s, Manitowoc Engineering Works introduced dry disc clutches for its crane’s swing and travel functions, allowing an exceptionally fine touch to the swing function. The Lima Power Shovel Company soon followed suit, using a similar system. After WWII, Osgood developed an air tube clutch for all functions, but this system did not gain favor in the industry.
A Boom Is Not Just a Loud Noise!
The design of the crane boom has evolved over the years, but it was the lattice construction that eventually gained universal adoption. Early booms for mobile cranes that had a small lift capacity were constructed merely of braced channels. P & H even offered a “camelback” or truss boom for some models. Lattice booms, which date back to the 19th century, have been constructed of many structural shapes including angles and square and round tubing. The early booms were of one-piece construction, but manufacturers quickly realized that offering intermediate boom sections of various lengths gave the user the flexibility they needed to address different job situations. These sections were universally bolt-connected to each other until Bay City introduced pin-connected booms in the early 1940s, thus enabling easier assembly and disassembly. Following WWII, several manufacturers offered folding lattice booms that could be transported with the truck crane. P & H pioneered and developed this concept in their long line of truck cranes .
Boom extensions, or jibs, also have been used since the inception of the mobile crane. These were also of lattice or channel construction, only smaller in scale. However, when not offered by the manufacturer, the crane owners did not hesitate to use their ingenuity to build their own.
More Mobile Crane Innovations
Mobility was, and is, key to making money in the crane industry. Early solutions included the introduction of collapsible gantries by American Hoist & Derrick and self-removal of counterweights, first offered on Lorain Moto-Cranes. Perhaps the most significant development occurred when Manitowoc needed a crane to handle submarine sections in their shipyard during WWII. There was no crane on the market with the capacity and mobility needed, so they converted two model 3500s by enlarging the swing circle and spreading out the crawler base. Now here, for the first time, was a crawler crane built to be a lift crane rather than an excavator. These 60-ton machines, now designated 3900s, were the forebears of a model that was so successful that it was produced for more than 40 years. Equally important is the fact that these were the first cranes to be equipped with torque convertors. This fluid clutch acted as a shock absorber between the engine and the deck machinery, thus allowing extremely smooth actuation of all crane functions. It also provided the operator with the ability to lower a load against the convertor, putting the machinery in a stall condition but not stalling the engine. With the hoist clutch engaged, the operator could control raising and lowering the load with the throttle, exactly as the old steam crane operators had. Load control had gone full circle.
It’s a Whole New Ball Game!
As stated earlier, wars push technology, and WWII required many new innovations in hydraulics. The first hydraulic crane was a strange-looking bomb and material handler built by Austin-Western during the war. Nicknamed the Anteater, this machine was mounted on an I-H crawler and boasted hydraulic controls. It was not until after the war, however, that a true hydraulic crane was introduced. Built by Milwaukee Hydraulics Corporation and named the Hydrocrane, it came on the market in late 1946, and the hydraulic crane concept has never looked back. Although it had no winches, all functions were still fully hydraulic. This machine was very mobile, carried all of its boom with it (it was telescopic), and required less skill to operate. By the 1950s, almost all mobile crane manufacturers began to develop and offer hydraulic crane models of their own.
From 1900 to 1950 the mobile crane industry was born, developed, and established as integral to construction markets of all kinds. The evolution of construction techniques has been closely tied to mobile crane evolution — cranes get bigger, construction gets bigger. As the next fifty years would show, there was no limit to the size and complexity of mobile crane development.
Acknowledgments: Troy Krumm, Link-Belt Construction Equipment Company, Lexington, KY.; Ron Kohner, Landmark Enterprises, St. Paul, Minn., (formerly of American Hoist & Derrick); Dave Brainard; Mark Dietz, P & H Mining Equipment; and Tom Berry, HCEA Archivist.
This article is reprinted with the permission of the Historical Construction Equipment Association from the Spring 2011 issue of its quarterly magazine, Equipment Echoes.