It's Not What You Think

Engines have improved immensely over the last decade, but with end-users and OEMs faced with high fuel prices and ever-tightening emissions regulations, alternative methods are being sought that will glean more work from a gallon of diesel fuel. We're seeing hydraulic or electric assistance installed to work with the compression ignition engine, and in some cases that engine has been removed completely. Bolting a second diesel engine to the chassis might, at first glance, seem to be heading in the wrong direction.

Recently Grove and Krone have done just that, and the two machines actually fall in-line with the efficiency goal because of their two compression-ignition engines.

Unique advantages

In the history of on- and off-road equipment, twin-engined machines aren't unusual — although saving fuel wasn't always the primary reason for their installation. A pair of engines was generally employed in heavy equipment to give the machine the extra horsepower and torque to do its job.

Caterpillar and Terex have offered twin-engined scraper models for years. On a scraper, one engine drives the front wheels (the tractor) while the other runs the scraper and pushes the machine through a heavy loading application.

The new Grove TM500E-2 truck crane from Manitowoc uses two different engines to great advantage: one diesel is rated for off-highway use, while the other is an on-highway powerplant. Both engines are certified to current United States Environmental Protection Agency (EPA) emissions standards (Tier 3 and EPA 2007 regulations).

In the Grove application, each engine is controlled from the respective cab and is completely separate in its function. The chassis engine is controlled from a chassis cab, and the other engine is controlled from the cab on the crane superstructure. The superstructure cab features armrest-mounted electric dual-axis controllers. In addition, the operator can monitor all engine functions from the in-dash gauges. The machine uses CAN bus for communication, although the two engines do not interact.

The TM500E-2's highway carrier uses a Cummins ISC six-cylinder 300 hp diesel that propels the 60,000-lb. machine up to 65 mph. Once at the jobsite, the operator shuts off the chassis engine and fires up the Cummins QSB 3.3 L four-cylinder 110 hp diesel in the crane superstructure. Once the outriggers are extended the crane is ready to use.

"Having two engines significantly reduces fuel usage," says Ruben Olivas, global product manager for Grove's truck crane line in Shady Grove, PA. "By using the superstructure engine to run crane operations, owners can reduce fuel consumption by gallons per hour. This allows customers to get more work from their cranes while reducing operating costs."

Using a separate off-highway engine for the crane also allows the operator to fill that engine's fuel tank with less-expensive dyed off-highway diesel.

Twin-engined cranes are not new to Grove. In 1961, the company's first truck cranes, the TM5 and TM8, had a pair of engines. The last of the smaller truck cranes to utilize two engines was the early 1980s TM200. Larger Grove truck cranes used two engines through the 1990s.

The 45-ton capacity TM500E-2 replaces the single-engined TMS500E Grove truck crane. "We started out to refresh the truck crane line and ended up going back to the future," says Doyle Bryant, director of product marketing, Grove.

Grove engineers were attracted to the twin-engine solution because of the new on-highway engine emissions regulations. "The regulations impact the cost of diesel and fuel mileage and thus the cost of operation," says Doyle. "That pointed us toward a second engine. We can save these guys money by putting a smaller engine upstairs to do the crane functions."

The Cummins QSB engine operates the crane's 29-ft. to 95-ft. four-section, full-power boom. Maximum tip heights are 102 ft. and 110 ft.

The Grove crane's chassis is built to Grove's specific requirements by Autocar LLC, Hagerstown, IN, and utilizes a spring front suspension and air rear suspension.