Reliability Makes RT Crane a Real Workhorse

Enlarge Image Image 1. MARCO's RTC 8070 RT crane.

Subject: RTC-8070 rough-terrain crane, manufactured by Link-Belt Construction Equipment Co., Lexington, Ky.

Serial number: D719-2403

Date in service: 7-18-99

Hours in service: 7,592

Equipment owner: MARCO Crane Rental has offices in Phoenix, Ariz., San Diego and Santa Fe Springs, Calif. While predominately a Link-Belt supplier, the company also carries Grove, Manitowoc, and Terex products in its fleet.

Service area: Southwest United States

Date of review: 8-26-05

 

September 8, 2005 • This Link-Belt RTC 8070 rough-terrain (RT) crane (Image 1), owned by MARCO Crane Rental, has spent most of its life as a bare rental unit in the never-ending construction of power plants being built to keep up with rapid growth in the southwest United States. As such, it hasn't been pampered, as it's logged a lot of hours for its age. Despite its heavy workload, the MARCO crew characterized the unit as a reliable, easy-to-operate machine.

 

Enlarge Image Image 2. The MARCO crew especially appreciates the method for locking and unlocking the jib.

First introduced in the second quarter of 1999, the Link-Belt RTC 8070 features a 70-ton base rating. Current 8070's now feature an improved 75 ton base rating.  The four-section full power boom is 41 feet to 127 feet and comes equipped with a two-section, 67-foot bi-fold jib. Offsets are at 2°, 20°, and 40°. The jib is unlocked from the carrier by extending the fly section a couple of feet, thus eliminating the need for the operator to climb onto the carrier to wrestle with any locks. When stowing the attachment, the operator leaves the boom extended a couple of feet, folds it back into transport position, and then sucks the boom back in. This action captures 

Enlarge Image Image 3. Other than an initial brake leak, the main and auxiliary winches have been trouble free.

the pin (as shown in Image 2) and locks everything down. Note: There are no capacity deductions for stowed attachments.

 

This particular unit is fitted with an optional auxiliary winch (Image 3). Both main and auxiliary winches deliver maximum available line pull of 17,100 pounds and maximum line speed (single part) of 451 f.p.m. on a 16-inch root diameter grooved drum.

 

Power comes from a 210-hp Cummins 6BT 8.3-liter engine mated to a Clark 3-speed, dual-range, forward and reverse power shift transmission.

Appearance

Enlarge Image Image 4. The very comfortable and cool operator's seat has held up exceptionally well.

The ULTRA-CAB™ is constructed of a laminated fibrous material, incorporating an acoustical fabric insulation to keep things quiet. Unpainted, it looks a lot like carbon fiber. I could find no evidence of any cracks anywhere on the interior or exterior of the cab. Inside, everything has really held up great. You can see that the cloth high-back operator's seat looks excellent, offering six-way adjustment yet still feeling comfortable and supportive (Image 4). The cloth is a nice option over hot sticky vinyl, especially on a day when the temperature hits 114 degrees, as it did the day I reviewed this machine. A pedestal-mounted steering wheel is easily titled away to allow excellent access for even the largest of operators. But just like those found on a commercial jet, the seat maybe a little snug between the armrest for a really big fella.

 

As you can also see in Image 4, there are six separate pilot-operated control valves. A four-section gear pump supplies a combined 136 gpm — more than enough to allow simultaneous operation of all six of these valves. Maximum system pressure is 3,500 psi. Service records indicate that with the exception of a few switches all the controls are original. The only repetitive problem of concern is a failure of the solenoid valve that activates the thumper in the hoist control handle. The Microguard 434-rated capacity limiter (RCL) is a Greer-supplied LMI. Again, the records show that this has been basically trouble free. When observing this unit's operation, I was impressed with how quiet it was. Standing on the ground, it was easy to carry on a conversation with an operator.

Enlarge Image Image 5. Paint adhesion is excellent, even under the fender wells.

You can see that this unit is not dressed in Link-Belt's signature red and white. It was ordered from the factory in MARCO's paint scheme. All components are pre-painted prior to assembly. Generally speaking, this paint finish has held up exceptionally well. Even under the fenders along the longest of welding beads — where rocks and debris can fly and chip the paint — I could not find a single spot where adhesion had failed (Image 5).

 

Service issues
A review of the unit's service records didn't reveal a lot out of the ordinary. There was a main winch brake cylinder repair in February 2000 that was covered under warranty and a couple of failures of the voltage converter that converts the 12 volts electrical system to a 24-volt starter system. Of course, there were the typical repair and maintenance repair and maintenance and inspections required to maintain a crane of this size. It was noted in the records that the boom slide pads needed to be carefully monitored. The MARCO crew explained that since this unit is fully proportional it allows for “scoping with a heavier load.” In bare rental applications, operators tend to use this capability with the boom at lower operating angles, thus magnifying the wear and tear on the top and bottom pads.

 

Owner's and operator's impressions

Enlarge Image Image 6. Operators would love to see a walking deck around the entire carrier.

The MARCO service department had only a couple of simple requests for improving the crane. In Image 6,  you can see that the walk deck is not continuous around the carrier.  Link-Belt has addressed this issue on many of there other new products and plans to do add this  at some point in the future on this model.  But it is important to note that it does offer six access points around the carrier so you really don't have a problem getting to anything. Also on  their wish list is a tilt cab.

 

After I had kicked the tires and talked with the service department, MARCO owner Dan Mardian shareed his personal opinions of the RTC 8070. Describing the crane as  “very smooth and easy-to-run,” the RTC 8070 is perfect for bare rental applications.. “We find that operator acceptance of this unit is very high,” he said. He also believes the RTC 8070 has the best chart, especially on rubber, of any machine in its class.

 

For the most part, he has been pleased with the overall reliability of the unit. His only complaint is an issue he believes is common to all RT cranes equipped with a power shift transmission, regardless of make or model.  He explained, for an engine to transfer power to the hydraulic pumps and the transmission, there needs to be mechanical link. But this link needs to be able to give in the event of a pump seizure or other catastrophic event. RT cranes typically use a composition or fiber drive ring, designed to break up if anything goes wrong. However, in the absence of a pump seizure, the rings typically hold up for about 4,000 to 5,000 hours of use. According to Mardian, the drive rings often break up at the most inopportune time—usually when the engine and pumps are under load and in the middle of a lift. Service records support this observation.

 

Mardian believes these types of rings are used because when the engine and transmission are mated the tolerances are imperfect, something the fiber ring compensates for. He doesn't know what the answer is but sure would like to see someone come up with an alternative.