Tools of the Trade - Mini Cranes and Lattice Boom Crawler Cranes
An exclusive series illustrates the highly effective and innovative ways cranes are being used across many industries and vocations.
Big jobs may bring to mind the need for large cranes, but sometimes big things come in small packages.
That has certainly been the case at Block 250, a high-rise 28-story office tower being built in downtown Houston that is the centerpiece of a three-block dining and shopping district.
For the project, , a Houston-based sales, rental and service provider, was called in by two contractors to supply mini cranes.
“Due to tight confines within the structure and close adjoining buildings, tower cranes could not be used to reach all areas under construction,” said John Carpenter, sales and rental manager, Inman Texas Company. “With their low weight, the Maeda MC285 mini cranes could travel and lift in various jobsite areas without causing ground pressure and floor loading issues. The narrow 30” width of the cranes in travel configuration also enabled them to access tight areas, fit material hoists, transit standard doorways, and maneuver in close quarters.”
One of the Maeda MC285 mini cranes from Inman Texas was used by a curtain wall contractor to install unitized panels on the building exterior.
The panels were staged on various floors throughout the building for installation on the facade from the interior.
“The Maeda MC285 weighs only 4,325 lbs. so it was moved to different floors in the material hoist on the side of the building,” Carpenter related. “With the mini crane positioned on a floor above where the panels were staged, the panels were hoisted from the floor below and precisely placed into position.”
Carpenter added that the installers were able to speed up panel installation because the the MC285 could lift and lower faster, thanks to its being able to handle each panel on just a single-part load line.
“With the capability to hoist a maximum 1,560 lbs. on one part of line and reach as much as 164’ below the machine level, the installers could set the mini crane in one position and install four or five panels in sequence without a machine move,” Carpenter said. “When it was time to reposition the crane, it only took a matter of a minutes to move and set up to lift another four or five panels.”
The second contractor on the Block 250 project, a steel fabrication company, used a Maeda MC285 from Inman Texas to install steel staircase sections in the interior of a multi-level parking garage.
“Each floor has only one workspace where the crane could be set up to hoist stair sections into position safely and precisely,” Carpenter explained. “With the mini crane, the contractor was able to avoid costly, time consuming, and less safe alternatives such as chain falls and specialty rigging to hoist the loads in the stairwells.”
Lattice Boom Crawler Cranes
Canada’s Cherubini Bridges and Structures has completed work on the Four Signature Bridges contract for Toronto’s Port Lands project.
The job wrapped up in style with the company successfully orchestrating a complex four-crane pick to get the final 446.6-USt segment of the bridge onto a self-propelled transporter for a trip up the St. Lawrence River by barge and later unloading and installation.
The lift of the 22.3-m (73.2’) wide, 57.1-m 187.3’) long Cherry Street North Bridge was performed by , a division of Nova Scotia’s .
It was completed using the four largest cranes in R&D Crane’s fleet: a Model 16000 lattice boom crawler, and GMK6400, GMK5250L, and GMK5240 all-terrain models. The lift was completed within four hours.
For the lift, the cranes combined to raise the structure from its supports in the yard at Cherubini’s fabrication facility in Nova Scotia, allowing a self-propelled modular transporter with transfer beams and a Cherubini-engineered turntable to take the load.
The transporter was driven onto a barge moored alongside the site’s dedicated wharf to begin its journey to Toronto.
The need to bring together the four cranes was the result of an engineering solution to help ensure the bridge was positioned as smoothly as possible at its final resting place.
“Loading the bridge sections onto the barge wasn’t the issue, as the transporters were able to pick the sections and drive straight on,” said Cherubini Group CEO Darren Czech. “But with this particular section and also a second one there were space restrictions. That meant we couldn’t just simply roll on and roll off the barge using the self-propelled transporters alone,” he said.
“Because of that, we engineered a solution that supplied the sections to the jobsite on a turntable structure,” Czech continued. “This allowed tugboats in Toronto to spin them around on the barge in the middle of the harbor, ideally positioning them to slot right into the final location. We used the four-crane pick at our yard to make sure the section was accurately placed on the turntable ahead of shipping.”
For the lift, one crane was positioned at each corner of the bridge, and all were configured with main boom and partial counterweight.
The Model 16000 lattice boom crawler had 36 m (118.1’) of boom with 134 USt of rear counterweight and 27 USt of counterweight.
All three Groves maximized their outrigger deployment, with the GMK6400 working with 95 USt of counterweight and 20 m (65.6’) of boom; the GMK5250L working with 70 USt of counterweight and 23.5 m (77.0’) of boom; and the GMK5240 working with 44 USt of counterweight and 23 m (75.4’) of boom.
“The lift went without a hitch in less than four hours,” said R&D Crane’s GM, Rob Blois. “The key was really the planning, working out how to maintain equal weights during the lift and spreading the load to reduce ground-bearing pressure. And on that day the cranes worked very well together.”
is a writer with 38 years of experience covering the trucking, utility, construction and related markets.