Can a 1972 Pettibone Crane Safely Lift Lock Blocks for Ranch Construction

[MikePhua]

The Legacy of Pettibone Cranes
Pettibone, founded in 1881 in Chicago, built its reputation on rugged lifting equipment tailored for railroads, construction, and industrial handling. By the 1970s, Pettibone had expanded into mobile cranes, offering compact models with lifting capacities ranging from 5 to 35 tons. These machines were often used in utility work, small-scale infrastructure, and agricultural settings. The 35TK series, introduced in the early 1970s, became a popular choice for contractors needing a nimble crane with decent reach and load ratings.
Though production of these models ceased decades ago, many units remain in service across North America, especially in rural areas where simplicity and mechanical reliability are prized over electronic sophistication.
Terminology Annotation

• Outriggers: Extendable supports that stabilize the crane during lifting operations.
  
• Load Chart: A manufacturer-provided table showing safe lifting capacities at various boom angles and radii.
  
• Boom Radius: The horizontal distance from the crane’s center of rotation to the load.
  
• Tipping Load: The maximum weight a crane can lift before becoming unstable, typically calculated at 75% of the tipping point for safety.
  

Assessing the Crane’s Capabilities
The 1972 Pettibone in question is estimated to be a 10-ton class machine, likely a derated version of the 35TK. While the nominal lifting capacity may suggest it can handle 2-ton concrete lock blocks with ease, the actual safe lifting capacity depends heavily on boom extension, angle, and load radius.
For example:

• At a 10-foot radius, the crane may safely lift 6,000–8,000 lbs
  
• At a 20-foot radius, capacity drops to 2,000–3,000 lbs
  
• At full boom extension over the side, capacity may fall below 1,500 lbs
  

These figures assume the crane is in good mechanical condition, set on firm level ground, and using properly cribbed outriggers.
Field Setup and Safety Practices
When placing lock blocks, especially on fresh fill or uneven terrain, several precautions are essential:

• Maintain a 1:1 setback ratio from any slope (e.g., stay 10 feet back from a 10-foot drop)
  
• Always lift over the rear of the crane when possible, as side lifts reduce stability
  
• Use cribbing under outrigger pads—two layers of 2"x6" rough-cut fir, 3 feet long, is sufficient
  
• Perform a test lift with the block just inches off the ground to verify stability
  
• Ensure the load is plumb to the boom tip to avoid side loading
  

In one British Columbia project, a similar crane tipped during a side lift on soft ground. The operator had skipped cribbing and misjudged the radius. Fortunately, no injuries occurred, but the boom suffered structural damage and required replacement.
Mechanical Condition and Structural Integrity
Older cranes like the Pettibone 35TK may suffer from wear in critical areas:

• Boom extension tubes may be thinned from decades of friction
  
• Turntable bolts and welds can loosen or crack
  
• Hydraulic seals may leak under load
  
• Control linkages may have excessive play
  

Before lifting heavy blocks, inspect:

• Boom welds and slide sections for cracks or deformation
  
• Turntable attachment points for rust or fatigue
  
• Hydraulic cylinders for scoring and seal integrity
  
• Brake and clutch systems for responsiveness
  

If the crane has a four-part hoist line, be cautious—while it increases lifting power, it also raises the risk of overloading worn components.
Load Chart and Operational Limits
If no load chart is available in the cab, one should be sourced from archival manuals or similar models listed on crane specification databases. Without a chart, operators must default to conservative estimates and avoid lifting near maximum theoretical capacity.
General rule of thumb:

• Never exceed 75% of the tipping load
  
• Factor in wind, slope, and operator error
  
• Use spotters and clear communication during lifts
  

Human Factors and Crew Coordination
Lock blocks are unforgiving—heavy, rigid, and prone to shifting unexpectedly. If working with a helper, plan each lift carefully:

• Keep hands and limbs clear until the block is fully stabilized
  
• Use tag lines to control swing
  
• Communicate clearly before each move
  
• Never rush or improvise under load
  

In one Alberta ranch build, a helper suffered a broken wrist when a block shifted during placement. The team had failed to use tag lines and the block rotated unexpectedly. After the incident, they revised their protocol and completed the wall without further injury.
Final Thoughts
A 1972 Pettibone crane can be a valuable tool for ranch construction, but only if operated with respect for its age, limitations, and the physics of lifting. With proper setup, conservative load handling, and diligent inspection, it can safely place lock blocks and perform other tasks. However, without a load chart and a clear understanding of radius-based capacity, every lift becomes a gamble.
Old cranes don’t forgive mistakes—and concrete doesn’t bounce. So take the time to prepare, test, and lift with care. The wall will stand longer, and so will the crane.