To help miners lift heavy loads in cramped quarters, an engineer at the Federal Spokane Research Laboratory in Washington state devised a mechanical lifting assistant.
Mechanical engineer Curtis Clark used Autodesk Inventor to design a mobile manipulator system that lets miners and other industrial users lift heavy objects.
The self-propelled platform carries a rotating turret equipped with a pneumatic powered load-handling arm with a lifting hook. Before lifting, outrigger legs level and stabilize the apparatus. A 120-V rechargeable battery powers the steering, drive-wheels, hydraulic-outrigger legs, and pneumatic arm.
As a starting point, Curtis Clark reverse-engineered an existing but oversized device called a manipulator. And because the redesign work would have overwhelmed his 2D design methods, Clark taught himself to model in solids with Autodesk Inventor from Autodesk Inc. (www.autodesk.com).
"The solid modeler let us reverse-engineer the manipulator to build a working digital model," says Clark. "Based on that model, we created assemblies for the lifting assistant and drove them through their range of motions on the computer to make sure they functioned properly."
The lifter presented several challenges. "The manipulator redesign had to be small enough to fit through narrow openings," says Clark. "It had to be self-contained with its own sources of electricity and air. It also had to lift heavy objects without tipping, balance them through a range of motions, and move fast enough to keep up with a miner."
The software assisted with several functions, such as finding physical properties. "I used it to keep tabs on the device's center of gravity and to determine forces generated by loads and lift-arm positions," says Clark. "We used the magnitude and orientation of forces to calculate loads on individual components. Those figures determined the cross-sectional areas of key parts and subassemblies." Part and assembly files were used to generate 2D shop drawings and, when necessary, AutoCAD files for flat-plate cutting patterns.