A Custom Tugger Solution for a 50-Ton Engine Cart
Case Study
Summary
A manufacturer of large engines builds engines that can weigh up to 80,000 pounds. Moving those engines through the plant means moving the custom cart they sit on, and for years the customer handled that job with a small propane powered tugger pulling the cart by a set of chains. Align Production Systems designed a GT tugger that ties directly into the existing cart’s hydraulic lift system, giving the customer an 80,000 pound towing capacity, a single point of remote control, and a set of safety features built around the one hazard unique to this application: the risk of jackknifing on a tight turn.
Key Highlights
Built to carry an 80,000 pound towing rating while handling the full downforce the engine assembly places on the hitching point.
Rather than replacing the customer's cart, the tugger slots into the cart's hydraulic cylinder system, which lifts it off its resting feet and onto its wheels.
A single operator drives the tugger with a radio remote, replacing a two piece forklift and trailer style setup with one low profile unit.
"The one piece of engineering that really sets it apart is the anti-jackknifing system, and that's a feature built specifically for this application."
Walter Para, Design Engineer, Align Production Systems
The Problem
For years, moving a loaded engine cart at the customer’s plant meant hooking a small propane powered tugger to the cart with a set of chains. That tugger weighs about 4,000 pounds and can pull with roughly 4,000 pounds of force, enough to move the cart but with little margin and no real control over how the load handled a turn. The setup functioned more like a truck pulling a trailer than a purpose built material handling system, and it depended on chains staying properly connected and an operator judging distances by eye. The cart itself was built by Align and has been in service since the 1990s or early 2000s, with a modification package added in 2012, so the equipment moving it needed to work with a cart design that predates the tugger project by decades.
The Solution
Align designed a single drive tugger, engineered to work with the customer’s existing cart rather than replace it. The cart already uses a hydraulic cylinder to drive a piston down into a receiver, lifting the weight off the cart’s resting feet and transferring it onto a set of wheels. Align’s tugger takes over from there. Its own steerable drive wheel provides propulsion while a set of idler wheels support the load, so the tugger only has to steer and pull instead of carrying the full weight of the assembly itself.
Because the cart’s cylinder position is fixed and a sharp turn can bring the tugger close to the cart, Align added a set of laser distance sensors to prevent jackknifing. The sensors measure the distance between the tugger and the nearest edge of the cart, and
as that distance shrinks in a tight turn, the tugger first slows down and then stops the operator from steering further in that direction until they back away from it. The tugger also carries electric safety bumpers on its exterior. If the tugger contacts an obstacle, the bumpers trigger the same response as pressing an emergency stop, and the operator has to reset the unit before continuing. Red perimeter lights, a horn, a stack light, and emergency stops mounted at each corner round out the safety package.
The tugger runs on Align’s standard 48 volt, 420 amp hour battery and is operated by a single person using a radio remote, the same control scheme used across Align’s GT Tugger line, which this unit is closest to in both size and function.
Implementation & Results
The tugger was engineered to a 50,000 pound downforce rating at the hitching point, matching the load the customer’s engine assemblies place there even though the assemblies themselves can weigh up to 80,000 pounds. The weight distribution across the cart’s other wheels keeps the actual force on the tugger within that 50,000 pound design target, with capacity to spare if conditions change. As a complete system, the tugger carries an 80,000 pound towing rating.
The customer expects the same benefit other GT Tugger customers see when they move from a forklift and trailer style process to a single operator, remote controlled unit: less manual handling, fewer people involved in each move, and a machine built around the one hazard specific to this job instead of a general purpose tow vehicle pressed into service.
Towing Rating
Hitch Downforce
Operator Per Move
Conclusion
This tugger shows how Align approaches a project that looks simple on the surface. The unit has few moving parts and a straightforward job to do, but the engineering behind it, from tying into a cart design to building in a jackknife prevention system for one specific turning hazard, is what turns a basic tow job into a safe, single operator process.
