Reverse Engineering a Screw Jack
The screw jack was the critical load-applying component at the heart of a long-serving materials test machine. After decades of reliable service, it failed due to fatigue-induced weld-line failures and severe gear wear, rendering an expensive asset unusable and no longer generating value for the business.
With no original drawings or detailed documentation available, DJH Bridgnorth Consulting Ltd was engaged to reverse-engineer a robust, improved replacement. This project became an ideal opportunity to demonstrate how Finite Element Analysis (FEA), combined with precision metrology, enables sustainable remanufacturing of legacy equipment.
Metrology
The essential first step
We began by fully disassembling the screw jack into sub-assemblies and individual components. Each part was meticulously measured using precision instruments, with particular attention to critical interfaces, load paths, and worn elements such as the screw shaft and worm drive (both requiring full replacement). Detailed CAD geometry was generated to support visualization and subsequent analysis.
Two major obstacles quickly emerged: weld-line fatigue failures and the unavailability of cost-effective replacement bearings for the original design.
Design and Simulation
Replacing Costly Prototypes with Virtual Insight
Traditional development often relies on expensive physical prototypes and iterative testing—impractical for a one-off, high-value component like this screw jack. Instead, we used early FEA to evaluate virtual prototypes, dramatically reducing time, cost, and the number of design iterations.
An initial concept was rapidly discarded after FEA revealed unacceptable fatigue stresses and unsuitable bearing arrangements. This simulation-driven iteration identified a superior alternative without any physical builds.
Gearbox tolerance stacks, vital for minimizing wear and noise, were analyzed in Mathcad to optimize alignment and center distances.
Innovative Bearing
Cassette Solution
The main-shaft bearings needed replacement having to cater for combined high axial loads, gear separation forces, and worm-drive tangential loads at low speeds. No off-the-shelf alternatives met the requirements affordably.
We developed a fully contained, sealed, and lubricated bearing cassette for easy installation and extended life. Analysis confirmed that angular contact bearings fell short of the required L10 life under these loads; tapered roller bearings proved the optimal choice. For the worm drive shaft, we selected a floating bearing paired with back-to-back angular contact bearings for balanced support.
Enhanced Communication
Through Visualization
FEA visualizations of stress, strain, displacement, and predicted fatigue life provided clear, compelling insights. These were shared with the client and manufacturing team, fostering better collaboration, faster decisions, and a shared understanding of the improved design's performance.
Conclusion
By integrating precision metrology with powerful simulation tools like FEA, DJH Bridgnorth Consulting transformed a failed legacy component into a more durable, maintainable replacement. This approach extended the test machine's service life, maximized ROI of the original asset, and delivered a genuinely sustainable outcome—remanufacturing instead of replacement or disposal.
Finite Element Analysis has revolutionized early-stage design validation, cutting costs, accelerating development, optimizing performance, ensuring safety, and enabling clear stakeholder communication.
Whether it's a screw jack in a materials test machine or any other complex mechanical challenge, DJH Bridgnorth Consulting turns problems into sustainable, innovative solutions.