For the chassis structure
Tata Steel employed an iterative approach using a finite element analysis, with the aim of minimising mass while ensuring that structural performance was comparable with the original design. The new designs considered both the functional requirements and manufacturing cost of the components. Every attempt was made to reduce the amount of weld, with a preference for folded sheet over welded assembly in as many areas as possible.
A 3.5tn forklift chassis was analysed using ABAQUS FE software. Tata Steel then designed a new concept chassis to match the structural performance of the original design at a lower cost. During the process, 41 design iterations were completed. The result was a structure which achieved a 30% reduction in mass, and a 20% reduction in the number of components.
The lightweighting savings comprised:
- 30% potential saving
- 20% fewer components
- Comparable welding/reduced bolted joints
- All gauges comply with current Hyster-Yale supply
- Comparable torsional stiffness
- General reduction in stress levels for major loadcases; payload, 3G Battery and racking
These innovations achieved the same structural performance as before, and were recommended for implementation in Hyster-Yale’s next generation lift trucks.
For the overhead guard (OHG)
In discussions with Hyster-Yale, Tata Steel identified an opportunity to save mass and cost in the OHG by using automotive-style crash analysis to study the behaviour of the structure during the test.
The guard above the drivers’ head needs to withstand 10x impacts of a 45kg rectangular block, and must not have a residual deflection beyond the code requirements. Tata Steel modelled a 3.5tn forklift OHG using LS-DYNA software. Using this analysis, it was able to reduce the mass of the OHG by 33%, remaining within Hyster-Yale’s design requirements.
To support the OHG design changes, Tata Steel undertook a series of practical tests at its R&D facilities in the UK. Hyster-Yale supplied two OHGs, which were subjected to the 10x 45kg impact test requirements. The OHGs were heavily instrumented and the results were compared to the crash analysis. The exercise demonstrated that the analysis results were very close to the practical results, adding further credence to the mass reductions obtained in the design/analysis project.
The lightweighting savings achieved comprised:
- Potential weight saving of 33%
- 20% reduction in number of components (number of reinforcements)
- Bar profile savings considered
- Analysis correlated to OHG tests:
- Static test (50kN pull on frame) to validate modelling assumptions
- Representative dynamic impact test (10x45kg drops)