Explainer
How three-point hydraulic grouping works
The statically determinate foundation of SPMT stability — why three points are better than four for most moves, and when to switch.
Three-point hydraulic grouping divides a trailer combination into three hydraulic zones. Each zone acts as a single support point located at the centroid of its axle lines. The three support points form a triangle, and the cargo’s combined centre of gravity must sit inside this triangle for the system to be stable.
Because three points define a unique plane, the load distribution between the groups is statically determinate — no assumptions about deck stiffness are required. This is the default recommendation in DNV-ST-N001 and in most company operating standards.
The stability angle θ is calculated for each of the three tipping lines (the sides of the support triangle). The governing angle is the smallest of the three.
Full explainer coming soon.