Positioning the H-Point Design Tool—Seating Reference Point and Seat Track Length
This SAE Recommended Practice describes how to position and posture the H-point design tool (HPD) described in Appendix B, and how to establish the seating reference point (SgRP), design H-point travel path, and other key reference points that are used in the design and specification of both driver and passenger seat positions.
This practice also provides a method for determining the length of the seat track for a driver seat that adjusts fore/aft. The seat track length is based on a desired level of driver accommodation, assuming a U.S. population containing an equal number of male and female drivers. The procedure can be used to establish driver seat track accommodation for new vehicle designs or to evaluate accommodation in existing vehicles.
A general method for determining driver seat track length for any driver population (male and female stature distribution) at any selected accommodation percentile and gender mix is given in Appendix A.
Application of this document is limited to Class A Vehicles (Passenger Cars, Multipurpose Passenger Vehicles, and Light Trucks) as defined in SAE J1100.
The 2008 revision of this Recommended Practice aligns the document with current industry procedures while preserving the advantages of the new tools and methods described in SAE J4002 and SAE J4003. The new definitions and procedures allow manufacturers flexibility to change accelerator pedal shape and orientation without necessitating changes in the Seating Reference Point (SgRP) location and simplify the communication of pedal and package requirements between manufacturers and suppliers.
A new Shoe Plane and Shoe Plane Angle (SPA) replace the Pedal Plane and Pedal Plane Angle defined in the previous revision. The SPA equation is now cubic, based on an improved empirical fit to the kinematics of the SAE J4002 HPM-II and SAE J826 HPM geometry. The SPA equation is now also based on an ankle angle fixed at 87 degrees, which is a current industry practice and identical in intent to the SAE J1516 theta equation. However, the new fit better characterizes the kinematics of the HPM and the H-point Design Tool (HPD).
The new Ball of Foot Reference Point (BOFRP) replaces the Pedal Reference Point (PRP) in the previous version as the reference for the SgRP locator curve. The key difference is that the BOFRP need not lie on the pedal surface, giving flexibility to change accelerator pedal shape and orientation without changing SgRP. The BOFRP is now 203 mm from the Accelerator Heel Point (AHP), consistent with SAE J826, SAE J1100:2008, and vehicle manufacturers around the world.
The recommended SgRP Z location for seats with vertical adjustment was revised in response to some manufacturers increasing the range of seat height adjustments beyond the ranges used to develop this document. Depending on the amount of height adjustment provided, SgRP_Z will either be at mid-height of the H-point travel window or lower, with a maximum height of 20 mm above the full-down H-point travel path.
The HPD has also been revised to include some elements of the SAE J826 2-D H-point template, based on requests from manufacturers. A 2-D profile that includes a shoulder reference point has been added to the standard form of the HPD CAD tool.
This document may be used with the SAE J826 design tool, provided that the flat shoe bottom defined in SAE J826 (2008) is used.