Occupant Geometry

Desired

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title	Click here to expand

This section describes the desired angles between the legs, torso, head etc. of the occupant

Image Modified

[4]

Location of H Point

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Seatback Bolsters Height: Maximum 288mm above H Point [4]

NOTE: All dimensions (below the one above) in the bolsters section are NOT explicit recommendations, rather these are values taken from a 1990 Nissan Maxima Seat

Please take these values with caution - the purpose of these measurements is to give a ballpark number of dimensions for bolsters.

While the below measurements are from a 1990 Nissan Maxima Seat, Appendix A within source 9 also has these measurements for seats from the following cars: 1990 Chevrolet Camaro, 1990 Nissan 240SX, 1990 Cadillac Seville. The dimensions for the Nissan Maxima were used as they seemed to be the most appropriate though looking at the dimensions for the seats from the other vehicles can give an intuition as to the range of dimensions for bolsters

Schematic Diagram of a typical production car seat [9]
- Section C represents H Point as viewed on the seatpan
- Section D represents H Point as viewed on the seatback

Seatback Bolsters [9]

NOTE: Main width is superseded by the other recommended seatback widths in this document, they are only used to calculate the angle of the side bolsters in this case

	Depth	Inside Width	Outside Width	Main Width
Section D	41mm	432mm	514mm	292mm
Section E	64mm	457mm	521mm	292mm
Section F	74mm	457mm	521mm	292mm

Rough Angle of Side Bolsters (with respect to horizontal)

	Angles
Section D	120.3581
Section E	127.8028
Section F	131.8911

Seatpan Bolsters [9]

NOTE: Main Cushion width is superseded by the other recommended seatpan widths, they are only used to calculate the angle of the seatpan bolsters in this case

	Cushion Depth	Inside Cushion Width	Outside Cushion Width	Main Cushion Width
Section A	56mm	432mm	508mm	279mm
Section B	53mm	419mm	483mm	279mm
Section C	43mm	381mm	470mm	279mm

Rough Angle of Seatpan Bolsters (with respect to horizontal)

	Angles
Section A	126.2051
Section B	127.1309
Section C	130.1355

Foam Stiffness

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title	This section describes a way to approximate how much the foam will compress and what foam stiffness to use for the seat

To approximate the stiffness of the foam needed (if there is a desired compression), the formula below can be used [4] (Note: This will give the 50% ILD/IFD value in Newtons)

T = maximum thickness of the foam (mm or inches)

P = peak pressure

Type of Occupant	Peak Pressure (psi)
Small	1
Medium	1.25
Large	1.5

Source 4 did not specify what qualifies as a small, medium or large occupant. thus it was assumed

Small = 5th Percentile Male/Female
Medium = 50th Percentile Male/Female
Large = 95th Percentile Male/Female

C = the amount of compression (in same units as T )

0.0462 = conversion from psi to N

Below is a sample calculation:

We have a large sitter (95th Percentile Male/Female) - peak pressure is 1.5 psi
Max thickness is 58mm of cushioning
We want 32mm of compression
To convert to pound-force (divide by 4.448)
To determine the compression (with a known stiffness of foam), the above formula can be rearranged into:
With ILD representing the 50% ILD value in Newtons