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Buffer Stroke & Runby

Minimum strokes per ASME A17.1 §2.22 — Table 2.22.4.1 verbatim for oil buffers, Table 2.22.3.1 for spring, and the §2.22.4.1.2 reduced-stroke rule where a terminal speed-reducing device is fitted.

Inputs

Buffer type

Rated car speed ft/min

Reduced striking speed ft/min — only with a terminal speed-reducing device (2.25.4.1); leave blank otherwise

Measured stroke inches — optional, to check the buffer in front of you

Enter the rated speed.

Table 2.22.4.1 — Minimum Oil Buffer Strokes (imperial), verbatim

Rated speed, fpm	115% of rated, fpm	Minimum stroke, in

Read from the printed page (book p. 102). Every row reproduces from §2.22.4.1.1's own physics — stroke = V²÷14,608 — to within a third of an inch, so the formula is what answers between rows.

Table 2.22.3.1 — Minimum Spring Buffer Strokes

Rated speed, fpm	Minimum stroke, in
100 or less	1.5
101 – 150	2.5
151 – 200	4.0

The table stops at 200 fpm because spring buffers do. Above that, the buffer is an oil buffer (or the unit uses another permitted means).

The physics, stated once. §2.22.4.1.1: the car must strike the buffer at 115% of rated speed and come to rest at an average retardation of no more than 32.2 ft/s² — one gravity. Everything in the oil table is that sentence solved for distance: stroke (in) = V² ÷ 14,608, V in ft/min.

While you are at the buffer — the rest of §2.22.4 that a test day touches:

Retardation (2.22.4.2): average ≤ 32.2 ft/s²; no peak over 80.5 ft/s² lasting more than 0.04 s, at any load from rated down to 154 lb.
Plunger return (2.22.4.5.1): gravity- and spring-return buffers return from full compression within 90 s; a spring-return buffer with a 44 lb weight, released after 2 in. of depression, within 30 s; gas spring-return buffers carry a switch that acts if the plunger is not within 0.5 in. of fully extended.
Level at the landing (2.22.4.8): a spring-return oil buffer may be compressed no more than 25% of its stroke with the car level at the terminal landing.
Oil (2.22.4.9): pour point 0 °F or lower (ASTM D97), viscosity index 75 or higher (ASTM D2270). The marking plate and the oil in it should agree.

⚠️ Adam — one read-through before anyone signs against this page: the oil table is transcribed from the rendered page of your A17.1-2022 (book p. 102) and every row was checked against §2.22.4.1.1's formula; the spring table and the §2.22.4 notes above came from the text layer of the same copy. What is yours: confirm the reduced-stroke floor wording matches how you read §2.22.4.1.2 (50% below 800 fpm; the greater of 33⅓% or 18 in. at 800 fpm and above), and check the edition your AHJ adopts if it is not 2022. Then delete this box.