Research — Transmission · Precomputed (draft, unvalidated)

H-frame: raise the crossbrace

An H-frame is two wood poles, a crossarm, and braces that tie them together. How far apart can the next structure be? Five points on the structure each set a maximum span, and the smallest one governs. Slide the crossbrace up the poles and the governing point moves: low on the poles the brace itself is the weak point, higher up the pole at the lower brace joint takes over. Pick a story or drag the brace yourself. The harness computes spans and never judges, so nothing is marked pass or fail; the point that governs is simply outlined.

Story

Draft, unvalidated harnessIllustrative geometry: the harness has no pole-geometry modelPoint D is not validated

Free play · drag the crossbrace, or pick any combination the harness was run at

Crossbrace height h2 · ft above groundline

Wind pressure · psf

Structure

Crossbrace rating

Pole class · Douglas Fir 80 ft

Every control snaps to a value the harness was run at; the page reads that cell and never estimates between two. The crossbrace rests only on the eight exported heights: drag the grip on the drawing with a mouse or pen, tap a stop dot, tap a column of the chart, press the arrow keys on the drawing, or use the stepper.

Elevation · heights and pole spacing to scale, pole widths drawn about 1.7 times wider

What limits the span · maximum horizontal span at each point

Span against crossbrace height · one dot per exported stop

governs: the smallest span of the five (an accent outline and the word, never a pass or fail color)next: the second smallestthe gap between them (exported)Bar and dot colors only say which point it is.

Every point at this state · the governing row is outlined

Rule column: the equation the data file cites for each span. Rank, ‘governs’ and ‘next’ are the exporter's comparison. Uplift sits below the dashed line because it is a foundation check and takes no part in the ranking.

How the checks read it

Reference check · does the harness reproduce the bulletin?

The harness's own exporter ran these before writing the data file. ‘= ok’ means the computed value is within the stated tolerance of the expected one; ‘≠ not ok’ is a known gap and is shown as one. Only the first group is a bulletin worked example; the formula-consistency group is hand-computed regression values and is not a bulletin number.

Every point · the first reading, the change, the last step

Columns are step labels. The spans are harness outputs read from the data file; ‘governs’, ‘next’ and the gap are the exporter's comparison of those five spans. ‘First to last step’ compares the first and last columns only (same, longer or shorter).

Precomputed results:every verdict, required value and margin on this page was computed by the real Python harness at export time and is played back from a data file. The page runs no harness logic and holds no standards tables, and it never interpolates between exported values. Not a live API call. Precomputed by the real utm-agent-harness h_frame functions (commit e61dd9d) at export time and played back from a data file. The harness is a DRAFT with no human subject-matter-expert sign-off; nothing here is a design or a compliance determination. The functions COMPUTE spans and never judge, so there is no pass or fail anywhere on this page: ‘governs’ (the smallest of the five spans), ‘next’, the gap and ‘uplift below’ are the exporter's own comparison (demo logic), and no color is chosen by a verdict. ONLY Structure 4 (RUS 1724E-200 Sec 13.f, Douglas Fir 80-2, 161 kV, NESC Heavy 4 psf) has a bulletin worked example; Structures 2 and 3 are formula-consistency tier and are computed on the Structure 4 geometry, and Structure 1 appears only in the reference checks. Point D is NOT validated: the bulletin quotes 811 ft and the harness does not reproduce it (reference check HSD, shown as not ok). The geometry is illustrative: the harness has no pole-geometry model, so moving the crossbrace uses a straight taper from 7.96 in at the top to 15.64 in at the groundline and the bulletin's internal offsets held fixed while the bracing assembly slides (back-solved from the bulletin's quoted numbers; not validated), and the wire attachment heights are illustrative. Pole class changes only the groundline capacity, so a stronger class honestly does little here. Wind: the bulletin's wire loads at 4 psf are scaled linearly with pressure (demo logic); 4 psf is NESC Heavy and the other pressures are what-if values. Uplift uses the bulletin's W1 and pole weight as inputs and is shown beside the ranking; the bearing check is not included. Domain maturity: schema draft, unvalidated; no structural or transmission-line PE has reviewed it.Real functions this maps to:horizontal_span_at_a_ft, horizontal_span_at_d_ft, horizontal_span_at_e_ft, horizontal_span_at_b_ft, horizontal_span_at_e_structure_2_ft, horizontal_span_at_b_structure_2_ft, horizontal_span_at_e_structure_3_ft, horizontal_span_limited_by_crossbrace_ft, uplift_relationship, groundline_moment_capacity_ft_k.Not modeled: a real pole-geometry model (diameters, taper and the placement of the bracing are derived, not measured), poles taller or shorter than 70 ft, pole classes with their own taper, the bearing check (Eq. 13-19g), conductor sag and ice, the iterative deflection re-check, any structure type other than the Structure 2, 3 and 4 H-frames, and whether a given span is acceptable. Heights and pole spacing are to scale; pole widths are drawn about 1.7 times wider; the string, wire and person are pictures, not results.See also:H-frame: raise the crossbrace, hands-off walkthrough · Structure loading walk · Pole groundline moment