Extinguisher Seat-Bolt Bracket

One-piece laser-cut, four-bend plate. Bolts to two seat-track bolts 16.250 apart and carries the extinguisher on a flat shelf parallel to the floor.

RevP
Date2026-10-13
Checks21/21
Seat bolt centers16.250fixed, measured on the car
Bar17.125 x 1.625length x depth
Shelf depth6.625bar + plate, one plane
Drop1.125bar underside to flange underside
Flange0.875 x 1.250width x length
Flat blank17.125 x 8.543as cut
MaterialMild steel 0.187A36 HRP&O at this gauge
Weight3.2 lbestimated

Sheet 1 — formed part

Top view, front elevation, end section, pictorial fit
7 6 5 4 3 2 1 A B C D FIRE EXTINGUISHER SEAT-BOLT BRACKET FORMED PART - THIRD ANGLE PROJECTION - DIMENSIONS IN INCHES UNLESS MARKED MM SHEET 1 OF 2 REV P 2026-10-13 16.250 BOLT CENTERS - FIXED 17.125 BAR LENGTH 6.500 5.000 0.551 (14.00 MM) SHELF EDGE TO LEFT PAIR 1.625 5.000 7.688 OVERALL 1.063 4X 1/4-28 UNF TAPPED THRU, TAP DRILL 0.221 2X DIA 0.413 (10.5 MM) THRU TOP VIEW SCALE 1:2.5 1.312 1.125 DROP 16.250 0.875 SHELF SPANS THE FULL LENGTH FLOOR / SEAT-BOLT PLANE FRONT ELEVATION SCALE 1:2.5 VIEWED FROM THE FLANGE SIDE 1.312 0.938 CLR 1.250 FLANGE 1.625 5.000 6.625 SHELF SECTION THROUGH A FLANGE Z-OFFSET RUNS ACROSS THE BAR END VIEW SCALE 1:2.4 PICTORIAL NOT TO SCALE MATERIAL MILD STEEL THICKNESS 0.187 QTY 1 BENDS 4 X 90 DEG BEND RADIUS 0.125 INSIDE K FACTOR 0.36 FLAT BLANK 17.125 X 8.543 WEIGHT 3.2 LB UNITS INCH TOLERANCE +/-0.010 ANGLES +/-1 DEG VENDOR SENDCUTSEND NOTES 1. MATERIAL MILD STEEL 0.187 (3/16 NOMINAL). 0.200 IS NOT A STOCKED THICKNESS. 2. 2X DIA 0.413 (10.5 MM) THRU FOR 10M X 1.5 SEAT BOLTS. CENTERS 16.250 APART - TAKEN OFF THE CAR, THIS DIMENSION IS FIXED. 3. 4X 1/4-28 UNF TAPPED THRU. DXF CARRIES PLAIN DIA 0.221 TAP DRILL CIRCLES; VENDOR RESIZES FOR THE TAP. 4. ALL BENDS 90 DEG +/-1 DEG. EFFECTIVE BEND RADIUS 0.125 AND K FACTOR 0.36 ARE THE VENDOR FIGURES FOR THIS MATERIAL AND THICKNESS (SKU HRP-188). 5. FLANGE LENGTHS FROM THE BEND APEX: FLANGE 1.250, RISER 1.312, BAR 1.625, AGAINST A 0.781 MINIMUM AFTER BEND. BEND LINE TO BEND LINE 0.990, WITHIN THE 0.826 TO 3.750 JOGGLE RANGE. 6. THE 1-1/8 DROP IS MEASURED UNDERSIDE OF BAR TO UNDERSIDE OF FLANGE, LEAVING 0.938 CLEAR FOR THE BOLT HEADS. 7. FLANGES TURN 90 DEG OUT OF THE BAR, AWAY FROM THE PLATE, AND DROP INSIDE THE SEAT TRACKS. 8. BREAK ALL SHARP EDGES. NO FINISH SPECIFIED.

Vector art — zoom in as far as you like and the dimensions stay sharp. Click the sheet to magnify at that spot, drag to pan.

Sheet 2 — flat pattern and details

Flat pattern, bolt flange, hole pattern fit
7 6 5 4 3 2 1 A B C D FIRE EXTINGUISHER SEAT-BOLT BRACKET FLAT PATTERN AND DETAILS - DEVELOPED AT K 0.36, BEND ALLOWANCE 0.3021 SHEET 2 OF 2 REV P 2026-10-13 B1 B2 B3 B4 B1 / B3 UP 90 DEG B2 / B4 DOWN 90 DEG 1.089 0.990 RISER 6.464 8.543 FLAT DEPTH 17.125 FLAT LENGTH CUT LAYER - ONE CLOSED CONTOUR + 6 CIRCLES FLAT PATTERN SCALE 1:2.5 AS CUT, BEFORE BENDING 0.875 FITS THE TRACK 0.438 1.063 0.187 X 0.332 RELIEF 0.652 TO B1 DIA 0.413 (10.5 MM) THRU B1 B2 DETAIL A - BOLT FLANGE SCALE 1:1 123.40 MM = 4.858 0.551 24.00 MM -1.391 2.000 STRIP 1.091 LEFT PAIR 14.00 MM FROM THE LEFT EDGE, CENTERED ACROSS THE 2.000 STRIP DETAIL B - HOLE PATTERN SCALE 1:1.8 BEND TABLE ID AT Y DIR LENGTH JOINS B1 1.089 UP 0.875 FLANGE TO RISER B2 2.079 DOWN 0.875 RISER TO SHELF B3 1.089 UP 0.875 FLANGE TO RISER B4 2.079 DOWN 0.875 RISER TO SHELF Y IS MEASURED FROM THE FLANGE TIPS (BOTTOM EDGE OF THE FLAT). DIRECTION IS AS SEEN WITH THE SHELF FACE UP. BEND DEDUCTION 0.322 PER BEND. RELIEF 0.187 X 0.332 AT EACH TAB ROOT. DESIGN CHECKS [PASS] CONTOUR [PASS] SEAT BOLT SPACING [PASS] BOLT HOLES LIE FLAT [PASS] REFOLD: FORMED DEPTH [PASS] REFOLD: SHELF RISE [PASS] BEND DEDUCTION VS VENDOR [PASS] BOLT HOLE TO EDGE [PASS] HOLE SIZES [PASS] BOLT HOLE TO BEND LINE [PASS] TAPPED HOLE EDGE DISTANCE [PASS] THREAD ENGAGEMENT [PASS] MIN FLANGE, FORMED [PASS] MIN FLANGE, FLAT PATTERN [PASS] JOGGLE, BEND LINE TO BEND LINE [PASS] PART SIZE [PASS] BAR BENDING AT 20 G [PASS] BEND RELIEF [PASS] CORNER RADII [PASS] CLEARANCE TO ROUNDED EDGE [PASS] BEND LINE LENGTH [PASS] METRIC HOLE PATTERN MATERIAL MILD STEEL THICKNESS 0.187 QTY 1 BENDS 4 X 90 DEG BEND RADIUS 0.125 INSIDE K FACTOR 0.36 FLAT BLANK 17.125 X 8.543 WEIGHT 3.2 LB UNITS INCH TOLERANCE +/-0.010 ANGLES +/-1 DEG VENDOR SENDCUTSEND FLAT PATTERN NOTES 1. DXF LAYER CUT CARRIES THE PROFILE AS ONE CLOSED POLYLINE PLUS SIX CIRCLES. LAYER BEND CARRIES THE FOUR BEND CENTERLINES. 2. FLAT BLANK 17.125 X 8.543. HOLES ARE SHOWN IN THEIR FLAT POSITIONS; THE FLANGE HOLES DO NOT MOVE WHEN THE PART IS BENT. 3. BEND LINE POSITIONS DEPEND ON THE VENDOR RADIUS AND K FACTOR. IF THEIRS DIFFER FROM 0.125 / 0.36, ALL FOUR MOVE - FLAG IT RATHER THAN MOVING THE HOLES. 4. CORNER RADII ARE IN THE DXF: R0.500 FAR PLATE CORNERS, R0.250 PLATE/BAR ROOTS, R0.125 FLANGE TIPS AND BAR ENDS, R0.030 RELIEF NOTCHES. 5. INSPECTION: BOLT CENTERS 16.250, BAR LENGTH 17.125, DROP 1.125.

Vector art — zoom in as far as you like and the dimensions stay sharp. Click the sheet to magnify at that spot, drag to pan.

Bend table

IDAt yAngleDir Length
B11.08990°UP0.875
B22.07990°DOWN0.875
B31.08990°UP0.875
B42.07990°DOWN0.875

Developed at K 0.36, bend allowance 0.3021, inside radius 0.125. y is measured from the flange tips.

Design checks

PASScontour32 vertices, shortest segment 0.0424
PASSSEAT BOLT SPACING16.250000 vs 16.250000 required
PASSbolt holes lie flatboth in the flange, clear of bend line B1 at 1.089
PASSrefold: formed depth7.688000 vs 7.688000 spec
PASSrefold: shelf rise1.125000 vs 1.125000 spec
PASSbend deduction vs vendor0.3219 computed from R 0.125 / K 0.36 vs 0.323 published
PASSbolt hole to edge0.231 wall vs 0.056 min (5.86 mm each side across the flange)
PASShole sizessmallest 0.221 vs 0.042 min
PASSbolt hole to bend line0.652 vs 0.499 (2t + R) min, margin 0.153
PASStapped hole edge distanceclosest 0.528 vs 0.167 min (tap hole/2 + 0.056)
PASSthread engagement5.2 threads of 1/4-28 UNF in 0.187 plate (2-56..1/2-20 tappable)
PASSmin flange, formedflange 1.250 from apex vs 0.781 min, margin 0.469
PASSmin flange, flat patternriser 0.990 vs 0.620 min, margin 0.370
PASSjoggle, bend line to bend line0.990 within 0.826 .. 3.750
PASSpart size17.125 x 8.543 within 44 x 30
PASSbar bending at 20 g27387 psi vs 41000 yield, 0.67 x (5.2 lb, plate 4.562 / 5.188 from the bolts)
PASSbend relief0.187 wide x 0.332 deep at each tab root, both tabs
PASScorner radii2 x 0.500, 2 x 0.250, 6 x 0.125, 6 x 0.030, none scaled back
PASSclearance to rounded edgetapped 0.528 (min 0.375), bolt 0.438 (min 0.394)
PASSbend line length4 bends, 0.875 each, max 44
PASSmetric hole pattern123.4000 mm x 24.0000 mm, left pair 14.00 mm in from the plate edge, right 27.70 mm

Open before ordering

  1. Nothing outstanding on the bend rulesEvery vendor limit is now checked against their published figures: minimum flange 1.250 vs 0.781 after bend, joggle 0.990 inside their range, part size, bend length, hole and tap edge distances. All pass.
  2. Bend figures are now the vendor's ownR0.125 and K 0.36 come from the SendCutSend datasheet for SKU HRP-188, not from estimates. As a cross-check, those two reproduce their published bend deduction to within 0.001.
  3. Vertical load at 20 gThe 5.2 lb extinguisher puts the bar at 0.67 of yield at 20 g vertical, at the point where the plate ends, against their published 41,000 psi. Fore-aft is far below yield. Stress falls linearly with bar depth if more margin is wanted.
  4. Confirm the plate direction against the carThe flanges turn one way and the plate the other. Mirroring means mirroring the DXF.

Corner radii R0.500 far plate corners, R0.250 plate/bar roots, R0.125 flange tips and bar ends, R0.030 relief notches · bolt hole 0.652 from bend line B1 against a 0.499 minimum · 0.938 clear under the bar for the bolt heads.
Generated from bracket.py and drawing.py — the sheets above are the same SVG the project emits, so this page cannot drift from the DXF.