Free PVC Train Horn Plans (Cut List + Diagrams)

What this page is

These are the dimensional plans for the multi-chime PVC train horn described in our PVC train horn build guide. The build guide explains the physics and assembly steps; this page is the reference cut sheet you print and take to the workshop.

Target output: ~120 dB at 3 ft. Target chord: Nathan K5LA-style B major 6th (5 bells: D♯, F♯, G♯, B, D♯ octave). Total build cost: ~$60 in PVC + fittings + foam diaphragm + air source.

Cut list — 5-bell K5LA chord

All bells use schedule 40 PVC, 1.5 inch nominal (1.9 in OD, 1.61 in ID). Bell length is measured from the diaphragm seat to the bell mouth.

These lengths are starting points. Actual frequency depends on diaphragm tension and end-flare geometry. Cut each bell ~1 cm long, then trim to tune by ear. A guitar tuner app will read each pitch.

Bill of materials (BOM)

Air source not included: a Viair 88P portable compressor is ~$70 from Amazon, or a 5-gallon shop air tank ($30) filled at a gas station works for occasional use.

Manifold diagram (text)

Air source (compressor or tank)
        |
        v
0.25" airline -> 0.25"/0.5" NPT reducer
        |
        v
   [0.5" tee 1] -> Bell 1 (D#3, 22 cm)
        |
   [0.5" tee 2] -> Bell 2 (F#3, 18 cm)
        |
   [0.5" tee 3] -> Bell 3 (G#3, 16 cm)
        |
   [0.5" tee 4] -> Bell 4 (B3, 13 cm)
        |
   [end cap]   -> Bell 5 (D#4, 11 cm)
                  (last reducer threads into end of run)
      

Each bell is a piece of 1.5" PVC with a 1.5"→0.5" NPT reducer at the throat end. The reducer threads into a brass tee on the air manifold. Diaphragm (3 mm EVA foam disk) sits between the reducer and the bell — held in place by the threaded fit.

Diaphragm cut

From the EVA foam sheet, cut 5 disks at 1.6 in diameter (matches PVC ID). Use a cookie cutter, hole saw, or a sharp utility knife with a circle template.

Foam thickness affects pitch and tone:

• 2 mm foam — easier to vibrate, brighter tone, slightly sharper pitch
• 3 mm foam — recommended starting point
• 4 mm foam — needs more air pressure to start vibrating, deeper tone, slightly flatter pitch

Tuning workflow

1. Cut all 5 bells ~1 cm long (use longer length from cut list as starting point).
2. Assemble the manifold — glue with PVC cement, thread fittings with Teflon tape.
3. Connect air source. Sound each bell individually (block the others temporarily).
4. Open a guitar tuner app on your phone. Each bell should hit its target frequency within a few cents.
5. If a bell is sharp (too high pitch), it's too short — recut a longer one. If flat (too low), trim 2–4 mm at a time and retest.
6. Once each bell hits target, sound all 5 simultaneously. Listen for the chord — should sound thick and "train-like".
7. If individual bells dominate the chord, adjust diaphragm tension by re-seating the reducer.

Variations

• 3-bell minor chord — Bells 1, 3, 5 only. Cheaper, simpler, sounds like an Atlantic Coast Line K3LA.
• 4-bell K3HL — Bells 1–4 only.
• Single-bell single-tone — One Bell 3 (G♯) by itself. Simple "blast" rather than a chord.
• Custom voicing — Pick any chord. Use the bell-length-to-frequency relationship from our how-it-works guide to compute lengths for arbitrary notes.

Sources

• PVC train horn full build guide (this page is the cut sheet)
• 3D-printed alternative
• DIY hub (full build comparison)
• How do train horns work (frequency physics)
• Train horn soundboard (audio reference for tuning by ear)