V8 Engine Kit - Cross-Plane Crank, Split Rods, Timing Gears

A printable V8 you assemble and turn by hand: cross-plane crankshaft, eight pistons on split connecting rods, and a camshaft driven at half speed by 20/40 timing gears.

• 90° V8, firing order 1-8-4-3-6-5-7-2, crank pins at 0°, 270°, 90°, 180° (real cross-plane layout)

• 20 mm stroke, 36 mm rods, Ø19.6 mm pistons in Ø20.4 mm bores

• Block split on the crank centreline so the one-piece crank drops in; 6 × M3 holes join the halves

• Connecting rods with bolt-less caps: two short pieces of 1.75 mm filament pin each cap

• Printable piston pins; camshaft with 5 journals larger than the lobes, so it slides in from the back

• Clearances made for FDM: main journals 0.3 mm, big ends 0.3 mm, piston pins 0.2 mm, pistons 0.4 mm, cam journals 0.4 mm

How it was checked

Designed in code (build123d). All 42 parts were checked for interference at 16 positions through the full 720° cycle (1680 part pairs, 0 collisions), and every moving fit was measured in the assembled model. This is v1 and has not been test-printed yet: the valve train (lifters, pushrods, rockers, valves) is not included and is planned for v2. Makes and feedback are very welcome.

What you need

• A 256 mm bed (A1, P1S, X1, MK4...): the crankshaft is 184 mm long

• 6 × M3 screws 25-30 mm (or glue the block halves), 16 × 8 mm pieces of 1.75 mm filament, a little glue for the heads and the gears

Print settings

Sliced in Bambu Studio for the A1, 0.20 mm, PLA. Four plates, 3MF included: plate 1 block 5 h 35 min (162 g, tree supports), plate 2 crankcase + heads 5 h 01 min (140 g, supports), plate 3 crankshaft + camshaft + gears + flywheel 3 h 43 min (76 g, supports), plate 4 pistons, rods, caps and pins 1 h 32 min (35 g, no supports). Total about 15 h 50 min and 414 g. Use a brim for the camshaft, which prints standing up. Source files included (Python / build123d): v8.py is the full animated engine with valve train, v8_kit.py makes this printable kit.

About this design

Pictures are 3D renders of the CAD model, not photos.

Español

Kit imprimible de V8: cigüeñal cross-plane, 8 pistones con bielas partidas (sombrerete sujeto con filamento de 1,75 mm) y árbol de levas movido por engranajes 20/40. Bloque partido para meter el cigüeñal. Comprobado en CAD sin choques en todo el ciclo; versión 1 sin tren de válvulas y aún sin imprimir. Necesita cama de 256 mm; unas 15 h 50 min y 414 g.

العربية

محرك V8 قابل للطباعة والتركيب: عمود مرفق متقاطع، ثمانية مكابس بأذرع مقسومة، وعمود كامات بتروس توقيت. الإصدار الأول دون صمامات ولم يطبع بعد.