Brackets and mounts
Single-Cylinder Otto Engine Assembly
- Bounding box
- 150.0 × 150.0 × 258.0 mm
- Engine
- Precision B-rep
- Parameters
- 38
- Published
- October 29, 2026
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The prompt
Design a simplified single-cylinder internal combustion engine assembly for a 4-stroke Otto cycle demonstration model, consisting of four parametric components: cylinder block, piston, connecting rod, and crankshaft. GLOBAL PARAMETERS - Bore (cylinder inner diameter): 70 mm - Stroke length: 70 mm - Connecting rod length (center to center): 140 mm - Compression ratio: 9:1 - Crank radius: 35 mm (= stroke / 2) - Units: millimeters 1. CYLINDER BLOCK - Hollow cylindrical body, outer diameter 110 mm, wall thickness 10 mm, inner bore diameter 70 mm - Overall cylinder height: 150 mm (enough to contain full piston stroke plus clearance volume) - Closed cylinder head at the top with two small circular ports (20 mm diameter each) representing intake and exhaust valve openings, positioned symmetrically - Open bottom to accept the crankshaft housing - Add 4 mounting bolt holes (6 mm diameter) evenly spaced around the base flange 2. PISTON - Solid cylinder, outer diameter 69.6 mm (0.4 mm clearance fit inside the 70 mm bore) - Height: 60 mm - Domed/flat crown on top (flat is fine for simplicity) - 3 piston ring grooves cut around the circumference near the top, each 2 mm wide, 1.5 mm deep, spaced 4 mm apart - Piston pin (wrist pin) bore through the skirt, 12 mm diameter, centered 30 mm from the top of the piston, perpendicular to the piston axis 3. CONNECTING ROD - Small end: circular eye, 12 mm inner diameter (matches piston pin), wall thickness 4 mm - Big end: circular eye, 25 mm inner diameter (matches crank pin), wall thickness 5 mm - Shaft: I-beam or simple rectangular cross-section connecting the two eyes, length 140 mm center-to-center, shaft width 10 mm, shaft thickness 6 mm 4. CRANKSHAFT - Main shaft diameter: 20 mm, total length 100 mm, centered along the engine's rotational axis - Crank pin (offset journal): 25 mm diameter, offset from the main axis by 35 mm (crank radius), length 30 mm - Two crank webs (counterweight plates) connecting the main shaft to the crank pin, each 50 mm diameter, 10 mm thick, with a cutout or added mass opposite the crank pin for counterbalance ASSEMBLY / CONSTRAINTS - Piston sits inside the cylinder bore, free to translate along the cylinder axis only - Connecting rod small end attaches to the piston pin via a revolute (pin) joint - Connecting rod big end attaches to the crank pin via a revolute (pin) joint - Crankshaft main shaft attaches to the cylinder block base via a revolute joint (rotation only), representing the engine's main bearing - At Top Dead Center (TDC), piston crown should sit
Parameters
| Name | Value | Range |
|---|---|---|
| Cylinder Bore | 70 mm | 40 – 120 |
| Stroke (= 2 x Crank Radius) | 70 mm | 30 – 120 |
| Connecting Rod Length (c-c) | 140 mm | 90 – 260 |
| TDC Squish Clearance | 8.75 mm | 2 – 25 |
| Crank Angle (assembly pose) | 30 deg | 0 – 180 |
| Block Outer Diameter | 110 mm | 70 – 200 |
| Block Overall Height | 150 mm | 100 – 260 |
| Cylinder Head Plate Thickness | 10 mm | 4 – 30 |
| Intake / Exhaust Port Diameter | 20 mm | 6 – 40 |
| Port Offset From Axis | 22 mm | 0 – 40 |
| Base Flange Diameter | 150 mm | 110 – 240 |
| Base Flange Thickness | 12 mm | 4 – 40 |
| Bolt Circle Diameter | 124 mm | 80 – 200 |
| Flange Bolt Hole Diameter | 6 mm | 2 – 16 |
| Number of Flange Bolts | 4 pcs | 2 – 12 |
| Piston Diameter | 69.6 mm | 40 – 120 |
| Piston Height | 60 mm | 30 – 140 |
| Crown Thickness | 20 mm | 5 – 60 |
| Skirt Wall Thickness | 5 mm | 2 – 20 |
| Number of Ring Grooves | 3 pcs | 0 – 6 |
| Ring Groove Width | 2 mm | 0.5 – 6 |
| Ring Groove Depth | 1.5 mm | 0.3 – 4 |
| Ring Groove Pitch | 4 mm | 2 – 15 |
| Top Groove Below Crown | 8 mm | 2 – 40 |
| Wrist Pin Bore Diameter | 12 mm | 4 – 30 |
| Wrist Pin Below Crown | 30 mm | 10 – 80 |
| Small End Bore | 12 mm | 4 – 30 |
| Small End Wall | 4 mm | 1 – 20 |
| Big End Bore | 25 mm | 8 – 60 |
| Big End Wall | 5 mm | 1 – 25 |
| Shaft Width | 10 mm | 4 – 40 |
| Shaft Thickness | 6 mm | 2 – 30 |
| Main Journal Diameter | 20 mm | 8 – 60 |
| Main Journal Length | 100 mm | 40 – 300 |
| Crank Pin Diameter | 25 mm | 8 – 70 |
| Crank Pin Length | 30 mm | 10 – 120 |
| Crank Web Diameter | 50 mm | 30 – 140 |
| Crank Web Thickness | 10 mm | 2 – 40 |
Every value above is a live dimension. Open a model like this in the editor and each one becomes a slider you can drag before exporting.
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