Xem Studiomeasured geometryLibrary › Stirling engines › Drives & mechanisms ·
Counterweighted crank discs, Ø5 bore, 10 to 30 mm stroke
How is a counterweighted crank disc for a small engine shaped? · Hardware · basis: Crank disc ending just past the pin and thickened opposite it; pin at stroke / 2, Ø5 bore, M3 grub
Long Earth Society build part. Balanced cranks for the 2 in gamma. The engines
Exact dimensions. Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part. Mating features
- sizes
- 5 in table
Notes
- A 6 mm disc (Ø32, 32, 34, 39, 44 for 10–30 mm stroke) with the Ø3 pin hole at half the stroke. On the pin side the disc ends 6 mm past the pin centre, with a Ø10 boss round the pin.
- Opposite the pin a raised segment 4.8 thick (10.8 overall) carries the counterweight; the description sizes it at about 50 % of a con-rod and piston at the pin radius.
- Ø5 bore and a radial Ø2.5 hole (M3 tap drill) at mid-thickness for a grub on the shaft's flat.
- Balance condition: m_cw × r_cw = m_rotating × r_pin + 0.5 × m_reciprocating × r_pin. A crank that stops at any angle when spun bare is statically balanced; at 200–600 rpm that is enough.
Sizes
| file | stroke | pin offset | disc Ø | thickness | envelope |
|---|---|---|---|---|---|
| cw-crank-disc-stroke10 | 10 | 5.0 | 32 | 6 / 10.8 | 27 × 32 |
| cw-crank-disc-stroke15 | 15 | 7.5 | 32 | 6 / 10.8 | 29.5 × 32 |
| cw-crank-disc-stroke20 | 20 | 10.0 | 34 | 6 / 10.8 | 33 × 34 |
| cw-crank-disc-stroke25 | 25 | 12.5 | 39 | 6 / 10.8 | 38 × 39 |
| cw-crank-disc-stroke30 | 30 | 15.0 | 44 | 6 / 10.8 | 43 × 44 |
Mating features
Drawn at the exact size. Open press, slide, run and socket features by your process's clearance; leave designed gaps and clamp fits as drawn.
| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| disc bore | Ø5 | Ø5 crankshaft (M3 grub) | slide | cw-crank-disc-* |
| disc pin hole | Ø3 | Ø3 crank pin | press | cw-crank-disc-* |
| disc grub hole | Ø2.5 | M3 tap drill | designed | cw-crank-disc-* |
Where the files are
Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.
| Wikipedia | Engine balance | web | CC BY-SA 4.0 (text) |
| Wikipedia | Crankshaft | web | CC BY-SA 4.0 (text) |
| Long Earth Society | Engine builds | web, video | LES site |
Free files
★ Free files 5 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json
| cw-crank-disc-stroke10 | counterweighted crank disc, 10 mm stroke (pin at 5.0), Ø5 bore, M3 grub, mass opposite the pin ≈ 50% of the con-rod+piston at the pin radius | STEP · STL |
| cw-crank-disc-stroke15 | counterweighted crank disc, 15 mm stroke (pin at 7.5), Ø5 bore, M3 grub, mass opposite the pin ≈ 50% of the con-rod+piston at the pin radius | STEP · STL |
| cw-crank-disc-stroke20 | counterweighted crank disc, 20 mm stroke (pin at 10.0), Ø5 bore, M3 grub, mass opposite the pin ≈ 50% of the con-rod+piston at the pin radius | STEP · STL |
| cw-crank-disc-stroke25 | counterweighted crank disc, 25 mm stroke (pin at 12.5), Ø5 bore, M3 grub, mass opposite the pin ≈ 50% of the con-rod+piston at the pin radius | STEP · STL |
| cw-crank-disc-stroke30 | counterweighted crank disc, 30 mm stroke (pin at 15.0), Ø5 bore, M3 grub, mass opposite the pin ≈ 50% of the con-rod+piston at the pin radius | STEP · STL |
Plain text: sheet.txt · JSON: /api/geometry?object=counterweighted-crank-discs
How it fits
Goes in or on
Crankshafts Ø3, Ø5 and Ø8 with full-length D-flatØ5 bore, M3 grub on the flat
Crank stands with a 625 pocket, 40 and 60 mm axis…on the shaft beside the 625 standConnects to
Connecting rods 30 to 80 mm centres with 623 pockets623 on the Ø3 pinAlternatives
Crank discs for a Ø5 shaft, 10 to 30 mm strokeplain discIn these build lists
Gamma Stirling, 2 in tri-clampHot spool with a shell displacer, a crank head that carries the crankshaft, the …Tri-clamp tee diaphragm gamma, 2 inA tea-light gamma in 2 in tri-clamp: displacer in a 3 in spool, a short-outlet t…Tri-clamp elbow diaphragm alpha, 2 inA torch-heated alpha in 2 in tri-clamp: a square of fittings with a diaphragm he…You might also need
Questions
How much counterweight does a single-cylinder engine need?
Enough that mass × radius opposite the pin equals the rotating mass plus about half the reciprocating mass at the pin radius.
Why does my Stirling engine walk across the table?
The crank is out of balance: the piston and con-rod pull outward once a turn. A counterweight opposite the pin cancels it.