# Stirling shafts and rods: Ø3 rods, Ø5 / Ø8 D-flat crankshafts, Ø5 tube rods, Ø3 pins, thrust spacers

> What shafts and rods does a model Stirling engine need, and can I print them?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: The shelf's interfaces: Ø3 displacer rods and pins, Ø5 shafts in 625 bearings, Ø8 in 608s, 5 mm tube piston rods with a Ø3.4 bore; D-flat 0.5 mm as on motor shafts so grub screws bite and the shaft cannot slip
- Page: https://xemstudio.com/objects/stirling-shafts-and-rods/ · JSON: https://xemstudio.com/api/geometry?object=stirling-shafts-and-rods · Plain text: https://xemstudio.com/objects/stirling-shafts-and-rods/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**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.

## Notes

- Every rod here is a solid model: you choose walls and infill. For shafts that carry load (crankshafts, pins) print 100 % infill or 6+ walls, lying flat (the D-flat side down on the bed gives a flat, accurate grub face and puts the layers along the shaft, which is how it bends).
- Which rod goes where: Ø3 rod: displacer rod from the displacer cap through the guide, bushings or the piston's crown bushing to the rod clevis or rhombic upper yoke. Ø3 crankshaft: in the crank head's 623 towers with the Ø3-bore crank discs. Ø5 D-flat: in the 625 crank stands and rhombic plates, carrying crank discs and the nut flywheel (b5). Ø8 D-flat: in the tri-clamp crank frame's 608s with the crank webs and flywheels (b8). Ø5 tube: piston rod from the piston plug, around the displacer rod. Ø3 pins: crank, wrist and link pins.
- Printed Ø5 / Ø8 crankshafts in bearings run fine at a few hundred rpm.
- Thrust spacers set the 1 mm gaps along the shaft (tower · web · rod · web · tower · flywheel): stack 1, 2, 3 and 5 mm pieces to fill a gap.
- Lengths: 2 in gamma crankshaft Ø5 × 100 between two 625 stands with the flywheel outside; tri-clamp crank frame Ø8 × 80; rhombic gear shafts Ø5 × 80 (one × 120 to carry the flywheel); displacer rod = displacer cap to clevis plus stroke, cut a 150 or 200 to length.
- LES: the shafts the engines turn on.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| shafts, rods, pins | Ø3 / Ø5 / Ø8 | the bores listed on each mating object | slide | rod-* |
| D-flat | 0.5 deep | M3 grubs in hubs | designed | crankshaft-* |
| tube rod bore | Ø3.4 | Ø3 rod (no contact) | designed | tube-rod-* |
| spacer bore | Ø3 / Ø5 / Ø8 | shaft | slide | spacer-* |

## Sizes

| part | dia_mm | length_mm | feature | fits | steel equivalent |
|---|---|---|---|---|---|
| Ø3 rod | 3.0 | 100 | — | displacer rod; rod clevis; displacer cap | music wire / drill rod Ø3 h6 |
| Ø3 rod | 3.0 | 150 | — | displacer rod; rod clevis; displacer cap | music wire / drill rod Ø3 h6 |
| Ø3 rod | 3.0 | 200 | — | displacer rod; rod clevis; displacer cap | music wire / drill rod Ø3 h6 |
| Ø3 crankshaft | 3.0 | 40 | — | crank head 623s; crank-disc-b3 | drill rod Ø3 |
| Ø3 crankshaft | 3.0 | 60 | — | crank head 623s; crank-disc-b3 | drill rod Ø3 |
| Ø3 crankshaft | 3.0 | 80 | — | crank head 623s; crank-disc-b3 | drill rod Ø3 |
| Ø5 crankshaft | 5.0 | 80 | D 0.5 | 625 stands; rhombic gears; crank discs; flywheel b5 | Ø5 h6 ground rod |
| Ø5 crankshaft | 5.0 | 100 | D 0.5 | 625 stands; rhombic gears; crank discs; flywheel b5 | Ø5 h6 ground rod |
| Ø5 crankshaft | 5.0 | 120 | D 0.5 | 625 stands; rhombic gears; crank discs; flywheel b5 | Ø5 h6 ground rod |
| Ø5 crankshaft | 5.0 | 150 | D 0.5 | 625 stands; rhombic gears; crank discs; flywheel b5 | Ø5 h6 ground rod |
| Ø8 crankshaft | 8.0 | 80 | D 0.5 | crank frame 608s; crank webs; flywheel b8 | Ø8 h6 rod |
| Ø8 crankshaft | 8.0 | 100 | D 0.5 | crank frame 608s; crank webs; flywheel b8 | Ø8 h6 rod |
| Ø8 crankshaft | 8.0 | 120 | D 0.5 | crank frame 608s; crank webs; flywheel b8 | Ø8 h6 rod |
| Ø5 tube rod | 5.0 | 80 | Ø3.4 bore | piston plug; rhombic lower yoke; flexure stack A | K&S 5 mm brass tube |
| Ø5 tube rod | 5.0 | 120 | Ø3.4 bore | piston plug; rhombic lower yoke; flexure stack A | K&S 5 mm brass tube |
| Ø5 tube rod | 5.0 | 160 | Ø3.4 bore | piston plug; rhombic lower yoke; flexure stack A | K&S 5 mm brass tube |
| Ø3 pin | 3.0 | 12 | — | crank / wrist / link pins | dowel 3 m6 |
| Ø3 pin | 3.0 | 16 | — | crank / wrist / link pins | dowel 3 m6 |
| Ø3 pin | 3.0 | 19 | — | crank / wrist / link pins | dowel 3 m6 |
| Ø3 pin | 3.0 | 20 | — | crank / wrist / link pins | dowel 3 m6 |
| Ø3 spacers | 3 | 1 / 2 / 3 / 5 | — | between bearings, webs, rods, flywheel | washers |
| Ø5 spacers | 5 | 1 / 2 / 3 / 5 | — | between bearings, webs, rods, flywheel | washers |
| Ø8 spacers | 8 | 1 / 2 / 3 / 5 | — | between bearings, webs, rods, flywheel | washers |

## Where the files are

- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (32 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/stirling-shafts-and-rods/index.json

- rod-3x100: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/rod-3x100.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/rod-3x100.stl) — Ø3 × 100 solid rod: displacer rod (into the displacer cap's grub, through the guide / bushings / piston bushing, into the rod clevis)
- rod-3x150: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/rod-3x150.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/rod-3x150.stl) — Ø3 × 150 solid rod: displacer rod (into the displacer cap's grub, through the guide / bushings / piston bushing, into the rod clevis)
- rod-3x200: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/rod-3x200.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/rod-3x200.stl) — Ø3 × 200 solid rod: displacer rod (into the displacer cap's grub, through the guide / bushings / piston bushing, into the rod clevis)
- crankshaft-3x40: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x40.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x40.stl) — Ø3 × 40 solid crankshaft for the crank head's 623 towers and the Ø3-bore crank discs; can engine skewer replacement
- crankshaft-3x60: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x60.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x60.stl) — Ø3 × 60 solid crankshaft for the crank head's 623 towers and the Ø3-bore crank discs; can engine skewer replacement
- crankshaft-3x80: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x80.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x80.stl) — Ø3 × 80 solid crankshaft for the crank head's 623 towers and the Ø3-bore crank discs; can engine skewer replacement
- crankshaft-5x80-dflat: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x80-dflat.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x80-dflat.stl) — Ø5 × 80 crankshaft with a full-length 0.5 mm D-flat (4.5 across) for the grubs; 625 crank stands, rhombic gears, crank discs, nut flywheel b5. Print flat side down
- crankshaft-5x100-dflat: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x100-dflat.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x100-dflat.stl) — Ø5 × 100 crankshaft with a full-length 0.5 mm D-flat (4.5 across) for the grubs; 625 crank stands, rhombic gears, crank discs, nut flywheel b5. Print flat side down
- crankshaft-5x120-dflat: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x120-dflat.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x120-dflat.stl) — Ø5 × 120 crankshaft with a full-length 0.5 mm D-flat (4.5 across) for the grubs; 625 crank stands, rhombic gears, crank discs, nut flywheel b5. Print flat side down
- crankshaft-5x150-dflat: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x150-dflat.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x150-dflat.stl) — Ø5 × 150 crankshaft with a full-length 0.5 mm D-flat (4.5 across) for the grubs; 625 crank stands, rhombic gears, crank discs, nut flywheel b5. Print flat side down
- crankshaft-8x80-dflat: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-8x80-dflat.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-8x80-dflat.stl) — Ø8 × 80 crankshaft with a full-length 0.5 mm D-flat (7.5 across); tri-clamp crank frame 608s, crank webs, flywheels b8. Print flat side down
- crankshaft-8x100-dflat: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-8x100-dflat.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-8x100-dflat.stl) — Ø8 × 100 crankshaft with a full-length 0.5 mm D-flat (7.5 across); tri-clamp crank frame 608s, crank webs, flywheels b8. Print flat side down
- crankshaft-8x120-dflat: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-8x120-dflat.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-8x120-dflat.stl) — Ø8 × 120 crankshaft with a full-length 0.5 mm D-flat (7.5 across); tri-clamp crank frame 608s, crank webs, flywheels b8. Print flat side down
- tube-rod-5x3.4x80: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/tube-rod-5x3.4x80.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/tube-rod-5x3.4x80.stl) — Ø5 × Ø3.4 × 80 tube piston rod: into the piston plug socket, onto the rhombic lower yoke or the flexure collars; the Ø3 displacer rod runs inside
- tube-rod-5x3.4x120: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/tube-rod-5x3.4x120.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/tube-rod-5x3.4x120.stl) — Ø5 × Ø3.4 × 120 tube piston rod: into the piston plug socket, onto the rhombic lower yoke or the flexure collars; the Ø3 displacer rod runs inside
- tube-rod-5x3.4x160: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/tube-rod-5x3.4x160.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/tube-rod-5x3.4x160.stl) — Ø5 × Ø3.4 × 160 tube piston rod: into the piston plug socket, onto the rhombic lower yoke or the flexure collars; the Ø3 displacer rod runs inside
- pin-3x12: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x12.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x12.stl) — Ø3 × 12 pin: crank pin, wrist pin, link pivot
- pin-3x16: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x16.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x16.stl) — Ø3 × 16 pin: crank pin, wrist pin, link pivot
- pin-3x19: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x19.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x19.stl) — Ø3 × 19 pin: crank pin, wrist pin, link pivot
- pin-3x20: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x20.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x20.stl) — Ø3 × 20 pin: crank pin, wrist pin, link pivot
- spacer-3mm-t1: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-3mm-t1.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-3mm-t1.stl) — thrust spacer for a Ø3 shaft, 1 mm: sets the 1 mm gaps between tower, web, rod and flywheel
- spacer-3mm-t2: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-3mm-t2.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-3mm-t2.stl) — thrust spacer for a Ø3 shaft, 2 mm: sets the 1 mm gaps between tower, web, rod and flywheel
- spacer-3mm-t3: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-3mm-t3.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-3mm-t3.stl) — thrust spacer for a Ø3 shaft, 3 mm: sets the 1 mm gaps between tower, web, rod and flywheel
- spacer-3mm-t5: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-3mm-t5.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-3mm-t5.stl) — thrust spacer for a Ø3 shaft, 5 mm: sets the 1 mm gaps between tower, web, rod and flywheel
- spacer-5mm-t1: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-5mm-t1.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-5mm-t1.stl) — thrust spacer for a Ø5 shaft, 1 mm: sets the 1 mm gaps between tower, web, rod and flywheel
- spacer-5mm-t2: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-5mm-t2.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-5mm-t2.stl) — thrust spacer for a Ø5 shaft, 2 mm: sets the 1 mm gaps between tower, web, rod and flywheel
- spacer-5mm-t3: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-5mm-t3.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-5mm-t3.stl) — thrust spacer for a Ø5 shaft, 3 mm: sets the 1 mm gaps between tower, web, rod and flywheel
- spacer-5mm-t5: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-5mm-t5.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-5mm-t5.stl) — thrust spacer for a Ø5 shaft, 5 mm: sets the 1 mm gaps between tower, web, rod and flywheel
- spacer-8mm-t1: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-8mm-t1.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-8mm-t1.stl) — thrust spacer for a Ø8 shaft, 1 mm: sets the 1 mm gaps between tower, web, rod and flywheel
- spacer-8mm-t2: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-8mm-t2.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-8mm-t2.stl) — thrust spacer for a Ø8 shaft, 2 mm: sets the 1 mm gaps between tower, web, rod and flywheel
- spacer-8mm-t3: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-8mm-t3.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-8mm-t3.stl) — thrust spacer for a Ø8 shaft, 3 mm: sets the 1 mm gaps between tower, web, rod and flywheel
- spacer-8mm-t5: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-8mm-t5.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/spacer-8mm-t5.stl) — thrust spacer for a Ø8 shaft, 5 mm: sets the 1 mm gaps between tower, web, rod and flywheel

## How it fits

### Goes in or on
- [Stirling linkage fittings: rod clevises, shaft adapter, 625 crank stands, Ø3 crank discs, rhombic frame heads](https://xemstudio.com/objects/stirling-linkage-fittings/): Ø5 shafts in the 625 crank stands; Ø3 rods in the rod clevises
- [Tri-clamp power pistons and crank linkage: full-bore ring-less pistons, con-rods, crank webs and a clamp-on crank frame for 1.5, 2 and 3 in spools](https://xemstudio.com/objects/tri-clamp-power-pistons/): Ø8 shaft in the crank frame's 608s
- [Rhombic drive kit (Philips beta Stirling): twin crank gears, links, yokes, frame](https://xemstudio.com/objects/rhombic-drive-kit/): Ø5 gear shafts in the plates' 625s
- [Alpha V-twin frame for two 10 mL syringes: frame, crank disc and con-rods sized so it actually runs](https://xemstudio.com/objects/alpha-v-twin-frame/): Ø5 shaft in the boss; Ø3 × 20 crank pin
- [Tri-clamp displacers and engine heads: 1.5, 2 and 3 in spools](https://xemstudio.com/objects/tri-clamp-displacers-and-heads/): Ø3 displacer rod and the crank head's Ø3 shaft
- [LTD (low-temperature differential, coffee-cup) Stirling kit: plates, chamber ring, displacer, top plate with syringe cylinder](https://xemstudio.com/objects/ltd-coffee-cup-engine-kit/): Ø3 crankshaft in the 623 stands

### Connects to
- [Nut-weighted flywheels: Ø100–200 with hex pockets for M8, M10, M12, 3/8 and 1/2 in nuts](https://xemstudio.com/objects/nut-weighted-flywheels/): Ø3 / Ø5 / Ø8 hubs on the D-flat
- [Crank discs, connecting rods and flywheels for model engines](https://xemstudio.com/objects/crank-conrod-flywheel-kit/): crank discs and flywheels
- [Counterweighted crank discs, crank webs and bolt-on counterweights](https://xemstudio.com/objects/counterweighted-cranks/): crank discs and webs

### Alternatives
- [Shafts, D-flats, set-screw collars, E-clips (DIN 6799) and circlips (DIN 471)](https://xemstudio.com/objects/shaft-collars-clips-and-shafts/): steel shaft stock dimensions
- [Hobby brass tube (K&S), 1/16–21/32 in and 1–12 mm, telescoping](https://xemstudio.com/objects/brass-tube-ks/): brass tube rods
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/): steel Ø3 pins

### Also needed
- [Ball bearings, 683 to 6210 and flanged F6xx (ISO 15)](https://xemstudio.com/objects/ball-bearings-metric/): 623 (Ø3), 625 (Ø5), 608 (Ø8)
- [Set screws (grub screws), M3–M8 (ISO 4026)](https://xemstudio.com/objects/set-screws-metric/): M3 grubs on the flat

## Questions

**Can I 3D print a crankshaft for a Stirling engine?**

Yes for Ø5 and Ø8 shafts at model speeds: print the D-flat shaft lying flat, flat side down, 100 % infill.

**What diameter shafts does this library use?**

Ø3 for displacer rods, pins and the crank head's shaft; Ø5 for crankshafts in 625 bearings; Ø8 for the tri-clamp crank frame in 608s; a 5 mm tube with a Ø3.4 bore for piston rods that carry a displacer rod inside.

**Why a D-flat?**

So the M3 grub screws in the crank discs, webs and flywheels bear on a flat and the part cannot slip around the shaft. 0.5 mm deep, as on motor shafts.

## Fits with

- [Stirling linkage fittings: rod clevises, shaft adapter, 625 crank stands, Ø3 crank discs, rhombic frame heads](https://xemstudio.com/objects/stirling-linkage-fittings/)
- [Crank discs, connecting rods and flywheels for model engines](https://xemstudio.com/objects/crank-conrod-flywheel-kit/)
- [Nut-weighted flywheels: Ø100–200 with hex pockets for M8, M10, M12, 3/8 and 1/2 in nuts](https://xemstudio.com/objects/nut-weighted-flywheels/)
- [Tri-clamp power pistons and crank linkage: full-bore ring-less pistons, con-rods, crank webs and a clamp-on crank frame for 1.5, 2 and 3 in spools](https://xemstudio.com/objects/tri-clamp-power-pistons/)
- [Ball bearings, 683 to 6210 and flanged F6xx (ISO 15)](https://xemstudio.com/objects/ball-bearings-metric/)
- [Shafts, D-flats, set-screw collars, E-clips (DIN 6799) and circlips (DIN 471)](https://xemstudio.com/objects/shaft-collars-clips-and-shafts/)