# Tube piston rods Ø5 × Ø3.4

> What tube piston rod lets the displacer rod pass through the piston?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: Ø5 OD tube with a Ø3.4 bore, so the Ø3 displacer rod passes inside without touching
- Page: https://xemstudio.com/objects/tube-piston-rods-5mm/ · JSON: https://xemstudio.com/api/geometry?object=tube-piston-rods-5mm · Plain text: https://xemstudio.com/objects/tube-piston-rods-5mm/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

- Ø5 OD × Ø3.4 ID tubes, 80, 120 and 160 long, 0.3 chamfers on both ends.
- The OD seats in the piston plug's Ø5 socket and in the rhombic lower yoke or the flexure hub collars; the Ø3 displacer rod runs inside with 0.2 mm radial gap by design.
- Wall thickness 0.8.

## 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 | all |
| tube rod bore | Ø3.4 | Ø3 rod (no contact) | designed | tube-rod-* |
| tube rod OD | Ø5 | piston plug socket / yoke / collars | slide | tube-rod-* |

## Sizes

| file | OD | ID | length |
|---|---|---|---|
| tube-rod-5x3.4x80 | 5 | 3.4 | 80 |
| tube-rod-5x3.4x120 | 5 | 3.4 | 120 |
| tube-rod-5x3.4x160 | 5 | 3.4 | 160 |

## Where the files are

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

## Free STEP/STL (3 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/tube-piston-rods-5mm/index.json

- 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

## How it fits

### Goes in or on
- [Tri-clamp flexure head: ISO 2852 cap with Ø60, Ø80 and Ø100 flexure seats](https://xemstudio.com/objects/tri-clamp-flexure-head/): Ø5 OD in the piston plug socket

### Connects to
- [Rhombic drive crank gear, module 1.5, 44 T, 7 mm throw](https://xemstudio.com/objects/rhombic-crank-gear/): Ø5 tube on the lower yoke
- [Rod clevises for a Ø2 or Ø3 rod or a Ø5 tube, 5 mm gap](https://xemstudio.com/objects/rod-clevises/): rod-clevis-5mm-tube socket

### Also needed
- [Displacer rods Ø2 × 60, 78, 100 and 180, Ø3 × 100, 150 and 200](https://xemstudio.com/objects/displacer-rods/): Ø3 rod runs inside

## Questions

**Why is the piston rod a tube?**

In a beta or free-piston engine the displacer rod passes through the piston: the Ø3 rod runs inside the Ø3.4 bore of the Ø5 tube.

**What does the tube rod connect to?**

The piston plug socket (Ø5) at one end; the rhombic lower yoke, the flexure hub collars or the 5 mm tube rod clevis at the other.

## Fits with

- [Displacer rods Ø2 × 60, 78, 100 and 180, Ø3 × 100, 150 and 200](https://xemstudio.com/objects/displacer-rods/)
- [Rod clevises for a Ø2 or Ø3 rod or a Ø5 tube, 5 mm gap](https://xemstudio.com/objects/rod-clevises/)
- [Rhombic drive crank gear, module 1.5, 44 T, 7 mm throw](https://xemstudio.com/objects/rhombic-crank-gear/)
- [Tri-clamp flexure head: ISO 2852 cap with Ø60, Ø80 and Ø100 flexure seats](https://xemstudio.com/objects/tri-clamp-flexure-head/)
- [Tri-clamp power piston: ring-less full-bore pistons Ø34.8, Ø47.5 and Ø72.9](https://xemstudio.com/objects/tri-clamp-power-piston/)