# Build list: Tri-clamp rolling-diaphragm Ringbom, 2 in

> What parts do I need to build a Tri-clamp rolling-diaphragm Ringbom, 2 in?

- Category: Stirling engines › Assembled engines
- Kind: List / guide
- Basis: Every part is a free STEP/STL on this site or a standard part with its own page; quantities are the full count, every screw, nut, pin, gasket and clamp.
- Page: https://xemstudio.com/objects/list-tri-clamp-rd-ringbom/ · JSON: https://xemstudio.com/api/geometry?object=list-tri-clamp-rd-ringbom · Plain text: https://xemstudio.com/objects/list-tri-clamp-rd-ringbom/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- The simplest mechanism I could draw: one crank, one con-rod, and a free displacer that the gas pressure itself moves between two stops.
- Numbers: Numbers (Schmidt with the free displacer taken as a 90° sinusoid, the optional finned cooler on; a real Ringbom's timing depends on speed and load): power swept 20.0 mL, displacer swept 29.9 mL, dead volume 58 mL (swept/dead 0.34); Schmidt work at 650 / 320 K and 1 bar mean 0.33 J per turn (1.38 pressure ratio, ±16 kPa); shaft power about 0.3–1.1 W at 200–400 rpm (0.25–0.5 of Schmidt).

## Sizes

| subsystem | object | parts | qty | note |
|---|---|---|---|---|
| None | tri-clamp-rd-engine-frame | rd-frame-2in | 1 | base, wall, gussets |
| None | tri-clamp-torch-stand | torch-stand-40 | 1 | on the base, post toward +Y; the heat source is a torch flame 40 mm under the cup |
| None | socket-head-cap-screws-metric | shcs-m4x10 | 2 | torch stand to the base |
| None | set-screws-metric | set-m4x10 | 3 | centre the torch head in the stand ring |
| None | tri-clamp-cups | cup-2in-150 | 1 | the hot end and displacer cylinder in one piece: no joint near the flame |
| None | spool-hanger-collars | hanger-2in-tab | 1 | on the cup under the top clamp; bar to the wall |
| None | spool-hanger-collars | hanger-2in-plain | 1 | closes the hanger |
| None | socket-head-cap-screws-metric | shcs-m5x25 | 2 | hanger bar through the wall |
| None | socket-head-cap-screws-metric | shcs-m4x20 | 2 | hanger ears |
| None | hex-nuts-metric | nut-m4 | 2 | hanger ears |
| None | tri-clamp-finned-cooler | cooler-half-2in-56 | 2 | optional: clamp-on fin halves on the cup under the hanger (the cold end of the displacer cylinder); without them the engine runs with less power, or cool that part of the cup any way you like |
| None | socket-head-cap-screws-metric | shcs-m4x30 | 4 | optional: cooler ears (only with the cooler) |
| None | hex-nuts-metric | nut-m4 | 4 | optional: cooler ears (only with the cooler) |
| None | rolling-diaphragm-top-hat | rd-diaphragm-1.50-h1.50 | 1 | 1.50 in bore, 1.50 in high, flat flange: clamped in the joint in place of a gasket |
| None | tri-clamp-rd-power-head | rd-power-head-2in | 1 | standard 2 in clamp face, Ø38.10 cylinder, bushing seat, crank tower |
| None | tri-clamp-rd-power-head | rd-seat-ring-2in | 1 | in the head's face recess, behind the diaphragm flange |
| None | tri-clamp-clamps | clamp-half-2in | 6 | 3 joints, two halves each |
| None | socket-head-cap-screws-metric | shcs-m5x30 | 6 | clamp bolts |
| None | hex-nuts-metric | nut-m5 | 8 | clamp nuts (6), hanger bar (2) |
| None | sleeve-bushings | bushing-5x8x12 | 2 | back to back in the head's Ø8 seat: guide the tube rod |
| None | tri-clamp-rd-piston | rd-piston-2in | 1 | Ø33.27, never touches the bore |
| None | tri-clamp-rd-piston | rd-retainer-26-blind | 1 | clamps the diaphragm head on the crown |
| None | button-head-screws-metric | button-m3x8 | 3 | retainer screws into the crown |
| None | tube-piston-rods-5mm | tube-rod-5x3.4x80 | 1 | piston to yoke, through the bushings |
| None | tri-clamp-rd-yokes | rd-yoke-tube5 | 1 | on the tube rod's end |
| None | set-screws-metric | set-m3x3 | 1 | tube yoke grub |
| None | connecting-rods-623 | conrod-80 | 1 | power |
| None | counterweighted-crank-discs | cw-crank-disc-stroke20 | 1 | 20 mm stroke, overhung on the shaft end |
| None | stirling-crankshafts | crankshaft-5x80-dflat | 1 | disc face to flywheel hub |
| None | shaft-spacers | spacer-5mm-t5 | 1 | disc hub to the front bearing |
| None | shaft-spacers | spacer-5mm-t1 | 1 |  |
| None | ball-bearings-metric | bearing-625 | 2 | in the tower |
| None | shaft-collars | collar-5mm | 1 | behind the tower |
| None | nut-pocket-flywheels | flywheel-150-m10-b5 | 1 | on the shaft's far end |
| None | hex-nut-weights | nut-m10 | 18 | one in each rim pocket |
| None | sanitary-clamp-tees | tee-2in | 1 | standard 2 in equal tee: run upright on the cup, branch toward +X for the power head |
| None | tri-clamp-gasket | tc-gasket-2in | 2 | Type B: cup to tee, tee to gland cap |
| None | tri-clamp-rd-tee-inserts | rd-tee-insert-2in-ringbom | 1 | fills the tee's run between the two gasket lips |
| None | tri-clamp-rd-tee-inserts | rd-branch-insert-2in | 1 | fills the tee's branch; its spigot locates the run insert |
| None | tri-clamp-rd-gland-caps | rd-gland-cap-2in-ringbom | 1 | closes the top of the tee's run, carries the rod's gland |
| None | set-screws-metric | set-m5x6 | 1 | plug in the gland cap's M5 port (or a gauge or one-way valve) |
| None | tri-clamp-displacer | displacer-shell-2in-120 | 1 | Ø46 × 120, 0.75 radial gap, free: 18 mm between its stops |
| None | tri-clamp-ringbom-displacer-cap | ringbom-cap-2in-r8 | 1 | closes the shell, holds the Ø8 rod |
| None | metric-shafts | shaft-8x300 | 1 | the Ringbom rod: D-flat end in the cap, up through the tee insert and the gland |
| None | sleeve-bushings | bushing-8x12x20 | 1 | in the gland cap's top: the rod's close-running gland |
| None | shaft-collars | collar-8mm | 1 | on the rod between the cap top and the bridge: the stops |
| None | set-screws-metric | set-m4x4 | 2 | Ringbom cap and collar grubs |
| None | ball-bearings-metric | bearing-623 | 2 | one in each con-rod eye |
| None | dowel-pins-metric | dowel-3x12 | 2 | crank pin; tube-yoke stub pin |
| None | set-screws-metric | set-m3x4 | 4 | grubs: piston, crank disc, collar, flywheel |

## Where the files are

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

## Build order

1. Frame on the bench; torch stand on the base, post toward +Y.
2. Displacer: shell, Ringbom cap, rod with its D-flat in the cap (M4 grub). Drop it into the cup.
3. Hanger, hang the cup on the wall. Optional: cooler halves under the hanger.
4. Type B gasket on the cup, tee on it (branch toward +X), clamp. Run insert down the tee's run onto the lower gasket lip, rod up its rod way; turn it so its passage faces the branch; branch insert into the branch, spigot into the run insert's counterbore.
5. Type B gasket, gland cap (rod up through the 8 × 12 × 20 bushing), clamp; collar on the rod above the cap, under the bridge, at mid-travel (M4 grub). Plug or valve in the M5 port.
6. Piston: diaphragm head on the crown, blind retainer, three M3 × 8 button screws; tube rod in the socket.
7. Power head: bushings, seat ring, tube rod through the bushings, diaphragm flange on the tee's branch face, power head, clamp. Yoke and stub pin, con-rod, crank with its pin, flywheel.

All printed STLs: https://xemstudio.com/objects/list-tri-clamp-rd-ringbom/stl-list.txt

## Questions

**What is a Ringbom engine?**

50 parts, every one a free STEP/STL on this site; see the table and the build order on this page.

**Will it start by itself?**

No more than any Stirling engine: give the flywheel a spin once the cup is hot. If the displacer does not move, it is too heavy for the pressure swing.

**Can I make it crank-driven later?**

Yes: the gamma uses the same cup, tee, frame and power head.

**Do I need the finned cooler?**

No. It is an optional heat exchanger that clamps on the plain cup; without it the engine runs with less power. Any cooling of the top of the cup works, even a wet rag. The numbers above assume the cold end held near 320 K.

## Fits with

- [Tri-clamp gland caps, 2 in: end caps with a rod gland, an M5 port and a stop bridge or bell-crank post](https://xemstudio.com/objects/tri-clamp-rd-gland-caps/)
- [Tee inserts, 2 in: volume fillers for the run and branch of a standard 2 in equal tee](https://xemstudio.com/objects/tri-clamp-rd-tee-inserts/)
- [Sanitary clamp tees and short-outlet tees (7MP, 7MPS): ½ to 4 in](https://xemstudio.com/objects/sanitary-clamp-tees/)
- [Ringbom displacer cap for an 8 mm rod, 2 in shell displacer](https://xemstudio.com/objects/tri-clamp-ringbom-displacer-cap/)
- [Top-hat rolling diaphragm, 1.50 in bore, flat flange: the one that clamps in a 2 in tri-clamp joint](https://xemstudio.com/objects/rolling-diaphragm-top-hat/)
- [Tri-clamp rolling-diaphragm power head, 2 in: standard clamp face, cylinder, rod guide and crank tower, with its diaphragm seat ring](https://xemstudio.com/objects/tri-clamp-rd-power-head/)
- [Frame for the rolling-diaphragm tri-clamp engines: base, wall, hanger and torch-stand mount](https://xemstudio.com/objects/tri-clamp-rd-engine-frame/)
- [Tri-clamp finned cooler: clamp-on halves for a 2 in tube](https://xemstudio.com/objects/tri-clamp-finned-cooler/)
- [Build list: Tri-clamp rolling-diaphragm gamma, 2 in](https://xemstudio.com/objects/list-tri-clamp-rd-gamma/)