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

> What parts do I need to build a Tri-clamp rolling-diaphragm beta, 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-beta/ · JSON: https://xemstudio.com/api/geometry?object=list-tri-clamp-rd-beta · Plain text: https://xemstudio.com/objects/list-tri-clamp-rd-beta/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

- A torch-heated beta in two pieces of pressure vessel: a 2 in × 150 cup with the displacer, and the rolling-diaphragm power head straight on top of it, the displacer rod running up through the power piston.
- Numbers: Numbers (with the optional finned cooler; cold end taken at 320 K): power swept 20.0 mL, displacer swept 33.2 mL, dead volume 38 mL (swept/dead 0.52); Schmidt work at 650 / 320 K and 1 bar mean 0.47 J per turn (1.57 pressure ratio, ±23 kPa); shaft power about 0.6–2.3 W at 300–600 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 | 2 | 1 joint, two halves each |
| None | socket-head-cap-screws-metric | shcs-m5x30 | 2 | clamp bolts |
| None | hex-nuts-metric | nut-m5 | 4 | clamp nuts (2), 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-gland3 | 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 | tri-clamp-displacer | displacer-shell-2in-120 | 1 | Ø46 × 120, 0.75 radial gap, 20 stroke |
| None | tri-clamp-displacer | displacer-cap-2in | 1 | closes the shell, holds the rod |
| None | displacer-rods | rod-3x200 | 1 | displacer rod: up through the piston's gland and tube rod |
| None | tri-clamp-rd-yokes | rd-yoke-rod3 | 1 | on the displacer rod's top, stub pin toward +Y |
| None | tri-clamp-rd-link-webs | rd-link-web-r10-90 | 1 | on crank pin 1, carries pin 2 a quarter turn away |
| None | connecting-rods-623 | conrod-40 | 1 | displacer |
| None | ball-bearings-metric | bearing-623 | 4 | one in each con-rod eye |
| None | dowel-pins-metric | dowel-3x12 | 2 | stub pins in the two yokes |
| None | dowel-pins-metric | dowel-3x20 | 1 | crank pin 1: disc, power con-rod, link web |
| None | dowel-pins-metric | dowel-3x16 | 1 | crank pin 2: link web, displacer con-rod |
| None | set-screws-metric | set-m3x4 | 6 | grubs: displacer cap, rod yoke, 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, cap, Ø3 × 200 rod through the cap (grub). Drop it into the cup.
3. Hanger on the cup; hang the cup on the wall. Optional: cooler halves on the cup under the hanger, four M4 × 30 and nuts.
4. Piston: diaphragm head on the crown, gland retainer, three M3 × 8 button screws; tube rod in the socket (grub). Thread the displacer rod through the gland and the tube.
5. Power head: two bushings in the seat, seat ring in the face recess; tube rod up through the bushings so the piston sits in the bore; diaphragm flange on the cup's face, power head on top, clamp.
6. Tube yoke on the tube (grub), rod yoke on the rod (grub), stub pins in both. Crank: bearings, shaft, spacers, disc with pin 1, power con-rod, link web with pin 2, displacer con-rod; collar and flywheel with its nuts.

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

## Questions

**What parts do I need for the rolling-diaphragm beta?**

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

**Why no piston fit?**

The power piston is a rolling diaphragm: the piston is 2.41 mm clear of the bore all round and the diaphragm rolls between them.

**Where is the gasket at the top joint?**

The diaphragm's flange is the gasket, with the seat ring behind it.

**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

- [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/)
- [Rolling-diaphragm piston and head retainers, 2 in power head](https://xemstudio.com/objects/tri-clamp-rd-piston/)
- [Rod-end yokes with a side stub pin: Ø5 tube and Ø3 rod](https://xemstudio.com/objects/tri-clamp-rd-yokes/)
- [Link webs: a second crank throw on the first crank pin](https://xemstudio.com/objects/tri-clamp-rd-link-webs/)
- [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 cups: closed-end spools (ferrule on a capped tube), 1.5, 2 and 3 in](https://xemstudio.com/objects/tri-clamp-cups/)
- [Tri-clamp finned cooler: clamp-on halves for a 2 in tube](https://xemstudio.com/objects/tri-clamp-finned-cooler/)
- [Build list: Beta Stirling, rhombic drive, 2 in tri-clamp](https://xemstudio.com/objects/list-beta-rhombic-2in/)