# Build list: Tri-clamp sealed diaphragm generator, 2 in

> What parts do I need to build a Tri-clamp sealed diaphragm generator, 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-sealed-diaphragm-generator/ · JSON: https://xemstudio.com/api/geometry?object=list-tri-clamp-sealed-diaphragm-generator · Plain text: https://xemstudio.com/objects/list-tri-clamp-sealed-diaphragm-generator/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 sealed, pressurised gamma Stirling generator in 2 in tri-clamp: a plain closed-end cup over a torch, a power membrane between the working space and a sealed cross, and a 2208 gimbal motor geared to the crank inside the cross, its leads out through a sealed pass-through.
- Numbers: Membrane 2 in at 12 mm: 11.33 mL swept · displacer Ø46 × 120 at 12 mm: 21.3 mL · dead volume 52.0 mL · swept / dead 0.218 · charge 2 bar gauge · Schmidt (600–700 K / 320 K): ±0.49–0.55 bar, 0.57–0.69 J per cycle · at 900 rpm about 4–8 W at the crank (West / Beale); 2208 gimbal generator at 2520 rpm, 19.7 V open circuit, about 2.1–5.5 W at 14–18 V out of 4–8 W at the crank

## Sizes

| subsystem | object | parts | qty | note |
|---|---|---|---|---|
| None | tri-clamp-sealed-generator-frame | sealed-generator-frame-2in | 1 | base, wall, gussets |
| None | tri-clamp-torch-stand | torch-stand-40 | 1 | on the base under the hot head, post toward +Y |
| None | socket-head-cap-screws-metric | shcs-m4x10 | 5 | torch stand (2) and shroud feet (3) to the base |
| None | set-screws-metric | set-m4x10 | 3 | centre the torch head in the stand ring |
| None | tri-clamp-burner-shroud | burner-shroud-2in | 1 | round the hot end, on its three feet |
| None | tri-clamp-cups | cup-2in-150 | 1 | the hot end: a plain closed-end 2 in × 150 spool, face up; the displacer inside |
| None | tri-clamp-hot-fin-sleeve | hot-fin-sleeve-2in-80x9 | 1 | optional heat exchanger: slides over the cup's closed end inside the shroud; without it the engine runs with less power |
| None | set-screws-metric | set-m4x4 | 3 | optional: hold the fin sleeve (only with the sleeve) |
| None | tri-clamp-jacket-shell | jacket-half-2in-56 | 2 | optional heat exchanger: round the cup under the clamp, the fill is the builder's choice; or cool the cold end any other way |
| None | tri-clamp-jacket-shell | jacket-port-cap | 2 | optional: one per jacket half (only with the jacket) |
| None | socket-head-cap-screws-metric | shcs-m4x30 | 4 | optional: jacket ears (only with the jacket) |
| None | hex-nuts-metric | nut-m4 | 4 | optional: jacket ears (only with the jacket) |
| None | hex-nuts-metric | nut-m4 | 2 | hanger ears |
| None | tri-clamp-displacer | displacer-shell-2in-120 | 1 | Ø46 × 120, 0.75 radial gap, 12 stroke |
| None | tri-clamp-displacer | displacer-cap-2in | 1 | closes the shell, holds the rod |
| None | stirling-crankshafts | crankshaft-3x60 | 1 | displacer rod (Ø3 × 60), through the membrane and the crosshead's guide |
| None | tri-clamp-through-rod-membrane | membrane-2in-hole5 | 1 | clamped between the hot cup and the cross, in place of a gasket |
| None | tri-clamp-diaphragm-crosshead | crosshead-2in-p29.25 | 1 | crankcase side of the membrane: Ø3 guide (the bleed), con-rod pin on its arm |
| None | tri-clamp-diaphragm-crosshead | backing-2in-m2-tapped | 1 | working side of the membrane, M2 tapped |
| None | socket-head-cap-screws-metric | shcs-m2x6 | 3 | heads on the crosshead, into the backing disc |
| None | sanitary-clamp-crosses | cross-2in | 1 | the crankcase: run vertical, branches along the crankshaft |
| None | tri-clamp-motor-mount-plate | motor-mount-plate-2in-2208 | 1 | on the top of the cross; the motor hangs from it |
| None | tri-clamp-port-cap | port-cap-2in-4x-npt18 | 1 | on the motor-mount plate |
| None | npt-thread-envelopes | npt-1-8-male | 4 | the 1/8 NPT stems of the fill valve, the pressure gauge, the relief valve and the sealed electrical pass-through (the bodies are the builder's choice) |
| None | tri-clamp-end-cap | tc-cap-2in-flat | 2 | close the two bearing plates |
| None | tri-clamp-gasket | tc-gasket-2in | 6 | cross–mount plate, mount plate–port cap, two cross–bearing plate, two bearing plate–end cap |
| None | tri-clamp-clamps | clamp-half-2in | 14 | seven joints, two halves each |
| None | socket-head-cap-screws-metric | shcs-m5x30 | 14 | clamp bolts |
| None | hex-nuts-metric | nut-m5 | 16 | clamp nuts (14), hanger bar (2) |
| None | tri-clamp-clamp-in-bearing-plate | bearing-plate-2in-623 | 2 | one in each branch, spigot inward |
| None | ball-bearings-metric | bearing-623 | 8 | bearing plates (4), con-rod eyes (4) |
| None | tri-clamp-cross-crank-webs | inner-crank-web-hub-r6 | 2 | −X on the displacer pin side, +X on the diaphragm pin |
| None | tri-clamp-cross-crank-webs | inner-crank-web-link-r6 | 1 | between the two pins, 90° apart |
| None | dowel-pins-metric | dowel-3x12 | 2 | displacer crank pin, displacer clevis pin |
| None | dowel-pins-metric | dowel-3x16 | 1 | diaphragm crank pin |
| None | dowel-pins-metric | dowel-3x10 | 1 | crosshead pin |
| None | connecting-rods-623 | conrod-40 | 1 | displacer, in its clevis gap |
| None | connecting-rods-623 | conrod-60 | 1 | diaphragm, beside the displacer clevis |
| None | rod-clevises | rod-clevis-3mm | 1 | on the displacer rod |
| None | stirling-crankshafts | crankshaft-3x80 | 1 | +X crankshaft: hub web to the pocket flywheel |
| None | displacer-rods | rod-3x100 | 1 | −X crankshaft: hub web to the pocket flywheel |
| None | tri-clamp-crankcase-flywheel | crank-flywheel-44x12-b3 | 2 | one on +X, one on −X outboard of the crank gear |
| None | tri-clamp-crankcase-flywheel | pocket-flywheel-42x8-b3 | 2 | one on each shaft end, in the bearing plate's pocket |
| None | tri-clamp-generator-step-up-gears | crank-gear-m1-42t-b3 | 1 | on the −X crankshaft beside the crank |
| None | tri-clamp-generator-step-up-gears | pinion-m1-15t-b6 | 1 | on the motor shaft, 2.8 : 1 |
| None | gimbal-motor-2208-envelope | gimbal-motor-2208-envelope | 1 | the generator: 2208 gimbal-class outrunner, KV 128, envelope at its published size |
| None | tri-clamp-generator-step-up-gears | pinion-adaptor-2208 | 1 | bolted to the motor's rotor top; carries the pinion |
| None | socket-head-cap-screws-metric | shcs-m2x4 | 4 | adaptor to the rotor top |
| None | countersunk-screws-metric | csk-m3x6 | 4 | motor base to the mount face, heads flush |
| None | shaft-spacers | spacer-3mm-t1 | 6 | each side: hub web to flywheel or gear, flywheel to inner 623, outer 623 to pocket flywheel |
| None | set-screws-metric | set-m3x3 | 5 | hub webs (2), pocket flywheels (2), pinion (M3 × 3: ends inside the tooth root) |
| None | set-screws-metric | set-m3x4 | 2 | displacer cap, rod clevis |
| None | set-screws-metric | set-m3x10 | 3 | flywheel discs and crank gear, down their radial holes |
| None | spool-hanger-collars | hanger-2in-tab | 1 | on the cross's lower run, bar to the wall |
| None | spool-hanger-collars | hanger-2in-plain | 1 | closes the hanger |
| None | socket-head-cap-screws-metric | shcs-m4x20 | 2 | hanger ears |
| None | socket-head-cap-screws-metric | shcs-m5x25 | 2 | hanger bar through the wall |

## 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 (post toward +Y) with two M4 × 10, torch head in the ring with three M4 set screws; shroud on its three feet with M4 × 10.
2. Displacer: shell and cap, the Ø3 × 60 rod right through the cap (flush with its spigot face) on the cap's grub.
3. Membrane stack: backing disc under the membrane, crosshead hub on top, three M2 × 6 from the hub into the backing disc; Ø3 × 10 pin pressed in the hub's arm.
4. Optional fin sleeve: drop it into the shroud. Cup face up through the shroud's lid (and into the sleeve); displacer in; the rod up through the membrane stack; membrane on the cup's face; cross (branches along the shaft line) on top; clamp. Spool hanger on the cross's lower run, bar to the wall with two M5 × 25. Sleeve's three M4 set screws through the shroud's exhaust windows. Optional jacket halves round the cup with four M4 × 30, port caps in.
5. Crank: con-rods with their 623s; displacer con-rod (40) in the rod clevis on a Ø3 × 12; clevis onto the rod; diaphragm con-rod (60) on the crosshead pin. Hub web on the −X shaft with its grub, displacer pin through it and the displacer con-rod, link web, diaphragm pin through the link web and the diaphragm con-rod, hub web on the +X shaft over the pin.
6. Spacers, the crank gear and flywheel discs on the shafts; each bearing plate with its two 623s over its shaft and into its branch with a Type B gasket and clamp; pocket flywheel on each shaft end; Type B gasket and flat end cap on each plate, clamp.
7. Motor: adaptor on the rotor top with four M2 × 4, pinion on its stub with the grub; base to the mount face with four M3 × 6 countersunk; leads up through the plate's bore. Type B gasket, motor-mount plate onto the top of the cross with the pinion in mesh, clamp.
8. Leads through the sealed pass-through in the port cap; Type B gasket and port cap on the mount plate, clamp; fill valve, gauge and relief valve in the other ports. Charge slowly (see the questions below).

All printed STLs: https://xemstudio.com/objects/list-tri-clamp-sealed-diaphragm-generator/stl-list.txt

## Questions

**What parts do I need for the tri-clamp sealed diaphragm generator?**

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

**How much electricity does it make?**

The engine should give about 4–8 W at the crank at 900 rpm (West and Beale numbers 3.9–7.7 W). The 2208 gimbal motor turns 2520 rpm and makes 19.7 V open circuit; after the gears (1–3 %), its drag (0.3–1.6 W, estimated) and its 14.4 Ω winding, about 2.1–5.5 W reaches the leads at 14–18 V and 0.12–0.39 A: a bridge rectifier and a buck converter rated for the open-circuit voltage make USB 5 V from it.

**Why this motor and 2.8 : 1?**

In a generator the winding loss is (torque / motor constant)², and the gears divide the torque, so the most gearing that fits wins. The motor can lies over the crank and the crank gear has to fit the 2 in bore: 42 : 15 at module 1 is the most that fits a Ø27.5 can. Of the low-KV motors with published size, KV and resistance that fit, the 2208 gives the most watts at a voltage a buck converter takes; the 2212 drone motor gives a little more power but only about 2.5 V. Driven straight from the crank (1 : 1) any of them would turn most of the power into winding heat.

**What pressure, and how do I charge it?**

2 bar gauge of air or helium through the fill valve on the port cap. Charge slowly: the working space fills only through the bleed along the displacer rod (time constant about 8 min at 5 µm clearance, 64 s at 10 µm), and until the two sides meet, the membrane carries the difference. Let the gauge settle between small steps; let it down the same way.

**Air or helium?**

The Schmidt work per cycle is the same at the same pressure and temperatures. Helium flows through the 0.75 mm gap and the bleed with less loss and lets the engine turn faster, which raises the generator's voltage.

**Why does the displacer rod pass through the membrane?**

The working space and the crankcase meet at one joint, the membrane's. The displacer sits under the membrane, so its rod comes up through the membrane's centre and guides in the crosshead hub, whose bore is also the bleed.

**Where can the gas leak out?**

There is no shaft seal. Every joint is a clamped gasket, the clamped membrane, or a threaded port; the motor leads leave through a sealed pass-through in one of the ports.

**Is the flywheel big enough?**

The cycle swings about 0.16 J. The two discs, the crank gear, the two pocket flywheels and the motor's can (counted 7.8 times through the gears) hold the speed swing to about 12–27 % at 900 rpm (disc density 7.8 to 2.7 g/cm³); it falls with the square of the speed.

## Fits with

- [Hot-end fin sleeve for a 2 in tri-clamp cup: slide-on ring fins, set-screw held](https://xemstudio.com/objects/tri-clamp-hot-fin-sleeve/)
- [Tri-clamp cups: closed-end spools (ferrule on a capped tube), 1.5, 2 and 3 in](https://xemstudio.com/objects/tri-clamp-cups/)
- [Burner shroud for a 2 in tri-clamp hot end](https://xemstudio.com/objects/tri-clamp-burner-shroud/)
- [Tri-clamp membrane with a centre hole: 2 in, for a rod through the diaphragm](https://xemstudio.com/objects/tri-clamp-through-rod-membrane/)
- [Diaphragm crosshead hub and tapped backing disc: 2 in, with the displacer rod through the centre](https://xemstudio.com/objects/tri-clamp-diaphragm-crosshead/)
- [Clamp-in bearing plate: 2 in, two ISO 2852 faces, spigot with two 623 seats](https://xemstudio.com/objects/tri-clamp-clamp-in-bearing-plate/)
- [Step-up gears for a generator inside a 2 in tri-clamp cross: 42 : 15, module 1](https://xemstudio.com/objects/tri-clamp-generator-step-up-gears/)
- [Motor-mount plate for a 2 in tri-clamp cross: clamps between two faces, holds a 2208 gimbal motor inside](https://xemstudio.com/objects/tri-clamp-motor-mount-plate/)
- [Crankcase flywheels: Ø44 × 12 disc and Ø42 pocket flywheel on a Ø3 shaft, inside a 2 in tri-clamp fitting](https://xemstudio.com/objects/tri-clamp-crankcase-flywheel/)
- [Tri-clamp port cap: 2 in, four 1/8 NPT ports for a fill valve, a gauge, a relief valve and an electrical pass-through](https://xemstudio.com/objects/tri-clamp-port-cap/)
- [Frame for the 2 in tri-clamp sealed diaphragm generator](https://xemstudio.com/objects/tri-clamp-sealed-generator-frame/)
- [Build list: Tri-clamp cross diaphragm gamma, 2 in](https://xemstudio.com/objects/list-tri-clamp-cross-diaphragm-gamma/)