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Tri-clamp flexure head: ISO 2852 cap with Ø60, Ø80 and Ø100 flexure seats
How do I mount flexure bearings on a tri-clamp spool? · Hardware · basis: ISO 2852 cap face; pedestal Ø = tube OD; plate Ø = flexure OD + 16 with a flexure-OD × 1 seat and 3 × Ø3.4 on the flexure rim-hole circle (0.88 × OD)
Long Earth Society build part. The connecting parts of the tri-clamp free-piston engine. The engines
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. Mating features
- sizes
- 3 in table
Notes
- The head of the tri-clamp free-piston engine: it clamps on the spool's open ferrule and carries the piston's flexure stack (stack A).
- Base: 6 mm ISO 2852 cap, pedestal the tube's OD (38.1 / 50.8 / 76.2) to 14 mm so the clamp clears, then a plate 4 mm thick, Ø76 / Ø96 / Ø116. Overall 18 mm.
- On top: a seat Ø60 / Ø80 / Ø100 × 1 mm deep (the flexure OD) and three Ø3.4 holes on the flexure's rim-hole circle (Ø52.8 / Ø70.4 / Ø88). A centre window Ø19.2 / Ø23.6 / Ø28 (hub + 6) lets the rods through.
Sizes
| spool_in | flange_od_mm | plate_od_mm | flexure_seat_mm | rim_hole_circle_mm | window_mm | height_mm |
|---|---|---|---|---|---|---|
| 1.5 | 50.5 | 76 | Ø60 × 1 | 52.8 | 19.2 | 18 |
| 2 | 64.0 | 96 | Ø80 × 1 | 70.4 | 23.6 | 18 |
| 3 | 91.0 | 116 | Ø100 × 1 | 88.0 | 28.0 | 18 |
Mating features
Drawn at the exact size. Open press, slide, run and socket features by your process's clearance; leave designed gaps and clamp fits as drawn.
| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| flexure pocket in the head / ring | flexure OD | spiral flexure leaf rim | slide | fp-flexure-* |
| head face | ISO 2852 | ferrule face + Type B gasket | clamp | fp-flexure-head-* |
| rim holes (head, ring) | Ø3.4 | M3 screw clearance | designed | fp-flexure-* |
| head / ring window | hub + 12 (Ø29.6 on Ø80) | hub collars and their pinch-screw heads (no contact) | designed | fp-flexure-* |
Where the files are
Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.
| NASA NTRS | Free-piston Stirling convertor flexure bearing development and life testing | US Government work | |
| Long Earth Society | Tri-clamp Stirling engine builds | web, video | LES site |
| Wikipedia | Free-piston engine | web | CC BY-SA 4.0 (text) |
Free files
★ Free files 3 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json
| fp-flexure-head-1.5in | 1.5 in flexure head: ISO 2852 cap face, Ø38.1 pedestal clearing the clamp, Ø76 plate with a Ø60 × 1 pocket (= flexure OD), a Ø25.2 window for the hub collars and 3 × M3 (Ø3.4) on the Ø60 flexure's rim holes; the piston's stack A bolts on it | STEP · STL |
| fp-flexure-head-2in | 2 in flexure head: ISO 2852 cap face, Ø50.8 pedestal clearing the clamp, Ø96 plate with a Ø80 × 1 pocket (= flexure OD), a Ø29.6 window for the hub collars and 3 × M3 (Ø3.4) on the Ø80 flexure's rim holes; the piston's stack A bolts on it | STEP · STL |
| fp-flexure-head-3in | 3 in flexure head: ISO 2852 cap face, Ø76.2 pedestal clearing the clamp, Ø116 plate with a Ø100 × 1 pocket (= flexure OD), a Ø34 window for the hub collars and 3 × M3 (Ø3.4) on the Ø100 flexure's rim holes; the piston's stack A bolts on it | STEP · STL |
Plain text: sheet.txt · JSON: /api/geometry?object=tri-clamp-flexure-head
How it fits
Parts that fit it
Linear alternator housing for Ø80 and Ø100 flexureson standoffs on the flexure head's rim screws
Tube piston rods Ø5 × Ø3.4Ø5 OD in the piston plug socketGoes in or on
Tri-clamp spool, 1.5 and 2 inchISO 2852 face on the open ferruleConnects to
Planar spiral flexure bearing leavesleaf rim in the flexure-OD seat, 3 × M3
Flexure ring for the displacer stack3 × M3 standoffs to the ring above
Linear alternator moveralternator housing on the same three rim holesAlso needed
Tri-clamp clamp, two-boltclamp and gasket on the faceIn these build lists
Free-piston Stirling, 2 in tri-clampNo crank: piston and displacer each hang on a stack of spiral flexures, with a t…You might also need
Questions
What flexure size goes on a 2 inch tri-clamp spool?
Ø80 leaves on the 2 in flexure head (Ø96 plate); Ø60 on 1.5 in, Ø100 on 3 in.
How are the flexures held on the head?
The leaf rim sits in the 1 mm deep seat and three M3 screws pass the Ø3.4 holes on the Ø70.4 circle (2 in) through the stack's spacers and clamp plate.