2 in end cap with a 1/2 NPT transfer boss, two 1/4 NPT bosses and a spigot (transfer cap) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/tri-clamp-transfer-cap/  (CC BY 4.0)
Basis: ISO 2852 2 in face as on this site; 1/2 and 1/4 NPT per ASME B1.20.1; passages and spigot are design values
Catalog version: 2026-10-20

Sizes: see table below
- A fabrication spec: a solid 2 in end cap with a 1/2 NPT boss on its side, two 1/4 NPT bosses and a spigot that fills the joint's dead space. Two of them, on two cylinders 120 mm apart with their transfer bosses facing, join with two 1/2 NPT × 1/2 in tube fittings and a 64 mm length of 1/2 in tube: the gamma's transfer passage.
- Gas path: spigot face → Ø11 axial passage (off-centre) → the 1/2 NPT port → fitting → tube (bore 10.9). Volume of the whole transfer path about 22.2 mL; its friction is in the engine's numbers.
- The rod-gland version carries the displacer rod in two 6 × 10 × 10 sleeve bushings 46 mm apart. The NPT bosses take the working space's fill valve, gauge, relief valve and a plug.

feature  value
face  ISO 2852 2 in
spigot  Ø44.0 to 3.15 past the face
transfer boss  1/2 NPT, Ø30, face 28 from the axis, z 24
NPT  2 × 1/4 at z 24, y 13, ±X
gland  Ø10 seat z 30–86 (rod version)

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- ISO (via iTeh sample): ISO 2852 clamp liners: face profile and flange / groove diameters — PDF — standard excerpt; dimensions are facts — https://cdn.standards.iteh.ai/samples/7850/eb49c396488d408c8ced3e2961d76cf3/ISO-2852-1974.pdf
- ASME: BPE Bioprocessing Equipment (clamp fitting dimensions, tube OD and wall) — standard — ASME; dimensions are facts [verify license at link] — https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment
- ASME: ASME B1.20.1 Pipe Threads, General Purpose, Inch (NPT): 1/4-18 major Ø13.72, tap drill 7/16 in (11.1), L2 10.2 — standard — ASME; dimensions are facts [verify license at link] — https://www.asme.org/codes-standards/find-codes-standards/b1-20-1-pipe-threads-general-purpose-inch
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 2 parts): https://xemstudio.com/files/hardware/tri-clamp-transfer-cap/index.json
API: https://xemstudio.com/api/geometry?object=tri-clamp-transfer-cap