LTD Stirling bottom plate, Ø120 and Ø170 — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/ltd-bottom-plate/  (CC BY 4.0)
Basis: Same outline and M3 hole circle as the LTD top plate and chamber ring; M3 clearance Ø3.4 (ISO 273)
Catalog version: 2026-10-20

Sizes: see table below
- The hot plate of the LTD engine: the cup or the hand warms it and the heat goes through it into the air in the chamber.
- Ø120 × 3 for the 100 chamber, Ø170 × 3 for the 150, with 6 × Ø3.4 on a Ø112 / Ø162 circle (at 30°, 90°, …) matching the chamber ring and top plate; an M3 × 12 from below goes into each tapped ring hole.

file  plate  holes  screw circle  centre mark
ltd-100-bottom-plate  Ø120 × 3  6 × Ø3.4  112  3.2
ltd-150-bottom-plate  Ø170 × 3  6 × Ø3.4  162  3.2

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine
- James R. Senft: An Introduction to Low Temperature Differential Stirling Engines — book — Moriya Press [verify license at link] — https://www.stirlingengine.com/
- 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/ltd-bottom-plate/index.json
API: https://xemstudio.com/api/geometry?object=ltd-bottom-plate