HTD power pistons: Ø48.00 × 72 for the bored 2 in spool — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/htd-power-pistons/  (CC BY 4.0)
Basis: Exact geometry at the finished bore Ø48.00
Catalog version: 2026-10-20

Sizes: see table below
- Ring-less: the seal is the fit. Two 8 lands carry it, 0.4 relief between them, 72 long (1.5 × bore) so it cannot cock. The crown faces the working space (down).
- The con-rod runs beside the axis (x 10.5..15.5) between two cheeks; the displacer rod passes up the centre tube (main piston) without touching the con-rod. The offset puts a small tilting moment on the piston, which the 72 length carries.

part  od_mm  length_mm  centre_bore_mm  pin
piston-48-rod6  48.0  72.0  6.0  Ø5 at z 86, x 5..21

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/htd-power-pistons/index.json
API: https://xemstudio.com/api/geometry?object=htd-power-pistons