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Stacked piston hydraulic unit

Three ring pistons stacked in one steel body, fed by a single port. A complete file set a machine shop can quote and cut from: 9 machined pieces, toleranced drawings and a machining guide covering every operation.

Tensioner prototype being manufactured in China. Arrival estimated 27 November 2026.

  • UK patent filed
  • PCT filed
  • CNC turning
  • Hydraulics
  • C45 / 40Cr steel
  • DFM review
machined pieces
9
machined pieces
unique parts
6
unique parts
drawing sheets
5
drawing sheets
turned and drilled
100%
turned and drilled
Stacked piston hydraulic unit: Quarter section of the assembly: three cups and three pistons stacked inside the body.
Quarter section of the assembly: three cups and three pistons stacked inside the body.
Stacked piston hydraulic unit: Assembled unit. One oil port, nothing welded.
Assembled unit. One oil port, nothing welded.
Stacked piston hydraulic unit: All 9 machined pieces laid out.
All 9 machined pieces laid out.

Bill of materials: 9 machined pieces

6 unique parts, each with its own STEP file and drawing. Repeat parts run from one program.

  • Body, CAD renderITEM 1

    Body

    C45 seamless tube

    Made from tube instead of solid bar, bored from one side in a single setup.

  • Cup, CAD renderITEM 2QTY 2

    Cup

    C45

    Face O-ring groove on the bottom, oil feed hole drilled from the OD.

  • Top cup, CAD renderITEM 2b

    Top cup

    C45

    Same program as the cup, plus one OD seal groove.

  • Plunger, CAD renderITEM 3QTY 3

    Plunger

    40Cr, Q+T

    Three identical pistons, all seal grooves on outside diameters.

  • Top ring, CAD renderITEM 4

    Top ring

    C45

    Threaded ring that clamps the stack. Thread cut to fit, no gauge needed.

  • Thrust sleeve, CAD renderITEM 5

    Thrust sleeve

    40Cr, Q+T

    Carries the full output force out of the unit.

Designed to be cheap to cut

  • Body machined from seamless tube, not solid bar: less material, less cutting time.
  • General tolerances everywhere except a short, listed set of sealing and fit features.
  • Fit on assembly: bores are measured, mating parts turned to suit. No grinding, honing or lapping.
  • No internal O-ring grooves. Every seal sits on an outside diameter or a flat face.
  • Only two drilled features in the whole unit. The oil gallery is a turned gap, not a drilled passage.
  • Repeat parts from one program: three cups and three identical pistons.

The complete file set

  • 01STEP model of the assembly plus one STEP per part
  • 02Five dimensioned PDF drawing sheets with BOM
  • 03Tolerance sheet for each part, listing only the controlled features
  • 04Machinist’s guide: stock sizes, operation route, assembly and test steps
  • 05Seal schedule with standard O-ring and backup ring sizes

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