# LTD Stirling top plate with syringe socket, Ø120 and Ø170

> What are the dimensions of the top plate of a coffee-cup (LTD) Stirling engine?

- Category: Stirling engines › Can & LTD engines
- Kind: Hardware
- Basis: Senft LTD gamma layout, sized in the assembled Ø100 engine on this site; syringe socket at the 10 mL barrel OD Ø15.9; rod bore at the 2 mm rod; M3 clearance Ø3.4 (ISO 273), M3 tap drill Ø2.5
- Page: https://xemstudio.com/objects/ltd-top-plate/ · JSON: https://xemstudio.com/api/geometry?object=ltd-top-plate · Plain text: https://xemstudio.com/objects/ltd-top-plate/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**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.

## Notes

- The cold plate of the LTD engine and its power cylinder mount. Ø120 (for the 100 chamber) or Ø170 (for the 150 chamber), 3 thick, with 6 × Ø3.4 on a Ø112 / Ø162 circle (at 30°, 90°, …) matching the chamber ring.
- At x −5 a Ø20 boss, 13 tall with the plate, has a Ø2 bore straight through for the 2 mm displacer rod (fit: run); the bore is the rod guide.
- At x 40 (45 from the rod guide, so the two con-rods can sit at the two ends of the crankshaft) a Ø21.9 boss rises to 20 mm with a Ø15.9 socket from 8 to 20 for a 10 mL syringe barrel (fit: socket) and a Ø10 port under it into the chamber: the barrel's closed end sits on the socket floor and its Luer tip ends flush with the plate's underside.
- Four Ø9 × 4 pads at (7.5, ±27) and (27.5, ±27) carry the two crank stands, each with an M3 tapped hole (Ø2.5) 6 deep.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| syringe socket | Ø15.9 | 10 mL syringe barrel | socket | ltd-100-top* |
| syringe socket | Ø15.9 | 10 mL syringe barrel | socket | ltd-150-top* |
| plate screw holes | Ø3.4 | M3 screw clearance (ISO 273) | designed | ltd-100-top* |
| plate screw holes | Ø3.4 | M3 screw clearance (ISO 273) | designed | ltd-150-top* |
| stand pad holes | Ø2.5 × 6 | M3 tap drill | designed | ltd-100-top* |
| stand pad holes | Ø2.5 × 6 | M3 tap drill | designed | ltd-150-top* |
| syringe port under the socket | Ø10 | syringe tip (no contact) | designed | ltd-100-top* |
| syringe port under the socket | Ø10 | syringe tip (no contact) | designed | ltd-150-top* |
| rod-guide bore | Ø2 × 13 | 2 mm displacer rod | run | ltd-100-top-plate-* |
| rod-guide bore | Ø2 × 13 | 2 mm displacer rod | run | ltd-150-top-plate-* |

## Sizes

| file | plate | screw circle | rod guide | syringe socket | height |
|---|---|---|---|---|---|
| ltd-100-top-plate-syringe | Ø120 × 3 | 112 | Ø2 × 13 at x −5 | Ø15.9 × 12 at x 40 | 20 |
| ltd-150-top-plate-syringe | Ø170 × 3 | 162 | Ø2 × 13 at x −5 | Ø15.9 × 12 at x 40 | 20 |

## Where the files are

- Wikipedia: [Stirling engine](https://en.wikipedia.org/wiki/Stirling_engine) — web — CC BY-SA 4.0 (text)
- James R. Senft: [An Introduction to Low Temperature Differential Stirling Engines](https://www.stirlingengine.com/) — book — Moriya Press (verify at link)
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (2 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/ltd-top-plate/index.json

- ltd-100-top-plate-syringe: [STEP](https://xemstudio.com/files/hardware/ltd-coffee-cup-engine-kit/ltd-100-top-plate-syringe.step) · [STL](https://xemstudio.com/files/hardware/ltd-coffee-cup-engine-kit/ltd-100-top-plate-syringe.stl) — top plate Ø120 × 3: rod guide boss at x -5 (Ø2 bore, 13 long through plate and Ø20 boss), 10 mL syringe socket at x 40 (Ø15.9 from 8 to 20 above the underside, Ø10 port below so the Luer tip ends flush), 4 stand pads Ø9 × 4 with M3 tapped holes 6 deep, 6 × Ø3.4 on a Ø112 circle
- ltd-150-top-plate-syringe: [STEP](https://xemstudio.com/files/hardware/ltd-coffee-cup-engine-kit/ltd-150-top-plate-syringe.step) · [STL](https://xemstudio.com/files/hardware/ltd-coffee-cup-engine-kit/ltd-150-top-plate-syringe.stl) — top plate Ø170 × 3: rod guide boss at x -5 (Ø2 bore, 13 long through plate and Ø20 boss), 10 mL syringe socket at x 40 (Ø15.9 from 8 to 20 above the underside, Ø10 port below so the Luer tip ends flush), 4 stand pads Ø9 × 4 with M3 tapped holes 6 deep, 6 × Ø3.4 on a Ø162 circle

## How it fits

### Parts that fit it
- [Coat-hanger wire Ø2.0 mm and paper-clip wire Ø1.0 mm](https://xemstudio.com/objects/coat-hanger-and-paper-clip-wire/): 2 mm rod through the Ø2 bore in the top plate (run)
- [LTD crank stand for a 623 bearing, axis 112 above the foot](https://xemstudio.com/objects/ltd-crank-stand/): 2 × M3 down onto the top plate
- [Displacer rods Ø2 × 60, 78, 100 and 180, Ø3 × 100, 150 and 200](https://xemstudio.com/objects/displacer-rods/): Ø2 rod in the top plate's Ø2 bore

### Goes in or on
- [LTD Stirling chamber ring, Ø100 and Ø150 × 20](https://xemstudio.com/objects/ltd-chamber-ring/): 6 × M3 on the Ø112 / Ø162 circle

### Connects to
- [LTD Stirling displacer Ø96 × 8 and Ø146 × 8](https://xemstudio.com/objects/ltd-displacer/): the displacer's 2 mm rod runs in the Ø2 bore
- [Plastic syringes 1–60 mL as pistons and cylinders](https://xemstudio.com/objects/plastic-syringes/): 10 mL barrel in the Ø15.9 socket
- [Syringe pistons: ring-less pistons with a con-rod fork for 10, 20 and 30 mL syringe barrels](https://xemstudio.com/objects/syringe-pistons/): power piston in that barrel

### Also needed
- [Hobby brass tube (K&S), 1/16–21/32 in and 1–12 mm, telescoping](https://xemstudio.com/objects/brass-tube-ks/): 2 mm rod

## Questions

**How does the displacer rod pass through an LTD top plate?**

Through a Ø2 bore straight through the plate and its Ø20 centre boss, 13 long, drawn at the 2 mm rod (fit: run).

**What syringe fits the LTD top plate?**

A 10 mL barrel (Ø15.9 OD) in the 12 mm deep socket; its Luer tip sits in the Ø10 port below and ends flush with the plate's underside.

## Fits with

- [LTD Stirling chamber ring, Ø100 and Ø150 × 20](https://xemstudio.com/objects/ltd-chamber-ring/)
- [LTD Stirling bottom plate, Ø120 and Ø170](https://xemstudio.com/objects/ltd-bottom-plate/)
- [LTD Stirling displacer Ø96 × 8 and Ø146 × 8](https://xemstudio.com/objects/ltd-displacer/)
- [LTD crank stand for a 623 bearing, axis 112 above the foot](https://xemstudio.com/objects/ltd-crank-stand/)
- [Plastic syringes 1–60 mL as pistons and cylinders](https://xemstudio.com/objects/plastic-syringes/)
- [Build list: LTD coffee-cup engine](https://xemstudio.com/objects/list-ltd-coffee-cup/)