# Mug LTD crank pedestal (one bearing block, two 623s)

> What holds the crankshaft above a small LTD Stirling engine?

- Category: Hardware › Stirling & thermoacoustic
- Kind: Hardware
- Basis: My geometry: crank axis 169 above the top plate, set by the 5 mL glass syringe (105 long) plus clevis and 45 mm con-rod; both cranks overhung, one each side of the block
- Page: https://xemstudio.com/objects/mug-ltd-crank-pedestal/ · JSON: https://xemstudio.com/api/geometry?object=mug-ltd-crank-pedestal · Plain text: https://xemstudio.com/objects/mug-ltd-crank-pedestal/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

- Both cranks are overhung: the flywheel crank on the displacer side and a crank disc on the syringe side, with a Ø3 × 30 shaft in two 623s in one 10 mm bearing block between them. No con-rod crosses the shaft, so nothing in the mechanism meets it at top dead centre.
- The post stands beside the syringe (y −27..−13) so the plunger clevis and barrel collar pass it; the foot's two arms reach round the syringe socket boss to two M3 × 8 at (35.5, ±20.5), through the top plate into tapped holes in the ring.
- The crank height comes from the glass syringe: its 105 mm barrel stands in the top plate, the plunger clevis pin is 12 above the plunger collar, and the con-rod is 45.

## 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 |
|---|---|---|---|---|
| bearing pockets | Ø10 × 4, one in each face of the block | 623 bearing OD 10 | press | all |
| shaft clearance | Ø5 | Ø3 shaft (no contact) | designed | all |
| foot holes | Ø3.4 | M3 clearance | designed | all |

## Sizes

| feature | value_mm |
|---|---|
| crank axis above top plate | 169.0 |
| bearing block | x 15.5..25.5 |
| bearings | 2 × 623 |

## Where the files are

- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/mug-ltd-crank-pedestal/index.json

- mug-ltd-crank-pedestal: [STEP](https://xemstudio.com/files/hardware/mug-ltd-crank-pedestal/mug-ltd-crank-pedestal.step) · [STL](https://xemstudio.com/files/hardware/mug-ltd-crank-pedestal/mug-ltd-crank-pedestal.stl) — crank pedestal: foot with two arms round the syringe boss (to x 38.5) with 2 × Ø3.4, post 10 × 14 beside the syringe, bearing block 10 thick at x 15.5..25.5 with a 623 pocket (Ø10 × 4) in each face and Ø5 between, axis 169 above the top plate

## Questions

**Why is the mug LTD so tall?**

The glass syringe is 105 mm long and stands upright in the top plate; the crank sits a con-rod length above its plunger.

## Fits with

- [Build list: Mug LTD (sits on a coffee mug)](https://xemstudio.com/objects/list-ltd-mug/)
- [LTD Stirling bottom plate, Ø120 and Ø170](https://xemstudio.com/objects/ltd-bottom-plate/)
- [LTD Stirling top plate with syringe socket, Ø120 and Ø170](https://xemstudio.com/objects/ltd-top-plate/)
- [Glass syringes 1–50 mL (all-glass, ground-glass plunger): barrel and plunger](https://xemstudio.com/objects/glass-syringes/)