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Free-piston mover for a 2 in honed spool: piston and alternator magnets in one, Ø48.00 × 130

Name: Free-piston mover for a 2 in honed spool: piston and alternator magnets in one, Ø48.00 × 130 dimension sheet
Creator: Xem Studio
License: https://creativecommons.org/licenses/by/4.0/

How do I make a free piston that is also the alternator's moving magnet? · Hardware · basis: Ø48.00 to the honed spool; magnet rows and pitch from the alternator design in tools/gen_ta_power.py

Used in Long Earth Society builds. Thermoacoustic engine spool (aluminum)

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. Mating features

sizes: 6 in table

Notes

The piston and the alternator's moving part are one: a 12-sided core carries 4 rows of 12 block magnets (30 × 10 × 4, magnetised through 4), rows alternately N and S outward at 32 mm pitch, and a sleeve Ø48.00 / Ø47 slides over them and runs in the honed bore. The core is the magnets' return path, so it has to carry magnetic flux; what it and the sleeve are made of is the builder's choice within that.
The crown is closed; an M4 threaded rod screws into it from inside the Ø20 bore and carries the two flexure stacks below. Moving mass with the magnets, rod and hub parts: about 1.39 kg (core and sleeve counted at 7.8 g/cm³, magnets at 7.5).
Design stroke ±8 mm: the 30 mm magnet rows stay fully over their 14 mm coils that far.
Fits: sleeve OD is the clearance seal in the honed bore (run); the sleeve's bore slides over the core's flanges (press); the magnets sit on the flats (bonded, designed).

Sizes

feature	value
length	130
sleeve	Ø48.00 / Ø47
magnets	4 × 12 blocks 30 × 10 × 4
row pitch	32
moving mass	≈ 1.39 kg
design stroke	±8

Mating features

Drawn at the exact size. Open press, slide, run and socket features by your process's clearance; leave designed gaps and clamp fits as drawn.

feature	exact	mates with	fit	files
sleeve outside	Ø48.00 × 130	honed spool bore Ø48.00: clearance seal	run	mover-sleeve-*
sleeve bore	Ø47.00	mover core end flanges Ø47.00	press	all
flats	12 × 10 wide on r 18.66, 4 rows of 30 at 32 pitch	block magnets 30 × 10 × 4 (bonded)	designed	mover-core-*
crown hole	Ø3.3 × 6 (M4 tap drill) from the Ø20 bore	M4 threaded rod	designed	mover-core-*
core bore	Ø20 from the bottom face to the crown	M4 rod (no contact)	designed	mover-core-*

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Appl. Phys. Lett. (S. Backhaus, E. Tward, M. Petach)	Traveling-wave thermoacoustic electric generator, APL 85, 1085 (2004): a thermoacoustic-Stirling engine driving linear alternators, 18 % heat to electricity	web	journal article; cited verify
Applied Energy (Z. Wu, G. Yu, L. Zhang, W. Dai, E. Luo)	Development of a 3 kW double-acting thermoacoustic Stirling electric generator, 136, 866-872 (2014): three engines and three linear alternators in a loop, 5 MPa helium, 86 Hz, 1.57 kW electric, 16.8 %	web	journal article; cited verify
Xem Studio	tools/gen_ta_power.py: the network model and every dimension on this page	code	CC BY 4.0
Long Earth Society	Engine builds	web, video	LES site

Free files

★ Free files 2 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

mover-core-2in-130	mover core, 130 long: 12-sided body (flats r 18.66) between Ø47 × 2 end flanges, Ø20 bore from the bottom to an 8 mm crown, M4 tap drill Ø3.3 × 6 in the crown	STEP · STL
mover-sleeve-48x130	mover sleeve Ø48.00 / Ø47 × 130: the running surface	STEP · STL

Plain text: sheet.txt · JSON: /api/geometry?object=free-piston-mover-2in