3D-PRINTED FOUR-VANE PLA AIR MOTOR

This is a compact rotary vane air motor built entirely from PLA on an
A1 mini 3D printer. Four sliding vanes seal against the stator wall as
the rotor turns inside an eccentric bore. A typical run from a single
standard 24-inch party balloon is on the order of thirty seconds, depending
on how tightly the balloon is inflated and how well the vanes seal after
print tuning.

The rotor is 25 mm in diameter. The stator uses a 2 mm offset (eccentricity)
between the rotor axis and the cylindrical chamber so that successive
pockets expand and contract as the shaft rotates, converting the balloon’s
pressure into torque. The rotor body is 37 mm long, not counting the
axles that extend beyond the housing for mounting or hand-holding. There
are no separate ball or roller bearings: shafts run directly in printed
journals, so expect break-in wear and occasional re-lubrication if you run
it often.

About vane air motors in general: a vane motor is a positive-displacement
pneumatic machine. Pressurized air enters one side of the eccentric chamber;
each vane traps a volume of air, the pocket grows as the rotor turns (doing
work), and exhaust escapes when the pocket opens to the outlet port.
Industrial vane motors use hardened vanes, precision bores, and proper
seals; this model scales that idea down for education and fun. They are
often chosen where simplicity, stall tolerance, and spark-free operation
matter more than peak efficiency—this toy version trades efficiency and
sealing for printability and low part count.

 • Four sliding vanes; rotary vane (eccentric-cylinder) layout.
 • Intended run time ~30 s from one 24-inch balloon (your mileage may vary).
 • Rotor diameter: 25 mm; eccentric offset: 2 mm; rotor length: 37 mm
   (excluding axles).
 • All PLA; no purchased bearings—plain printed journals on the axles.
 • Good conversation piece for pneumatics, positive displacement, and
   eccentric-bore kinematics.

YouTube link: