Mecha Shark 250

An armoured shark whose tail curls on 5 ball joints. Keep scrolling and it bends, one joint at a time, from the body back to the fin.

Out of open water

Faceted navy armour, 9.8 in from nose to fin. The tail is 4 segments and a fin on 5 ball joints, which swing side to side as well as up and down.

One rigid body

Head, dorsal fin and both pectoral fins print as a single part. Nothing on the body moves: all of the motion lives behind it.

Joint 1, at the body

A 12.5 mm ball on the body's tail stem sits in the C-shaped socket of the first segment. Pitch it 8° and the tail starts to drop.

Joints 2, 3 and 4

Each segment carries the ball for the next, a size smaller every time. The display pose gives them 12°, 14° and 14°.

Joint 5, the tail fin

The smallest ball, 9 mm, carries the caudal fin at 12°. Add the five together and the tail curls 60° from straight.

Onto its stand

The support's peg keys into a slot in the belly and its foot keys into the oval base, with no screws. Posed, it stands 9.7 × 5.2 × 6.0 in.

The printed shark seen from behind and to one side: body level on its grey support, the tail dropping in a long curve past the navy oval base to a forked fin just above the desk.

Banking, on your desk

This is the pose it was drawn in: the body level on its support and the tail swept down past the stand, as if the shark were turning under you.

None of it is fixed. Each joint was checked in CAD to 15° up, down and to either side, so the tail can lie straight, hook the other way, or curl tighter than this.

Where the 60° comes from

Five joints, each a ball that clips into a C-shaped socket on the next part. The balls shrink towards the tip, so the tail tapers the way a real one does.

Joint	Joins	Ball	Display pose
1	Body to segment 1	12.5 mm	8°
2	Segment 1 to 2	12 mm	12°
3	Segment 2 to 3	11 mm	14°
4	Segment 3 to 4	10 mm	14°
5	Segment 4 to tail fin	9 mm	12°
Total curl			60°

Side view of the printed shark on its stand, the tail bending down segment by segment until the forked fin points at the desk. — Side on, the display pose: each segment drops a little further than the one before it.

Diagram: the shark's eight parts pulled apart. Body, four tail segments and tail fin in a row, the curved support and oval base below. — The eight parts, pulled apart. A CAD diagram, not a photograph.

8 parts, one way together

Seat the support's foot in the slot in the base.
Press the peg at the top of the support into the slot under the belly.
Clip the tail on in order, from the body back to the fin. Hold each segment by its neck and socket while you press, not by the thin fin tips.

The joints are drawn with 0.20 mm of clearance around each ball.

Mecha Shark 250

Posed on its stand: 9.7 × 5.2 × 6.0 in
Straight, nose to fin: 9.8 in
Weight: 5.2 oz
Printed parts: 8
Ball joints: 5, each checked to 15° in pitch and in yaw
Ball sizes: 12.5 mm at the body to 9 mm at the fin
Print time: 15.1 hours

Joint fit, grip and wear have been checked in CAD, not yet on a printed shark. The motion checks cover each axis on its own, not both at once.