Konglungen Tennisklubb
A community that happens to play tennis
Build an oscillating sand sifter from an old drill, an eccentric disc and a steel mesh basket. Let the machine do the work — while you do something else.
You fill the basket with sand, shake it back and forth, and after a few minutes your shoulders and back are done. The solution is simple: let a drill do the job.
The machine is built on a classic crank principle — the same principle that drives a steam locomotive or bicycle pedals. A drill rotates an eccentric disc, and a connecting rod converts that rotation into a steady back-and-forth motion. The sand basket shakes, fine sand falls through the mesh, and stones and twigs migrate out at the end.
Three simultaneous views — from the side, from the front and from above — show exactly how the eccentric mechanism converts rotation into oscillating motion. Adjust speed and stroke length using the controls below.
The machine will have to wait until winter; made a makeshift solution with rollers in a hurry :-).
Two drawings cover the complete machine. The overview shows how all parts connect seen from the side. The detail drawing isolates the eccentric mechanism — the critical assembly that converts rotation into oscillating motion
Overview — seen from the side. Carriage, rails, frame, eccentric disc and drill.
Eccentric mechanism — detail cross-section. Drill, shaft, bearings, eccentric disc (holes A/B/C) and connecting rod.
The base frame that holds the entire machine. Build from 48×98 mm timber or light steel profile. Working height approx. 80–90 cm.
Two parallel rails on top of the frame. The carriage slides back and forth along these.
The frame that holds the basket and slides along the rails. A slight forward tilt (5–10°) causes coarse material to migrate out at the front.
The drill rotates an eccentric disc via a shaft resting in two bearings. The eccentric bolt travels in a circle; the connecting rod transfers motion to the carriage.
Drill, shaft, two bearings, eccentric disc and connecting rod. Build this part correctly — the rest will follow.
Stroke length = 2 × eccentric radius. Drill all three holes in advance — you can then adjust without rebuilding anything.
| Hole | Radius from centre | Total stroke |
|---|---|---|
| A — recommended start | 20 mm | 40 mm |
| B | 30 mm | 60 mm |
| C | 40 mm | 80 mm |
Everything available at hardware stores or online industrial suppliers. Estimated total cost: 400–900 NOK depending on what you already have.
| Part | Specification | Qty | Note |
|---|---|---|---|
| Drill | Old cordless drill with low-gear and variable speed | 1 | A used one works fine |
| Shaft | M12 or ø12 mm round steel, 200–250 mm | 1 | Hardware / online |
| Ball bearings | 608ZZ or matching shaft diameter | 2 | Biltema / online |
| Bearing bracket | U-bracket, screw-mounted to frame | 2 | Hardware / online |
| Eccentric disc | 12 mm plywood, ø140–160 mm | 1 | Cut yourself from offcut |
| Eccentric bolt | M8 bolt with nut and washers | 3 | For holes A / B / C |
| Connecting rod | Flat steel strip 25×4 mm, ~300 mm long | 1 | Hardware |
| Pivot bolt (top) | M8 with nyloc nut | 1 | |
| Pivot bolt (bottom) | M8 with nyloc nut | 1 | |
| Rails | Steel tube ø25 mm, 2× 120 cm | 2 | Alternative: 48×98 timber |
| Carriage wheels | V-wheels / rubber wheels with bearings, ø40–50 mm | 4 | Biltema / online |
| Carriage frame | 48×98 mm timber, 4× 60 cm + 2× 110 cm | 6 pcs | Build yourself |
| Rubber feet | Ø30–40 mm, screw-mounted underneath | 4 | Biltema |
| Bolts / nuts | Assorted M6/M8, 30–60 mm | 1 bag | |
| Wire mesh basket | IKEA BOAXEL 60×40 cm | 1 | Alternative: welded mesh |
Too much speed is the most common mistake. The sand bounces uncontrollably and nothing is sifted. Start slow, increase gradually. Optimal: 2–4 strokes per second.
Fill with moderate amounts at a time. Wet, heavy sand places a large load on the drill and bearings. Start with a 5–8 cm layer.
A slack frame absorbs energy that should go into sifting. Minimum 48×98 mm timber, reinforce all corners.
The machine can walk across the floor when the eccentric forces kick in. Rubber feet at all corners are the most important fix. Add ballast weight on the frame.
Always use a shaft with two bearings. Take breaks — let the drill cool between long sessions.