A ram press uses a salvaged hydraulic bottle jack to push a piston into a perforated seed chamber, and it needs no screw to cut. A 2-tonne jack on a 10 cm bore gives 2.5 MPa and a 20-tonne jack gives 25 MPa, but the frame must be built for the jack’s full rated force (19.6 kN or 196 kN), far more than the 1,000 lb often quoted, and the jack’s hydraulic fluid must never touch the oil.
Part of Oil Pressing at Scale
Pressing oilseed with a hydraulic jack and a ram, as an alternative to a screw: the pressure it gives, the frame it needs, and how to keep the jack’s fluid out of the food oil.
A Jack Replaces The Screw, Not The Frame
The carrier says a car bottle jack mounted in a steel frame makes an effective hydraulic press. The jack makes the force with no thread to cut, which is its advantage where steel and a machine shop are scarce. It still pushes against a frame: the frame carries the jack’s full rated force as tension in the uprights and bending in the beam (Manual Screw Press Construction shows the same method).
Here ram means a piston pushed by a hydraulic jack. It is unrelated to a hydraulic ram pump, which is a water-lifting device.
What The Jack Gives
Force is the rating times 9.81. A 2-tonne jack is rated for 2,000 x 9.81 = 19.6 kN and a 20-tonne jack for 20,000 x 9.81 = 196 kN (bottle jacks in those ratings are common, recalled). The pressure on the cake is the force divided by the piston area.
| Jack | Force | 6 in (152.4 mm) bore, 0.01824 m2 | 10 cm bore, 0.00785 m2 |
|---|---|---|---|
| 2 tonne | 19.6 kN | 1.08 MPa | 2.5 MPa |
| 20 tonne | 196 kN | 10.8 MPa | 25 MPa |
The oil-crop page in the chemistry section notes a claim of 200 kg/cm2 being needed; 25 MPa on a 10 cm bore is 255 kg/cm2 (25 x 10^6 Pa / 98,100 Pa per kg/cm2), in range for a 20-tonne jack on a small bore (Oilseed Crops). Pressures here are in pascals; always check you are not mixing kilograms with newtons, which is a 9.81 times error.
The carrier’s 1,000 lb frame (4.45 kN) is far below even the 2-tonne jack’s 19.6 kN: 19.6 / 4.45 = 4.4 times, and 196 / 4.45 = 44 times for the large jack.
What You Need
- A bottle jack in good condition, with a rating known from its plate
- A frame designed for the rating: steel section or heavy oak, pinned and strapped
- A piston plate and a perforated chamber, 6 in or 10 cm bore
- A drain tray and a clean collecting vessel
Method: Building A Ram Press
Step 1: Choose the jack and read its rating and stroke. Do not guess; a bottle jack’s stroke is short, so the seed must compress within it.
Step 2: Build the frame for the full rating, with a safety margin, and fix the jack to it.
Step 3: Keep the fluid out of the oil. Put the jack above or beside the chamber with a separating plate, so a leaking seal drips on the frame and not into the oil. Use cloth guards and clean the plate before each pressing.
Step 4: Proof-test with no seed. Raise the jack to the design force with a solid block, standing to the side, and watch for movement.
Step 5: Press slowly. Pump gradually: the oil needs time to flow, as the carrier says.
Common Mistakes
- Exceeding the jack’s rating, or extending it to the end of its stroke under load, where it can tip or lose its seal.
- Letting hydraulic fluid contaminate the oil. It is not food.
- A frame sized to the old floor. It must take the jack’s rating.
A jack holds its load until it is released
A loaded jack stores up to 196 kN, and a failing frame or a jack that tilts under load throws metal and hot oil. Stand to the side, never over the chamber or in line with the piston, and keep a block under the platen as a stop. Open the release valve slowly. Hydraulic fluid is toxic: keep it out of the food oil. Seed dust is combustible, so keep open flame away and never test for dust with a flame.
What’s Next
- Learn next: Pressing and Extraction - using any press well
- Combine with: Screw Press Design - the screw alternative