Pressing oil takes very little power: a screw press holding 40 kN turned at 1 rpm needs only about 19 W, so a water wheel or animal is chosen to crush the seed, not to press it. A village pressing 2,079-4,158 kg of seed in a 180-hour season must crush 11.5-23.1 kg an hour, which at 15-60 Wh/kg is 173-1,386 W, within reach of one horse or a small stream, and needs two or three presses working in parallel.
Part of Oil Pressing at Scale
Connecting an oil press and seed crusher to a water wheel or animal gin: where the power goes, how many presses a season needs, and the drive designs that stay safe.
The Press Needs Force, The Crusher Needs Power
Power is force times speed, and a pressing screw moves very slowly. The carrier suggests a water wheel or animal driving a press through a cam, lever or wedge. Check what that power buys:
- Screw press. For a force F = 40 kN, a pitch p = 10 mm and a screw efficiency of 0.35, the torque is F x p / (2 x pi x 0.35) = 40,000 x 0.01 / 2.2 = 182 N-m. At 1 rpm (0.105 rad/s) the power is 182 x 0.105 = 19 W.
- Weighted lever press. Raising a 500 kg stone 0.3 m is 500 x 9.81 x 0.3 = 1.47 kJ; once every 10 minutes that is 2.5 W.
- Wedge press with stampers. A 100 kg stamper falling 0.5 m delivers 100 x 9.81 x 0.5 = 491 J a blow; lifted once every 5 seconds it takes 98 W. The Dutch oil mills used cam-lifted stampers to drive wedges, a historical design recalled here.
The pressing itself is a few watts to about a hundred watts. The torque is the hard part: 182 N-m on a screw means a big gear reduction (a wheel turning at about 5 rpm geared down further to 1 rpm), not a big motor.
Crushing Is The Real Load
Take the middle case for the village budget: 1,100-2,200 lb of oil a year from seed at 40% oil and 60% recovery needs 1,100 / 0.24 = 4,583 lb up to 2,200 / 0.24 = 9,167 lb of seed, which is 2,079-4,158 kg (Community Oil Budget). Pressed over a 30-day season at 6 hours a day, 180 hours:
- Rate: 2,079 / 180 = 11.5 kg/h up to 4,158 / 180 = 23.1 kg/h
- Crushing power, using the grain band of 15-60 Wh/kg as a stand-in (oil seeds have not been measured here; see Bushels per Hour by Power Source): 11.5 x 15 = 173 W up to 23.1 x 60 = 1,386 W
- Energy for the season: 2,079 x 15 = 31 kWh up to 4,158 x 60 = 250 kWh
A horse in a gin delivers 397-595 W at the stone and a small overshot wheel 775 W, so either can run the crusher; hand cranking at 50-100 W would need two to 28 people. The grain mill can do the crushing if its stones are set wide (the oil-pressing carrier says so), but a wet oily paste clogs fine furrows, so keep a separate coarse pair if you can.
How Many Presses
The carrier gives 15-30 minutes of pressing per batch and 5-10 lb of seed per pressing. At 10 lb (4.5 kg) every 30 minutes one press handles 9.1 kg an hour. To press 11.5-23.1 kg an hour needs 11.5 / 9.1 = 1.3 up to 23.1 / 9.1 = 2.5 presses, so build two or three, or bigger chambers sized against the force as in Manual Screw Press Construction.
Method: A Safe Powered Press
Step 1: Drive the crusher from the wheel or gin through a belt or gear train you can disengage (Clutches and Engagement).
Step 2: Drive the screw through a torque limiter. A slipping flat belt or a friction clutch (Friction Clutch, Belt Drive) set to slip a little above 182 N-m caps the force at the frame’s design load.
Step 3: Pack the chambers by hand, stopped, and warm the cake first.
Step 4: Run the pressing slowly until oil flow slows, then stop and back the screw out.
Common Mistakes
- Sizing the motor for the press. The press needs tens of watts; the crusher and the heater take the energy.
- No torque limit. A driven screw will keep turning until something breaks.
- Feeding the crusher with unclean seed. A stone chips the crushing faces.
A driven press cannot be stopped by hand
A screw press driven from a wheel or gin carries tens of kilonewtons and keeps pressing until the drive is stopped. Name the stop: a clutch or belt shifter within reach of the operator, and a torque limiter so that a jam slips instead of breaking the frame. Never reach into a chamber or past the plate while the drive is connected, and never stand in line with the screw. Seed dust is combustible: keep flame out and never test for dust with a flame.
What’s Next
- Learn next: Crushing and Heating (Expeller Method) - what happens to the seed before the press
- Combine with: Ram Press Alternative - a jack-driven press