A Sizing Rule for a Hand Lever Press: Achievable Pressure, Briquette Density and the Usable Density Window

This design paper derives a sizing rule for a hand lever press for fuel briquettes, from stated geometry and a stated sustainable operator force. The design is SIMULATED, NOT MEASURED. With an effort arm of 1.20 m, a load arm of 0.06 m (ratio 20), an operator force of 250 N and a mechanical efficiency of 0.85, the ram force is 4250.0 N and the pressure on a piston of diameter 0.060 m is 1.503 MPa. Under a stated exponential compaction law, that pressure produces densities of 899.8 kg per cubic metre for sawdust, 900.7 for charcoal fines and 605.7 for rice husk, in a standard briquette 0.060 m in diameter and 0.080 m long. The usable density window is stated as 550 to 1050 kg per cubic metre: below 550 the briquette crumbles in handling, and above 1050 it will not light reliably because its core is starved of oxygen. All three feedstocks fall inside the window with the reference press, and their modelled end-on burn durations are 10.0 h, 10.01 h and 6.73 h respectively. Inverting the compaction law gives the design rule directly: the lever ratio needed for any target density is the required pressure times piston area, divided by efficiency times operator force. A brief push at 400 N raises the pressure to 2.405 MPa and the sawdust density to 1018.8 kg per cubic metre, still inside the window but close to its top.