Getting started together
Build a platform, connect the pump and pump once. The prepared parts fit the car, so no size or force adjustment is needed first. Quick buttons change loads, cylinders and pumps. Crane arm, two platforms and fine controls are expandable. Change only the lifting cylinder: does it require less force but more strokes? Two branches have independent loads, cylinders and valves. The force setting is an available upper limit, not a command to exert that force continuously. The goal stays in the yellow band; the workbench gives the next step.
Force and distance belong together
Pump force divided by pump area gives the available pressure. At the lifting piston, pressure acts over its area. Ideally, the force ratio equals the area ratio. Doubling diameter quadruples area. The pump must supply the liquid volume corresponding to the chosen lifting height.
What do valves do?
Check valves prevent liquid simply flowing backward on the return pump stroke. A reservoir supplies the next stroke. The visible release valve opens a return path to the reservoir: the load sinks and liquid returns. A disconnected line transmits no new pump pressure to the load.
Two cylinders on one pump
Both cylinders share a pressure circuit but do not automatically move equally. Required load force divided by piston area sets the pressure threshold. In this quasistatic model, the branch with the lower threshold moves first. At equal thresholds, volume divides equally; identical cylinders rise together. A piston at its maximum travel leaves further pump volume for the other branch, if the force is sufficient.
The crane arm
An ideal lever adds to the hydraulic cylinder. The travel ratio is load-arm length divided by cylinder-arm length. A ratio of two doubles load travel for the same cylinder stroke and requires twice the load force at the cylinder. Energy is conserved. The drawing uses an idealised lever with a moving support; joint geometry and side forces are not separately modelled. Cylinder travel and load travel therefore differ.
Steer two platforms
Each branch has a shut-off valve. A closed branch accepts no new pump volume and holds its height. Only open branches descend when the release valve opens. Lift one load, hold it, then move the other. With both branches open, required load force divided by piston area determines where volume flows first.
Compare fairly
Save a trial with the car and change only lifting-piston diameter. Compare required force and height after the same 15 strokes. Predict what becomes easier and what moves less far. Maximum available force and the separately displayed required force are different quantities.
Away from the screen
An adult can gently demonstrate with two tightly connected needle-free plastic syringes and water. Different syringe sizes make the force–distance relationship visible. Use small hand forces only; do not lift people or heavy objects.
Model and limits
The lab calculates piston areas, pressure, volume and work. Pump travel is adjustable from 5 to 25 cm. Motion is slow and quasistatic, with limited pump force, simplified seal friction and pump losses. Fast flow, flexible lines, leakage and air bubbles are not included. The gauge shows active pump-circuit pressure. When blocked, it is limited by available force and pump efficiency. Stroke count includes failed attempts. Disconnected lines transmit no new pressure, while check valves hold already raised loads. The release valve lowers them. Car travel is exaggerated visually; centimetre readings are authoritative. Parallel-branch flow losses and height-dependent pressure differences are omitted. Cylinder travel is limited to 32 cm; a lever may make load travel larger. Energy counts only actual delivered volume and mechanical work. This is not a real lifting-machine design tool.
Keep investigating
Write a prediction, save a finished trial as A, and change one part. Compare at equal stroke counts. Results retain predictions and list changed parts. Mission feedback names conditions to restore; free building remains available.