Two hydraulic cylinders with the same bore produce equal force and move at the same speed under the same pressure

Two hydraulic cylinders with the same cross-sectional area, but different stroke lengths, connected to the same hydraulic pressure source. What happens? If you’re thinking like a mechanic or a student juggling the ASA topics, the answer is surprisingly clean: they produce equal force and they move at the same rate of speed. Let me unpack that a little so it sticks—and so you see why stroke length doesn’t change the picture at the moment of actuation.

The basics: pressure, area, and force

Think of hydraulic power as a simple equation you can trust: force = pressure × area. If the pressure pushing on the piston is the same, and the piston area is the same, both cylinders press with the same force. No mystery there. This is the kind of relationship you’d find sketched in any hydraulic handout or in the notes from the ASA topics that cover how fluids translate pressure into motion.

So with two cylinders sharing the same piston area, the moment you fire them from the same hydraulic source, they push with equal force. It doesn’t matter that one cylinder has a longer stroke than the other. The distance each piston can travel is a separate piece of the puzzle—one that comes into play after the initial push, not during the instant when pressure is applied.

Speed is a matter of flow, not just pressure

Here’s where people often pause, scratch their heads, and then smile when the light goes on. The speed at which a cylinder moves—its velocity during actuation—depends on how quickly fluid can fill and evacuate the cylinder, i.e., the flow rate, and the piston area. If both cylinders have the same cross-sectional area and are fed by the same flow rate, they’ll move at the same speed. Stroke length doesn’t change that instantaneous velocity; it only determines how far the piston can travel before reaching the end of its travel.

Let me explain in a more down-to-earth way. Imagine you have two identical water pistons in a closed system, both fed by the same pump. If the pump pushes, say, a fixed volume of hydraulic fluid per second into both cylinders, the piston in each cylinder has to move enough to accommodate that volume. Since the area is the same, the distance each piston must travel per unit of fluid moved is the same. So the speed—the rate of movement—lines up. The longer-stroke cylinder just has more room to go before it tops out; it doesn’t sprint faster or slower because of that extra length in the middle of the action.

Stroke length and its practical significance

Stroke length matters, but it’s about reach, not power or speed. A longer stroke means the piston travels a greater distance from fully retracted to fully extended. In a machine, that translates to the range of motion you can achieve, the ability to reach a distant component, or the capacity to compress a long load. Shorter strokes are great for compact spaces or rapid, short-range motions. The key point: stroke length changes the distance traveled, not the force exerted at a given moment, nor the speed of movement if the flow rate is the same.

This distinction is handy when you’re designing or troubleshooting hydraulic systems. If you swap a short-stroke cylinder for a long-stroke one, you don’t automatically change the push force or the speed. You change the travel path and the time it takes to reach the end of that path, assuming the flow rate and pressure stay the same.

A few caveats that won’t surprise anyone who’s gotten their hands dirty with real equipment

No real-world system is a perfect, frictionless ideal. Even with identical cylinders, a handful of factors can nudge the outcome:

• Friction and seals: The seal quality and the internal friction inside the cylinder walls add tiny resistances. In practice, these can slightly slow things down and create a small difference in measured speed if the loads differ or the fluid isn’t perfectly clean.

• Load and back pressure: If one cylinder is pushing a heavier load or encountering more resistance downstream, that cylinder may travel more slowly, even with the same flow rate. The speed isn’t guaranteed to be the exact same in every case when the load isn’t identical.

• Flow distribution: If you’re feeding two cylinders from the same source and through a common valve, slight differences in line length, fittings, or valve settings can cause tiny variations in how much flow each cylinder actually receives.

• Temperature and viscosity: Fluid properties creep into the equation. Warmer fluid is often less viscous and flows a bit easier, which can affect speed marginally, especially in high-precision work.

So yeah, under ideal conditions, equal force and equal speed are expected, but real-life quirks decide how perfectly those ideals hold up every day on the shop floor.

Relating this to what you’ll encounter in the topics

When you study the ASA materials, you’ll see this principle pop up again and again. You’ll meet the idea that hydraulic systems translate pressure into force through the piston area, and that the flow rate governs how fast movement occurs. It’s one of those foundational relationships that unlocks the rest of the puzzle: mass flow, valve sizing, system efficiency, and control strategies all ride on this relationship.

Here are a couple of quick, practical takeaways you can tuck away:

• If you’re checking two cylinders that are supposed to act in parallel and you measure different speeds, first check flow distribution and any downstream load differences before rechecking the cylinders’ apparent “power.”

• If you need longer reach, you can swap for a longer stroke cylinder without changing the push force or speed, provided the hydraulic source can keep delivering the same flow rate and pressure.

• If you’re aiming for equal performance in two cylinders, keep the cross-sectional areas matched and ensure the supply line and valve configuration don’t bias one side with more flow.

A light digressions moment: analogies that help the idea click

Think about water taps and hoses. If you’ve got two hoses of the same diameter connected to the same faucet, the water pressure in both hoses is the same. If you push a plunger in each hose with a plunger of the same size, the force pushing the plunger will feel identical. The one with a longer hose doesn’t push harder or faster; it just has more hose to fill before the flow stops. Stroke length is like the distance you can pull the plunger back—the same push, different reach.

Why this matters for real-world work

technicians and engineers bring this knowledge into every machine they design or troubleshoot. When you’re sizing a hydraulic circuit, you want predictability: equal force means predictable actuation, and knowing speed is tied to flow rate helps you pick the right pump, the right valves, and the right lines. It’s not just about getting things to move; it’s about doing so with control and reliability.

If you ever find yourself staring at a schematic and thinking, “Which variable is dominating here?” you’ll have a ready answer. Pressure and area set the push. Flow rate and area set the pace. Stroke length? That’s the distance, not the pace.

Bringing it home with a concise reminder

• Same pressure, same piston area → equal force.

• Same flow rate, same piston area → same speed.

• Stroke length changes distance, not the force or the instantaneous speed under equal pressure and flow.

• Real-world quirks (friction, load, line resistance) can nudge the ideal into a close-enough reality, but the core relationship remains a strong guide.

If you’re building a mental map of hydraulic behavior, think of it as a simple formula with a practical punch. The moment you pin down the pressure and the area, you’ve got the force pegged. The moment you pin down the flow and the area, you’ve got the speed pegged. Stroke length? It’s the distance, not the tempo.

Final thoughts: keep your intuition sharp

Two cylinders with identical area and the same pressure—your intuition should tell you they behave like twins in this moment of push. A lot of hydraulic design boils down to keeping that intuition aligned with how fluids actually move in real systems. So next time you’re staring at a schematic, pause on the bigger questions and check the basics first: pressure, area, and flow. They’re the trio that makes the machine talk in predictable terms.

And yes, this tidy relationship isn’t just a classroom curiosity. It’s the backbone of how you evaluate hydraulic circuits, how you select components, and how you troubleshoot when a system seems to lag or misbehave. The more you internalize that force-by-pressure-and-area rule and the speed-by-flow-and-area rule, the quicker you’ll spot what’s off and what’s on track.

If you’re curious to see real-world examples, look for hydraulic manufacturer guides from brands you trust—Parker, Bosch Rexroth, and Eaton often lay out these core principles with diagrams that click. A quick glance at a few setup diagrams can turn a dry equation into a tangible, everyday sense of “that’s why it moves like that.”

Bottom line: when two cylinders share cross-sectional area and ride the same pressure from the same source, they push with equal force. If the flow is the same, they move at the same speed. Stroke length doesn’t change the tempo—it just changes how far they go. And that distinction is exactly the kind of clarity that makes hydraulic systems feel a lot less mysterious and a lot more controllable.