Electric vs Hydraulic Rotary Actuators for Mobile Machinery
Both can drive a heavy joint. They win in different places. Here is an honest side-by-side — including where hydraulics are still the better choice.
How they compare
| Hydraulic rotary actuator | Electric rotary actuator | |
|---|---|---|
| What it needs | A pump, tank, valves, filters, hoses and often an oil cooler, driven by an engine or an electric motor. | A cable from the battery to a motor controller at the joint. Nothing else. |
| Torque | Very high torque in a compact body. Helical rotary actuators reach several thousand Nm. | Comes from a high-ratio gearbox behind a small motor. The RG600 is rated to 6,000 Nm with 10,000 Nm max, at about 20 kg. |
| Strength both ways | Most joints are driven by a cylinder, which pushes with its full piston area but pulls with only the ring around the rod — often 50–70% of its push force. The joint is strong one way and weaker the other. | The RG600 drives with the same torque in both directions, so the joint is equally strong lifting and lowering, opening and closing. |
| Speed | Fast. Speed is set by oil flow, so a big pump moves a joint quickly. | Slow by design: a high ratio trades speed for torque. The RG600 comes in 800:1, 1,200:1 and 1,600:1 as standard — up to about 3.1, 2.1 and 1.6 rpm — with custom ratios from 400:1 (about 6 rpm) to 2,400:1. A higher ratio reaches the same torque with a smaller motor. Ideal for lifts, folds, tilts, legs and levelling, not fast swing. |
| Rotation range | Fixed by the actuator's design — typically a set range such as 90°, 180° or 360°. A cylinder-driven joint is limited further by the cylinder's geometry. | Limited only by the machine around it, and torque stays the same across the whole range. |
| Shock and overload | A strength. Relief valves open and the oil gives a little, so a sudden hit is cushioned. | The gear train takes the hit directly, so it needs current limiting in the controller and real design margin. Size for the shocks your machine sees, not just the steady load. |
| Holding a load | Needs counterbalance or lock valves. Internal leakage can let a held load creep down over time. | Held by the drive, a brake or the gearing — no oil to leak past a seal, so no creep from leakage. |
| Energy use | Losses in valves, hoses and internal leakage. Studies of heavy-duty hydraulic arms put actuator efficiency below 50%. | Draws power only when the joint moves. On a battery machine that is run time you get back. |
| Leaks and maintenance | Hoses, seals and fluid to inspect and change. A burst hose means downtime and a clean-up. | The RG600 is sealed and grease-free, with no scheduled service items. |
| Control | Needs proportional valves and added sensors for precise position control. | The motor controller already knows position and current, so precise and automated motion comes built in. |
| Cost | Cheaper per Nm — especially when the machine already has a pump running. | Wins when the machine has no hydraulics at all: there is no pump, tank, cooler or hose run to buy, fit or power. |
Stay hydraulic when…
- The machine already runs a hydraulic pump for other jobs
- The joint has to move fast, many times a minute
- It takes heavy, unpredictable impacts, like a digging bucket
Go electric when…
- The machine is battery-electric with no other hydraulics
- The joint is slow and heavy: a lift, fold, tilt, level or leg
- The joint has to be just as strong in both directions
- Leaks, servicing or drift are a problem — or you want automation
An electric joint for arms, lifts and legs
The RG600 bolts on at the pivot and drives the joint straight off the battery: rated to 6,000 Nm, 10,000 Nm max torque, about 20 kg, sealed and grease-free. It is built for people making custom electric machines who want to leave the pump, tank and hoses off entirely.
Electric vs hydraulic FAQ
Can an electric rotary actuator replace a hydraulic rotary actuator?
Yes, where the joint is slow and heavy. An electric drive at the pivot can match hydraulic torque, holds position without drift and needs no oil. Where a joint must move fast, or take big shock loads with no electronic protection, hydraulics still have the edge.
Is electric actuation stronger than hydraulic?
Not inherently. Hydraulics pack more force into a smaller body. Electric drives reach the same torque by gearing a small motor down hard, which costs speed. The RG600 is rated to 6,000 Nm with 10,000 Nm max in a unit of about 20 kg.
When does it make sense to go electric?
When the machine is battery-electric and has no other reason to carry a hydraulic system. Then every hydraulic joint drags in a pump, tank, hoses and losses. Driving each joint electrically removes all of it.
How do I know how much torque my joint needs?
Use our hydraulic cylinder to joint torque calculator. Enter the cylinder bore, pressure and lever arm, or the load and its reach, and it gives the torque at the joint in Nm and lb-ft.
Not sure which way to go?
Send us the joint — torque, speed and how often it moves — and we'll tell you straight whether electric suits it.