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Gerotor & Geroler Torque Motors

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Gerotor and geroler torque motors are low-speed, high-torque (LSHT) orbital motors that trade shaft speed for the running torque needed on augers, winches, conveyors, wheel and track drives, and other direct-drive jobs. The orbiting gerotor gear set (or roller-equipped geroler element) multiplies torque at low RPM, so motor selection comes down to matching displacement, torque and speed range, shaft style, mount pattern, and port type to your circuit. Running an obsolete Char-Lynn, Eaton, or White unit? send your specs for a cross-reference.

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How to Choose a Gerotor or Geroler Torque Motor

Pin down these specs before you buy, and confirm each against the equipment or the motor you are replacing:

Displacement (cu in/rev): The single biggest driver of speed and torque. Larger displacement gives more torque per revolution and lower output speed at a given flow; smaller displacement runs faster with less torque.
Speed and torque range: Match the motor's rated continuous and intermittent torque to the load, and check that the resulting RPM at your system GPM lands in the motor's usable speed band.
Shaft: Confirm style and dimensions — straight keyed, tapered, splined, or wheel-mount — so it mates to your coupling, sprocket, or hub.
Mount: Verify the bolt pattern and pilot — 2-bolt, 4-bolt flange, or wheel/magneto mount — against the bracket or housing.
Ports: Match port type and size (SAE straight thread, NPT, or manifold) and note whether the design needs case drain for higher-pressure or two-speed use.
Pressure rating: Confirm continuous and peak operating pressure are within your circuit's relief setting.

Which Torque Motor Is Right for the Job?

Gerotor designs use a meshing inner/outer gear set and are a cost-effective choice for general low-speed, high-torque duty. Geroler designs add rollers between the star and ring, which typically reduces internal friction and wear and can improve efficiency and starting torque under load — often the better pick for higher-pressure or longer-duty applications. If your job needs higher continuous speed instead of maximum torque, compare against high-speed Gear Motors, or browse the full range of Hydraulic Motors to weigh displacement and speed trade-offs. When you are unsure which body and displacement fit, match the motor you are replacing by displacement, shaft, mount, and ports rather than by model name alone.

Complete the System

A torque motor is one part of the circuit. Pair it with a Hydraulic Pump sized to deliver the flow and pressure your motor needs, control direction and speed with a Hydraulic Valve, and route flow with the right Hydraulic Hoses rated for your working pressure. Quick Couplers make it easy to swap motor-driven attachments without breaking the line.

Cross-Referencing an Obsolete Torque Motor

Many gerotor and geroler motors in the field are discontinued Char-Lynn, Eaton, or White units, and the original part number may no longer be cataloged. We have cross-referenced obsolete and superseded torque motors since 1963 by matching displacement, shaft, mount, and port configuration to a current equivalent — so you get a motor that drops in and runs, not just a close guess. Send the casting numbers, nameplate data, and a photo of the shaft and ports, and we will confirm the fit. request a cross-reference.

Gerotor & Geroler Torque Motors – Frequently Asked Questions

How do I select the right gerotor torque motor for my application?

Start with the load: figure out the torque you need at the shaft and the output speed (RPM) you want, then work back to displacement at your available flow (GPM) and pressure. Confirm shaft style, mount pattern, and port type match your equipment. If you are replacing an existing motor, match it by displacement, shaft, mount, and ports rather than by model name alone.

What does displacement mean on a torque motor, and how does it affect speed and torque?

Displacement is the volume of fluid the motor uses per revolution, usually given in cubic inches per revolution. At a given flow, a larger displacement produces more torque and turns slower, while a smaller displacement turns faster with less torque. It is the main spec to match when sizing or replacing a motor.

What is the difference between a gerotor and a geroler motor?

Both are orbital low-speed, high-torque motors. A gerotor uses a meshing inner star and outer ring gear set. A geroler adds rollers between the star and ring, which typically lowers internal friction and wear and can improve efficiency and starting torque under load. Gerotor is often the more economical choice; geroler tends to suit higher-pressure or longer-duty work.

Gerotor torque motor vs. gear motor — which should I use?

Use a gerotor or geroler torque motor when you need high torque at low RPM for direct drive, such as augers, winches, and wheel drives. Choose a Gear Motor when you need higher continuous speed and lower torque, often through a gearbox or pulley. The job's required speed and torque decide which design fits.

Do these motors need a case drain line?

Many standard single-speed gerotor and geroler motors do not require a separate case drain, but higher-pressure, two-speed, or certain shaft-seal configurations do. Check the motor's rating and the application: running without a required case drain can blow the shaft seal. When in doubt, confirm the configuration before installing.

What shaft and mount options are available?

Common shafts include straight keyed, tapered, splined, and wheel-mount, with various mounts such as 2-bolt, 4-bolt flange, and wheel or magneto patterns. The right combination depends on how the motor couples to your sprocket, hub, or coupling, so verify shaft dimensions and the bolt pattern against your equipment before ordering.

Can you cross-reference an obsolete or discontinued torque motor?

Yes. Many field units are obsolete Char-Lynn, Eaton, or White motors whose part numbers are no longer cataloged. We match a current equivalent by displacement, shaft, mount, and port configuration so it drops in and runs. Send the casting numbers, nameplate data, and a photo of the shaft and ports, and we will confirm the fit — request a quote.

Are torque motors in stock and ready to ship?

We stock a broad range of gerotor and geroler torque motors across many displacements, shafts, and mounts, with in-stock items shipping the same day from Great Falls, MT when ordered before the daily cutoff. For obsolete cross-references or bulk orders, send your specs and we will confirm availability and lead time.

Gerotor & Geroler Torque Motors

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How to Choose a Gerotor or Geroler Torque Motor

Which Torque Motor Is Right for the Job?

Complete the System

Cross-Referencing an Obsolete Torque Motor

Gerotor & Geroler Torque Motors – Frequently Asked Questions

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