Air Motors / Gear Motors

Air Motors / Gear Motors

Table of Contents

Air Motors / Gear Motors

          Air Motors / Gear Motors are both important technologies that play important roles in a wide range of industrial applications. Air motors use compressed air to generate mechanical energy, while gear motors use gears to reduce speed and increase torque.

          Air Motors / Gear Motors can be combined to create air-powered gear motors, which are used in many industrial applications where a high level of precision and control is required. Air-powered gear motors are often used in automated assembly lines, machine tools, and other industrial applications where precise control over the speed and torque of the motor is critical.

          The choice between Air Motors / Gear Motors will depend on the specific needs of the application, including factors such as speed, torque, power, and environmental conditions. Air Motors / Gear Motors are commonly used in industrial applications where electric motors may not be practical or safe, such as in explosive environments or in wet or dirty environments. Air Motors / Gear Motors are also preferred in some situations because they are lightweight, easy to maintain, and can be designed to provide high torque at low speeds.

Air Motors / Gear Motors

Why use a Gast Air Motor?

Variable Speed

You can vary air motor speed between 300 and 10,000 rpm
(depending on model selection) with a simple valve put in between
the air source and air motor.

Non-electrical Sparking
As a non-electrical device, the possibility of explosion from igniting flammable gases is greatly reduced.
Instantly Reversible
A four-way valve in the air line enables a Gast Air Motor to be instantly reversed. A turn of the valve causes a complete reversal of rotation, even when the motor is running at full speed.
Cool Running
As the air motor turns, expanded air cools the motor. Units can be used in ambient temperatures up to 250 °F (120 °C) in a non-hazardous atmosphere.
Compact and Portable
Get maximum horsepower with minimum size and weight.
Minimum Maintenance
Will Not Burn Out
Gast Air Motors can be stalled or overloaded for long periods without damage.
Low Price
Cost is less than other motors of equal horsepower and capabilities.
Operate in All Positions
Mount them sideways, upside-down, or in any position so long as adequate lubrication* is provided and end thrust is kept to design limits. Gear Motors will operate in almost any position, see model data.
Low-shock Starts
Because Gast Air Motors go to work with air-cushioned smoothness, they cut stress on your equipment.
Self-sealing Vanes
Vanes are self-sealing and automatically take up their own wear, thus ensuring con stant output for thousands of hours of use.
Mounting Flexibility
Foot, hub, face, NEMA-C, or metric flange motor mountings are standard equipment for most air motor sizes.
Four-vane or Eight-vane
Four-vane units meet most requirements, but for more precise inching control and minimum blowby in applications where motor is operating in a stalled condition, specify eight-vane models.
Long-life Accessories

To ensure long life, Gast offers accessories designed to extend unit life including air filters that remove water and particles down to 5 microns, and air line lubricators that supply a constant flow of lubrication automatically*. We can supply a pressure regulator that provides precise control of power and operating speed. Options like
these help you get smooth performance with minimum maintenance.

*Non-lubricated series does not require a lubricator

You can put a Gast Air Motor in places where they will not get much service, because there’s virtually nothing to service on a Gast Air Motor, providing it is operated on a clean, dry, and lubricated air supply*.

How to Select an Air Motor ?

Air motors differ in many ways from other power sources. These unique operating characteristics must be considered when selecting an air motor for a particular job. It is easy to change horsepower and speed of an air motor by throttling the air inlet. Therefore, the best rule of thumb for selecting an air motor is to choose one that will provide the horsepower and torque needed using only two-thirds (²/₃) of the line pressure available. The full air line pressure will then be available for overloads and starting.

Output Power vs. Speed

The output power of an air motor is relative to speed and to air line pressure

Torque vs. Speed

1. An air motor slows down when load increases… at the same time its torque increases to a point where it matches the load. It will continue to provide increased torque all the way to the stalled condition, and it can maintain the stalled condition without any harm to the motor.
2. As the load is reduced, an air motor will increase speed and the torque will decrease to match the reduced load.
3. When the load on an air motor is either increased or decreased, speed can be controlled by increasing or decreasing air pressure.
4. Starting torque of an air motor is lower than running torque. While this provides smooth, low-shock starting, it is necessary to have additional air line pressure for starting under heavy loads.

Air Consumption vs. Speed

Air consumption increases as speed and air pressure is increased.

Air Motor/Gear Motor Performance Overview

Whatever your rotary air motor power requirements, chances are we have what you’re looking for.

Stainless Steel and Standard Air Motors Specifications

rpm HP kW lb. in. Nm cfm m3/h rpm lb. in. Nm
1AM 10,000 0.45 0,33 2.75 0,31 20.5 35,1 650 5.6 0,65
4AM 3,000 1.70 1,30 36.00 4,1 78 132,5 300 56.00 6,3
6AM 3,000 4.00 3,00 84.00 10,00 128 228 300 115.00 13,00
1AM (A) 10,000 0.45 0,33 2.75  0,31  20.5 35,1 650 5.6 0,65
1UP (B)  6,000 0.45 0,33 5.25   0,58  27 47 500 6.00 0,68
2AM (A)  3,000 0.93 0,68 19.50 2,20  30 49,5 350 26.10 3,05
4AM (A)  3,000 1.70 1,30 36.00  4,1  78 132,5 300 56.00 6,3
6AM (A)  3,000 4.00 3,00 84.00  10,00  128 228 300 115.00 13,00
8AM (A)  2,500 5.25 3,90 132.00 14,40  175 293 300 185.00 31,00
16AM (A)  2,000 9.50 7,10 290.00 34,00 275 475 300 372.00 43,0

Gear Motors Specifications

rpm HP kW lb. in. Nm cfm m3/h rpm lb. in. Nm
Gear MotorS
1AM-NRV 15:1  350 A 0.34 0,26 62 7,1 21.0 36 30 72 8,1
1UP-NRV  15:1  400 C 0.32 0,23 49 5,5 2 36 30 71 8,0
2AM-43A  20:1 150 C 0.26 0,39 110 12,4 18 30,6 60 145 16,4
2AM-43A  20:1 150 A 0.58 0,43 240 27,1 42 71,4 60 270 30,5
4AM-RV  10:1  300 B 1.26 0,94 274 31,0 57.5 98 30 425 48,0
4AM-RV  15:1  200 B 1.25 0,90 400 45,2 60.0 102 20 640 72,0
4AM-70C  20:1  150 A 1.17 0,87 487 55,0 71.0 120 15 740 83,6
4AM-70C  40:1  75 A 0.95 0,71 800 90,4 71.0 120 7 1255 141,8
4AM-70C  60:1  50 A 0.82 0,61 1040 117,5 71.0 120 5 1640 185,3
6AM-22A  10:1 300 A 3.40 2,54 720 81,4 130.0 221 30 950 107,4
6AM-22A  20:1  150 A 2.65 1,98 1100 124,3 130.0 221 15 1550 175,6
6AM-22A  40:1  75 A 2.10 1,57 1725 194,9 135.0 230 8 2500 282,5
8AM-32A 20:1  125 A 3.70 2,76 1850 209,1 177.0 301 15 2550 288,2
16AM-13 20:1  100 A 6.50 4,85 4175 471,8 275.0 468 15 5175 584,8

A – 100 psig and 7,0 bar line pressure for imperial and metric data, respectively.
B – 80 psig and 5,5 bar line pressure for imperial and metric data, respectively.
C – 60 psig and 4,1 bar line pressure for imperial and metric data, respectively.

Catalog Performance Specifications

The specifications listed are that of a unit at sea level with an ambient temperature of 70 °F (21 °C), operating with normal electrical current conditions. The figures stated in this catalog are nominal approximations for models without accessories. Intake filters and exhaust mufflers, and the accumulation of contaminants in them during operation, will decrease the flow of air as well as the achievable pressure.

The units that we list in this catalog are a small portion of what we actually make. Those listed are considered “standard units” and are normally available from stock in small quantities. Variations are produced for many customers and by providing to us the application specifications we might find an existing unit that fits your requirement. If we don’t and the quantity is sufficient, we will design a “special unit” for the application.
Pictorial and dimensional data is subject to change without notice.
The information presented in this catalog is based on technical data and test results of nominal units. It is believed to be accurate and is offered as an aid in the selection of Gast products. It is the user’s responsibility to determine suitability of the product for intended use and the user assumes all risk and liability whatsoever in connection therewith.

The chart below shows general performance ranges of our lubricated Air Motors.
See if we have the right offering for your application.

Use of Air Motors in Hazardous Atmospheres

Most of the Gast Air Motors and some of the Gast Gear Motors in this catalog meet the requirements of the EC directive 94/9EC (ATEX 100a). They may be used in zones 1 and 2 where explosive atmospheres of gas or dust are likely to occur. These are marked with εx II 2 G D c T4 in the catalogue and on the product. This indicates the air motor is Group II, Category 2, Gas and Dust Atmospheres, and a maximum surface temperature of 275 °F/135 °C. Check that the product driven by the air motor meets ATEX directive.

There are several points regarding the safety of air motors. Our air motors are not a source of electric sparks. However, it is possible that an article which is not part of the air motor (e.g., wrenches, hammers, etc.) could create a spark by sharply impacting a cast iron or aluminum case or the steel shaft of the air motor. [Note that electric motor enclosures for both class I and II hazardous locations can be made of “…iron, steel, copper, bronze, or aluminum…” (UL 674, Electric Motors and Generators – Hazardous Locations, June 23, 1989; paragraph 4.2, page 6)].

Gast Air Motors are designed to be operated by compressed air, the expansion of which creates a cooling effect. As a result, the outside surface temperature of the air motor will not reach ignition temperature and a maximum surface temperature of 275 °F/135 °C. Operation of the air motor with compressed air purges a flammable mixture from the inside of the air motor.
To prevent static electricity from being an ignition source electrically ground the metal air motor.
We do not guarantee the safety of any application, but to ensure the safe operation of an air motor in your application, always follow the product operation manual, follow ATEX 100a when operating in a hazardous atmosphere and consult with a qualified engineer.

Performance, Features and Typical Applications


  • Up to 9.5 HP (7,1 kW)
  • Variable speeds to 10,000 rpm Gear
  • motor maximum torque to 5200 lb. in. (587 Nm)


  • Variable speed
  • Non-electrical sparking
  • Cool running
  • Compact and portable
  • Operate in all positions
  • Mounting flexibility

Typical Applications

  • Typical
  • Applications
  • Mixing
  • equipment
  • Conveyor drives
  • Pump drives
  • Food packaging
  • Pharmaceutical
  • packaging
  • Hoists and
  • winches
  • Hose reels
  • Fiberglass
  • choppers
  • Tension devices
  • Turntables
  • Tire/wheel
  • balancers

Air Motors

  • Foot mounting
  • Any plane operation
  • Metal muffler AC990 adds 2″ height when installed

Air Motors Other Spec.

Stainless Steel Air Motors

  • Sanitary design
  • 304 stainless steel housing, rotor, and output shaft
  • Hub, face, or flange mounting
  • Any plane operation
  • Fully sealed

Stainless Steel Air Motors Other Spec.

Metric Models

Delivers up to 1,5 kW (2 HP). Speeds may be varied from 300 to 3,000 rpm. Max.recommended operating pressure, 7 bar (100 psi).

Metric Models Other Spec.

Non-lubricated Air Motors

The NL Series - an alternative to our traditional lubricated styles because no lubricator is necessary
For those air motor applications where contaminated exhaust cannot be tolerated in the workplace, Gast’s non-lubricated Air Motors, the NL series, provide the solution.
Rugged and Reliable

Like our traditional lubricated air motors, the NL series will provide thousands of hours of service-free life. Vanes are just as easy and inexpensive to replace.

Performance Flexibility

Gast’s non-lubricated air motors are designed so that com-pressor carry-over will not gum up the vanes. In fact, whileno lubrication whatsoever is required to operate the motors,small amounts of oil and water will actually improve the performance.

Corrosion Resistant

Because the body, rotor, and end plates are specially treated,
these air motors can tolerate unfavorable moisture-laden

No Oil Expenses

If you are using several quarts of oil throughout the year, you’ll eliminate that expense with non-lubricated air motors.

No Periodic Inspection
With no in-line lubrication system to replenish, the need for time-consuming maintenance checks is eliminated.

Gast’s non-lubricated Air Motors provide the advantages and benefits of traditional lubricated air motors which include:

  • Variable speed
  • Non-electrical sparking
  • Cool running
  • Minimal maintenance
  • No-shock starts
  • Any plane operation

Non-lubricated Air Motors Other Spec.

Air-Powered Gear Motors

Pictured: typical right angle, worm gear reducer.
A. Bearings​
Ball bearings used on input shaft; tapered roller bearings used on output shaft.
B. Case

Fine close-grain cast iron; crankcase sealed; duplex-milled for parallelism of mounting surfaces.

C. Worm

8620 alloy steel thread rolled to give uninterrupted grain pattern;  carburized and hardened after rolling; high-burnish contact surface from rolling reduces friction coefficient for less heat generation, lower power losses. In large sizes, worms are cut, hardened, and ground to a good micro-finish, providing the ultimate in efficiency and torque capacity.

D. Worm Gear

Forged bronze; geometry and high helix angle give maximum beam strength, high efficiency.

E. Cap Screw
High-strength fasteners with corresponding torque specifications prevent loosening or breaking.
F. Seals​
Double-dipped and spring-loaded for leak proofing; tested to ensure compatibility with lubricant.

Get the right gear motor with all the right options

More reasons why you should switch from electricity to air

If you compare Gast Air-Powered Gear Motors with any electric-powered gear motor, there’s really no comparison. Here’s why :

More Horsepower

Size for size, weight for weight, you can’t beat a Gast Gear Motor. A typical rotary vane air motor – the type used in gear motors – developing 2 ¹/₂ HP (1,9 kW) at 1800 rpm and 90 psi (6,2 bar), weighs just 17 pounds (7.7 kg). A comparable electric motor may be two or three times heavier.

More Speed Control

You can’t get more precise turning power than with a Gast Gear Motor. In applications where you need variable speed – like bolt tensioning equipment or rock drilling rigs – one-speed electric motors just won’t fit the bill. Precise lifting, lowering, or turning is simple with Gast Gear Motors.

More Flexibility

More than most standard electric-powered gear reducers can provide. Gast Gear Motors give you infinitely variable turning power from 73 to 5200 lb. in. (8 to 587 Nm) of torque. And Gast Gear Motors are instantly reversible through easy valving in the air line.

More Configurations

That makes it easier for our product to work in your product.
Our Gear Motors are available in four mounting configurations.

More Life

Unlike electric-powered gear motors, there’s no chance of burnout with a Gast Gear Motor. They can be stalled indefinitely with no heat buildup. They’re non-electrical sparking too, which makes them ideal for use in potentially explosive environments
– places where you couldn’t even consider electricity.

Duty levels and applications may requiredifferent FRL’s than recommended.
5 microns
All ports NPTF
Regulator Two ports – ¹/₄ ”NPTF, can be used as additional outlet ports, full flow ¹/₄ ,” ¹/₈ ” NPTF for AH101R model.

– Regulator Maximum primary pressure: 250 psi (17 bar)
– Secondary pressure range: Standard 2-125 psi (.14 to 8.6 bar)
– Temperature rating: -10 °F to 175 °F (-23 °C to 80 °C)


– Polycarbonate Bowls
200 psi at 120 °F (14 bar at 49 °C) or less
100 psi at 175 °F (7 bar at 80 °C) or less

– 250 psi at 175 °F (17 bar at 80 °C) or less
– Metal bowl

– 1 ounce for ¹/₈ ” model
– 5 ounce for ¹/₄ ” model
– 8 ounce for ¹/₂ ” model
– 32 ounce for 1″ model

Filters • Regulators • Lubricators


Gast Part
Dimensions - in.(mm)
+AH100F   ¹/₈" NPTF  18 1AM/1UP/NL22   1.63 (41,4)  3.25 (82,6)  0.38 (9,7)
 +AH103F   ¹/₄ " NPTF  50 2AM/4AM/NL32/NL42   2.75 (69,9) 5.84 (148,3)  0.69 (17,5)
 +AH106F   ¹/₂ " NPTF  117 6AM/8AM/NL52   3.91 (99,3)  6.69 (169,9)  0.67 (17,0)
 +AH109F  1" NPTF  365 16AM  4.75 (120,7)  10.44 (265,2)  1.25 (31,8)

*SCFM = Standard cubic feet per minute at 100 psi inlet and 5 psi pressure drop.
+Metal Bowl


Gast Part
Dimensions - in.(mm)
+AH101R ¹/₈" NPTF  11 1AM/1UP/NL22   1.63 (41,4)  2.38 (60,5)  0.38 (9,7)
+AH104R ¹/₄ " NPTF  50 2AM/4AM/NL32/NL42   2.75 (62.0) 4.00 (101,6) 1.54 (39,1)
+AH107R ¹/₂ " NPTF  130 6AM/8AM/NL52   3.50 (88,9)  5.36 (136,1) 1.50 (38,1)
+AH110R 1" NPTF  360 16AM  4.25 (108,0)  5.69 (144,5) 2.38 (60,5)

*SCFM = Standard cubic feet per minute at 100 psi inlet, 80 psi secondary setting and 10 psi pressure drop.


Gast Part
Dimensions - in.(mm)
+AH102L ¹/₈" NPTF  13 1AM/1UP  1.77 (45,0)  3.37 (85,6) 1.76 (44,7)
+AH105L ¹/₄ " NPTF  20 2AM/4AM  2.56 (65,0) 5.75 (146,1) 1.85 (47,0)
+AH108L ¹/₂ " NPTF  90 6AM and 8AM  3.91 (99,3)  6.69 (169,9) 1.88 (47,8)
+AH111L 1" NPTF  290 16AM  4.50 (114,3)  10.24 (260,1) 2.22 (56,4)

*SCFM = Standard cubic feet per minute at 100 psi inlet and 5 psi pressure drop.
+Metal Bowl

A filter helps ensure efficient operation
by removing solid and liquid contaminants
before they enter the air motor.

An air pressure regulator is necessary in most air motor applications to maintain a constant pressure regardless of the rise and fall of line

Mist lubricators provide uniform lubrication for the traditional lubricated style air motor.
This results in reduced friction,
extending the life of moving parts.

Gauges • Mufflers • Foot Assemblies


If a gauge is required for your Gast Regulator, please order as a separate item:
 Gast Part No.  Used On  Description
AA806 AH104R
¹/₄" NPS, 0-160 psi 


Gast Part
Dimensions - in (mm)    
AF350 (Metal) 1AM/1UP/NL22  1.06 (27)  2.81 (71)  1/8" NPT 
AC980 (Metal)   2AM/4AM/NL32/NL42  1.72 (44) 2.31 (59)  1/4" NPT
AC990 (Metal)   6AM/8AM 2.72 (69)  2.94 (75)  1/2" NPT
AG601* (Metal)   16AM  3.12 (79)  21.22 (539)  1 1/4" NPT

* Not included with 16AM series, but is recommended.


Gast Part Number Used On
Food Grade Oil AS117  Only stainless steel air motors
Oil AD220  All other Lubricated air motors


GAST now offers two foot assemblies in kit form: AG585 for 1AM and 1UP Air Motors, kit includes foot, three mounting screws, and instruction sheet. AG586 for 1AM and 1UP Gear Motors, kit includes foot and three mounting screws.