FAQ

Yes, we manufacture both types of brakes in Cudahy, WI.

You can use the Stearns Product Selector, to select the brake yourself. Or, you can provide Stearns with the necessary information described on the referenced Selection Sheet, and Stearns will select/recommend the proper brake model for your application. You can also refer to the Stearns Brake Catalog table of contents.

Yes, we manufacture brakes with a full range of torque ratings, to match any typical motor combination of HP and speed. This typical approach, for determining the required torque rating of the brake is successful for most applications.

Note: For applications for overhauling loads, high-inertia loads, or where variable frequency drives are used, it is best to determine the required brake torque based on the application/load data. Please refer to the "Application Engineering" section in the Stearns catalog, or consult a Stearns Application Engineer.

Yes. Most Stearns brakes are suitable for both static and dynamic duty. If the brake will be used for dynamic duty, you need to check that the thermal capacity of the brake is sufficient for your application. Stearns can also check this for you.

Yes. Stearns offers a variety of enclosures (described as IP Enclosure Types) to meet the demanding needs of most environments for modern industrial and processing operations, including outdoor applications.

Yes. If the frame size is a typical NEMA C-face frame size.

Not at this time.

We are the North American leader in motor bakes, and yes, we would be happy to supply them.

Stearns manufactures electromagnetic motor brakes. They are primarily spring-set, electrically-released disc brakes, which are also known as power-off or safety brakes.  We also have an offering of spring-released, electrically-set brakes which are also known as power-on brakes.

The spring-released brakes, Super-Mods, are shown on catalog pages 113-120. All other brakes offerings, Solenoid Actuated Brakes and Armature Actuated Brakes, are spring-set designs.
 

Yes. Stearns offers both Marine duty and Maritime brakes.

Marine, Maritime & Navy Brakes

Yes. Stearns offers model 7EC5. 

7EC

All SAB and AAB motor brakes are rated for dynamic/stopping and holding duty. However, AAB design brakes have models specifically for holding-only or dynamic/stopping duty.

Yes. We offer the 82 series brake that is certified by MSHA.

MSHA

Yes. This is a significant feature and benefit of the Stearns SAB brakes.

Yes. We offer them for frame sizes 56C to 256TC

Double C-Face Coupler Brakes

1.5 - 1,000 lb-ft.

48C - 505TC

1/6 to 500 HP

Depending on the specific brake model, Stearns offers enclosure ratings from IP 21 to IP 57

Depending on the specific brake model and the installation orientation, Stearns offers brakes that can operate up to 5,000 RPM.  The Stearns catalog lists the speed limitations for individual brake series. Please refer to the first catalog page for each specific brake series' max operating speeds. The maximum allowed speeds display on the top of the page, under "design features." 

Acceptable ambient temperature range is between 20°F to 104°F (-7°C to 40°C). Brakes can be modified for warmer or colder environments.  

Stearns offers a number of finishes for optimized corrosion control and product appearance. The following list is an explanation of finishes commonly used at Stearns. Stearns sales and design engineers are available to work with you to select and specify the appropriate internal or external finish for the application.

Water Based Primer

A red-brown primer routinely applied as a single coat on cast iron surfaces at Stearns. The water based primer should be top coated for rust and corrosion protection.

Zinc Rich Primer (Option M14)

This green colored primer is applied to ductile iron castings as a corrosion inhibitor. This is an anti-corrosive zinc molybdate primer for use in marine and industrial environments which meets Navy specification TT-P-645B. The primer passes the 500 hour mark of an ASTM B 117 test at 3 mils thickness.

Ferritic Nitrocarburizing (FNC) (Option M39)

This endplate option improves wear and corrosion resistance in the disc pack surface area and is recommended in severe duty applications. The FNC process is standard on some armature actuated brake (AAB) armatures and pressure plates. The cast iron part surface may appear sooty or rusty (oxidized) in appearance as a result of the FNC process. The part surface absorbs nitrogen and carbon during a 90 minute 580°C process which is followed by a quench.

Zinc Electroplating

Zinc electroplate is commonly used on select magnet bodies. A thin coating of zinc, typically around 5-10 microns and has a bright clear coat finish. The zinc electroplate is RoHS compliant. An optional top coat sealer further improves corrosion protection to over 400 hours before red rust appears as tested according to the ASTM B117 standard.

Electroless Nickel (EN)

EN finish is an option for severe duty applications with demanding corrosion resistance requirements. The finish may be used on internal brake parts or applied externally. This is an optional plating finish applied for corrosion control and improved wear properties. The hard finish is resistant to galling and pitting. The finish is rated at over 300 hours of salt spray testing. The EN finish is RoHS compliant.

Top Coat Paint (Option M14B external paint, M14E BISCC white)

Stearns offers a range of enamel and epoxy finishes to meet a variety of specifications including chemical resistance, corrosion control, chip resistance and appearance. A specification can be reviewed on request or a general top coat finish selected as an option.

Autophoretic Epoxy Paint

This smooth finish is used on select magnet bodies. The part is dipped in an acidic diluted paint solution which etches and applies the paint. This finish is a primer for other top coats. The process requires a large volume of identical parts and is currently an OEM option on select brake parts.

Anodize & Impregnate Seal of Aluminum

This optional external finish is the result of an electrically charged chemical bath. The surface oxidizes resulting in a hard corrosion resistant coating. Stearns resin impregnates the casting for IP 54 and IP 56 ratings. An additional optional seal coat expands the weather resistance to 330 hours of surface protection.

We offer several IP ratings, to meet the environmental requirements for typical industrial and outdoor locations.  These include the following:  Enclosure specifications are written in a variety of ways:

• The traditional ODP, DTWP and TENV type descriptions
• IP rating system such as IP 23 or IP 53.
• NEMA enclosure system such as NEMA 2, 4 or 7.
• Application descriptions such as Marine, Jacking Rig, Washdown, etc.
• General categories such as Hazardous Use or Severe Duty.

Watch out for a conflicting combination of styles such as a drip-proof IP 54.

Stearns considers the mounting as part of the overall enclosure. The brake rating is determined by testing the brake while mounted to a closed and gasketed surface. A gasketed and closed mount surface is required to meet NEMA 4 and IP 53 or higher ratings.

Enclosure Rating:
Stearns IP and NEMA ratings are established by test on a brake sample using the method detailed by the standard. The enclosure rating should be considered along with the enclosure material description and any options available for the brake.

Based on sample testing, Stearns may assign similar ratings to variations of a brake series. Check the enclosure description before selection.

As an example: sheet metal, cast aluminum, cast iron and stainless steel enclosures will perform differently over time depending on the end use. Each can be gasketed to meet the test standard, yet options such as release locations and the enclosure openings, material & construction are selection factors.

Shown: A 1-056-900 cast stainless enclosure is rated NEMA 4x and IP56 and a 1-056-000 brake with a white epoxy finish on a drawn steel enclosure is rated NEMA 4x and IP 54.

Fan Mount:
Water can migrate along key shafts, openings such as the mounting thru holes, housing nuts as well as any NPT openings in the brake. A gasketed IP 53 or higher enclosure should be mounted against a closed and gasketed surface or a surface that doesn’t pool water against the brake.

Vertical Mount:
An IP 23 brake is shown vertically above the motor mounted in an unheated but covered building. Liquids will not gather on the sheet metal enclosure, a standard brake was used. If the same brake were used outside, a cast iron or cast aluminum housing would be used and possibly an under-cover or side release.

A hazardous rated 1-082-300 series brake is shown vertically below mounted on a fan cover. In an exposed environment, liquids can gather and migrate along the shaft and keyway. This site was later modified to include a shaft seal and dust slinger to meet the UL and IP rating needed. 

Consult the catalog and work with Stearns to identify and select the options for demanding applications.

Severe Duty Enclosure:
The brakes pictures shown below have been used in earlier e-letters. The specifier selected a closed and gasketed brake mounting with a cast enclosure. The encoder is gasketed and a painted finish applied. In both cases, a smart and proper system selection for the intended environmental protection needed at this site
 

The accepted ambient temperature range for Stearns brakes is 20°F to 104°F. Most Stearns brakes can be provisioned for operation down to -40°C.  This provision requires certain options such as heaters, which are only available on specific Stearns products. Contact Stearns for more information and assistance with your application.

The accepted ambient temperature range for Stearns brakes is 20°F to 104°F. Most Stearns brakes can be provisioned for operation down to -40°C. Some brakes can be modified for operation at -50C. This provision requires certain options such as heaters, which are only available on specific Stearns products. Contact Stearns for more information and assistance with your application.

Stearns provides coil inrush and holding values for end users and OEMs to be able to appropriately size fuses and circuits for their applications. Due to variables outside of Stearns' control, we are unable to advise what size breaker to use. For example, wire runs over a distance, other items in the circuit, etc. The inrush values are listed in our catalog or contact Stearns for application assistance.

The 81 and 82 series have the same support plate assembly including springs and coils. Both series have the same Nema C-face mounting register dimensions. The brakes differ in the disc pack construction. The 81 series has a (3) tab disc pack design suitable for lighter dynamic applications. The 82 series disc pack has a full gear cut construction which results in greater mass and contact area resulting in higher thermal capacity making it more suitable in dynamic stopping and high torque applications.

Stearns provides coil inrush and holding values for end users and OEMs to be able to appropriately size breakers and circuits for their applications.  Due to variables outside of Stearns' control, we are unable to advise what size breaker to use.  For example, wire runs over a distance, other items in the circuit, etc. 

Yes, our brakes can be easily adjusted for wear. In addition, our larger Solenoid Actuated Brakes (SAB), 87 series and above, have automatic wear adjustment.

We are the only manufacturer that offers self- adjusting brakes. This major feature greatly reduces brake maintenance, by eliminating the time required to periodically adjust the brakes for wear. Especially if the brake is mounted on a hoist on the ceiling of a plant, or in another hard-to-reach area.

To adjust brakes for wear, please consult the Installation and Service Instructions provided with the brake, or consult our resource library for the appropriate documentation. For any questions, please contact Stearns for application assistance.

Yes. Knowing the duty cycle is essential to choosing a brake. If the duty cycle includes dynamic stopping, not just holding duty, heat is generated within the brake. In this case, the thermal capacity of the brake must be considered when selecting the brake.

The life of our brakes is very much dependent on cycle rate, energy the brake sees, ambient temperature, among other values.

For longest life, for holding only applications, our Armature Actuated Brake (AAB) products generally provide for the longest life between servicing.

For applications which require dynamic stopping, our Solenoid Actuated Brake (SAB) products are best in class due to the self-adjusting feature, requiring less maintenance which provides a greater uptime on a torque to torque basis.

Our Solenoid Actuated Brakes generally have a higher thermal rating than our competition.

Ex. Stearns 87,000 series has a thermal rating of 17.5 hp-sec/min, while a typical competitive brake is rated at 10 j-sec/min,

We achieve this with larger diameter friction discs that we manufacture ourselves, while our competitors purchase their discs.We have been able to fine-tune our formula to provide the optimum thermal capacity.

The Stearns catalog includes linkage style and direct acting brakes. The solenoid and coil design is termed the SAB (solenoid actuated brake). The direct acting DC brake is termed the AAB (armature actuated brake).

Both the SAB and AAB designs are spring set, electrically released brakes. The obvious difference is the SAB uses a linkage mechanism to relieve the spring pressure and the AAB armature draws directly back against the spring pressure.

Coils & Electrical Performance:
Comparing designs within the same torque rating,

• Within the same torque rating, the SAB solenoid coil is smaller than the AAB coil.
• The smaller coil will energize and de-energize more rapidly than the larger coil.
• The larger AAB coil will produce more heat than the smaller SAB coil.
• The AAB response time will depend on rectifier choice and AC or DC side switching.
  Comparative electrical response time is listed in the catalog.
• The solenoid coil has a brief inrush amperage requirement due to the larger air gap.

The AAB coils are not replaceable as the coils are potted into the machined magnet body. Solenoid coils for the SAB style of brakes are easily replaced as a repair item. A possible reason for coil failure in either design is applying the incorrect voltage.

Dynamic use may result in friction disc wear requiring re-set of air gap on AAB and some SAB.

Small AAB brakes are replaced rather than re-gapped following wear. Larger AAB brakes have a precision air gap setting which is measured at several locations around the circumference of the brake using a feeler gage.

Some SAB brakes require manual air gap adjustment, others are self-adjusting. Manual adjust air gap is measured with a scale after turning one or two adjustment screws. Auto-adjust SAB designs are self-adjusting for disc pack wear.

Neither brake style has to be disassembled for the airgap to be adjusted.

Friction Discs:
Replacing friction discs on both styles of brakes is easy. The difference between the styles of brakes is in the re-assembly.

The SAB is faster to re-assemble as the support plate of the brake mounts to the endplate and fastened with 3 to 6 screws depending on the brake series. After replacing an AAB magnet body, the airgap must be re-adjusted using feller gages at several points.

SAB may have one or more friction discs which are compressed between plates. The AAB has one friction disc bonded to a carrier (metal) plate. Friction discs of either design are located on a gear cut hub. The SAB generally has the better thermal capacity in dynamic use.

Dynamic or Static Use:
All SAB are designed for rapid stop and / or holding applications. The AAB is generally a holding brake due to coil reaction time and thermal capacity limitations. The AAB has a superior mechanical life in holding only use. The SAB is the better selection for dynamic use because of the larger air gap and greater thermal capacity.

Enclosure:
The SAB product has a variety of metal covers and gasket options. All SAB have a maintained external release which is automatically re-set with application of power. 

The AAB generally follow the European practice of placing a gasket band around the brake to shield the air gap with the option of a plug in the center clearance area for an IP 53 rating. The 350 & 360 AAB series have a cast iron or ductile iron cover enclosure. Some AAB sizes have a drawn steel cover option. The AAB manual release is usually non-maintained or maintained by threading retracting bolts Picture 7: AAB with band into the brake to relieve the spring force.

Selection:
The AAB is a DC voltage brake that can be rectified. The SAB single phase coil can be AC or DC with a shunting switch to manage the inrush to holding amperage drop.

The SAB is a proven industrial brake that is forgiving in all kinds of applications and is the easier brake to mount and maintain. The SAB has the more rapid electrical response. The AAB style brake doesn't have a linkage mechanism which results in a longer mechanical life when used for holding only but can be difficult to work on, especially setting the air gap.

A range of options are available for either brake as described in the catalog or by your sales contact.

The bottom line of AAB vs. SAB brake selection is that whatever your brake design preference, or requirement, you can call Stearns.

Stearns Brakes available for crane applications include:  

Brakes for holding or dynamically stopping a load.
One to three-week availability on most brakes.

Solenoid & Linkage Brakes (SAB brakes) are the standard choice for rapid-acting brakes in dynamic or holding applications, offer the widest range of options for specific applications and rapid site coil or friction disc replacement. 

Armature Actuated Brakes (AAB brakes) are DC brakes that can be rectified to standard NEMA voltages. The AAB brakes are recommended for holding applications and have a long mechanical life. 

Options available include: 

• IP 23, IP 54, IP 56 enclosures available.* 
• Space heater 115 or 230 V for internal condensation control.
• Class H encapsulated coil construction for temperature extremes or high cycle rates. 
• Brake release/status switch, normally open or normally closed to indicate if brake is spring set or released, also if the brake is electrically or mechanically (manually) released.*
• Friction disc wear indicator switch.*

Brake manual release options include: 

• Side lever full manual release, with manual reset, which allows high-speed shaft rotation with no drag from the brake.
• Side lever or rear pull standard manual release with auto reset. Brake automatically resets when brake is energized, brake is manually released enough to move load in the event of a power failure. Side lever release recommended for IP55 enclosure or vertical above motor mount.
• Non-maintained manual release (deadman release): constant force is required to keep brake manually released.
• Internal release: no external release visible brake cover must be removed in order to manually release brake.*

Encoder mount:  shaft/tether mount, rigid (face) mount and internal encoder mounting.*
    
Material:    

• Internal endplate finish: corrosion control, low cycle rate. 
• Brass disc pack (brass pressure plate and/or stationary disc) for corrosion control.
• Carrier Ring Friction Disc (metal ring with bonded friction linings), a safety feature for high risk applications to include: hot metal, moving people or moving overhead loads. 
•  Alternate friction materials, application based, consult factory.

*Availability varies by series    
**additional options and designs such as hazardous duty brakes are listed in the catalog or contact the factory for application assistance.  Options vary by brake series. 

Application engineering support is available for selection of brake, options or sizing by inertia calculations.

When selecting Brake Specify: 

• Frame size, C-face mount 
• Brake Type 
• Shaft and keyway dimension 
• Mount:  Horizontal, Vertical above motor, Vertical below motor. 
• Voltage
  • Options Crane & Hoist Brakes

It's not something Stearns can advise on, Div 2 brakes are used in environments that are normally not hazardous.

Duty cycle is limited by the Thermal Capacity of the brake, and by the reaction time of the DC coil.  The 321 series brakes have a Thermal Capacity of 5hp-sec/min.

Typically, at least IP 54 enclosure rating.