foot-munted motor brake with side release knob SAB 56,703

SAB Series 56,703: Foot-Mounted Solenoid Actuated Brakes with Side Release Knob

Features & Benefits

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Foot Mounted, Bearing-Supported Thru-Shaft

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NEMA C-Frame 56C - 145TC
Torque (lb-ft) 1.5 - 25
Torque (Nm) 2 - 34
Enclosure UL Type 1
Additional Options IP Rating: 23

Questions about Modifications? Contact Customer Support

Phone: 414-272-1100
Email: [email protected]

M17: Terminal Strip

A terminal strip is located in the inside of the brake, on the support plate. It allows for easy connection and identification of lead wires.

M35: Special Internal Lead Wire Hole with Bushing

Any non-standard, internal lead wire hole in the endplate.

endplate with internal lead wire hole with bushing for Stearns motor brakes

Frequently Asked Questions

How can I identify a brake for repair or replacement when the identifying nameplate is removed or unreadable?

There is some basic information that can help us to identify the brake.

Gather the basic Information:

  • If the brake is to be replaced and the brake part number is not available, note the hp, rpm, frame size, shaft size, voltage, orientation (horizontal, vertical above or below) and any environmental or ambient considerations and treat as a new application. The mount bolt circle and mount register (pilot) are critical. There are many pre NEMA brakes still in operation today that do not conform to NEMA C-face standards.

Two examples of gathering unknown brake information:

Example One:
Description: The brake is about 9 inches in diameter. The spring is located at the center, the coil has an identifying sticker, the support plate isn’t flat, pressure plate has four tabs and the lever arm extends through the housing. The brake has brass parts. The friction disc is 7 ¼ inch in diameter and has a square hub. By description and picture, this brake is obsolete. The coil and disc continue to be available; other parts are not.

Action: The disc & coil are available, parts are not. Replace the brake. Focus on the mounting bolt circle and the brass disc pack option.

Example Two:
Description: The brake is about 9 inches in diameter. The spring is at 6 o’clock, the solenoid and coil at five o’clock. There are a series of capacitors on the right side and the voltage is DC with a black mechanical switch attached to the solenoid. By description, picture, HP & RPM information, the brake was identified for part replacement and repair.

Action: The brake is an early revision of a current brake. The part sheet was identified for repair part selection.

Stearns coils are marked with a part number. If the marking is destroyed, coils can be identified by measuring the outside and inside dimensions. Coils range from the size 4 family to size K9. The size 4 family of coils ( 4, 4+, K4, K4+, L4, M4, M4+ and P4+ ) and the size 9 ( 9 & K9) are similar in size within their groups. Identify the specific size 4 or size 9 coil by measurement, the brake torque as identified by HP & RPM and counting the number of friction discs.

Friction Discs:
Stearns formulates & manufactures friction discs to meet the performance specifications, and dimensional requirements, of the brake. Stearns supports and guarantees the performance of genuine Stearns parts. Discs and hubs can be identified by length, outside diameter, inside shape and the number of teeth on a gear profile hub.

To identify discs: measure, count the teeth or tabs, location of gear cutting as inside or outside diameter and number of discs.

Parts, Castings and Stampings:
Measurements, combined with digital pictures or sketches, are the quickest way to identify the correct brake and repair parts list. If parts are no longer available, move to identifying the mounting dimensions for a replacement brake as described in the “gather basic information” section. The replacement release rod and housing release mechanisms were identified by a sketch or picture. The lever arm was identified as obsolete by picture and dimensions. The casting number, along with basic sizing information, was used to select a replacement.

Kit brakes:
Shaft extenders and fan covers are proprietary to motor manufacturers. If the full brake number can be identified, the shaft extender hub may be available as a repair part. Other repair parts are available through Stearns distributors. Otherwise, kit brake replacement occurs through the motor manufacturer.

Can Stearns brakes be mounted in a vertical orientation?

Yes. Some models require the brake to be slightly modified from the standard horizontal orientation. For vertical installations, please advise Stearns if the brake will be installed above or below the motor. Stearns will provide any required modifications.

How do I install a brake so that it is compatible with a VFD (Variable Frequency Drive)?

When a VFD is used, the brake must have an independent power supply as the brake will only release with a specific voltage and frequency. For reference, if the application is holding only, most likely you are using a VFD motor controller. These controllers can provide dynamic stopping electrically.

Is there an inspection port on 87,700 series coupler brakes or any other brake, to measure for friction disc wear?

There is not. It is necessary to disassemble the brake to measure friction disc wear.

Can the brake pressure spring(s) be adjusted?

Pressure springs are factory set and should not be adjusted in Stearns Brakes with the exception of the 56,000 series brakes. Per their instructions brakes from 3 - 25 lb-ft pressure torque can be reduced by up to 50% of rated torque. See instructions for adjusting torque in the installation and service instructions.

View Installation & Service Instructions for 56,000 Series

Does Stearns offer any circuit protection for EMI generated by a Solenoid Actuated Brake coil?

Yes, we can provide a line filter. Just call Stearns product support and advise the part number for the brake coil, or the model number for the brake.

Does Stearns have replacement parts available nationwide? If so, what information is required to specify the part?

Stearns parts are available throughout North America, through local Power Transmission distributors – including all of the major national chains. Stearns model number & revision and/or serial number (located on brake nameplate) is all that is required to identify the brake, and a description of the part you need will be all that is necessary to order.

How is a brake wired to a motor?

Stearns Brake coils are single phase coils and can be wired directly to single-phase voltage inside the motor junction box. For more information, please contact the motor manufacturer.

When do I change my friction discs?

Friction discs must be changed once they have worn to 1/2 their original thickness.  This can be measured by evaluating the wear surface and non wear surface on the disc. 

Do you have replacement parts available and, if so, what information is required to specify a part?

Stearns parts are available throughout North America through distribution. Stearns model number, revision and/or serial number (located on brake nameplate) is required to identify the brake. Please include a description of the part you are replacing.

What are the motor mounting options for Stearns brakes?

Stearns brakes can be mounted in a variety of ways.

  • Close coupled - Mounting directly to the back (often referred to as the "non-drive" or "accessory" end) of the motor
  • Brakes can mount to the fan guards on the back of the motor
  • Double C-Face Coupler - Brakes that mount to the drive end of the motor, between a C-Face motor and C-Face gearbox
  • Foot Mount - Floor stands are also available to support this brake

Are Stearns brake coils 3-phase or single-phase? How do I wire for each?

All Stearns coils are single phase. See reference document for wiring instructions. Solenoid coils can have two, three or four leads. A two lead coil is a single voltage and frequency coil. A three lead coil is a single voltage coil with a dual frequency option and a four lead is dual voltage & single frequency. Each has a specific wiring requirement which is detailed in the coil kit or the brake installation sheet.

The coil label information should be compared to the power supply as well as the wiring diagram. A general wiring sheet can be found here.

Solenoid coils have a brief inrush or pull in amperage requirement that is much higher than the amperage necessary to keep the brake released. The inrush time is measured in milliseconds yet still needs to be considered in the power supply especially in smaller single phase motors. Stearns AC coils are single phase. DC Solenoid coils have a polarity requirment. The solenoid coils do require a fixed frequency and a voltage within plus or minus 10% of the rated voltage.

Stearns solenoid coils must be wired separately from any Variable Frequency Drive (VFD) output as the coil pull force is designed with a fixed frequency.

When the brake is wired across the motor, there can be a delay between removing power to the brake-motor and the brake spring setting action. The amperage necessary to keep the brake power released is very low. The brake will continue to be power released until the motor is no longer generating at or above the holding amperage.

Wire brakes separate from the motor for a rapid stop and generally in gravity affected loads such as hoists and lifts.

Direct acting brakes with a small air gap do not have the inrush amperage requirement. Direct acting brakes have a DC coil. An AC to DC rectifier is selected based on the DC amperage, available AC power supply and performance specifications such as rapid set, rapid release, filtered full wave or half wave power supply. The AC rectifier input voltage is matched to the required output DC voltage. The rectifier should be selected at the same time as the brake specifications are set. Rectifiers can be installed in the electrical panel or closer to the brake. Armature actuated brakes should be wired separately from a Variable Frequency Drive output.

Solenoid coils can be changed at site depending on available voltage. Direct acting brake coils are part of the magnet body assembly and are changed out as sub-assembly. A separately wired brake voltage may be different than the motor and drive voltage.

Voltage and amperage should be checked as close to the brake as possible. Line power drop and wire gage size should be considered due to cable run length and other electrical equipment sharing the same power lines. Coils are wound with voltage spike resistant wire.

Use a fuse chart for correct fuse selection, considering the inrush and holding amperage requirements as listed on the coil and in the catalog. Reaction times for solenoid & AAB style brakes are listed in the catalog. Solenoid style brakes generally react under 40 ms for brakes less than 20 lb-ft, and 60-80ms for larger brakes. Direct acting brake reaction time is affected by the rectifier choice.

The common coil failures are: incorrect wiring, incorrect power, high or low power, and finally an incorrect air gap on solenoid product.

Installation sheets are shipped with brakes, housed on our website's resource library and can be requested directly from Stearns.

Can Stearns brakes be foot-mounted?

Yes. We have standard models and floor stand kits for standard Solenoid Actuated Brakes (SAB).  Please refer to catalog pages 48-49 and 98.

Can Stearns supply coils for special voltages for the SAB brakes?

Yes. Please consult the Stearns catalog for standard coil voltages for each model and size of brake.  Stearns coils are manufactured in house in Cudahy, WI. We have the capability to design and manufacture to OEM specifications for application specific requirements. Contact Stearns for details and to discuss you applications.

Why are my friction discs wearing out so quickly?

There could be several causes - see reference pdf.

Reasons for Premature Friction Disc Wear

What do the colors of the pressure spring mean?

Each pressure spring for Stearns SABs is color-coded to indicate the torque rating of the brake for example: 

56,000 series - green spring is for 1.5 and 3 lb-ft brakes, clear coated (silver) spring is for 6 and 10 lb-ft brakes and the gold spring is for 15, 20 and 25 lb-ft brakes. 

87,000 series - Black spring is for 6 and 10 lb-ft brakes, white spring is for 15 lb-ft brakes orange is for 25 and 50 lb-ft brakes and purple is for 35, 75 and 105 lb-ft brakes. 

82,000 series brakes green spring is for 125 lb-ft brakes, yellow springs are for 175 and 230 lb-ft brakes and the red spring is for 330 and 440 lb-ft brakes. 

All 86,000 series brakes have red springs (500 lb-ft, 750 lb-ft and 1000 lb-ft).

Why did the friction disc shatter?

There are several causes that can result in shattered friction disc(s), including: 

  • Improper hub placement (see installation and service instruction for the appropriate brake series). 
  • Brakes have an older "square hub" design. In this case, the hub & discs can be replaced by newer "splined" parts, where the loads are better distributed. 
  • Other potential causes could be shock loading, rapid instant reversing, excessive disc wear without changing discs or high-speed rotational burst (rotating friction discs in excess of 5000 rpm). 

Call Stearns product support to discuss the application.

Does Stearns offer an explosion proof coupler brake?

Not at this time.

Why is my brake noisy?

The most common cause is the hub placement on the shaft.  If the hub is not set in the correct position, the friction discs can float, thus causing a chattering noise to occur. 

See installation instructions for correct hub placement on the shaft.

For 56,000 series brakes, anti-rattle clips can also be assembled to the friction disc(s). See installation instructions for the proper placement of anti-rattle clips.

How can I identify the coil part number, to order a replacement coil?

The stock part number is on the coil. However, to order you will need to reference the coil kit part number. Refer to the parts list for the appropriate series brake, or consult Stearns customer service or your local distributor.

How do I find the amps of the coils?

Inrush and holding amperage is listed on the brake nameplate, or refer to the Stearns Brake catalog.

Why is my brake overheating?

There are several reasons a brake could overheat. Please use this troubleshooting guide to help identify your next steps. 

Trouble Shooting Guide for Overheating

How do I switch the coil in my brake from a DC-operated coil to an AC coil, and vice versa?

Refer to the parts lists, or consult factory. For reference, DC coils require a separate DC switch (to switch between the "pull-in" and "holding" windings that are within the DC coil). This DC switch can be either a mechanical switch or an electronic switch. Also, such a change would require a new nameplate - so that, over the life of the brake, the correct replacement parts are ordered.

What is the difference between a Class B and Class H coil?

Class B, which is the standard insulation is injection molded and has a maximum temperature limit of 266°F (130°C). Class H is a more robust, encapsulated insulation and has a maximum temperature limit of 356°F (180°C).

What is the acceptable ambient temperature range for Stearns brakes

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.  

Why did the brake coil swell?

The most common causes are low voltage applied, or the plunger linkage is binding. Refer to coil section of troubleshooting page.

What paints or finishes are available for Stearns brakes?

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.

What size circuit breaker should I use for my brake?

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. 

Can you adjust your brakes for wear?

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.

Is the “duty cycle”, or number of stops over a given time period, important to know in choosing a brake?

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.

How many cycles can I get from my 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.

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