Overview

This document provides comprehensive technical information on the GMR-S and GMR40-S Disc Brake Calipers, which are spring applied and air released. These calipers are intended for industrial braking applications and support a range of disc diameters.

Specifications and Performance

• Supported disc diameters range from 610 mm to 1830 mm.
• Braking torque depends on disc diameter and air pressure, with maximum braking forces up to 36 kN.
• Minimum air pressure for full brake retraction varies between 4.8 and 8.4 bar depending on the model; maximum pressure is 9 bar.
• Braking torque formula: Torque (Nm) = Braking Force (N) × (Disc Radius - 0.06 m).
• Thruster type S has a maximum displacement volume of 1.3 liters.
• Calipers are available in right-hand or left-hand configurations and can be customized with marinisation or nodular cast iron on request.

Parts and Components

The caliper and thruster assembly includes front and rear caps, thrust collar, pushrod, seals, springs, bolts, and O-rings. A detailed parts list with part numbers and quantities supports maintenance and replacement.

Installation Guidelines

• Mount caliper on a rigid support capable of withstanding up to 36 kN braking force.
• Ensure symmetrical positioning relative to the disc.
• Use three M16 grade 8.8 bolts tightened to 150 Nm torque for secure fixing.
• For inclined mounting, use an adjustable stop screw and bias springs (kit Part No. 6700458).
• Install thruster separately with air inlet uppermost; air connection is G 1/2 BSP.
• Use flexible tubing for air supply and consider a quick exhaust valve for rapid brake response.
• Control via a 3-port, 2-position valve with open exhaust; compatible with electrical, pneumatic, or hydraulic controllers.
• Air supply must be dry and oil-free; thruster requires approximately 1.3 liters of compressed air per full stroke.

Operation Procedures

• Brake is spring applied and pneumatically released; air pressure controls braking torque.
• Retraction screw (M16 x 130) is for emergency release and maintenance safety; it must be removed during normal operation and replaced with a red plastic cap.
• Maintain thruster stroke at about 20 mm by adjusting the pushrod when brake is off.
• Monitor pad wear by measuring the gap between pad pressure plates and caliper frame; maximum allowable wear is 10 mm.

Maintenance Instructions

• Keep brake pads and discs free from oil and grease; replace contaminated pads.
• Replace pads from the rear without releasing spring clips; use part number 7080080 for new pads.
• Regularly lubricate caliper arm surfaces, knuckle joints, and pivot pins with recommended greases.
• Service or replace pivot pins after approximately one million operations or three years.
• Thruster maintenance includes cleaning pushrod, draining water, and inspecting seals and bushes.
• Seal replacements (diaphragm, rod seal, wiper seal) can be done without decompressing the spring pack; other repairs require decompression and authorized personnel.
• Never decompress springs by unscrewing the retraction screw.
• Thruster servicing involves disassembly, inspection, seal replacement, lubrication, reassembly, and leak testing.
• Pushrod removal requires thruster removal and lubrication of bearing surfaces and threads.

Recommended Lubricants

• Caliper: Medium grease with molybdenum disulphide (e.g., Castrol LMM, Shell Alvania 2 + MoS2).
• Thruster: Medium lithium-based grease with rust inhibitors (e.g., Duckham’s Keenomax L2, Castrol AP 2, Shell Alvania R2).

Spare Parts and Service

• Store spare brake pads, diaphragms, and seals in a cool, dry, contamination-free environment.
• Refer to Data Sheet DB 3604 for caliper spare parts.
• Maintain spare components for air-line equipment including filters and controllers.
• Contact Twiflex Limited or authorized agents for service and inquiries.

Critical Notes and Safety

• Always remove the retraction screw before placing the brake into service and fit the red plastic cap.
• Maintain safe clearance when adjusting the pushrod to prevent injury.
• Do not decompress springs by unscrewing the retraction screw.
• Use specified torque settings for bolts and nuts during installation and assembly.

Brake Performance Specifications

Performance data is provided for braking forces of 25 kN and 19.5 kN, detailing minimum and maximum air pressures for full retraction and operation:

• At 25 kN: Minimum retraction pressure 7 bar, maximum operating pressure 9 bar.
• At 19.5 kN: Minimum retraction pressure 6 bar, maximum operating pressure 7 bar.
• Additional noted range: Minimum retraction pressure 4.8 bar, maximum operating pressure 7 bar.

Braking torque increases with both disc diameter (610 mm to 1830 mm) and air pressure (up to approximately 18-26 bar). The relationship is graphically represented, confirming proportionality.

Unit Conversions

• 1 kNm = 736.6 lbf-ft
• 1 bar = 14.5 psi

Summary of Critical Parameters

• Minimum air pressure for full brake retraction ranges from 4.8 to 7 bar depending on braking force.
• Maximum air pressure ranges from 7 to 9 bar.
• Braking torque is directly proportional to disc diameter and air pressure.

Recommendations and Best Practices

Maintain air pressure within specified limits to ensure optimal brake performance. Select disc diameter appropriate to the required braking torque, considering the proportional relationship between diameter, air pressure, and torque. Follow installation, operation, and maintenance guidelines strictly to ensure safety and longevity of the brake system.