2026-10-27
The foundation brake device transmits and amplifies brake cylinder force, distributes it to the wheels and converts it into friction at the tread, determining stopping distance, tread wear and availability.
Chinese freight car bogies widely adopt lever-type single-side brake shoe braking: brake beam, brake levers, middle (lower) pull rods, brake shoes and fulcrums, with flat-hole round pins and pull rivet pins. All connecting points use wear-resistant pin bushings with minimized clearance and higher assembly precision, improving bushing stress and extending service intervals. Pull (compression) rods are arranged as middle or lower type depending on bolster position.
The brake beam is a key fitting: it absorbs the load amplified through the lever mechanism and keeps the brake shoe pressed firmly against the tread. Chinese freight cars mainly use combined type brake beams — L-A (integral forged frame), L-B (integral hot rolled frame) and L-C (integral hot shrink-fit frame) — serving 21 t and 25 t axle load wagons, while L-B1 serves 27 t axle load wagons. L-B and L-B1 are the highest-volume types. For BAB integrated bogies, BLB (hot rolled frame) and TMX (welded frame) series are used, subdivided by the wheel diameter their brake shoe holders accommodate.
| Brake beam model | Wheel diameter (mm) |
|---|---|
| BLB-1 | 915 |
| BLB-2 | 840 |
| TMX-915 | 915 |
| TMX-840 | 840 |
The brake shoe is the final executing part of the braking system. Cast iron shoes include grey cast iron, medium phosphorus and high phosphorus grades; composite shoes are hot pressed from resin, asbestos, graphite, iron powder and barium sulfate and split into low and high friction coefficient types. Because the composite friction body has limited strength, a steel back is pressed onto its rear face, so the shoe is steel back plus friction body. Chinese freight cars mainly use high-friction composite shoes, with one shoe type fitted to every wheel of a car for ease of management.
The slack adjuster automatically adjusts wheel-to-shoe clearance, holding the brake cylinder piston stroke within the specified range, preventing decay of braking force, keeping piston strokes consistent across the train and reducing longitudinal impact. Chinese freight cars mainly use the ST type (body, control and connecting sections):
| Model | Screw length | Mounting position | Features |
|---|---|---|---|
| ST1-600 | 600 mm | Above No.1 upper pull rod position | Two-way automatic adjustment |
| ST2-250 | 250 mm | Between front and rear brake levers | Compact, light, good two-way adjustment, adaptable |
| Performance | ST1-600 | ST2-250 |
|---|---|---|
| Max. adjustment range (mm) | 600 | 250 |
| Max. allowable pull force (kN) | 78.4 | 78.4 |
| Action mode | Two-way | Two-way |
| Max. installed length (mm) | 2566 | 1420 |
| Min. compressed length (mm) | 1966 | 1170 |
| Max. single shortening (mm) | 135 | 60 |
| Max. single elongation (mm) | 30 | 30 |
| Body mass (kg) | 33 | 28 |
| Manual adjustment | Yes | Yes |
Integrated braking devices are divided into side-mounted and back-push types. Side-mounted units suit locomotive and passenger car bogies where underfloor equipment is dense and space is very tight. Freight bogies generally use back-push integrated braking devices, typically consisting of the brake cylinder, brake beam, push rod and slack adjuster. Chinese freight cars mainly use the BAB and DAB integrated devices.
The BAB device comprises the manual brake lever, brake cylinder, push rod assembly, brake beam, rear brake lever, non-cylinder-side J-type lever, slack adjuster, cylinder-side J-type lever and high-friction composite brake shoes. It can be configured to different brake cylinder specifications, braking ratios, slack adjuster specifications and wheel diameters — for example BAB-1 for 915 mm wheels and BAB-2 for 840 mm wheels.
The DAB device consists of the DAB unit brake cylinder, front brake lever, rear brake lever, right combined brake beam, left combined brake beam and chain hoof rings, and is offered in versions with and without manual braking. Its unit brake cylinder is arranged at the middle pull rod position and its slack adjuster uses a built-in control device. Configuration is again matched to cylinder specification, braking ratio, slack adjuster specification and wheel diameter — for instance the SQ6 automobile transport dedicated car uses a DAB device with a pressure ratio 5.4 unit brake cylinder and a braking ratio of 6.6.
Drawings, material certificates, configuration data and model selection tables for these foundation brake components are available on request.
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