News and Events
Our Associates

M/s Holland l.P. USA.
M/s Silver Batts, Australia.
M/s Durel, Germany..
M/s Faigle, Austria.
M/s Duflot, France.
M/s Interep, France
M/s Smc Pneumatics, India
M/s Bayer, Germany.
M/s Seaclear Industries, USA
M/s Mason Industries, USA
M/s Rock Delta, Denmark
M/s Vaber Industries, Italy
M/s Aquasys, Austria
M/s Changzhou Jiangnan, China
Automatic Twist Locks.
Rail Pads
Insulation System
Brake Parts


Brake Parts- Slack Adjuster :: Product Details

The Slack Adjuster DRV 2A 450 / 600 is a Brake Slack Adjuster i.e. a device for automatic adjustment of the clearance between brake blocks and wheels. It is built into the brake rigging as a part of a pull rod. This slack adjuster is double acting and rapid working i.e. it quickly adjusts too large or too small clearances to the predetermined value, it has been set to maintain.

The slack adjuster DRV 2A 450 / 600 is composed essentially of the following parts
• Adjuster spindle provided with screw threads of quick pitch.
• The traction unit containing adjuster nut, adjuster tube and adjuster ear.
• The leader nut unit containing leader nut, barrel.
• The control rod with its head.

Outstanding Features

The brake shoe clearance is adjustable to its correct value in both directions, either when it has become too large owing to wear of the brake blocks and wheels, or when it has become too small, e.g. owing to renewal of worn brake blocks, or due to loading of the wagon altering the brake shoe clearance.

Rapid action
Correct brake shoe clearance is automatically restored after one or two brake application.

If resistance occurs in the brake application, caused by corrosion, icing on brake blocks, etc., the DRV 2A does not pay out slack immediately, but indexes the amount of slack to be paid out. If the slack really is too small, the DRV2A will pay out this indexed slack at the next brake application. Thus false pay-out will not occur.

True Slack Adjuster
Adjustment based on total piston stroke must cause variation of the slack. The DRV2A adjusts on slack only, thus giving the brake its best possible range of piston strokes, and ensuring a smooth and efficient braking force at all times.

If the desired piston stroke is not obtained after successive full service brake application, distance 'A' can be lengthened to increase the piston stroke or shortened to reduce stroke. By rotation of the barrel by hand the slack adjuster can easily be lengthened or shortened. The two nuts are being simultaneously screwed on the spindle in the desired direction.

Principle of operation
The position of adjuster nut on adjuster spindle determines the length of the slack adjuster. The leader nut follows the movement of the barrel and its purpose is to lead the adjuster nut to its correct position on the spindle. Control rod is fixed to the brake rigging or the under frame so that when the brake is applied, barrel moves towards the control
rod head proportionately to the piston stroke. The distance between the head and the barrel, when the brake is fully released is called the control dimensions 'A'. This corresponds to the correct slack.

If the slack is correct, the control rod head touches the end of the barrel at the moment when the brake blocks start to apply against the wheels and no adjustment will then take place.

If the slack is too large, the control nut head pushes on to the barrel increasing the distance between it and the suspension ear by an amount corresponding to the excess of slack before the brake blocks apply. The leader nut follows rotating on adjuster spindle. When the brake is released, the leader nut is, however, locked against the seat
of leader nut casing and the barrel spring causes adjuster nut to rotate on the spindle towards the leader nut. This advance of adjuster nut on the spindle shortens the slack adjuster and adjusts the slack to the correct value.

If the slack is too small the first brake application causes the barrel to screw towards the control rod head until stopped by it. The distance between the two nuts i.e. leader and adjuster has been shortened by an amount corresponding to the deficiency of slack. At the start of the next brake application leader nut is locked in its new position on its adjuster spindle and pay out spring pushes adjuster nut rotating on the spindle until the normal distance between the adjuster and leader nuts has been restored. The slack adjuster is in the way lengthened by proper amount and the slack adjusted to normal.

As the brake rigging is not completely stiff, it will give somewhat under braking force, but thus elastic deflection will not influence the proper adjustment of the slack. The brake rigging deflection shows itself, as a rotation of the barrel during the first part of the brake release movement, but this rotation does not indicate that an adjustment is taking place.


 Slack Adjuster Brake Slack Adjuster automatic adjustment Double-acting Rapid action Verification True Slack Adjuster