AUTOMATIC SLACK ADJUSTER

ECO MASTER

Adjustment pointBraking process

H E V

SB

Sequence of the braking process H = Free stroke of the brake cylinder to cover the clearance (SB) between the brake lining and the

brake drum E = Elasticity of the wheel brake and its transmission elements V = Increase in stroke due to wear and heating SB = Clearance

Brake linings and brake drums are parts subject to wear. As the thickness of the material is reduced thebrake cylinder stroke increases by the value (V), meaning that the brake camshaft has to rotate further. At a maximum rotation of 17.5°, depending on the version, the automatic adjustment mechanism of theECOMaster automatic slack adjuster makes the appropriate adjustment.

As a result the brake cylinder stroke is always kept within the same optimum zone of action. The adjustment stroke is designed so there will always be a sufficient air gap even at higher levels of elasticity and thermalexpansion.

WORKING PRINCIPLEWORKING PRINCIPLE

Sequence of braking processH = Free stroke of the brake cylinder to cover the clearance (SB) between the brake lining and the brake drum.E = Elasticity of the wheel brake and its transmission elements.V = Increase in stroke due to wear and heating.SB = Clearance.

Brake linings and brake drums are parts subject to wear. As the thickness of the material is reduced, the brake cylinder stroke increases by the value (V), meaning that the brake camshaft has to rotate further. At a maximum rotation of 17.5°, depending on the version, the automatic adjustment mechanism of the ECO Master automatic slack adjuster makes the appropriate adjustment.

As a result, the brake cyclinder stroke is always kept within the same optimum zone of action. The adjustment stroke is designed so there will always be a sufficient air gap even at higher levels of elasticity and thermal expansion.

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Hub

StrokeCourse

Brake application

0N

H

E’H

E

V

MA

4

3’

4’

5’

3

2

1

5

NB

WORKING PRINCIPLEWORKING PRINCIPLE

H = Free stroke.H’ = Free stroke when the stroke is increased. E = Elasticity.V = Increase in stroke due to wear and heating.N = Adjustment corresponding to V.NB = Adjustment range.MA = Contact torque.

1 Initial position (internal springs of the brake produce a negative cam torque.2 Brake threshold overcome.3 Clearance )mm = brake lining is in contact with the brake drum.4 Maximum braking torque.5 Initial position reached by releasing the brake.4’ Maximum braking torque, adjustment point is reached, the coupling sleeve engages in the next tooth space in the worm shaft.5’ Start of the adjustment range.

N.B. In the adjustment range, the coupling sleeve rotates the worm shaft and with it, the worm gear and the brake camshaft. This reduces the clearance between the braking lining and the brake drum. The BPW ECO Master slack adjuster is designed to ensure there is always a sufficient amount of clearance even with large strokes, e.g. thermal expansion of the brake drum, brake lining wear, elasticity.

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Adjustment lever

Coupling sleeve Reaction bracket

Worm shaft

Limit stop

Brake lever

FUNCTIONAL DESCRIPTIONFUNCTIONAL DESCRIPTIONInitial position

Initial Description

The BPW ECO Master automatic slack adjuster is connected to the axle beam via the control lever and the reaction bracket. The inner stop of the control unit permits a lever travel of 30°. This protects the adjusting device contained within against damage in the event of extreme strokes.

The control lever is in a positive engagement with the adjustment lever. The latter engages in the coupling sleeve. The adjustment lever and the coupling sleeve are designed so the clearance is always optimum. The coupling sleeve has a special tooth profile on its end. The force of a compression spring causes this to engage in the gearing on the head of the worm shaft.

Independent rotation of the worm shaft is prevented by the compression spring on the one hand and by the holding bracket on the other hand. The worm shaft head has a hexagonal profile and can be adjusted using a size 19 ring spanner. The plastic cap seals the entire coupling space. All adjustment parts are therefore accommodated in the protected interior of the slack adjuster. Its function cannot be affected by dirt, mositure, ice or snow.

The internal springs in the brake exert a negative torque in the initital position. The coupling and adjustment are in the initial position.

Control level

FUNCTIONAL DESCRIPTIONFUNCTIONAL DESCRIPTION

The brake threshold is overcome when the automatic slack adjuster is operated. The brake lining is brought into contact with the brake drum. The adjustment lever moves against the upper grooved side of the coupling sleeve.

If the adjustment point is reached during a braking process, the teeth on the coupling sleeve engage in the next tooth gap of the worm shaft

The coupling sleeve is turned by the adjustment lever as the cyclinder stroke increases. If the adjustment point is not reached, the teeth do not move on one position. The stroke to the adjustment point is set by the groove width and the length of the teeth on the coupling. Braking strokes within this range do not cause the automatic slack adjuster to reposition.

Adjustment takes place when the brake is released during the last portion of the return stroke. The adjustment lever moves back and, once the clearance within the coupling has been overcome, applies a tractive force to the lower grooved side of the coupling sleeve.

Brake application

Brake application

Brake application

Brake release

Adjustment lever

Coupling sleeve

Worm shaft

FUNCTIONAL DESCRIPTION

Adjustment

In the adjustment range, the coupling sleeve is rotated by the engaged teeth, the worm shaft and with it, the worm gear and brake camshaft. This reduces the clearance between the brake lining and the brake drum. The adjusting device is designed to ensure there is always a sufficient amount of clearance even with large strokes (e.g. thermal expansion of the brake drum, brake lining wear, elasticity.)

Adjustment

The initial position is reached at the end of adjustment. The toothed coupling only adjusts in small, positive engagement steps from one position to the next. Its adjustment is not infinitely variable using static friction. This means the adjustment distance is always exact.

SET UP PROCEDURES

All BPW drum brake axles are fitted with a brake lining wear indicator that is bolted directly to the camshaft adjacent to the slack adjuster.

These are made of plastic material and coloured either black, or in the case of later versions, orange.

When new linings are fitted, the indicator is set to the vertical position. As the lining wear takes place, and adjustment is taken up, the indicator will rotate with the camshaft. When the indicator has rotated 90° to the horizontal position the linings are due for replacement.

Wear indicator

SET UP PROCEDURES

SET UP PROCEDURES

The brake cylinder push rod length needs to be set correctly. In the example, a BPW standard air chamber bracket is shown on an H series axle. The correct effective push rod length for this axle is 227mm.

The 227mm dimension is measured from the brake cylinder mounting interface to the centre line of the clevis pin hole with the brake in the OFF position.

Other types may have different requirements for the effective push rod length dimension. If you are unsure about this dimension, contact BPW Technical Services with the axle code and this information can be verified.

The air chamber brackets are designed in such a way that the fixing holes for the cylinder are offset so as to allow the brake cylinder push rod to align to the appropriate lever hole position without having to use the +/-3° of deflection allowed by the cylinder manufacturer.

Provision is made in the air chamber bracket to locate the external cylinder pull off spring.

120, 135, 150, 165 and 180mm hole positions are available in the bracket but in practice the 180mm position is seldom used.

The 8mm thick brackets will accept both diaphragm and piston spring brake units without any additional reinforcement.

Many different types of air chamber brackets are available across the BPW range of axles but all encompass the features listed.

Always consult the cylinder manufacturer for mounting details.

BPW brake chambers

Tighten alternate side lock nuts to 180Nm (180Nm-210Nm)

◄(1) Tighten yoke lock nut to 80Nm

Other chamber makes:

Consult manufacturers mounting instructions

ECO Master - Brake push rod length

Brake cylinder installation

SET UP PROCEDURES

The slack adjusters are secured with a nut and washer to give a positive location on the camshaft. This method prevents undue wear to the splines. The camshaft also falls short of full engagement into the slack adjuster splined boss preventing a step wearing into the splines.

The slack adjuster is drawn up to either a shouldered end of the splines or to a snap ring, depending on the design of the camshaft.

The splines are coated with BPW ECO Li Plus grease prior to assembly.

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2. Installation - ECO Master

Final tightening of the camshaft nut and positioning of the wear indicator is best left until all set up adjustments are made.

The reaction bracket bolts should be loose at this stage.

SET UP PROCEDURES

● Brake off.

● Push rod length set.

● Remove rubber closure cap.

1. Adjust the auto slack into position so that the clevis pin can be engaged and secured.

2. The pin should pass freely into position and be lubricated prior to assembly.

The adjustment bolt of the auto slack is a 19mm hexagon profile. By fully engaging a standard socket onto the adjustment bolt, the dog clutch is disengaged allowing the whole unit to be manipulated

2. Installation - ECO Master

SET UP PROCEDURES

3. Installation ECO Master

ECO Master - pointer aligned

With the 19mm socket fully engaged onto the adjusting bolt, align the pointer on the reaction bracket with the pin on the side of the slack adjuster. No more than hand pressure in the direction of the arrow should be required for this operation.

REMEMBER: Brake off - pin and pointer aligned.

Pin and pointer aligned correctly.

Automatic adjustment function enabled.

SET UP PROCEDURES

Double check that the brake is off and the pin and pointers are still aligned.

Secure the reaction bracket to the inner camshaft bearing support plate.

The objective is to set the lining to drum clearance to 0.7mm - 1.0mm.

This is achieved by rotating the 19mm adjustment bolt of the auto slack until the free play equals 10 - 15% of the effective lever length dimension.

Remember to fully engage the 19mm socket to disengage the internal clutch mechanism.

Position the brake lining wear indicator and tighten the camshaft nut.

Example: A set up with a 150mm brake lever length will have an initial free play of 15 - 22mm.

4. Installation - ECO Master

Setting free play ‘a’

SET UP PROCEDURES

ECO Master - Setting free play

ECO Master - Setting free play

ECO Master - Fitting pull-off spring

Adjustment procedures

1. Measurement method:

a) Measure from the brake chamber front to centre of clevis pin. (standard overslung measurement = 227mm).

b) Adjust until measurements is 10 - 15% greater. (Example: A set up with a 150mm brake lever length will have a final measurement of between 242mm and 249mm.

Adjustment procedures

2. Measurement method:

a) With a fully engaged 19mm socket and the wheel free to rotate, adjust the automatic slack adjuster until the brake is ‘Just On’ - DO NOT OVERTIGHTEN.

b) Rotate the adjuster mechanism by a ‘Half Turn’ (180°). The free play should then be at least 12%.

Lubricate the slack adjuster with BPW ECO Li Plus grease until clear grease emits from the adjustment bolt housing.

Refit the rubber protective cover.

Fit the external pull-off spring.

BPW Limited Centurion Way, Meridian Business Park, Leicester LE19 1WHPhone + 44 (0)116 281 6100info@bpw.co.uk - www.bpw.co.uk