Document ID: chunk:federal_register_of_legislation:F2006L03061:body:0:p22
Version: federal_register_of_legislation:F2006L03061
Segment Type: other
Provision Reference: 
Character Range: 60813–63868

performance with two brake assemblies rather than wheel performance.

38.4.6.3.                    Suspension Behaviour

38.4.6.3.1.              Suspensions shall be classified by the 'Administrator' as 'Brake Reactive Suspensions' or non 'Brake Reactive Suspensions'.

38.4.6.3.2.              Suspensions being determined as brake reactive shall be further specified in accordance with the remainder of clause 38.4.6.3.

38.4.6.3.3.              The 'Skid Limit' for each 'Axle' as determined by the need to provide service, emergency and parking 'Brakes' shall be determined.

It is necessary to determine the 'Skid Limit' for each braked 'Axle 'in a group of 'Axles' connected by a 'Brake Reactive Suspension' to ensure that brake induced 'Axle Load' changes do not lead to premature wheel lock-up. Note: Premature wheel skid could either be unsatisfactory in its own right (service brake effectiveness) or it could invalidate calculations based on no-skid performance (parking and emergency brake effectiveness).

38.4.6.3.4.              For a 'Service Brake System' 'Axle Group' the 'Skid Limit' value, or a range of values, at a total retardation not less than 0.45 the 'Axle Group' load shall be determined.

The test result shall be reported as the value of the indicated retardation force for each 'Axle' divided by the greatest of the 'Axle' retardation forces.

In the case of 'S-Cam' air 'Brake Systems' the overall effect of changing actuator and slack adjuster sizes can be simulated by individually adjusting the air pressure to each 'Axle'.

38.4.6.3.5.              For an 'Emergency Brake System' or a 'Parking Brake System 38/00' the 'Skid Limit' value shall be specified as the dimensionless ratio:

Indicated retardation force
Static 'Axle Load.'

The limit value should be determined by increasing the braking uniformly on all the wheels concerned until one wheel locks.

38.4.6.3.6.              For the purpose of testing the suspension shall be installed in a typical trailer application, be fitted with 'Axles', wheels and tyres of a size appropriate to the mass rating of the suspension, and be fitted with identical calibrated 'Brakes' at each 'Axle'.

"Calibrated" in this case means that the relationship between the input 'Control Signal' and the output torque for the 'Brakes' on each 'Axle' has been measured.

'Skid limits' may be determined either dynamically or at a low speed under drag conditions, in either case at a test mass not less than one half 'GGALR'.

Note. Rigid 'Drawbar'/chassis installations will not be considered as typical of installations on 'Pig Trailers' having a pivoted 'Drawbar'.

38.5.                                ALTERNATIVE STANDARDS

(Refer to clause 38.3.1.2.)

Table 1

Group 'Axle Load' Limits

Figure 1

Service Brake Effectiveness

Figure 2 – Calibration of Test Rig

Figure 3 – Testing the Trailer

NOMENCLATURE FOR FIGURES 2 AND 3

A =  Supply connection with single check valve and regulator set at 650 kPa

CF = trailer brake actuator

L  = coupling