Chapter 6 Transmission The transmission system comprises all of the components that transfer the force and movement from the Braked Coupler to the inertia brakes in the axles. Fit the axles to the trailers as detailed in Chapter 3.The next step is to connect the components as shown in the following drawings. NB DO NOT HAVE ANY TENSION IN THE CABLES BEFORE THE BRAKES ARE PROPERLY ADJUSTED! Failure to observe the rule will lead to problems with the brake system. 1. TRANSMISSION COMPONENTS A. BRAKE ROD We recommend that a 10mm threaded rod be used to connect the transmission lever in the coupler to the compensator on the brake cables. B. BRAKE COMPENSATORS C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 195 of 321
Extracts from SANS20013 paragraph 5.2 follow: 5.2.2.4. The service braking system: 5.2.2.4.1. shall act on all the wheels of the vehicle; 5.2.2.4.2. shall distribute its action appropriately among the axles; 5.2.2.5. The action of the service braking system shall be distributed between the wheels of one and the same axle symmetrically in relation to the longitudinal median plane of the vehicle. Compensation and functions, such as anti-lock, which may cause deviations from this symmetrical distribution, shall be declared. In an overrun brake system, the requirements of 5.2.2.4.2 and 5.2.2.5 are achieved using Brake Compensators. BURQUIP supplies compensators for single and tandem application: i. Single Axle Compensators. Code BC02 C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 196 of 321
ii Tandem Axle Compensators C. BRAKE CABLES See Chapter 4 Paragraph 8C. 2. DRUM BRAKE SYSTEM MOUNTING AND ADJUSTMENT The next step is to connect the components as shown in the following drawings. NB DO NOT HAVE ANY TENSION IN THE CABLES BEFORE THE BRAKES ARE PROPERLEY ADJUSTED! Failure to observe the rule will lead to problems with the brake system A. FIT BRAKE CABLES TO THE WHEEL BRAKES: C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 197 of 321
i) KNOTT Type Cables: DO NOT REMOVE THE BRAKE DRUMS FROM THE AXLE TO FIT CABLES. Step1 Remove PVC cover and loose Cable Bracket Step2 Fit the banjo on the cable into the groove in the exposed link. Step 3 Fit the cover plate. Slide the cap of the cable into position. The assembly is ready to use. C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 198 of 321
ii) GSM Type Cables DO NOT REMOVE THE BRAKE DRUMS FROM THE AXLE TO FIT CABLES Step 1 Release the Spring Clip in the Cable Eye. Step 2 Remove PVC Plug from the Brake Cable Entry Hole in the back plate. Slip the Eye of the Brake Cable over the end of the Lever in the Brake Expander. Step 3 Push the Spring Clip back into position in the Cable Eye. (A small screwdriver works well). Step 4 Fit the cable holders (BSCRP) into the hole in the Back Plate. Ensure that the cap on the Cable Outer End fits snugly over the tube formed by the cable holders. Bend the lock strips on the cable holders over the cap end of the Cable Outer with a pair of pliers. C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 199 of 321
B. BRAKE ADJUSTMENT The same procedure is used in both the Knott & the GSM type brakes: Fit the wheels to the trailer. Ensure that all the wheels are in the air and they can rotate freely. The expander on the brake must not be under tension (if necessary the brake rod can be loosened. Check the actuation of the expander and the cable. Adjust each wheel brake as follows NB The wheel may only be rotated in the FORWARDS direction during brake set-up. The brake system will not function correctly if the wheels are rotated backwards at any stage of the brake set-up. While rotating the wheel turn the Adjuster Bolt (opposite the cable inlet) CLOCKWISE until the wheel can no longer be turned or else rotates with great difficulty. Loosen the Adjuster Bolt by turning anti-clockwise (approximately ½ turn) until the wheel rotates freely forwards. Slight grinding noises that do not affect the free running of the wheel are permitted. Do not use any turnbuckles etc fitted on the brake rod to adjust the brakes. Do not use the brake rod itself to adjust the brakes. Fit the brake cables to the compensators as shown. C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 200 of 321
Tandem set up viewed from under the axle. Note the grouping of the brake cables to correctly distribute the brake input forces Single axle set up viewed from under the axle. Note the use of compensator and nuts to correctly distribute the brake input forces. In all cases, all the M8 nuts must be in front of the compensators. Do not fit a nut to the M8 threaded end behind the compensator, as this will prevent the compensator from sharing the input force evenly between the brakes (violation of 5.2.2.5 above). After all of the brakes have been set, balance the brakes as follows: Ensure that the coupler shaft is in the fully open position. Adjust the length of the brake rod until the transmission lever touches the back of the coupler shaft (slight play < 3mm is acceptable). Pull up the Hand Brake Lever and check the position of the brake compensators (they should be perpendicular to the brake rod). If necessary, adjust brakes until the compensators are perpendicular to the brake rod when the hand brake lever is pulled. Actuate the handbrake a few times then gently pull the lever further to correctly set up the brakes. Release the hand brake. Spin the wheels forwards and pull up the hand brake. With over-center hand brakes, the braking effect should start when the lever is 10 15mm over center. On ratchet hand brakes, the braking effect should start on the third tooth. C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 201 of 321
Lower the trailer and take for a test drive. Single Solid Axle Layout C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 202 of 321
Tandem Solid Axle Layout C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 203 of 321
Single Rubaride Axle Layout C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 204 of 321
Tandem Rubaride Axle Layout C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 205 of 321
Solid braked axles are marked with a red sticker on the right hand side top face of the axle. This shows the correct installation of the axle. DIRECTION OF TRAVEL R It is vital that the axle is installed correctly as the brakes must be on the correct side of the trailer in order for them to function. It will be noticed that we only supply single axles and tandems. Some clients have wanted to mount three axles on a trailer. BURQUIP does not recommend this practice, as the trailer will be almost impossible to maneuver. In addition, in the case of overrun-braked axles, it will not be possible to meet the requirements of SANS20013 5.2.2.5. 2. HOW THE OVERRUN BRAKE SYSTEM FUNCTIONS (SEE SANS20013 ANNEX 12) This section should be read in conjunction with SANS20013 Annex 12. When the axles etc are installed as shown in the diagrams above then the trailer will comply with the requirements of SANS20013 Annex 12 Paragraph 3 GENERAL REQUIREMENTS. When the correct Couplers are used for the trailer then the requirements of SANS Annex 12 Chapter 4 REQUIREMENTS FOR CONTROL DEVICES will be met. C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 206 of 321
When a trailer equipped with correctly installed overrun brakes is towed, the braking performance will be according to road ordinance requirements. A. OVERRUN BRAKING When the towing vehicle pulls away, the inertia of the trailer causes the coupler to be pulled fully open. The trailer then follows behind the vehicle, as one would expect. Slight variations in speed of the combination are compensated by the hydraulic damper that is inside the coupler. When the towing vehicle is slowed down significantly, the inertia of the trailer causes the trailer to push against the towing vehicle. The coupler then slides closed - this sliding action is moderated by the hydraulic damper. In the process, the piston of the coupler pushes on the transmission lever in the coupler. Movement is reduced by the lever ratio while the applied force is increased by the lever ratio. When the transmission lever moves backwards against its pivot it pulls the brake rod forwards. The brake rod then moves the brake compensator forwards, which pulls the brake cables. When the brake cables are pulled, the expander inside the brakes forces the brake shoes against the brake drum. Friction forces then develop which slow the wheel (ultimately the trailer) down. The swiveling ability of the brake compensators ensures that the available force is correctly distributed among all the brakes. The ratios used are carefully calculated to ensure that the brake performance is optimised. There is more movement in the coupler shaft than is required to fully activate the brakes when the trailer is moving forwards. Therefore, the brakes will always be applied if they are correctly adjusted. The condition of the brake shoes can be easily checked using the inspection holes in the brake mechanism back plates. The shoes should be re-lined / replaced as required (see CHAPTER 4 Paragraph 11 BRAKED AXLE MAINTENANCE INSTRUCTIONS above. B. AUTOMATIC REVERSING When the trailer is reversed, the coupler is pushed inwards and the movement is transmitted to the wheel brakes. Drum Braked axles supplied by BURQUIP feature automatic reverse. Therefore, trailers C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 207 of 321
equipped with these brakes and the recommended couplers satisfy SANS20013 Annex 12 Clause 3.4 The inertia braking system must allow the trailer to be reversed with the towing vehicle without imposing a sustained drag force exceeding 0.08.g.GA. Devices used for this purpose must act automatically and disengage automatically when the trailer moves forward. When the brake shoes contact the brake drum, the sliding shoe (trailing shoe) is dragged OPEN by the friction developed. Therefore, the drum is free to rotate again. Eventually all of the movement in the coupler shaft (typically 90mm) will be used up and the shaft cannot move further backwards. The wheels can still rotate backwards so the trailer can be reversed. This feature even works when reversing uphill. When the trailer is pulled forwards again, the coupler shaft is pulled back into the fully open position and the springs in the sliding shoe in the drum brake return the shoe to its normal closed state. The auto-reverse brakes are made in left hand and right hand versions. It is essential that the left hand brake be used on the kerb side (i.e. Left) of the trailer and that the right hand side brake be used on the road side (i.e. right) of the trailer. If this is not observed then the trailer brakes will NOT function in the forward direction and will lock when the trailer is reversed. This often results in serious and costly damage to the trailer and the axle components. C. PARK BRAKE SANS20013 Paragraph 5 defines all of the requirements for braking systems of all vehicles category M, N & O. Obviously we are mainly concerned with category O vehicles. In the case of overrun brakes we only need to consider category O 2. Paragraph 5.2.2 deals specifically with category O vehicles, in particular 5.2.2.10. On every trailer which is required to be equipped with a service braking system, parking braking must be assured even when the trailer is separated from the towing vehicle. The parking braking device must be capable of being actuated by a person standing on the ground; however, in the case of a trailer used for the carriage of passengers, this brake must be capable of being actuated from inside the trailer. C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 208 of 321
The Parking Brake performance required of a vehicle is defined in SANS20013 5.1.2.3. Parking braking system The parking braking system must make it possible to hold the vehicle stationary on an up or down gradient even in the absence of the driver, the working parts being then held in the locked position by a purely mechanical device. The driver must be able to achieve this braking action from his driving seat, subject, in the case of a trailer, to the provisions of paragraph 5.2.2.10. of this Regulation. The trailer air brake and the parking braking system of the towing vehicle may be operated simultaneously provided that the driver is able to check, at any time, that the parking brake performance of the vehicle combination, obtained by the purely mechanical action of the parking braking system, is sufficient. SANS20013 Annex 4 deals with tests to be carried on brake systems. Paragraph 2.3 of this annex deals with the performance of parking brake systems as follows: 2.3. Parking braking system 2.3.1. The parking braking system must, even if it is combined with one of the other braking systems, be capable of holding the laden vehicle stationary on an 18 per cent up or down gradient. 2.3.2. On vehicles to which the coupling of a trailer is authorized, the parking braking system of the towing vehicle must be capable of holding the combination of vehicles stationary on a 12 per cent up or down-gradient. 2.3.3. If the control is manual, the force applied to it must not exceed 40 dan in the case of vehicles of category M1, and 60 dan in the case of all other vehicles. 2.3.4. If it is a foot control, the force exerted on the control must not exceed 50 dan in the case of vehicles of category M1, and 70 dan in the case of all other vehicles. 2.3.5. A parking braking system that has to be actuated several times before it attains the prescribed performance is admissible. 2.3.6. To check compliance with the requirement specified in paragraph 5.2.1.2.4. of this Regulation, a Type-0 test must be carried out with the engine disconnected at an initial test speed of 30 km/h. The mean fully developed deceleration on application of the control of the parking brake system and the C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 209 of 321
deceleration immediately before the vehicle stops shall not be less than 1.5 m/s2. The test shall be carried out with the laden vehicle. The force exerted on the braking control device shall not exceed the specified values. The handbrake features an hydraulic piston and spring that is activated when the parking brake lever is lifted. This spring has two functions it supplies more movement to the brake rod than can be obtained from the coupler shaft and it supplies force into the brakes. When the parking brake lever is lifted past its centre then it automatically continues to move (as a result of the force supplied by the spring cylinder). In the process the brake cables are pulled and the brake shoes are forced against the brake drum. If the trailer is pushed forwards, the brakes will lock and the trailer will remain stationary. However, if the trailer is pushed backwards, then the sliding shoe of the brakes opens as described above and the wheel will rotate backwards. After approximately ½ turn of the wheel the sliding shoe can no longer open as it reaches its limit of travel. The autoreverse spring and cylinder still release sufficient movement and force into the brake to ensure that the wheel is locked in the forward and reverse directions. The automatic braking requirement is satisfied by the breakaway cable. The purpose of this device is to actuate the parking brake of the trailer in the event that the trailer and towing vehicle become accidentally uncoupled. 3. TROUBLESHOOTING THE BRAKE SYSTEM A. BRAKES PULL ON ONE SIDE Symptom: brakes pull to one side of the trailer and the trailer does not keep track with the towing vehicle during braking. Solution: Jack up the trailer with all wheels clear of the ground. Check the brake cable carefully if a cable is broken or kinked it must be replaced. Release all tension from the brake cables. Adjust the brakes as described above. B. TRAILER BRAKES VERY SENSITIVE C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 210 of 321
Symptom: The trailer brakes apply when the vehicle is only slightly slowed. Alternatively, the trailer brakes intermittently during normal driving. Solution: Check the hydraulic damper. It must be very stiff when slowly pushed. If it is easy to depress or leaking oil then the damper must be replaced. Follow the steps in Coupler Maintenance above. If the damper is still good: jack up the trailer, loosen the cables and re-adjust the brakes. Examine the cables if the cables are stretched then replace. Reconnect the cables. Check the brake rod and the gap between the transmission lever and the piston in the coupler. Adjust the rod if necessary. C. BRAKES ARE VERY INEFFICIENT Symptom: The trailer starts to push the towing vehicle during braking. Solution: Jack up the trailer. Check the thickness of the brake linings through the inspection holes in the brake back plate. Reline / replace the brake shoes as required. To replace the brake shoes the brake drum must be removed. Follow the instruction from Chapter 4.11 B BRAKED AXLE MAINTENANCE INSTRUCTIONS. Examine the brake shoe surface in the brake drum. Have the brake drum skimmed if necessary. If the grooves are too deep or the drum can no longer be skimmed then the brake drum must be replaced. Check the brake rod. If it is bent then it must be replaced. Adjust the brakes. Reconnect the brake cables. Re-adjust the brake rod. D. BRAKES OVERHEATING Symptom: The brake drums get very hot when the trailer is towed even a short distance. Solution: If the axle is newly installed or the brakes have recently been adjusted then the brake adjusting screw is too tight. Jack up the trailer, release the brake cables from the brake rod. Re-adjust the brakes. If the axle has been on the trailer for some time and the brakes have been functioning correctly for a long period then the culprit is most likely a kinked brake cable. Check cables and replace as C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 211 of 321
required. If this does not solve the problem then the return springs inside the brakes may be worn out. Replace the return springs. At the same time, check the brake shoes surface in the brake drum. It may be rusty if so clean it if possible or replace the brake drum if the rust is too deep. E. BRAKES LOCK WHEN THE TRAILER IS REVERSED Symptom: The trailer cannot be reversed. Solution: If a solid axle is fitted ensure that the brakes are on the correct side of the trailer as indicated on the mounting sticker B01. If the axle is not correctly installed, remove it and install correctly. Adjust the brakes as described above. Reconnect brake rod. If the axle is a RUBBARIDE axle or a correctly mounted solid axle then the brake adjustment has not been done as prescribed. Disconnect the brake cables from the brake compensators on the brake rod. Jack the trailer up ensure that all wheels clear the ground and are free to rotate. Adjust the brakes as prescribed. Connect cables to the brake compensator. Readjust the brake rod. Test. C:\Users\Hilton\Documents\Burquip Training Manual 2011-01-21.doc Page 212 of 321