Q / have two identical 8-ton lorries and in ‘a• one
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case the front brakes squeal when braking fairly hard at a speed of about 15 mph. The brakes of the second vehicle, which is also the oldest, do not squeal under any speed/load condition.
The distributor has fitted new linings to the front brake shoes of the offending vehicle, but the trouble persists. Can you suggest a cure? In both cases the brakes operate efficiently.
AThe type of brake squeal you mention is known as the "slip-stickphenomenon, the friction surface of the lining alternately gripping the metal surface of the drum and then sliding. A squeal is produced because of the very high frequency of the on-off cycle. Special linings are available that reduce or eliminate squeal by virtue of the fact that the difference between their static and dynamic friction is relatively small.
Squeai can also result from the absence of sufficient or appropriate damping. DampiN depends in part on the structure of the shoe anchors and in your case the fault may be in the condition of the anchor assemblies. possibly sortie minor assembly error, lack of proper lubrication or looseness may account for the squeal produced. A detailed check of the anchor assemblies may well reveal the error.
You are also advised to make certain that the shoes are in good condition. A fractured web could, for example, promote squeal because it would reduce the resistance of the shoe to flexing I have read of the RTITB's h.g.v. driving instructors' course. I am a long-service driver with a motor transport company operating 60 tankers and would like to become a driving instructor. How do I go about it?
AAs reported in CM the RTITB course to
which you refer is based on London until October when it will be transferred to the new RTITB centre at High Ercall in Shropshire for education and training.
These courses are being attended at present by staff who already have some experience of instruction in their own companies, but it is intended that these courses will provide a means for senior drivers and staff with similar experience to become proficient as driving instructors However, it is for the employer to recommend candidates for these courses and we therefore suggest that you tell your employer that you are interested in this type of work and will be glad of the opportunity to attend one of these courses.