TECHNICAL SOLUTIONS FOR
FRICTION MATERIAL

Complaints, as they say,”come with the territory” and we try to resolve problems with out delay because we don’t want unhappy customers.

Experience tells us there are a few fundamental sources or causes of brake problems, more accurately described as loss of brake effectiveness. Very often the complaints occur soon after reline and are often preventable.

Loss of brake effectiveness is usually expressed in more colorful language, and of all the brake components critical attention or blame is always directed toward the brake lining--”won’t hold as good”,”wore out”, “noisy”,”too hard a lining”. Let’s take this last first one first. What the operator means is poor brake action. An old notion persists, that hard dense lining means low friction-not necessarily so. There are metallic, ferrous, and semi-met materials, very hard, dense yet some have very high friction. It’s the compounding, friction elements, resins, etc. that determine coefficient of friction.

Before condemning the brake lining let’s check the following:

THE BRAKE DRUM - Is the drum surface scored or heat checked? If severe, resurface the drum or disk. A scored drum or disk means that poor brake action will continue until the lining “wear

A check of the old lining with a straight edge will also act as an indicator that you have a drum or rotor that may be scored or worn.

If the drum has been turned a few times, thicker or “oversize” lining might be needed to fill up the drum. New drums? Could be undersize in diameter, preventing proper running clearance, not a frequent occurrence but it happens.

WEAR PATTERN OF THE LININGS - Drum surface might be OK, but is the geometry off? Wear patter will show this. Again, this may be checked with a straight edge on the lining.

Loss of lining contact across the width or along the length means a "dead" brake. Shoe or band may be twisted---must be reworked to proper arc or shape. Check the linkage for worn parts. Repair or replace as needed.

The wear surface of the lining might show poor factory grind, a “washboard” appearance. If this is the case, replace the lining. Hibbing Int’l linings are ground to close tolerance and will not exhibit this problem.

SOME DO'S AND DONT'S -

Don’t try to salvage linings contaminated by grease, oil, or brake fluid.

Do use a feeler gauge to check proper running clearance.

Don’t, on a long band, try to use once piece of lining. Try to set at least three sections of lining.

Do be careful to use the correct size rivet head, shank diameter, taper and length. Rivet clinching tool must not “bottom”on solid portion of rivet shank. Use a torque wrench to tighten bolts. Never use a star clinch for brake lining.

Don’t conterbore linings too deep to get more wear. Material remaining under rivet head should be approximately 30% of lining

Last but not least, all brake lining, if possible, should be allowed an added measure of brake in. In other words, try to avoid using the brake to its maximum for the first applications. Given the opportunity afforded by careful workmanship and proper installation, you will have a proper performing brake with maximum life.

NOISE - Noise is probably the hardest problem to solve in the friction material industry.

Let us first understand that no good supplier would offer a friction material that would be noisy. During the compound development process noise is one of the first things looked for. If their is noise the compound is usually disqualified as a potential new product. So where does the noise come from?

1. Look for glazing on the friction material. Often, in constant drag applications glazing will form after awhile causing noise. Often a light application of ordinary vinegar ( yes the cooking type) which is a weak acid will break the glaze and eliminate the noise. Naturally, check with your supplier to be sure you are using a compound designed for constant drag.

2. Check all mechnicial linkages to make sure they are lubricated and there is no binding. Make sure any bushing in the system are not worn.

3. If this is a new design there may be inherent noise harmonics being generated. If this is the case we need to change the frequency of the harmonic. This can often be done by simply drilling a hole or two in the mating member. Another solution that often works is to use a composite friction material. We at Hibbing have had good results with composites such as cork and fiber materials.
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