Why Are Our Go Kart Drive Belts Failing?
When your kart's drive belt fails it is quite common to blame the belt quality, but that's not always the case.
The belt failing may simple be the symptom to your problem, the cause of the problem could be much deeper.
In this article we look at some of the primary reasons drive belts fail. The way the drive belt fails usually leaves clues to the cause of the failure.
Match your failed belt to the pictures below and it will give you an indication to the real cause of the failure.
It is quite a technical read (i fell asleep writing it, twice!) but this document has helped several of our customers diagnose and solve their issues of drive belt failure. There is a glossary at the end for all the tech speak.
Cause of Failure - Over Tensioning the Belt
Over tension on small pulley's will usually result in land cracks with eventual tooth shear or tensile member break.
2. Over tension on moderate size pulley's will usually result in pulley footprint cracks (root radius cracks) leading to tooth shear and/or tensile member break.
3. Over tension on large pulley's will usually result in the land fabric being crushed under each cord with the cord eventually showing through. The belt will most likely fail by tooth shear or tensile member break.
The corrective action for these types of failures is to reduce the tension of the drive belt. If this is not possible then we would suggest using one of our High Power (HP) belts.
Cause of Failure - Moderate Under Tension
Moderate under tension on heavily loaded drives using small pulley's can result in excessive tooth rotation leading to land separation and rubber tear within the tooth body along the cord line. The belt teeth will usually come off in strips and will resemble an adhesion failure.
The corrective action is to increase the belts tension
2. Moderate under tension on moderately loaded drives will usually result in excessive tooth flank wear leading to tooth shear and potential tensile member break. The break will resemble a crimp type failure but the tips or the cord will be frayed.
The corrective action is to increase the belts tension
3. Moderate under tension on lightly loaded drives may result in excessive jacket wear and eventually hook wear on the tooth flank. Shifting the manufacturing length tolerance toward the long side may mitigate or exaggerate this condition. If the belt is on the long side of the length tolerance no abnormal wear may occur. If the belt is to the short side of the length tolerance rapid flank wear may occur.
The corrective action is to increase the belts tension. A special belt length tolerance may in some cases be developed or a modified pulley diameter specified. Cause of Failure - Low Tension
Low tension on moderate or heavily loaded drives will result in excessive tooth rotation leading to land separation and rubber tear within the tooth body along the cord line. The belt teeth will usually come off in strips and will resemble an adhesion failure (it is in fact a form of adhesion failure). If the tension is low enough or the load high enough, the belt will ratchet before the land separation/rubber tear occurs. The belt may now fail with a crimp type tensile member break, shock load type tensile member break, belt edge roll up, tooth shear, or the belt jumping off the pulley.
The corrective action is to increase the belts tension.
2. Low tension on lightly loaded drives, if not adjusted for, will usually result in excessive tooth or hook wear. This condition usually occurs where a deep tooth belt is used to compensate for a weak drive structure. The deep tooth is used to prevent belt ratcheting at startup when the structure flexes and the center distance is reduced.
The corrective action is to increase the belts tension. If it is not practical to increase the tension, reduce the belt length or adjust the pulley sizes (diameter) to fit the belt tension required.
Cause of Failure - Pulley Misalignment
Angular shaft misalignment or tapered pulleys, belts run on drives with angular shaft misalignment's or tapered pulleys will exhibit a tapered wear pattern across the belts tooth flanks as well as tapered compaction in the lands. Belt failure will normally occur by tooth root tears starting on the side of the belt that is carrying the most tension on the pulleys and then propagating across the belt width resulting in tooth shear. The edge of the belt may also show significant wear due to the high tracking force and may even roll up or try to climb over the pulley flange.
The corrective action - align drive or replace tapered pulleys.
2. Parallel Misalignment belts running on drives that have parallel misalignment will usually show excessive belt edge ware on both edges of the belt. Belt failure will normally occur by tooth root tears starting from both edges of the belt eventually extending across the width of the belt resulting in tooth shear.
The corrective action - align drive or replace tapered pulleys.
Cause of Failure - Extreme Pulley Run-out
The lands of belts run on drives with extreme pulley run-out will have a crushed appearance similar to belts run at high tension on moderate sized pulleys. The belt will usually fail by tooth shear or tensile break. This type of failure most often occurs where bushed pulley's are used and the recommended bushing installation procedure was not followed or where a minimum plain bore pulley was improperly bored.
The corrective action is to reinstall and realign the bushed sprockets or, replace the plain bore sprockets.
Cause of Failure - Sustained Belt Overload or Too Few Teeth in Mesh
Wire belts, mold side of twin power belts, belts with shimmed or heavy upcoated jackets will fail when the rubber between the cord and the jacket tears (land separation) or in the case of the wire belt when the jacket separates from the wire in the land area. the belt teeth will come off in ribbons rather than by individual tooth shear. This is because the rubber between the cord and the jacket cushions the land allowing the belt to run until the cushion layer tears.
