Exploitable results
This CRAFT project has developed an economical NDT method for detecting rust and broken cords in a tyre casing, has assessed the replacement of organic solvents for water in tyre cements and has developed a laboratory/factory method for ranking tread wear resistance under service conditions.
The work on electromagnetically detecting rust and broken steel cord in casings has been performed at the RWTH.IE in Aachen and at Telemeasurement, with support from Reifen Darley in Luedinghausen and Bekaert in Zwevegem together with idea input from Bandvulc, Mesas, Rula, Lang, RTS, Vacu-Lug, Kraiburg and Dr Grosch. Laboratory tests have shown the feasibility of detecting rust on steel cords buried within the tyre casing. Much depends on signal sensitivity. The result of the project work is that signals can now be detected from the belt packages, it is possible to find as little as 7.5% rust conversion, to say in which layer region lies the fault and to distinguish between faults in the outer or inner belts. This allows decision of accept/reject for a particular casing. Other casing defects, such as fretting in the shoulder region may also be detectable using the new electromagnetic method. The expectation is that Telemeasurement will move the work forward to produce a novel tyre casing evaluation machine that would be in the market place for the new millenium.
The laboratory work on water-based tyre cements has been performed at TARRC/MRPRA and Bekaert, with support service testing by Bandvulc, Major and TTS, using retread materials supplied by Empobor and Kraiburg. Spray patterns and depth consistence of deposited cement have been examined and it is concluded that the spray patterns are satisfactory for commercial production. Measurements of tack level show that tack for all cements is equivalent. Drying times for water-based cements were found to be longer than for solvent-based cements by about 25% and tack was 80% that of solvent-based cement. Laboratory studies of a comparison of tread adhesion for solvent and water-based cements showed that no failures occurred at the bond interface. The comparative durability of water-based cements was assessed for retreaded tyres run against a rolling drum tester and for use under service conditions (fleet testing). The results show that water-based cements have no adverse effects on steelcord corrosion, nor on adhesion, and therefore they are satisfactory in practice. Their use makes for a better factory environment.
%The work on predicting tread wear resistance was performed by TARRC/MRPRA, by Dr Grosch and by Cabot, with the support of all the SME Proposer retreaders for in-service tread wear results, and Lang for abrasion machine design. A broad range of tread wear in-service results were obtained as a basis for comparison with data from laboratory abraders to see whether any of the presently available abraders can be 'tweaked' to produce a reasonable prediction, or whether a new abrader can be designed and built to do this. The retreaded tyres were placed onto truck fleets for wear testing, and also some retreaded tyres were tested under accelerated conditions using a vehicle trailer with its wheels angled to the direction of travel. Laboratory abrasion data for the same tread compounds was gathered at the same time in readiness for the ultimate comparison. This was a long-term exercise. A meeting was convened to discuss the comparison and to arrive at a consensus on abrasion testers best suited for retreaders. In broad comparisons of tyre road wear data with abrasion test data it was found that the Grosch abrader gave a correct ranking, whereas other abraders did not. Plans are being made for producing a commercial prototype Grosch abrader especially for the purpose of helping SME retreaders, and this aim will be pursued beyond the official end of this project.
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