NewTread From OTR
New retread technology for mine and quarry tyres
As new legislation regarding the disposal of earthmover tyres comes into place, the need to prolong tyre life, reduce running costs and minimize disposal costs is becoming increasingly important. To help meet these needs, OTR Tyres — Europe’s largest earthmover tyre specialists — have launched NewTread, a completely new type of retread aimed directly at harsh mine and quarry environments. Based on a process that has been used exclusively and with great success in Germany for the last 30 years, the product was unveiled to the UK quarrying industry at Hillhead 2001.
Unlike traditional ‘smooth and groove’ retreads, which can only be produced using natural rubber compounds, OTR’s NewTread tyres utilize a preformed tread made from a synthetic rubber compound which is vulcanized on to a prepared used casing. The process was developed and perfected by the German firm Schelkman, but the technology has now been adopted and improved by OTR under a franchise arrangement. Setting up the new manufacturing process, which commenced full production in April 2002, has involved around £100,000 of capital investment in new equipment as well as some internal factory reorganization at OTR’s Alfreton headquarters.
To the uninitiated, the most obvious difference between a NewTread tyre and a traditional earthmover retread is that the former looks very similar to a new tyre, whereas the latter bears a distinctive ‘retread’ appearance. However, the difference between the two is more than just visual. Of greater significance is the ability to use synthetic rubber in the production of NewTreads, which, unlike natural rubber, makes them highly resistant to cuts and therefore prolongs their operational life and maximizes uptime on site. In pre-production trials at an opencast coal mine in South Wales, NewTreads were found to last 85–90% as long as new tyres, whereas smooth and grooves only lasted about 50% as long.
In addition, OTR say NewTreads cost around 25% less than new tyres and are about 30% less expensive to run. The only potential drawback is that NewTreads are less resistant to heat than traditional retreads. This makes them more susceptible to degradation at high temperatures, although this is unlikely to pose a serious problem to operations in the UK.
Existing production processes at Alfreton currently constrain the output of NewTreads to four tyres a week. These are produced in the two most popular tyre sizes, 2700R49 and 2400R35, with manufacturing being conducted almost exclusively on a ‘casing exchange’ basis. In simple terms, on arrival at the factory the used casings are checked, cleaned and skimmed before being fitted with segments of preformed tread — seven segments in the case of the smaller tyre size and eight on the larger one. The tread and casing then have an inner and outer rubber envelope vacuumed on to them, which forms a tight seal around the entire tyre and provides the pressure needed to secure the tread to the casing while vulcanization takes place.
The NewTread vulcanization process is fundamentally different to OTR’s traditional retreading operations, with curing taking place over a period of 12h in a new water autoclave at a temperature of 95°C, unlike traditional retreads which are cured at 140°C. This lower curing temperature results in greater casing reliability and reduces processing costs, while the use of synthetic rubber compounds gives NewTread retreads the look of a new tyre and virtually the same operational advantages, but at a lower cost.
Commenting on the new manufacturing process, OTR’s managing director, Chris Skelton, said: ‘NewTread has required a major investment by the company, but we believe it is a positive move that will give our customers another reason for choosing OTR to handle their total tyre requirements.’
OTR Tyres Ltd, Bluebell Close, Clover Nook Industrial Park, Alfreton, Derbys DE55 4RD; tel: (01773) 520885; fax: (01773) 520882; website: www.otr-tyres.co.uk