Never Bury Alive a Sound Tyre Casing
Page 35
If you've noticed an error in this article please click here to report it so we can fix it.
THE temporary loss of our East Indian rubber supplies has raised the matter of tyre conservation • from the level of ordinary business economy to that of urgent national importance, for there is no getting awayfrom the 'fact that for a time we shall be very short of rubber. In these circumstances, the remoulding of worn tyres which still have a sound internal casing renders an important contribution to the conservation of existing stocks.
The casing, however, must be sound, otherwise a satisfactory remould is impossible. This fact was particularly emphasized by Mr. H. E. Pope, general manager of the Regent Tyre and 'Rubber C., Ltd., on 'a recent visit which we made to this concern's works at Edmonton. The Regent company is associated with the Marsham Tyre Co., Ltd., an important concern with 33 branches, and the Edmonton plant is thoroughly up to date.
On arrival at the works, tyres are examined to see if they will stand a remould, and many have to be rejected as unsuitable. Chief causes of rejection are treads worn too far down into the fabric, bad cuts, breaks in the side walls, and signs. of strain from overloading, or from having been run when under-inflated.
The tendency to run tyres beyond the point at which remoulding becomes impossible is one that will have to be checked shortly by dire necessity. When a cover is ripe for the process, it probably has about 1,000 miles of life left in it and no more, but if taken then, and sent to an up-to-date remoulding factory, the tyre will be ready to do at the least 80 per cent. of its work all over again.
• Compressed-air spreaders are employed for the first examination. On these machines, hinged arms grip the beadings and open out • the cover so that every square inch can be clearly viewed, inside and 'outside; After • examination, sound covers go to the buffing shop, where old rubber is removed with rotary rasps, emery grinders and poker strippers.
The last-named appliances resemble lathes, in principle, and strip off the entire treads while the covers are 'revolving slowly.
At the end of this shop, more examiners view the casings so that only good ones are passed into the drying ovens. In these, the tyres remain for three days, at a temperature of about 120 degrees F. to extract all moisture, an operation of particular importance in winter,
From the ovens they are wheeled to the solutioners, who apply rubber solution, after which they have another short dryinab of 20 to 30 minutes before going to the building shop.
The tyre builder is a skilled hand with a "delicate job to do. He must select the correct, uncured profile strip and' wrap this firmly around the solutioned casing. The power-driven chuck on which the casing is carried during this operation helps the builder to form what is virtually a truly circular, uncured tyre.'
Women workers assist in this shop. They apply patches where minor damage has occurred, •the edges of small cuts and holes being previously pared away, with rotary rasps on flexible shafts. Remoulders are actually opposed to putting in patches, but to save the maximum number of tyres, they must often do so, in order to restore a casing to its original strength.
Finally comes the actual -moulding. Smaller tyres are treated in single moalds which have the, halves of the mould hinged together; in these, steam heating is applied through the casing of the mould. Large tyres, however, are treated in batches, moulds containing • half a dozen at a time being lowered into an immense heating cylinder below ground level.
Before closing the mould, a thick airbag is inserted into the tyre, and this is subsequently inflated at 200 lb. per sq. in., pressure while curing is in progress, the steam being maintained at a temperature of 300 degrees F.
In the case of large heavy-vehicle tyres, this curing operation takes approximately 2i• hours, although lighter tyres may need only one hour's treatment.
Last of all comes a final expert• inspection before the tyres are passed out for service. In this connection, as Mr. Pope pointed out, the user's safety depends upon the reliability of the finished article as well as the re
moulder's reputation. It is a rare occurrence for a. fault to 'escape detection.