Cycle Repairing and Adjusting
With a Chapter on building a Bicycle from a Set of Parts

6o CYCLE REPAIRING out the old one a little to strengthen it. If the valve is a pin with a conical rubber head, this will be all that is neces- sary ; but if it has a brass head, this should be ground in to its seat with a little crocus and oil, or a little “ Globe ” or “ Matchless ” metal polish. Cold Vulcanising Tyre Repairs.—There is a process of cold vulcanising which those who are not content with the effects of ordinary solutioning may care to put to the test. In ordinary vulcanising, rubber mixed with sulphur is maintained at a good heat until chemical reaction is complete, and the properties of the rubber have altered in several important particulars. There is now on the market a number of small steam-heat vulcanising plants designed to meet the requirements of motorists, who find that patches stuck on with solution alone are quite unreli- able. Vulcanisation converts rubber cement into a material almost identical with the tyre itself, and obviously greatly increases the strength of the joint ; but hot vulcanisation is out of the question in the case of the huge majority of repairs to ordinary cycle tyres. Possibly, however, cold vulcanisation would prove successful if rapidly and skilfully carried out. The agent employed is a solution of 1 part of sulphur chloride in 12 or 15 parts of carbon bisulphide (the latter is also a well-known solvent of rubber). Experiment should proceed on the following lines : Apply a solutioned patch in the ordinary way, and then cover the patch and the edges with the solution. Another suggestion is to get the rubber-solutioned part of the tyre and the patch to the critical state of tackiness, have both ready to come into contact, coat one of them