The New Zealand Railways Magazine, Volume 5, Issue 9 (April 1, 1931)
Electric Heating Process
Electric Heating Process.
With the advent of the reorganisation scheme, the procedure of applying new tyres has been improved still further. The tyres are still bored out on the tyre boring mills, but an electric overhead crane in the machine shop picks up the tyre immediately it is bored and whisks it into position on the new electric heaters. These, three in number, take power at 230 volts, single phase. Heating of the tyres is effected by electror-magnetic induction, producing a large flow of current through the tyre, thereby causing a high temperature. By simple changes in the terminals, a temperature to suit different sized tyres is obtained. The tyre rests on suitable supports over the central core of the heater, but without touching any portion of the machine.
Next, the regulator arm is brought forward, and downward, by means of a hand-wheel and screw, until its under side makes contact with the top of the central core. The core, and regulator arm, are composed of a series of flat laminated strips of soft iron. These strips constitute the medium for the transference of the current through the machine. It is this flow of current through the heaters, setting up electro-magnetic induction, which causes the tyre to heat up.
With the tyre in position, all the operator has to do is to switch on the current. Whilst one tyre is heating up, which occupies from ten to twenty minutes, according to the size of the tyre, others are similarly positioned on the rest of the heaters, and wheel centres placed in readiness.
Small pellets of a special fusible metal are laid upon the tyres. “When these melt, it indicates to the operator that the desired temperature has been reached.
When tyres are sufficiently cooled, the wheels are smartly removed to the powerful, up-to-date, high speed, wheel lathes, for turning.
A succession of heated tyres is thus assured. The conditions of the operator are greatly improved, as he is independent of the state of the weather, has the advantage of an efficient electric crane service, and is not inconvenienced by the smoke, sparks, and dust nuisance, as obtained in the past.
Many accidents are caused by the care-lessness or indifference on the part of those who make use of cranes, chains, slings, lifts, etc. Always see that the, apparatus used is suitable for the work you want it to do. Remember that no machine, chain or rope, is stronger than its weakest part.—Sir Gerald Bellhouse, C.B.E. (H.M. Chief Inspector of Factories).