STRKTl'Il I NT. CAST IRON", KTG. 423
The author will now describe a deviee which he has designed with the oh feet of testing and proving that cast iron stretches as well as expands. While the cuts K<) and 90, pat^es 424 and ..|:»s, will explain clearly to some the exact working of the device, I will describe it in detail in order that all interested can criticise and fully understand its construction and working.
A, Pi<4\ 90, is the pattern used. The shoulders at ' I> and C are for the purpose of providing means to stretch the bar by clamping or holding one end to a support at I), Fi^. S<;, which has a recess forming a part of the Iron frame at the end I) into which the projection X of the test bar pattern A is inserted when moulding the bar, and which, when cast rigidly, prevents the test bar from contracting or pulling away from this end, the other end bein^' pulled by weights as seen at 1C where one, two or more 5o~potmd. standard weights are suspended over the roller II. There arc two moulds cast side by side?, tl open sand " with independent runners R and T from the same ladle of iron as quickly as they can be poured. The only difference existing in these two moulds, lies in one beiiu> strained by the weights, while the other is free from any weight or restraint to prevent contraction, other than the restraint of the mould's sides, and this affords the most favorable arrangement to observe and record any difference which may exist in the contraction, etc., of free and restrained bars. Independent pointers are attached to these bars by means of levers and show their readings on scales behind them.
The first movement of the pointer to be noticed is its passing to the riijfht of zero. This action commences about 30 seconds after the bars are east andn can be stretched. J I