The authors have tried to interplete the shear and compression strength of green sand from the standpoint of friction between sand grains. Systematic experiments have done to determine these two strengths as a function of porosity and moisture of the sand. And these results were analysed and discussed. The results are as follows :
  1. The shear strength of green sand S varies linearly with the stress normal to the shear plane N, i. e.,
    S = S₀ + _μN
where S₀ and _μ are constant respectively when the conditions of sand are kept constant. This expression corresponds to the friction phenomena in ordinary cases when S₀ = 0. S₀ obtained in the experiments coinsides fairly with the tensile strength T of the same sand in the same conditions reported previously by the authors. μ, the coefficient of friction increases from 0.6 to 1.0 with decreasing porosity in every cases, and is independent of moisture and size of sand grains.
  2. μ obtained in the experiments coinsides fairly well with the tangent of rest angle of dry sand in the same porosity.
  3. The compression strength of green sand C is (5 − 20 times) as large as the tensile strength T of the same sand in the same conditions, and they are related as follows ;
    T/C = S₀/C = (1/2)(1−_μ)

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  We intended to get hot iron to make good iron castings, and succeeded in melting iron in the reasonable high temperature by the cupola, then solved some problems on defects which appeared in castings.
  The effect of the melting temperature on some properties of castings had been made clear by our study in these several years. I am desiring to report on these points in this paper.
  (1) Pressure tightness of castings ; pressure tightness in cast states, not machined, is good when the pouring temperature is high. Leakage by internal shrinkage cavities decreases remarkably when melting temperatures are over 1530°C.
  (2) Mass effect on hardness ; mass effects decrease when the melting temperature becomes higher.
  (3) About carbon pick up ; it increased according as the melting temperature rised when we studied about the behaviour of carbon in the cupola, and therefore, I proposed my ideas about construction and operation of the cupola.

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  Is it true that complete sand molds can hardly be furnished by several jolting hits of a jolt molding machine? yes, it is believed so, because the sand ramming power of the jolting machine is too weak to make a complete sand mold. But the author thinks that, if any means are found to strengthen the power of jolting hits, the jolt molding will become the cheapest process of making molds. Thus the process firstly found out by the author was that ascended sand mass in a flask which naturally droped down was restricted by a rapidly ascending heavy rigid mass to hit hard at the lowest of the jolting stroke about several cm. As the rapidly ascending mass holds big energy, the hit exerted a powerful ramming on sand to make a fine mold.
  The second recently found out by the author is that, ascended sand mass in a flask which is pulled down with as a pull several times strong as the gravity pull, hits upon a rapidly ascending heavy rigid mass at the lowest of the jolting stroke about 10 cm. As the hits of this kind hold enormous energy, a perfect and strong mold can be produced by several jolting strikes.

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  This paper is presented to report the results of the experiments of shell molding fundamentals, especially the properties of “Shell”.
  This process is, in general, so expensive that it should be economically adapted. This will be successfully performed by controlling the usage of a resin bond and elevating the efficiency of this process.
  In essentials, it must be advised that the fineness numbers of the sand grain and the band of grain size distribution would be fully discussed.
  The briefing of these experimental results are as follows :
  1. The most suilable sand is sub-angular or rounded and uniform in the grain size distribution. Inclusion of fine particles in sand, however, is strictly prohibited.
  2. In view of economy and the curing of shell, the optimum content of the synthetic resin in sand is about 10% in this experiment.
  3. The “Shell” is best cured in 5 to 8 minutes at 250 to 300°C. for the sake of polymerization of the resin. (T. O.)

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