[in Japanese]

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On the strength of crankshaft many investigations have been carried out, but there are very many unknowns which have not yet been elucidated.
The author has investigated and previously reported on the strength of crankshaft, and in this report he describes on the crankshaft fillet stresses obtained by the measurements for many engines in service condition, and compares the measured stresses for the ones calculated by his method.
The results are as follow,
1. On solid forged crankshafts, axial vibration of crankshaft is hardly measured. Measured stress diagrams on these crankshaft fillets accord fairly well with calculated ones.
2. When the crankshaht fillet stress is computed, the effect of resilience of supporting bearing is not to be neglected, especially for two stroke cycle engine.
3. The mode curve of axial vibration obtained by measurement agrees fairly well with the one calculated by neglecting damping effects.
4. At resonance point of torsional vibration and its vicinity, the bending stress was observed at almost all of crankshafts fillets. But the amplitude of this bending stress does not always become its maximum at the fillet which is expected from the mode curve of torsional vibration.
Moreover the author appointed that several problems, for instance, computation of amplitude and phase of additional stress by forced vibration, more precise estimation of resilience of journal supports or of fatigue strength from ultimate tensile strength, must be investigated in future.

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Recently, the remote control apparatuses of marine main diesel engines have been used generally. and the computer control systems of main engines for the super automation of vessels are being developed. As marine main engines are larger and super charging level is higher, the response delay of engines when loads change suddenly, the durability for troubles caused by thermal loads, mechanical or vibratory stresses, etc. are coming into problem. And moreover, a change after aging (including a torque rich condition) according to the dirtiness of vessels and main engines are taken a matter.
In case of studying above problems and a future super automatic system, the characteristics of an engine under various conditions including the standard propeller and cycle characteristics must be grasped fundamentally.
Then, at the shop trial of a large bore two cycle diesel engine, with a water brake, some experiments were carried out under twenty kinds of conditions combined various torques and revolutions, and the characterstics of combustion, gas flow, cycle, etc. were measured and analyzed. And under lower scavenging pressure levels by about ten per cent (at an adiabtic pressure), than the normal state the same items as above mentioned were measured and analyzed.
Consequently, the factors affecting on combustions, gas flows, performances, thermal loads and others of large bore diesel engines were made clear. And effective data to estimate the transient states and the various characteristics due to a change after aging including torque rich condition Were obtained.
These data will, be utilized effectively for the purpose of deciding the charcteristics of propeller and cycle initially when a marine diesel engine plant and a future superr automation of that are planned.

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