5.3.2 Partial Slope
General tendencies of Deflection of FB/F and Bearing Load, Partial Load, Relative Inclination, Thickness and Press. of Oil Film of AB are same as the case of Simple Support.
Shaft is floated at FB/F in the all range of AOS and the floating value is bigger than the case of Single Slope. The characteristic curves of Bearing Load, Partial Load and Relative Inclination are of smooth figure not having any knuckle point.
Comparing with the case of Single Slope, as for the Partial Load, AB/Ahalf is smaller and AB/Fhalf is bigger and as for the Thickness of Oil Film, values at AB/A and AB/F are larger but value at AB/M is smaller. Regarding the Press. of Oil Film, AB/Pmax is considerably smaller and press. at AB/M is larger a little bit. Position of Pmax moves to more inner side.
5.3.3 Double Slope
General feature is same as that of Partial Slope except the Relative Inclination at AB/M.
Comparing with the case of Partial Slope, as for the Partial Load, AB/Ahalf decreases and AB/Fhalf increases a little bit and as for the Thickness of Oil Film, values at AB/A and AB/M increase a little bit and value at AB/F decreases. Regarding the Press. of Oil Film, AB/Pmax decreases and press. at AB/M increases a little bit.
5.4 Oil Film Support (Aft & Fore ST Bear) Calculation (Refer Fig.3-4)
The features mentioned in the following are common to Single, Partial and Double Slope.
Bearing Load exist on FB, but its value is very small.
In the viewpoint of comparison with Simple Support and Spring Support, general feature is same as that of Oil Film Support (Aft Bear only).
Comparing with the case of Oil Film Support (Aft Bear only), although the value is small, there are the following changes.
Deflection at FB/F increases. As for the Bearing Load, AB decreases and IB decreases too. As for the Partial load, AB/Ahalf does not change but AB/Fhalf decreases. As for the Thickness of Oil Film, values at AB/A decreases and values at AB/M. AB/F increase. Regarding the Press. of Oil Film, AB/Pmax increases and press. at AB/M decreases. Position of Pmax move to outer side.
6. CONSIDERATION ON THE RESULTS OF CALCULATION
6.1 Mutual Relation in the Bearing Characteristics between the Three Types of Calculation Methods
As explained in the above, mutual relation in the bearing characteristics between the Simple Support and Spring Support is good. Namely the tendencies in shape of graph (Fig.3-1 and Fig.3-2) of Deflection, Relative Inclination, Bearing Load, Support Point Load, Local Unit Load, etc. are same between the Simple Support and Spring Support. Consequently it can say it is possible to take proportional consideration in estimating the bearing characteristics of Spring Support from that of Simple support.
On the contrary, there is a point to notice in the mutual relation between the Simple Support(Spring Support) and Oil Film Support. That is, in case of Simple Support(Spring Support) there exist the knuckle points in any graphs (characteristic curves), however in case of Oil Film Support, there is no knuckle point in any graphs and any graphs are of smooth figure.
The knuckle point in the Simple Support (Spring Support) exist at the point that in case of Single Slope, the shaft begins to touch on to the bearing surface at AB/F and in case of Double (Partial) Slope, the shaft begins to touch on to the bearing surface at AB/M. Consequently, in estimating the bearing characteristics of Oil Film Support from Simple Support (Spring Support), it is necessary to recognize that the condition of shaft is before touching or after touching on to the bearing surface at AB/F or AB/M. For instance, in the case that shaft condition is after touching, it should not use the Relative Inclination as consideration data for estimating the bearing characteristics of Oil Film Support, because there is scarcely any change of value in Relative Inclination (Fig.3-1 and Fig.3-2). In this case, Bearing Load, Support Point Load and Local Unit Load whose values change should be used as consideration data.
6.2 Difference of Bearing Characteristics between the Three Types of Slope Paying attention to the thickness of Oil Film and AB/Pmax
which are the representative parameters of the bearing characteristics, it can understand the following.
In the comparison between Partial Slope and Double Slope, bearing performance is that Double Slope is better than Partial Slope, however the difference is very small.
On the other hand, in the comparison between Single Slope and Double (Partial) Slope, there is considerable difference in the bearing performance. For instance, Thickness of Oil Film and AB/Pmax at AOS=0.2 of Double (Partial) Slope are same as those at AOS=0.4 of Single Slope. That is, in the Double (Partial) Slope, equal performance with that of Single Slope is obtained by the half value of AOS of Single Slope.
7. CONCLUSION
Some cases of calculations on the shafting with 710 mm dia. propeller shaft were carried out by applying the three types (Simple, Spring, Oil Film Support) of calculation methods and the three types (Single, Partial. Double) of slope and some considerations on the result of calculations were done. These study results can be summarized as follows.
1) Mutual relation in the bearing characteristics between the Simple Support and Spring Support is good.
However, regarding the mutual relation between the Simple (Spring) Support and Oil Film Support, it needs notices, because the features of the mutual relation change by that the condition of shaft is before touching or after touching on to the bearing surface at AB/F or AB/M.
2) There is not much difference of bearing performance between Partial Slope and Double Slope.
However, there is considerable difference between Single Slope and Double (Partial) Slope. In the Double (Partial) Slope equal performance with that of Single Slope is obtained by half value of AOS of Single Slope.
The shafting taking up for the study in this time is that the distance between AB and FB is rather short and the bearing length of AB is L/Ds=2 type as shown in the Calculation Model (Fig.1). In case of the shafting that it provided with long distance between AB and FB (long stern tube) and/or the bearing length is more short (for instance L/Ds=1.5), the feature of Bearing Characteristic difference between the three types of slope may change from the results of this study. I intend to study on these questions in the next opportunity.
