RN Subs

Chapter 26: Main Motors and Batteries

26.1 Main Motors

1. Details of the main motors in the various classes are given in Appendix VII. Those in Appendix VIIA up to the M Class are for vessels built by Vickers and are taken from Vickers' records. It can be assumed that in vessels of these classes built by other firms the motors were generally similar. Where actual differences are known the fact will be mentioned. For the classes in Appendix VIIB the information given has been obtained from other sources, usually Admiralty records. The figures given for speed and horse-power of motors represent the maximum for the duration of discharge rate of the batteries at full speed submerged as used at the time. For duration of discharge rate see Para 19.

The fact that some figures for the power of the main motor up to the C Class are given in ehp and others in bhp is confusing. In other cases the motors could be overloaded by increasing the amperage for a duration of discharge rate less than that used for the legend full speed. Such cases as are known will be mentioned.

2. The main motor in the Holland Class was of the single armature shunt wound open type made by Electric Dynamic Co, USA, the designed horse-power was 70 bhp at 800 rev/min, 500 amps, 120 volts. The motor was geared to the propeller shaft with a gear ratio of about 4:1, the shaft revolutions at full power being 200 rev/min. The motor was used to start the engine.

The ehp of the main motor was 80 and this figure was originally used as the bhp to give an estimated submerged speed of 7 knots. In 1912 DNC quoted a speed of 6.5 knots at 74 bhp. Vickers gave 70 bhp with a motor efficiency of 0.87 and this figure is taken as correct at the duration of discharge rate at full speed of 3¾ hours.

3. The A Class had twin armature open type motors, compound wound in A2-13 and shunt wound in A1 and there were three major changes in size, weight and power or revolutions between A1, A2-4 and A5-13. The powers developed by the motors as given below were for running at the specified duration of discharge rate of 4 hours. Bursts of speed at higher powers could undoubtedly be obtained. The working voltage rose to 240 as against 120 volts in the Hollands.

In A1 the main motor was of 126 ehp at 450 rev/min. Assuming a motor efficiency of about 0.87 the bhp would have been of the order of 110. The shaft revolutions at this power were 450 rev/min, the armatures being on the main shaft and this practice continued in all the following classes except in the K Class.

The motor in A2-13 was larger than in A1 and developed 150 ehp equivalent to about 130 bhp at 375 rev/min in A2-4 and 280 rev/min in A5-13.

4. The B Class had triple armature compound wound open type motors of 200 ehp at 280 rev/min. The weight was double that in the A Class and the working voltage dropped to 100. Widely varying figures for power have been quoted. The figures for the C Class were sometimes given for the B Class but at the specified duration of battery discharge of 3¾ hours for full speed in the B Class the motor power was 200 ehp and in the C Class at 2⅓ hours battery discharge rate it was 300 ehp. At different discharge rates the powers in the two classes might have been evened up but it was the specified period of discharge for full power which undoubtedly caused confusion.

In Appendix VIIA Vickers give 225 bhp for the B Class but for the specified duration of discharge of the battery at full speed it was 200 ehp, which could mean about 170/175 bhp. Some years after the boats completed both Vickers and DNC quoted 189 bhp at 280 rev/min. The motor could be overloaded to give 300 rev/min.

5. The C Class reverted to twin armature open type motors as in the A Class but shunt would and the voltage changed to 160. They developed 300 ehp at 275 rev/min equivalent to about 255 bhp. With overload it is claimed that the motor could develop 300 bhp at 300 rev/min. Both Vickers and DNC consistently quote 300 bhp for this class but from the trials in C22 mentioned in Chapter 3 Paragraph 50 this was not possible. When running at 294 rev/min the power obtained was only 270 ehp equivalent to about 237 bhp. The rating for full speed was 2½ hours with Chloride cells and 3 hours with Exide cells.

An important point is that with an increase of nearly 50% in power over the B Class the motors were smaller and lighter.

6. All the main motors for the A Class to C Class had been built by the Don Works and presumably designed by that firm. It had been a period of experiment with many changes in type, size and power, working voltage and speed. From then on there was not so much variety. As far as is known triple armature motors were never used again. Compound winding was used again only in the Odin Class in 1927.

7. From A1 onwards, except in the K Class, the motors were on the main shafts and were used for starting the main engines. In A5-12 in addition the engine could be started by air but although this was dropped for A13 and in the B Class and C Class it was resumed in the D Class and starting the engines by both motor or air became standard practice.

8. The D Class had twin shafts with a single armature shunt with interpoles wound open type motor on each shaft. In D1 each motor developed 310 ehp at 265 rev/min. The bhp is given as 277 which gives a motor efficiency of 0.90. In D2-8 each motor developed 325 ehp at 265 rev/min. The bhp is again given as 277 which gives a motor efficiency of 0.85. In D3-8 the motors could be overloaded to 1400 amps giving 412 ehp, say 350 bhp, at 300 rev/min.

Most authorities give a total of 554 bhp at 265 rev/min for the class. In estimating the submerged speed of D3-8 DNC did use a total of 580 bhp which is what would have been expected in these boats using a motor efficiency of 0.90 as for D1.

The rate of battery discharge at full speed for D1 was 1 hour and for D2-8 just over 2 hours.

The working voltage in D1 was 200 volts as against 160 volts in the C Class. In D2-8 it rose to 220 volts. Again there was a considerable decrease in size and weight for increased power of the motors.

9. In E1-8 the two single armature open type motors produced 970 ehp or 840 bhp with a motor efficiency of 0.86 at 280 rev/min. The working voltage was 220. With overload of 2100 amps (the normal was 1650 amps) the shaft speed rose to 330 rev/min at g hour rating.

In E9 onwards with the same general motor characteristics the shaft speed on overload was 320 rev/min. In E19 onwards both ratings were quoted 1650/2100 amps which should give powers of 840/1060 bhp. Vickers gave 1120 bhp with this overload and must have been using an efficiency of over 0.9.

The increase in power of over 50% from that in the D Class motors was achieved on the same overall length of motor and one foot increase in diameter of yoke with an improvedhp per ton weight. The weight per motor steadily decreased as the class progressed from 12.35 tons in E1 to 11.29 tons in E19-24.

10. As would be expected there were changes from the pattern set in the E Class in the many types of submarines built in the next few years. The known differences are as follows:

• The S Class, an Italian design, had the luxury of a separate motor room for each of the main motors. The total power was 400 bhp.
• For V1 the two main motors were built by Laurence Scott and developed a total of 300 bhp at 300 rev/min. The motors could be overloaded to 750 amps (normal 480 amps), 350 rev/min with about 470 bhp total. For V2-4 the motors were made by the Don Works and developed a total of 380 bhp at 610 amps and 570 bhp at 920 amps. In both classes the overload would seem to be high. All the figures are based on a motor efficiency of approx 0.9. The working voltage was 260 volts. The motors were of the single armature open type with shunt windings in V1 and shunt with interpole windings in V2-4.
• The two single armature open type motors in the Nautilus developed 1100 ehp total or 1000 bhp which gives the motor efficiency as 0.91. The motors could be overloaded to 1950 amps (normal 1200 amps). The working voltage was 340 volts, the shaft speed at full power 210 rev/min. The motors were made by the Don Works.
• The G Class motors were of the E boat type of the same size and weight as the later boats of that class. The power was the same at 420 bhp per motor but the voltage was reduced to 200 volts and the amperes increased to 1720 (as against 220 volts and 1650 amps in the E Class ) and the revolutions were 280 rev/min as in the earlier vessels of that class. The reason for these changes is that only 200 cells were carried as against 224 cells in the E Class.
• No definite statement has been seen but judged by the urgency and the general trend to fit proven equipment in the boats it seems fairly certain that the J Class were fitted with two E Class type motors, one on each of the wing shafts. There was no motor on the centre-line shaft. Due to the high capacity battery cells fitted the increased battery output 'allowed 1350 bhp to be developed by the two motors, as against 1060 bhp in the E Class for g hour '.
• The K Class were fitted with two tandem high speed shunt wound open type motors, each tandem consisted of two of the standard open type motors. One tandem was sited each side in the wings of the engine room somewhat above the main shaft centres and drove the main shaft through double helical gearing with a gear ratio of 5:1. A disengaging clutch was fitted between each pair of motors and the pinion.
• At the 1½ hours rating each tandem pair of motors with armatures in parallel developed 720 bhp per shaft at a speed of 800 rev/min (shaft speed 160 rev/min) at 210 volts. Motor efficiency 0.905. At the 20 minute rating the bhp per shaft was 1020 at a speed of 900 rev/min (shaft speed 180 rev/min) at 230 volts. With the motor armatures in series the speed was 275 rev/min (shaft speed 55 rev/min) at 115 volts which would be used for the slow speed of 1.5-2 knots. The design bhp is taken as 1400. The working voltage was 220.
• The main motors could be declutched from the propeller shafts when desired but the motors had to be disengaged when the shaft revolutions, when being driven by the turbines, rose above about 200 rev/min. This operation could be done by hand, but it was found necessary to fit an emergency arrangement to cut out the main motors automatically should they have been inadvertently left in gear when the main shaft revolutions reached 200 rev/min. Scotts claim to have devised a self-declutching gear to meet these conditions. The arrangement consisted primarily of a centrifugal trip governor which was fitted to the main motor spindle and controlled a Hele-Shaw pump, the pump being driven by gearing from the motor spindle. The governor was adjusted so as to operate at a predetermined rate of revolution and when this point was reached the pump was caused to discharge oil to a ram thereby actuating the clutch. This gear was proved in service to be a success.
• One complaint made about the K Class was the unreliability of the electric generating plant when required to run for lengthy periods.
• In the H Class the two main motors developed 620 bhp at 375 rev/min for 1 hour. The motor efficiency was 0.90. At the continuous rating of 320 rev/min the total bhp was 320 with motor efficiency of 0.85. The voltage was 220. The motors were of American design. An auxiliary drive motor was not fitted.
• The R Class were single shaft boats with the accent on submerged speed. The two single armature main motors were coupled on the main shaft and developed a total of 1200 bhp at 2260 amps, 220 volts and 600 rev/min at continuous rating with armatures in parallel. With armatures in series and at 110 volts the speed was 150 rev/min. An auxiliary drive motor was fitted on the main shaft.

11. The L Class was the first conventional design to follow and replace the E Class. Two open shunt with interpoles wound type motors were coupled together on each shaft giving 800 bhp per shaft, a total of 1600 bhp, at 300 rev/min and 220 volts at the 1½ hour rating. The motor efficiency was 0.935. For continuous rating the total power was 1220 bhp at 234 rev/min. The total power could be increased to 2000 bhp for ½ hour. An auxiliary propelling motor was fitted.

This same arrangements of main motors was fitted in the M Class and L50L50 Class.

12. X1 carried a twin armature motor on each shaft with a total of 2400 bhp. The main motors could be driven by the battery (2400 bhp) or by generators (2000 bhp). The electrical plant was very much tied in with the main and auxiliary engines as described in Chapter 25 Paragraph 29.

13. Details of the main motors for Oberon have not been seen but there is every reason to believe that they were of the same principle as fitted in the Odin Class, that is a tandem set of two armatures on each shaft of the closed type. They were designed to develop a total of 1300 bhp at approximately 300 rev/min. On original submerged speed trials the maximum achieved was 1250 bhp (motor efficiency 0.92) at 1650 amps, 308 volts and 294 rev/min. The power was eventually raised to 1350 bhp probably for 1 hour rating with overload. The working voltages were 330 and 220 which may have been first used in X1,

So far motors had been of the open type which resulted in high temperatures in the motor room. The introduction of closed type motors with coolers and fan circulation was a big advance.

14. The main motor on each shaft in the Odin Class was a tandem set of two armatures of the closed type which developed 660 bhp per shaft, a total of 1320 bhp at 240 rev/min on a 2 hour rating. The motors were compounded. At continuous rating the total power was 1000 bhp at 220 rev/min and 330 volts with the voltage across the forward and after armatures of 198 and 132 volts respectively. At 220 volts the bhp range was 550 and 180 over a speed range of 175 and 105 rev/min.

In the Parthian Class and Rainbow Class tandem sets were fitted but the motors were not compounded but worked with the armatures in parallel or series. In general the bhp / speed range was the same as in the Odin Class but the motors were guaranteed to develop a total of 1880 bhp for ½ hour at a motor efficiency of 0.89. Under normal loading this efficiency varied from 0.91 to 0.92. This change was at the expense of weight which rose per tandem set from about 20 tons in Odin to from 22 to 25 tons in the Parthian Class and Rainbow Class.

The legend submerged speed in all classes was based on 1320 bhp. In Odin on trials the legend was not obtained. The full power for full speed was later given as 1390 bhp in Odin Class, 1635 bhp in Parthian Class and 1670 bhp in Rainbow's, these powers presumably being at the 1 hour rating.

For Thames Class, Swordfish Class and Porpoise Class Chapter 15, Chapter 16 & Chapter 17.

26.2 Auxiliary Drive

15. An auxiliary propelling motor was first fitted in the L Class consisting of a 20hp motor, weighing 0.65 tons, actuating the starboard shaft only through a worm drive. It also drove the after bilge pump through a sliding clutch. A similar auxiliary drive was undoubtedly fitted in the L50 Class and M Class.

In the R Class the auxiliary motor was on the main shaft and of 25 bhp.

In the Odin Class, Parthian Class and Rainbow Class the auxiliary motor drove both port and starboard main shafts through a worm drive. It developed 50 bhp at continuous rating or 58 bhp for g hour and weighed 1.27 tons. This motor also drove an LP blower, Oxley and Otway had a similar auxiliary drive motor but not Oberon.

Thereafter auxiliary drive was not fitted except in the T Class which had a 25hp auxiliary propelling motor weighing 3.4 tons on the starboard shaft.

In those classes not fitted with auxiliary drive slow speed was obtained with the armatures of the port and starboard motors in series and in the case of tandem sets with the armatures of the tandem sets in series and the port and starboard sets in series.

26.3 Switchboards

16. In the Holland Class various switchboards and items for operating the motor and battery were sited piecemeal on the starboard side of the engine room. In the A Class, B Class and C Class all the electrical gear switchboards, main battery fuses, etc were concentrated on the starboard side of the control room abreast the conning tower hatch. As was found from one or two accidents when water came through the conning tower hatch this was a rather vulnerable position for such equipment. In D1 and D2 the main and auxiliary switchboards were moved well forward of the control room and the space occupied was considerable. In D3 they were moved back into the control room both port and starboard sides. The only justification for this would appear to have been to improve the accommodation forward especially for the officers. The early E boats were similar but about this time the policy was adopted of placing the switchboards etc. in the motor room and it is probable that this happened in the later E boats. The V Class and Nautilus as examples were certainly so fitted and this became the policy in all later classes. The only known exception to this was in K26 when a switchboard compartment was built forward between the officers' quarters and the control room.

26.4 Batteries

17. Details of the batteries fitted in the various classes are given in Appendix VII.

Chloride cells were used in the Hollands of overall height 3ft 4⅝ in, width 1ft 4⁵/16 in and depth 1ft 0⁵/16in and weight 924lb per cell. This same type of cell of the same weight but with slight variations in size continued in all boats until towards the end of the C Class.

18. C21 was fitted with Exide cells of less weight than previously used. Some calculations were made by

Vickers in May 1908 between C22-30 with 166 normal (Chloride) cells including acid but without wax filling of weight 69.06 tons and the same number of Exide cells in C21 weighing 65.0 tons. All other weights in the boats were taken as the same and to make up the difference of 4.06 tons an additional 3.0 tons of lead ballast in the keel and 1.06 tons of extra auxiliary ballast water was taken into C21. The effect was to increase both the surface GM and the submerged BG in C21 by about 0.5in which was about 10% of the surface GM. The calculations were made in the early stages of building and the actual battery weights given later by Vickers were Chloride cells 68.5 tons, Exide cells 63.3 tons. In addition to the reduction in weight the Exide battery was stated to have a higher capacity with a longer duration of normal discharge rate (by over 30%). It was presumably of approximately the same size as the Chloride cell and was certainly sufficiently near to go into the same size battery tank.

From C35 onwards up to and including the L Class all boats built at Vickers had Exide cells except E1-16 which had Mercury cells. For uniformity it is assumed that the boats built at Chatham during this period also had Exide cells. The L Class specification gave 336 Chloride Exide 3810 type cells.

19. In the early classes the rate of battery discharge was limited by the design of the main motor/s. Taking the Holland Class as an example the battery was of 60 cells and working voltage 120. The duration of battery discharge was 3 hours 45 minutes and the output at this rate 500 amps. The capacity at this discharge rate was therefore 1840 ampere-hours and this figure is quoted by Sueter. At 500 amps, 120 volts the power is 80 ehp which was the power for which the motor was designed. Although the discharge rate of the battery could be increased there is no suggestion that the motor could carry very much overload if any.

The duration of discharge rate at full speed is given for the various classes as follows:

In the E Class onwards the motors were designed to take the full output of the battery at the 1 hour discharge rate and also take an overload at higher discharge rates to allow at short bursts of speed. This was a standard for the motor design only. The bhp of the motors used for the legend maximum submerged speed was not necessarily the power developed at the 1 hour battery discharge rate. The discharge rate used for the legend bhp varied between classes but was never less than 1 hour.

20. In the Holland Class the main battery of 60 Chloride cells was stowed in two steel battery tanks, 35 cells in the forward tank and 25 cells in the after one. The working voltage was 120. The tanks were built of 15Ib plate with 7Ib angle bar stiffeners, a light structure in view of the fact that the main ballast tank was under and at the sides. This was a source of danger as experienced in Holland No 4 during her preliminary dives, when the caulking in way of the battery tanks gave out and sea water entered the tanks every time the main tank was blown.

The battery tanks were lead-lined and rosbonited and covered by 2in battery boards supported on 3in x 4in teak beams. These boards were fitted in place but were not clipped down. The cells stood on a false wood bottom 1in thick and were wedged round the sides. The overall height of the battery tank from the top of false floor to the underside of battery boards was 3ft 5½in, the overall height of the cell was 3ft 4⅝in so that there was little clearance. Wax was run in to seal the cells.

21. The A Class had 120 Chloride cells and the working voltage rose to 240. In A1 the cells were in one battery tank as against two tanks in the Hollands. The overall length of the tanks was 37ft l0in with maximum width 7ft 2½in and depth 3ft 7in. The cells were split into two sections of 60 cells each with a 6in space between sections filled with wood wedges, all on a l½in false wood floor. In January 1906 the cells were rearranged and Podmore containers fitted. The height of cells over containers increased by about ½in. The one battery tank arrangement continued until the E Class.

In A2-4 the shape of the battery tank was changed. The length of the tank was shortened from that in A1 by 5ft l0in. to 32ft and the beam increased to 8ft 4in. at the after end, decreasing in two steps to 5ft l¼in at the forward end. The depth of the tank was also increased by l½in to 3ft 8½in although the cell height over containers remained practically the same at 3ft 3⅜in. The battery was split into four sections of 30 cells each all in the one tank.

22. So on through the B Class, C Class and D Class as shown in Appendix VIIA the number of cells changed and the working voltage changed with only one battery tank, until in the E Class two battery tanks were fitted again for the first time since the Holland boats with 168 cells in one tank forward of the amidships torpedo tubes and 56 cells in the second tank just aft of the tubes. In some of the later E Class boats the after battery was moved right aft between the main shafts. The 224 cells were capable of being grouped into four groups of 56 cells and worked in parallel and series at 110 and 220 volts respectively.

E1-16 had Mercury cells which were 'based on a life of ten years with a loss of original capacity at the end of ten years of not more than 25%'. It was supposed to be possible to obtain an output of 500 amps for six hours on a weight per cell complete of 940lb. From the figures given in Appendix VIIA it would appear that it was eventually not as good as the Exide cell which in E25 had been brought down in weight to 865lb per cell. The latter were Exide 3800 type.

23. By 1917 a standard had been set more or less as follows:

• The main motors were designed to take the full output of the battery at the 1 hour discharge rate and for bursts of speed at higher discharge rates.
• The battery was split into sections of cells so that they could be 'grouped up' in series and 'grouped down' in parallel.
• The cells were stowed in battery tanks with portable wooden covers and from circa 1917 onwards the tanks were tested to 2 or 3lb/in² after the covers had been fitted. The precedent had also been established to fit battery compartments in larger vessels when possible. At some point, the exact date of which is not known. the waxing in of cells was deleted.
• Exide cells were in favour but competitors were coming into the field.

24. Points of interest and change from the principles in Paragraph 23 during this period are:

• The V Class had a small battery for the size of boat of only 132 Exide cells in one battery tank divided into two sections of 66 cells each. The working voltage was 130 volts in parallel and 260 volts in series,
• The battery in the W Class consisted of 220 cells of either the Fulsen or the Tudor type.
• In the Swordfish the battery of 128 cells was stowed in two compartments one forward and the other aft with built-in passageways at the side to allow communication through the boats without entering the battery compartments. Individual cells were on bearers directly on the pressure hull with the cells banking up at the sides to allow for the curvature of the hull. Other equipment such as air bottles were stowed in these battery compartments.
• In the J Class the main engines and motors took up over one third the length of the boat and space elsewhere was at a premium. However, 'height was available to increase the height of the cells over that in the E Class. ' They carried 232 cells as against 224 cells in the E boats but their increased output allowed 1350 bhp to be developed by the two motors as against 840 bhp in the E Class.
• The Nautilus has 352 Exide 3660 type cells in two battery compartments. It was split into sections to allow working at 170 volts in parallel and 340 volts in series.
• In the R Class the 220 cells (some references say 216 cells) of the type fitted in the J Class were split into four groups of 55 cells, each group in a separate battery tank. They were Chloride E4400 type cells with a capacity at the 4-hour rate of 4240 ampere-hours. The main motors could be used as generators for charging batteries but 'being coastal boats of a special type the batteries were usually charged from a Depot ship or shore. '
• A great advance was made in K26 by the introduction of battery compartments which in the designs of the 1920's became standard.
• The L Class carried 336 cells with 112 cells in each of three battery tanks. They were grouped to allow working at 220 volts in series and 110 volts in parallel.

25. The Odin Class had 336 cells of the Exide 3820 LS type when first completed. The working voltages were 330 volts in series (grouper up) and 220 volts in parallel (grouper down). For further details see Para 33-37.

Three battery compartments carried 112 cells each. The batteries were not stowed on an athwartship deck. From the centre line going towards the ship side there were two cells on bearers on the pressure hull, then two more cells on a raised step and then a further single cell on a higher step, ten cells abreast in all. Battery cooling plant was fitted.

The number and arrangement of cells in the Oberon Class, Parthian Class and Rainbow Class wereas in Odin. High Capacity type cells were fitted in the two submarines Parthian and Rainbow only.

26. From the L Class onwards to the PORPOISE Class the battery became a standard 336 cells except for 224 cells in the Swordfish Class. The Parthian Class saw the beginning of trials of high capacity type cells in the Parthian. The weight of the normal cell was of the order of 920lb increasing up to 960 Ib in the high capacity type cell. X1 had 330 cells of special type each of which weighed 1475 Ib as did the special large type in the Thames. The following gives some guidance on the types of cells first fitted in the various classes but is by no means exhaustive:

The standard size of cell, other than for odd types such as in Thames, was breadth 13⁷/16 in, width 17⅞in. and height over terminals 42⅜in. Some other details are:

All the above figures are with acid of sg 1.250-1.260. With acid of tropical density 1.210 to 1.22 the capacity is 12-13% less.

26.5 Battery Ventilation

27. In the Holland boats with two battery tanks, originally one 4in. fan was fitted for battery exhaust ventilation. Fixed trunking led from the battery tanks to the fan and a canvas hose from the fan to a 3in ventilator on the hull with a portable outboard trunk extension. Later on each tank was fitted with a separate fan, a 5hp motor and blower in the buoyancy tank compartment between the two batteries for the forward battery and a 1/5hp motor and blower overhead for the after battery. These fans were connected to separate Sin. ventilators with portable extension trunks outboard. Supply to the battery tanks was natural from inboard.

28. Two battery fans were fitted to the one tank in the A Class and by A5-13 consisted of one l0in supply fan which could suck air from just below the conning tower and discharge it into the forward end of the battery tank and a 14in exhaust fan exhausting from the after end of the battery tank and discharging into two 3½in ventilators which extended outboard well above the top of the conning tower level. The outboard lengths of these ventilators were portable. It is seen from this that the battery ventilation was self contained.

29. Various systems of ventilation were tried in the boats that followed until in the later vessels of the C Class a ½hp exhaust fan was fitted with a suction from the forward end of the battery tank discharging to the open air through a 4in ventilator amidships. Another ½hp exhaust fan at the after end of the battery tank had suctions from the tank and from the extreme after end of the boat and exhausted to the open air through two 4in. ventilator amid ship. Two supply trunks, each port and starboard sides, were fitted near the middle of the battery tank with open ends high up inside the boat. The exhaust fans were therefore used for both ship and battery ventilation. The outboard portions of the trunks were portable,

30. In D1 the battery ventilation was similar to that in the C Class except that two outboard ventilators were sited over each fan and could be hinged down into the superstructure. In addition a lead from the forward fan was led to the fore end of the boat for ship ventilation exhaust, whilst the lead in the C Class from the after fan to the after end of the boat for ship ventilation was deleted. In D2 this was again changed with a battery exhaust fan fitted over the forward end of the tank which exhausted into an outboard ventilator aft of the conning tower, whilst two exhaust fans drew air from the after end of the tank and in addition a long lead of trunking was connected to one of them and led to the torpedo tube space for ship exhaust ventilation. The fans had separate outboard ventilators. In neither D1 nor D2 were the battery fans used for ship ventilation aft. Supply to the batteries was natural from inboard through four trunks near the middle of the battery tank.

A further change was made in D3-8. Natural supply was from inboard at the fore end of the battery tank with two exhaust fans at the after end. A separate ship ventilation fan was fitted for exhausting the after end of the boat.

31. In the E Class the battery ventilation was again changed. Two fans exhausted air from the larger forward battery tank and one fan from the after tank to a ventilator for each fan led outboard at the after end of the bridge structure. Drain valves at the bottom on each ventilator trunk were operated from inboard to drain the outboard length of trunking. Supply was natural through trunking which led from the forward and after ends of the boat to the battery tanks. The ship and battery ventilation was therefore once again combined.

32. Experience in these early classes led to a standard system in later boats of ventilating the battery compartment by natural supply from inboard and fan exhaust to outboard, with a separate fan system to give air circulation inside the boat. In discussions on the Oberon requirements it was decided that an arrangement should be investigated whereby the battery fan exhausts should be led to the engine induction system with a by-pass to outboard for use if required. It is understood that a system of this sort was fitted in some later classes.

Individual cell ventilation was tried in the 1920's but was not a success.

26.6 Electrical Arrangements

33. The arrangement of main circuits in the Odin Class are given below since the motors were compound wound which was a departure from the normal practice. The only other submarines fitted with compound wound motors had been A2-13 and the B Class. A schematic arrangement of the circuits in the Odin Class is given in Fig 26.1

26.6.1 General

34. Main motors grouper up at 330 volts; No 3 battery is split into two halves and the halves connected in series with Nos 1 and 2 batteries respectively. With main motors grouper down at 220 volts all three batteries are in parallel. In both cases the main motor shunt fields are fed from 220 volts busbars. The grouper switch on the main battery board in the control room is worked electrically from the motor room.

Batteries can be charged from the motors or from shore either grouper up or grouper down.

Current can be supplied to the shore at a constant 220 volts by running the reducer. Current can also be supplied at approximately 220 or 330 volts by grouper down and grouper up arrangements.

One submarine can charge another.

26.7 Main Motor and Reducer Switchboards

35. Details of the various switches shown in Fig 26.1 and their operation are:

• Q is the-ve return switch for the B machine and must therefore always be made whenever the machine is running either as a generator or motor.
• R connects the B machine with the auxiliaries and must therefore always be made when this machine is running as a generator, except when A and B machines are generating in series when switch R is broken.
• S (up) is the-ve return for A machine. It must always be made whenever this machine is operating separately either motoring or generating.
• S (down) connects A and B machines and must therefore always be made when A and B machines are in series either motoring or generating.
• T (up) merely short circuits the series field of A machine and is made whenever this machine is charging at 220 or 330 volts.
• T (down) connects A machine with the auxiliaries and must therefore always be made when this machine is running as a generator on the auxiliary load.
• T and R are always off in all phases of motoring.
• X contactor connects the 220 volt busbars to the constant panel. It is therefore always made except when charging of any description is taking place. It also supplies current to the D machine when starting the reducer at 220 volts.

26.7.1 Position of Switches when Motoring

• 36 (a) Grouper up 330 volts. In this condition all the auxiliaries are being fed from Nos 1 and 2 batteries only. To avoid these batteries being run down at the expense of No 3 battery the reducer is run as a leveller. To do this M machine is fed off the 330 volts busbar and D machine placed in parallel with Nos 1 and 2 batteries and generating enough current to balance the auxiliary load.

The motor switches are positioned Q on; R off; S down; T off.

The reducer switches are Z down to feed M machine from 330 volt busbars;

• X on to the variable panel with the reducer system and to put D machine in parallel with Nos 1 and 2 batteries; Y on so that the current generated by D machine can reach the auxiliaries.
• (b) Grouper down 220 volts.
• Motor switches Q, R, S and T as for grouper up. The auxiliaries are fed direct off the batteries. The reducer is ready to run as a motor to drive the blower. Reducers switches: Z up to feed M machine at 220 volts; Y off as D machine is not generating; X on to supply current to the constant panel.
• (c) A machine at 220 volts and B machine idle.

This is an emergency position to get a big torque on the shaft suddenly when the grouper is down. Switches Q, R and T are off and S up. The auxiliaries will be direct off the batteries. The reducer must be ready to run as a motor as before.

26.7.2 Position of switches when charging

37

• In all phases of charging the reducer works in exactly the same way. M machine is supplied at 220 volts and D machine is run in parallel with the auxiliaries so keeping the voltage at the constant panel at 220. Reducer switches: Z is up supplying M machine from the 220 volt busbars; Y is on placing D machine in parallel with the auxiliaries; X is off as the auxiliaries are being supplied by B or A machine with D machine in parallel.
• A machine at 330 volts and B machine on auxiliaries.
• Grouper up. Switches Q and R on; S and T up. T is used only when A machine is charging.
• A machine at 220 volts and B machine on auxiliaries,
• Grouper down. Switches Q, R, S and T as before.

Fig 26.1

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