Tores mailbox VIIC and VIIC/41 operation and technical details

[Don Prince]

Hello Mr. Tore,


I completed the section on Rudders and Hydroplanes in Skizzenbuch on pages 168 - 173 and uploaded the latest versuon to dropbox...  Now to look at the hydraulic source for the Schnorchel.


Regards,
Don_

[Don Prince]

Hello again Mr. Tore,


Figuring out the Hydraulic plate was not a problem (I Think!)...  I will attach my understanding of it.  However, I know where most of the schnorchel components are located, but the general hydraulic components are questionable?  I believe on the hydraulic plate the two main pumps are electrically driven and the other 3 (two in the tower for training and raising/lowering the attack periscope, and one in the control room for the aerial periscope raising/lowering are oil pressure driven pumps.


I don't know the location of the 2 electrical driven main pumps, the 93 gallon oil reservoir tank, and the 3 31 gallon HP oil tanks, and most importantly where the schnorchel taps into the HP oil and Return oil.  It looks like it all may all be in the cabinet area where the schnorchel control valve is located, except for those 4 tanks...


Regards,
Don_

[tore]

Don.
I guess the easiest way is I give an explanation of the system.
The hydraulic system is operating the two periscopes and the schnorchel. It consist of two IMO type screw pressurepumps, one as auxiliary, taking hydraulic oil from a system tank and controlled by micro pressureswitches within a pressurerange govern by the oil level in the system tank. The oil is supplied to three aircushioned accumulators having each a capacity of 118 liters and a pressure working range between 48 to 84 bar. All situated in the controlroom between the attack periscopecasing and  stb. pressurehull. The system is adjusted by filling the accumulators with air  at 10 bar. where upon oil is pumped into the accumulators up to the lowest level testpipe,and the air is admitted to 48 bar being the lowest pressurelevel where the pump has to start.The  accumulators are then filled with oil until the pressure is 84 bar being the max. pressure where the pressure switch is adjusted to stop the pump. The unusual with this system is that the pressure switches are controlled by the static level pressure in the system tank rather than the pressure in the accumulators.
From the accumulators the oil is delivered to a oil slide, after a branch off with stopvalve to the schnorchel, which is controlling the operation of an IMO type screwmotor ( converter) engaging the drivespindle via worm geardrive to both  winches for raising and lowering the periscopes by wire. The IMO type converter is a screwpump able to run as motor (converter) when pressureoil is supplied and the direction of rotation is determined by which inlet the oil is supplied. The oil intake is controlled by the controlslide, see drawing, which again is controlled by the raising/lowering periscope handle. On the sketch, red are the pressurelines, purple are the return. When the handle is pushed down (lowering periscope) the slide admits pressureoil to the endstopper (which is preventing the periscope to exceed the adjusted travel). The endstopper consist of a rod driven by the periscopewinch and having a threaded end engaging internal threads in a sleeve inside the endstopper casing. As the winch rotates the rod, the sleeve travels back and forth between the travel ends and the slide opens for oilsupply and return to the operating slide of the IMO converter moving same up or down allowing pressure and returnoil to the selected inlet/outlet ( selected rotation direction). At the end of the periscope travel the sleeve shut  the supply and open to return on both ends of the slide which is the pushed by the balancing springs on both ends of the slide to a shut position and the periscope stops regardless pushing the periscopehandle beyond the limit.
The attack periscope has a different raise/lower handle but the working is the same. However an additional handle is provided next to the depthgauge. This handle can be switch in by a selectorslide, see drawing. The purpose for this arrangement is to have a man accurately controlling the periscope height above the surface. The attack periscope has a direct footcontrol of the controlslide, skipping  a foothandle, for turning the periscope.
The schnorchel hydraulic system takes its supply and return from the direct supply/returnlines as can be seen on the sketch, then further to the raise and lower handle via hullvalves to the schnorchel cylinder in the casing outside the pressurehull as previously discussed.

[Don Prince]

Hello Mr. Tore,


WOW!!!  I am so impressed with your knowledge of the technical details of this U-Boat.  Sir, you continue to amaze me!


Kind regards,
Don_

[Don Prince]

Hello Mr. Tore'


I updated Skizzenbuch with the latest info and uploaded it to dropbox...


Hydraulic Periscope   pages 213 - 219
Schnorchel  Pages 324 - 331


Regards.
Don_

[tore]

Don.
I had a brief look into your latest Skizzenbook and have a few remarks which I shall revert to a bit later, however right now I shall just mention the hand operation of the hydroplanes.
May be you should include a description of the rather elaborate yet simple mechanical system consisting of rods, stuffingboxes, bearings with grease nipples and bevelgears going from the controlroom to the fwd. and aft torpedorooms ending at the gearboxes with clutches to the hydroplanes.
Tore

[SnakeDoc]

Hi Gentlemen,

here are some additions to Tore's excellent explanations.

The air operated clutches for the hydroplanes are situated locally at the hydroplane gear disengaging the electric drive and engaging the mechanical drive. The operation is controlled from the controlroom, I assume the clutching valves are situated as marked on my image below close to the hydroplaneoperators. As far as I remember the electric and the mechanical hydroplane indicators are operating in both configurations.

The valves controlling pneumatic clutches were marked by Tore correctly. As Tore said, electric and mechanical angle indicators were operating in both configurations (mechanical indicators were moved by means of flexible wire - so called Teleflex system, the electrical indicators were DC systems, utilizing the voltage divider principle).

The clutches were located near the electric motors - the forward motor with the clutch is invisible (under the bow torpedo room floor, in the bilge, between lower torpedo tubes), but you can clearly see the aft motor with the gear and clutch (with the compressed air line connected). There should be noted, that the clutches were engaged remotely from the control room (by means of control valves), but to disengage them, the crew man had to be sent to the clutch and he had to disengage it manually (by means of the handle).


--
Regards
Maciek

[SnakeDoc]

Some comments to the hydraulic system.
On the first photo you can see the control room of HMS Graph (ex-U570) - you can see, that some parts of hydraulic installations related to Schnorchel are missing (or to be more specific - in the control room of U995 there are some additional elements )
I have also attached the drawing, which presents the periscope winch wires.
On the second photo, I have marked the particular elements of the control room periscope winch. The markings are as follows:
1. Periscope lowering/rising "pilot" valve ("Fahrschalter" on the German drawing)
2. The periscope winch drum
3. Hydraulic motor driving the periscope winch/drum
4. The "control" valve" ("Steuerschieber" on German drawing)
5. The shaft for manual rising/lowering the periscope
6. The pulleys for the wires  rising the periscope
7. The guide for the wire lowering the periscope

I have also attached one more drawing, presenting pilot and control valves as well as limit-valve and hydraulic motor.

Finally, on the turm07.jpg photo you can see the winch for the attack periscope in the conning tower, together with the hydraulic  motor and control valve and the shaft for the manual drive.

--
Regards
Maciek

[tore]

Don.
Maciek has published some excellent drawings which I have never seen and I have included his photo of the IMO type converter with lower/raising slide and endstopper which gives a better image of the component. The IMO converter I included as I did not have the German drawings, is a double scewtype for balancing the axial forces on the screw, whereas the German type of converter is a single screw type which means you have to balance the axial forces hydraulically. On the very good cross section drawing of the converter shared by Maciek you can clearly see the balancing bore in the casing going to the balancing piston at the end of the screw. Thank you Maciek for sharing these drawings.
Tore

[tore]

Don .
Macieks pictures of the dogclutches for the hydroplanes gives a good impression how they work. I have made some colour on the components to explain the working. The yellow parts are the parts moving when the electric motors are connected, the normal configuration. On this shaft are two sleeves having rims with outside teeth and a bore with axial four grooves. The sleeves can be moved axially on the yellow shaft having four axial keys matching the inside grooves of the sleeve bore. In normal service the emotor is engaged by moving the left sleeve into the e motor wormdrive wheel which have a bore with rollerbearings on the hyroplane shaft and a bore with internal teeth matching the outer teeth of the left sleeve. As the sleeve is locked to the yellow shaft by the four keys and connected to the e motor by the worm gear, the e motor is the operating the hydroplanes. At the same time the other sleeve to the right is disengaged from a similar unit on the right side and the manual operation is disengaged, the manual operation sleeve is rotating free on the yellow  shaft which is supported in a rollerbearing inside the coupling flanges of the manual driveshaft. When air is admitted to the pneumatic cylinder from the controlroom two forks engaging both sleeves via sleevegrooves and moves both sleeves to the right thereby disengaging the motor wormgearwheel and engaging the internal teeth of the manual drive shaft which then is in operation. The yellow shaft is rotating freely on the roller bearing in the wormgearwheel.
Tore

[Don Prince]

Hello Mr. Tore or Maciek,


On the hydroplane clutch casing where the pressure vessel is located there looks to be a pressure release cap or valve.  Is this to relieve the pressure so the disengage lever cam move back to motor control?


Regards,
Don_

[tore]

Don.
May be you are referring to the springloaded catch?
Tore

[Don Prince]

Hello Mr. Tore,

Oh, I see...  It's sort of like a buffer.  Restricted air in and out???

Don_

[tore]

Don.
It is a springloaded locking pin which rest in the rodgroves keeping the rod and couplingsleeves in the two positions, electric or hand drive. As Maciek says the pneumatic piston controlled from the controlroom works only one way, disengaging the the electric drive /engaging the handoperation by admitting air to one side of the piston (green), the other way has to be set locally by hand thus no airconnection on the other side only venting bore ( blue).  The lockingpin snaps in either of the two rodgrooves by the spring.
Tore

[Don Prince]

Hello Mr. Tore,


I have a problem understanding the working of the end stopper used in the periscope wench raising or lowering.  If we use the detailed drawing provided by Maciek here is what I see...[size=78%]…  [/size]


The internal threads and the shaft look to have the possibility of just a few terns, and then the internal sleeve will come in contact with the top or the bottom of the end stopper casing depending on the drive shaft direction of rotation.  So, it looks like the periscope will not move very far before the end stopper comes to a stopping point and the shaft cannot rotate any more.


The aerial periscope eyepiece is normally in a well and below the control room floor.  Therefore, there is a fairly long distance to move up to be at eye level when standing on the control room floor.  The only thing I can figure is the gearing ratio is such that the bottom of the end stopper represents the bottom of the well and the top of the end stopper represents the maximum height the periscope can be raised.


The end stopper details of the channels on the sides of the sleeve are mostly blacked out.  Do you have a drawing with those details?  I can guess, but I don't like to do that!


As usual. I'm lost in the technical details...


Regards,
Don_