yvesvidal

To stay on the subject of the Diesel engines used in the Type VIIc vessels, it is important to note that these motors could turn in both directions. Switching from one direction to the other did not take much time and could be done in less than 30 seconds by seasoned mechanics. The reversing mechanism was cleverly designed and was controlled by a single cylinder on top of each engine: The control was done from the front of the engines and the following drawing provides a detailed diagram of the mechanism: Finally, these engines had rather fragile bearings. It was not uncommon to have to replace them during a cruise and trained mechanics could do that daunting and extremely dirty task in a few hours. The movie Das Boot depicts such intervention being done: Mr. Tore, the expert who navigated the U-995, recounts in his memoirs how delicate and tedious it was to replace one or multiple crankshaft bearings while navigating. Yves

So, the U-552 was built in the shipyard of Blohm und Voss, in Hamburg on September 25, 1939. U-552 was part of a sub-series of eight vessels, ranging from 551 to 558. These units were equipped, apparently, with the volumetric compressor driven by gears (not turbo-charged also known as Buchi Super-charged) and as such, used the G.W engines made by Krupp. Here is what the Type VIIc Manual tells us: G.W. diesel engine installation. Diesel engine installation of some Type VII C boats consists of 2 G.W.-engines with associated auxiliary machinery. The engines are single-acting four-cycle with fuel spray injection and supercharging. Both engines are reversible. a) G.W. general and performance figures. Type Germaniawerft Marine diesel engine, Model e.v. 40/46 with forced induction by Roots type blower Power Full load 1400 SHP Overload 1500 SHP Maximum load 1600 SHP Speed 470/480/490 RPM Fuel oil consumption 254 kg/hour (full load) Cylinders 6 Cylinder diameter 400 mm Stroke 460 mm Displacement 6 x 57.8 liters Overall length 5600 mm Overall height 2895 mm Overall width 1525 mm b) Construction of the GW propulsion plant. Bed plate and engine block (lower part) are constructed as one welded block, which consists of single, vertically standing cast steel frames, which are held down by welded steel plate. The two cylinder blocks (three cylinders each) are connected with this bed plate by means of tie rods passing through flanges on the lower edge of the cylinders. These tie rods relieve the working cylinders of the combustion gas forces and transfer them to the upper part of the raised bed plate. The cylinder heads are pressed by studs on the working cylinders and thus form the upper abutment for the cylinder cans. The fuel oil is injected into each cylinder by a fuel oil injection pump (Bosch design) and a fuel oil injector (type G.W.) into the combustion chamber. Oil from a fuel oil feed pump (gear pump) is transmitted to the individual fuel oil injection pumps. The delivery rate of the fuel oil pumps is controlled by shifting the regulator linkage (changing volume by means of beveled edge). The control regulator linkage can be moved by governor as well as by fuel oil control lever at the operating station. The governor is built as a centrifugal governor and is driven by an idler gear from the camshaft drive. Charging (increase in the amount of air to burn) takes place via a Roots type supercharger (G.W. type). The charger is arranged on the clutch side of the engine and is driven from the crankshaft by means of gear wheels through a hydraulic clutch. This hydraulic clutch and interlocking mechanism allows the charger to be used only while driving forward and engaging and disengaging it only when the engine is running. Cylinder barrels, cylinder heads, exhaust valves and exhaust manifolds are cooled by sea water, which is fed by a coupled cooling water pump (piston pump). The coupled lubricating oil pumps (gear pump) feed lubricating oil that is used to operate the hydraulic governor as well as for lubrication of the crankshaft bearings, cylinder barrels, camshaft bearings, the fuel oil pump control linkage and drive as well as for supercharger blowers. The engine can be reversed either by means of compressed air or by means of a special hand oil pump. Altering the direction is controlled by shifting the cam shaft in the longitudinal direction, so that the cams for the opposite direction of rotation engage push-rod rolls. c) Auxiliary machinery associated with G.W. engines. 1. Superchargers. In order to have a greater air supply available, a Roots type blower is mounted on the clutch side of the engine. The blower is powered from the crankshaft of the engine by means of gear wheels. The blower is driven by means of a wrap-spring coupling, which prevents torsion vibrations and which takes up the distortion of the rotating motion. The supercharger clutch is a double cone type which can be engaged and disengaged from the operation station only while in "Ahead" drive, and only when the engine is running at full operational speed. In order to preserve the friction lining, the operating speed is to be lowered if possible when engaging to on. 2. Pumps. Cooling water pump. The cooling water for cooling the engine oil cooler, cylinder barrels, cylinder heads and the exhaust is fed by a double piston pump, which is at the front of the engine. The drive takes place via a crank, which is driven by gear wheel transmission from the crankshaft of the engine. A safety valve on the discharge side of the pump should respond when outlet valves are closed. Lubricating oil pump. The entire engine as well as all important contact surfaces are lubricated by oil fed from lubricating oil pressure line under appropriate, reduced pressure. The lubricating oil pump is driven by the gear wheel of the cooling water pump drive. It is a gear pump and operates in both directions of rotation. The adjustment of oil pressure takes place via a pressure control valve from the operating station. Fuel oil feed pump. The fuel oil is supplied by a special feed pump from the gravity fuel oil tank to the fuel oil injection pumps. It is a gear pump and is suitable for both directions of rotation. It is arranged over the camshaft. Auxiliary cooling water pump. For the cooling of the engines in case of failure the coupled cooling water pump an electrically driven centrifugal pump is provided in the diesel engine room as an auxiliary cooling water pump. The pump performance is 48 m³/hour of water against 30 meters H2O. The pump housing is directly connected with the associated driving motor. Hand cooling water pump. The hand operated water pump is designed as a double-acting piston pump. It draws sea water and discharges it to the cooling water control manifold. Auxiliary lubricating oil pump. The auxiliary lubricating oil pump serves for the lubricating of the engines in case of failure of the coupled lubricating oil pumps and before start-up. The pump is an electrically driven vertically arranged screw pump and supplies 38 m³/hour of oil with discharge head of 50 meters H2O and suction head of 5 meters H2O. The auxiliary lubricating oil pump can be also be used for the distribution of fuel oil. Hand lubricating oil pump. The hand lubricating oil pump is used to transfer lubricating oil from supply tanks to the collective tanks, and in case of failure of the auxiliary lubricating oil pump to pump oil before the start-up of the engines. It is designed as double acting piston pump and its performance is 4.2 m³/hour. 3) Governor, filter, lubricating oil cooler, starting air tanks, lubricating oil purifying system. Governor. A centrifugal regulator is used as a governor which is mounted on the clutch side of the engine and is driven by an idler gear from the cam shaft drive. The governor prevents exceeding the maximum permissible engine speed by more than 10 percent. If the maximum permissible engine speed is exceeded, the governor pushes control linkage towards the zero position. As soon as the number of revolutions decreases, the governor returns to its previous position and the control linkage brings the fuel oil lever back to the operational position by means of a spring. Fuel oil and lubricating oil filter. The purifying of the fuel oil is done by means of a system of EC-edge disk filters. To protect these filters against coarse impurities in the fuel oil a coarse sieve is inserted in the line before the fuel oil gravity tank. For purifying lubricating oil an EC-edge disk filter is used for each engine. The bearing lubricating oil as well as oil for the clutches and the hydraulic governor is filtered by these filters after branching from the oil cooler. Lubricating oil cooler. The entire lubricating oil cycling installation is cooled by a lubricating oil cooler attached to each engine. The cooling effect is achieved by forcing oil through coils, around which sea water flows. The cooling water installation is so designed that oil cooler can be bypassed as a whole or partially. Starting air tanks. Starting and reversing the engines is done by means of compressed air at 30 at. The compressed air is stored in dedicated tanks of capacity 200 liters each, connected together to the high pressure distributor (high pressure air bank 1 – high pressure manifold) through the reduction valve. The pressure reducing valve works automatically and holds the pressure in the starting air cylinders at 30 at. The tanks have safety valves set at 30 atmospheres at as well as necessary connecting valves, drain valves and control valve with pressure gauge. Lubricating oil purifying system. An electrically driven purifier with a capacity of 250 liters/hour is provided in the diesel engine room for purifying dirty lubricating oil. The purifier is equipped with an electrical oil pre-heater and a hot water pre-heater. Directly coupled with the drive shaft are the pure oil and dirty oil feed pumps. These two geared pumps arranged one after the other. The attached dirty oil pump sucks the contaminated oil from the lubricating oil collecting tanks and passes it over the oil pre-heater into the lubricating oil purifier. The cleaned oil is then pumped by the pure oil pump. The waste water from the oil purifying process drains into the bilge. A hot water pre-heater is provided for better cleaning of engine lubricating oil. 1-1 Comparison between engines M.A.N. - G.W. M.A.N. Krupp (G.W.) Number of cylinders 6 6 Piston displacement 57.8. liters 57.8 liters Piston speed 7.2 meters/second 7.2 meters/second Efficiency 82.5 81.0 Speed 470 RPM 470 RPM Supercharger speed 10,900 RPM 10,900 RPM Performance 1400 SHP 1400 SHP Stroke 460 mm 460 mm Cylinder diameter 400 mm 400 mm Length (whole engine) 5630 mm 5600 mm Width (whole engine) 1400 mm 1400 mm Height 2810 mm 2895 mm Engine weight 38.476 tons 43.440 tons Weight to power ratio 13.75 kg/SHP 15.5 kg/SHP Fuel oil consumption (+) 0.165 kg/SHP 0.182 kg/SHP Supercharger Buchi Exhaust gas turbine B.B.C. Roots type charger G.W. Fuel oil regulation Over flow adjustment Chamber volume by means of beveled edge adjustment Yves

Katuna, I am not planning to drop any pistons, but you are right about the pairing. That is exactly how they worked. Also, Pistons have a little crown on top, made of 4 segments. Enough insanity for me.... 😉 Yves

The starboard engine is more or less completed: Each cylinder of the engine has a bore of 400 mm which is about 8 mm at the 1/48 scale. I happen to have aluminum tubes of that exact size, for their inner diameters. I have decided to represent the engine during its construction or rather during extensive repairs. The long threaded rods to hold the head and block around the sleeved cylinders, are made of brass rod. I did not have a 1 mm die (smallest I have is 2 mm), otherwise I would have tapped the extremities of each rod. I hope it does not look too bad....from a distance. At this point, the second engine can be placed on its cradle: This makes for a cramped compartment, as is the prototype. It also allows a nice view on the Port engine with all its finished details. Some funny views.... Soon, we will be closing the lid (installing the ceiling) on these engines. Yves

What a gorgeous little boat. I love how you built that spine. Yves

You may not like what you are doing at that moment, but we sure do enjoy it, from our perspective. 🙂 Yves

Katuna, I think I know which modeler you are referring to. This is gorgeous but if it is the Hachette kit, they only have two compartments to build....not the entire vessel. Besides, once inserted in the hull, you cannot see any of these incredible details. Finally, I do not have the patience for this level of details, nor would I know where to find the information. But thank you for the picture....it is quite incredible. Yves

Beautiful story. Thank you for sharing it with us. Yes, the magic of flying.... Yves

Well, the engine has been installed in its cradle, similar to what these mechanics were doing on these historic pictures. I have tried to shorten the stand of some of the rockers, to give the overall engine a more realistic look. If all the rockers were in the same position (as implied by the Trumpeter kit), then the engine would have a hard time running. It is not perfect, but at least it is better than what the kit is proposing. Also, I have added the six hand valves on top of the engine. Again, these are present in the PE sheet, but the instructions are not mentioning them. I added a small washer between the shaft and the bulkhead, to make it look more convincing: Still trying to focus my poor camera on these gauges: And finally, giving the engine some offset, like the prototype:. The rear of the engines are closer to each other than the front (shaft/output) side. Now, to work on the ceiling and on the other engine. Katuna, I am still debating about that oily look... It is very tempting but also difficult to represent in a realistic way. Yves

A few pictures of the engine. It is almost finished and I have waived the oily look.... I was ready to use real dirty oil (from my car) but decided otherwise: I still have to paint the exhaust and assemble it. Yves

Katuna, you beat me for the posting. Yes, of course, I noticed these wonderful and historical pictures posted by RAYMIC1 on the models.rokket.biz forum. Quite a different perspective: Those diesel engines are colossal: Finally, a picture taken from the library of "Das Boot". Yves

Very true. There are so many short cuts with basically no savings at the end of the day for the Manufacturer. This kit could be "top", with a little bit more care and a few more parts. Yves

That elevator takes the whole model to another level: Museum quality! Superb. Yves

Lovely. Yves

Much better stand that allows you to admire the beautiful curves of that hull. Yves

Don, I am humbled that the famous Mr. Prince is taking a look at my model. I am in awe at the extraordinary amount of work you have done on these German submarines and have learnt so much by reading your book (the PDF version). Also, thank you for introducing Mr. Tore to this community as he is probably one of the very few men having served on a Type VIIc vessel, still in existence today. There will be more of your material being used in this Blog. It is my absolute reference. Yves

My eyes are exploded. That engine is a challenge to build and to paint. It must have at least 100 parts to put together. I am building it pretty much out of the box. The only change I made was to cut the plastic pushers and replace them with metal wires for more realism. Not an easy thing to do: you need to drill 12 holes with the proper alignment. Trumpeter has been placing a lot of hoses and it makes the assembly a challenge: at the scale of 1/48th, these hoses are too big and are crammed, preventing a nice organization of all the parts, especially around the rockers. I have seen some modelers push the insanity at replacing the plastic valve springs with real springs. I just cannot do that. Besides they are almost invisible once the engine is in place. After painting the entire engine, some kind of "Hemp" color, it is time to install the pushers and paint all the details. My eyes are too shot to go any further today. Yves

Very nice mast. Yves

Thank you Katuna for all this very interesting material. I have thought about showing the oil pan on the engine and regrets that Trumpeter did not include that part in their otherwise extremely well detailed engine. I may fabricate it for the starboard engine, as nothing will be visible on the port engine. I wish you could show in a separate thread, the beautiful work that you have done with your engine, all the piping and oil tanks in the frame of the compartment. Maybe you will start your own thread on the U-371, as you are depicting it, in the Mediterranean sea. Yves

Please, post here what you think is relevant to the Diesel engines compartment. I'd love to see what you have. Yves

Katuna, I know you know, since we frequent the same very specialized forums. I simply hope I can get close enough to what You and Bianco are doing. I am humbled when I see the masterpieces and the extent of research and details that you are putting into these models. Katuna, I use your work as the reference for a lot of details and understanding of that submarine. Thank you for sharing your knowledge and skills with us. With gratitude. Yves

Let's look at some of the information I found on the Diesel Engine compartment. As shown by the blueprint, there are three main tanks in that compartment (and there are many secondary and very important tanks to operate such complex machine). There are two Fuel tanks located under the engines and multiple lubrication tanks located right between the engines, under the walkway. These 3D renderings will help: That first drawing shows the fuel cells under each engine and the multiple oil/lubrication tanks, pipes and associated pumps. Quite complex. The drawing above shows the two engines and the walkway installed between them. Notice that the two engines are not parallel to each other. This is not correctly represented in the Trumpeter kit. I will see if I can give the model some offset on the engines. The three following drawings are showing the armature holding up the two massive diesel engines. Fuel tanks are built in between the frames, whereas oil tanks are installed as separate cells between the main longitudinal frames. I have decided to not represent any of these fuel and oil tanks, as I like to be able to show the nice ribs arrangement. Here again, the Trumpeter kit does not provide the two elevated frames marked with a warning signs. The next diagram show the cooling and anti-corrosion system used for the diesel engines and electrical motors: We saw that the diesel engines were introduced by an opening on the pressure hull. That opening was bolted and carefully made waterproof. the two following pictures show that large opening. On the second picture, the opening is shown in greater details, but it is a later model than the U-552 (possibly even a Type IX). You can also see the large pipe bringing fresh air to the engine compartment. On the U-552, that pipe would be almost straight. Finally, some views and blueprints of the engine itself: I have to say that Trumpeter did an excellent work on the engine details. It is rendered in great details as we will see. Yves

Le Chasse Maree is an excellent magazine which has been published for many years and covers various subjects related to the sea and boats, in depth. I have a few issues at home and really like it. You picked up an excellent and traditional subject for your build. Yves

I am now moving away from the Trumpeter instructions.... not that I have followed them very much, since the beginning. What should have been glued last, is actually done first. This is done to allow me to fine tune the alignment of the engine(s) and transmission shaft(s). If you do that task at the end, as suggested by the assembly instructions, you run the risk of having the shaft not match the opening in the bulkhead (which is exactly what is happening, already). So, some intervention will be necessary at this location. I have two diesel engines, but they are identical and not symmetrical as are the real ones. So, we need to perform some important surgery on the starboard engine. In addition, keeping the two engines fully assembled will hide the "prototypical" and correct looking engine and presents to the observers, something that is not right. So, I have decided to cut down to the crankshaft case the second engine and prepare it for a little surprise..... If I can do it. More will come later, in a few days.... This is where we stand at this moment. hopefully, most details of the port engine will be visible over the "cut" starboard engine. This is going to be a very busy compartment. Thank you for all the "Likes", encouragement and support. Yves

This wonderful 360 spherical view of the Engine compartment is very useful: https://www.360cities.net/image/submarine-u-995-machine-room I already spotted another error done by Trumpeter, who installed the indicator lights over the rear bulkhead (wall between Diesel and electric engines) when in fact they are suspended to the ceiling, near the wall between Diesel engine and kitchen. When looking at this presentation, please keep in mind that the pictured U-995 is somewhat different from the early U-552 that we are depicting. In addition, U-995 has been modified heavily and retro-fitted with more technology than the early U-Boots. Therefore it may explains some of the differences between the pictures and the model. Yves