1:48 Engine Room #3 Battleship USS New Jersey for Permanent Display on Board.

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As I've said too many times to count, the ying and yang of custom designing and 3D printing models is there are very few excuses for not getting it right. Case in point… the foundation that surrounds the Main Condenser. I chose to print it as three parts with the upper foundation, the flanges and lower foundation as separate. When I attempted to test assemble the flanges to the upper works, the fit was terrible. I had to cut and chop, force and otherwise mess around with it and the results looked it. I've recast the print to integrate these two parts. I'm going to print that this morning.

It's not easy to seein the photo, but it's not very good.


Here's the modified integrated part on the slicer before adding supports. In this orientation the supports will all be on the bottom and not foul any of the details. Previously, I printed it in the reverse and was not happy with the support removal.



The LP turbine drawing continues to grow. It's 90% complete. All that's left is the shroud and details on both ends.




Drawing it is one thing… getting it to print is an entirely different problem. I will be printing the back upper cutaway as one part, the entire rotor as another, and the entire lower section as the last. I'm not sure how the end details will be printed… maybe integrated, maybe separate. We'll see. This is uncharted territory.
 
The revised condenser foundation print was successful. Here is the entire condenser assembly held together with tape. The main is a true 1:48 figure to give some scale to this device. I will paint the insides and then assembly can begin. Meanwhile work continues on the LP turbine. The geometry is NOT simple and intersecting angled pieces, while doable in SketchUp, take a lot of time.

Here's the integrated foundation on the housing.




And the entire unit. Two handwheels broke, requiring reprinting a bunch more and fastening them with 1/32" brass. The condenser is a really big piece of apparatus. BTW: all of the propulsion equipment was installed in the hull and the ship build around it all. It was not meant to ever be removed.



The non-shaft end of the turbine is finally almost finished. Shown behind is an image of the LP turbine in #1 engine room. You can see that the facing is not vertical. It would all be much simpler if I wasn't insisting on doing the cutaway. But then it wouldn't be as much of a challenge. Printing this is going to be an exercise in insanity, i'm predicting.

 
While 3rd Gen 3D Printers can reproduce almost anything, it doesn't mean it's successful. I have reached the ultimate limit of what they can do. I violated one of my own rules: Don't make parts their scale size if it's below the threshold of structural integrity when printed in 1:48 (or smaller). I made those turbine blades scale size. The resulting test print proved my rule. Everything but the two largest sets were so frail that the just flopped over and stuck to one another. Saying that, if you looked at them with a microscope, you'd actually see each blade retains the airfoil shape I drew. Just because you can draw it doesn't me it will print well.





This will require a bit of experimentationa, which I anticipated. I've done some redesign already, thickening all the blades and making the edge seals all connected so they act as a continuous band. I'm also rethinking the entire printing process of the turbine body. I built the model as the prototype is constructed, which is a fun exercise, but it won't work. I'm gong to make most of the unseen body out of a solid object. Only the visible, open front lower portion will follow the prototype. I'm also rethinking the inclusion of the stator blades. They will suffer the same fate in the printer and will complicate assembly. I don't think they'll be see and folks won't miss them. Again… it was a fun drawing exercise.
 
I printed out a first draft of the entire LP turbine. It's in three part: base, back upper and rotor. Each needed tweaking, especially the rotor and the rear upper part. I had forgoten to remove stock on the upper part to accept part of the rotor diameter. In SketchUp, especially working with shapes that are not "true solids" in 3D CAD terms, you have to mess around a bit to get it to work.

The process is somewhat arcane. You put the two assemblies in contact and then "Intersect Faces" (an SU function). You have to open each group to do this. First you intersect the faces with the open rear asssebly. And then reverse it by intersecting faces with the rotor. You are left with lines that separate the faces, which you must remove by erasing them from the part you wish to remove the stock. This leaves a gaping hole, which you could fill by carefully recreating lines to make a new surface in the hole. But that gets almost impossible on an old-shaped cavern. Instead, there's a trick. You open the rotor's group, copy the faces that were intersected there, and close the group. Next open the rear assembly group nad PASTE IN PLACE. This restores the missing face in the carvern perfectly. One more thing. The new face is inside-out, since you're now viewing it from its backside. Before doing anything else, since this face is still selected, reverse the faces so they are "normal". 3D printers do not recognize reversed faces! Whew!

Anyway, I opened up the back part to accept the rotor's profile. I will print them today.

Here's yesterday's print. You can see that the rotor will NOT nestle into the back assembly because those spaces were NOT created pushing the rotor forward.



I redesigned the rotor blades to make all of the smaller ones into a solid disk. I'm only printing the true contours on the biggest. They were the only ones that had the strength to hold up to the real world. If that still has trouble I'll have to come up with plan D. Here is the final drawing. I only drew and printed enough blades to be seen. A full 360º spread would be very hard to print.

 
The latest print is hanging on the drain fixture on the machine and it looks like a winner. The blades look nice and regular and I think the latest version will work.


The laser-etched surface on the build plate holds like crazy. To avoid damaging it when trying to pry the work off, I developed a two-step approach. I use a razor scraper to just lift one corner. I then use a plastic scraper to then work the part free. It happens with essentially no damage to the plate. If you attempt to use a steel sharp-edged scraper, you will catch the plate and eventually damage it.

The draining rig is a Cults3D part that you can download for this printer that hangs the entire build plate assembly on a 45º angle and lets all the excess resin drain back into the vat before you remove it. It greatly reduces cleanup and saves expensive resin in the process.
 
Well… The blades are still not viable. After the resin dripped off of them, they got a little squirrely and will not work. The Reverse blading at either end of the rotor didn't do so well either. I'm going to have to rethink the whole blading design to make it work. The lower body came out perfectly. The upper body came out well, but I realized that I didn't draw some of the details on the lower half, and that's not acceptable. Meanwhile, I got a good start on the engine that drives the main coolant pump. The photos sent by Ryan didn't show me the reverse view and I don't know what's holding up the back side of the gear box and turbine. The turbine is so enclosed in insulation that you really can't see what its shape is. Therefore; I am imagining it. There are three insulated pipes entering the insulated space. One is superheated steam, one is exhaust, but I have no idea what the third one is. Ryan's going to capture some more images for me. I'm also in a quandry about the foundation holding up the high pressure turbine. I have fabulous dimensioned drawings for this piece of gear, but very ambiguous drawings about what it's sitting on. I will gather more info about that too.

To solve the warping blades I'm going to cheat and build up the bases of each row so the blade portion will be much smaller. It seems to be isolated to the first four wheels.



It looks like this big pump is driven by a single wheel impulse turbine. It also seems like it has a double reduction gear transmision to step down the many thousands of turbine RPMs to more manageable pump speeds. The pump assembly is a separate printed part and I merged the shapes using Interface Surfaces to mold the pump supports to the piping below. It should nestle in nicely when it's ready to be assembled. There's lot of smaller lube piping that will be printed also.




I'll do it over and over until I get it right.
 
John Miano came through again! He sent me a full 3-view engineering drawing of the entire main condensate pump. Most of my drawing was a little bit off and I'm attempting to redraw it. Once I have real drawings, I no longer have the excuse to imagineer the details. That only works when it's only what I conjure that determines the output.

The trickiest part (so far) was figuring just how these three views related to one another. Initially I had one of them backwards. Even with the drawings, the actual shape of the steam turbine itself is still ambiguous to me. Lots of valves and piping needs to go on. It will make it a very intesting item. The real machine has a single rotor impulse turbine and a single stage reduction gear reducing the 10,000rpm turbine speed to around 600rpm. I don't intend on making a cutaway of this. At least not now...




I finally have a usable rotor! Strange delamination on the central core, but it doesn't look like it's going to causse a problem. The main thing is that the blade wheels are intact.



I also got a good print of the top half and test fit it together.



It wasn't fitting right on the RH big wheel and I found out why. A drawing error that I hadn't picked up earlier.



I'll fix this and reprint. All it costs is a bit of resin and time. Since I often print overnight, time doesn't matter much either. Right now I'm printing a new condenser end cap. I dropped it and it broke, in a way that would be hard to repair.
 
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