As I wrap up the current model I’m looking at the list of possible new projects. Looking for something other than space, something that not many people are building. One thing that very few people are building are cranes. The Apollo LUT had a small crane on top which was a very interesting build. The challenge with cranes is that they are light and airy but very strong. This seems like a perfect project for a 3D printer where you can get thin, small parts with good detail.
But which crane to model? I always tend to go big. What is the biggest, baddest crane out there? That would be the Sarens SGC-250, aka The Big Carl. Their motto: “Nothing too heavy, nothing too high.” This bad boy can lift 5,000 tons. It is 250 meters tall in its largest configuration. It is a rail based crane that rotates on a circular rail and can travel on straight rails to three different rotation circles. The crane was transported in containers and assembled at Hinkley Point in Somerset England. 52 of the containers were filled with 100 tons of gravel each and stacked on the back of the crane as a counter weight for total of 5,200 tons.
This is the overall crane from the Sarens brochure.
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Now that the crane is selected, what scale to build? With 3D printing, whatever scale I choose can be scaled up or down easily to whatever scale you want. What I usually go with is the largest model that can be reasonably printed on a typical standard printer. It usually comes down to a balance between scale and detail. Too small and you loose detail. Too large and it won’t fit in the room. I went max height with the Apollo LUT at about 7 feet tall. I want this model to fit on a table top so max height would be about 4 feet tall. A scale of 1/100 would give a model of about 5 feet tall, just a bit too tall. Backing off to 1/120 gives a model of about 4 feet tall so that’s just about right. Next I look at the largest parts. There are two massive box beams that make up the platform. These are 375mm long at scale, too large for the printer but they can be split in half. The base platform will be 8.4" x 14.8".
I have started drawing up the base platform. All the other parts fit fine on the printer. The larger base parts are being made to interlock so it doesn’t rely on glue for strength.
Even the model will depend on counterweight to stand upright. The shipping containers stacked on the back are hollow to allow weight to be added, either sand or maybe old nuts and bolts I have been saving for years. These shipping containers will be screwed to each other so they can be removed and refilled if required.
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This is going to be a fantastic model! Looking forward to your build.
Push Plastic has a nice Dark Teal PLA that looks close to the lower structure color.
Thanks for the tip. Colors are tricky thing depending on the light. I am going with something called Stone Blue. For the yellow most of the yellow I have used in the past is fairly transparent and won’t look good for the thin boom structures so I am going with a Dark Yellow which is still very yellow but not as transparent.
As always for test prints I use either black or white which is cheaper and only use the colors for the final print. The one concern is the booms which have to be printed in multiple parts. Glue alone probably won’t be strong enough so I sketched up two lower boom parts and decided to have holes in the ends that will fit M2 threaded rod. Gluing these in place should provide enough strength.
Here is a first print of a storage container.
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You’re right, colors are tricky. The colors you choose look way better based on photos I’ve seen.
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I figured the best picture to go with might be the underside which might be less affected by the light. The stone blue was the closest I could come to a match.
Some of the equipment on top, mostly the winches, are a more standard blue. That color should be much easier to match.
The people in the picture give a good idea of the size of this monster.
It’s crazy how big that thing is. The blue looks like their corporate color.
Base structure test print: The two long main beams are too large to print as one part. Simply splitting the structure in half and gluing the butt joint is too weak. This needs to be the strongest part of the crane. Being a wood worker I know the strongest joint is a dovetail so I went with a half blind dovetail. The joint is tight enough you don’t need glue. I then chose to use the center cross beams as another joining mechanism. This test print has revealed a number of modifications needed before a final print. 1) I missed a front cross beam that needs to be added. 2) The cross bars should be raised to be level with the top surface which will provide a better glue surface for the decking. 3) Flip the exposed dovetails to the top since these will be covered by the decking. 4) The underside has indents that the trucks will fit into. This allows for simple alignment. Do the same for the four end cross bars that support the counter weight cargo containers. 5) Beef up the swing boom attachment points.
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Platform Layout: Did an initial sketch of the platform top with outlines of various components that sit on top; 10 winches, 6 generators, the control cab, stairs and other various boxes. What I noticed (see picture above) is that there is what looks like grating strips. This makes sense given the size of this platform. These would help manage rainwater runoff. Given the scale there is no way to print holes that small so these strips will have to be solid. The color looks to be dark, probably because most of what you see is what is below which is dark, in shadows. My thought here is to use a dark metal color. Colors on the spool always seem to be different than printed colors so I printed a nice box and sample cards by Extrutim. These cards have multiple layer thicknesses so you can see the filament transparency. This picture shows the stone blue and a gun metal grey to use for the gratings.
And here is the platform sketch with the gratings highlighted. The gratings can be printed as one piece on my printer. The plan is to do a two color print, start with the grey and then add strips on top in the blue.
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Before creating the rest of the trucks I went ahead and laid out the track that it sits on. This consists of a circular set of tracks that the crane rotates on (there are 3 of these in the real installation, I am only modeling one) and a set of parallel tracks that it uses to move between the circular tracks. The rails will be a steel color and the base it sits on is concrete. I use a bone color for concrete. The tracks are indented into the concrete (see picture below). The question is how to print this base? It is big enough it will have to be sliced up into multiple parts. Since the tracks are very small and delicate it would be very difficult to try and line up all these tracks if they are printed separately. My decision is to separate the track/base from the raised base, then split those parts. The track/base parts will be two color prints. This is achieved in the slicer by creating a pause point to allow a filament change. The tracks will be printed on top of the base material, strong and straight. This part splits out into 24 parts. The thousands of bolts that hold down the tracks are too small to model.
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Goodness me that’s a big crane. I look forward to see your continued work! How tall is the model going to be when it’s completed?
The height depends on what angle the boom is at. In the most upright position it would be 1.4m or 4.6’. My plan is to angle it over some without fear of it tipping over. That all depends on how much weight I can put in the counterweight containers.
The bogies are designed. There are 56 of these. It is sliced up so the wheels can be printed as steel. The rest of the bogie is sliced up so it can print decently and hopefully be assembled without much effort. There will be a total of 616 printed parts to make these. For sure I will test print one of these before printing 56 of them.
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I have test printed the bogie 5 times now. I like to add as much detail as possible but with a part this small there is a dilemma. To get detail this small I usually use a resin printer which can print down to about 20x20 microns which gives fantastic detail but the resin color pallet is so limited there is no way to match the stone blue color. The part would have to be painted which would also be tricky to color match without lots of paint mixing. Ideally these parts will be printed with the stone blue filament and steel for the wheels. The issue with filament printing is a resolution of about 0.1mm in height and 0.4mm in width. I could switch from a 0.4mm nozzle end to a 0.2mm nozzle end but I would have to purchase one of those. The goal is a part that looks reasonably accurate without being so blocky it looks like a Lego model. Here is where I am at right now, printed in black and white so you can see the wheels are separate parts. I have also test printed a portion of the track to make sure everything aligns.
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Starting to print the real parts. The base structure interlocking works well. You almost don’t need glue but I did anyway. The smaller cross beams get glued in place. You can also see that I included small indents to help locate and align the four major cross beams that hold the 5,200 tons of counterweight. The black test part is set in place to show where they will go.
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The container beams are printed and installed and the first four containers are attached with screws. This will need over 200 M2x4mm screws to attach all the containers so waiting for those to arrive. In the mean time I am playing around with the size of the inner stiffeners on the sides of the containers, making them a little larger and trying different supports, I think organic will be the best. Once I have the container prints where I want them these four containers will probably be inside ones that you can’t see except for the ends. Also converted one of the printers to a Prusa Core One and it is working great so I’m in the process of converting the other one. Got both kits just before the tariffs hit.
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