large scale telescopic crane

[Aerolight]

Imagine the mark ii if its tires where Unimog style that's the scale I'm aiming for.

Finally got to actually building and I started with the hardest part, the jib. Originally I wanted 7 tiers (to match the largest cranes irl) but with 6 the largest section is 7x11 (cross-section) which is big enough for the scale I want (think 500tonne rather than 1200tonne style) so I built a halve length section to gauge how plausible this was going to be as a functional MOC. The test section has 6 teirs that are 30 studs long and overlap 4 when extended for a total of  130 studs of raw extension (for perspective this test section is shorter than the main jib of the mark ii but extents to twice it's extended length). The jib is more than strong enough even without a y frame to lift several kilos at its tip (yeh I was shocked too given its length of almost 1.5 meters) so with a y frame I should be able to extend the sections to 60 studs each (fully extended almost 3 meters). But before extending them I started building with the halve size version and when I came to rigging the extension I found why scale crane enthusiasts hate this part. I must have spent 4 hours just trying to find a way to get the string just right to extend the jib, first I tried a single loop for simplicity but there was just too much friction (over a dozen U-turns) so now its uses the same method that the mark 2 uses.. just 4 times! all connected and all needing to be tight to work correctly. There is still a lot of friction but now its a more manageable amount , once I have the test jib mounted with y frame (and a big counterweight) I will update with pics. Oh and before it was rigged the boom made an excellent classic telescoping lightsabre.  

Update; Actually made an error with scaling, if I scale the lowest section correctly the highest section is way too spindly so new scale is each section 45 studs. With the new longer sections they want to close up in the middle causing flex but with a little more overlap this no longer occurs, so now the boom is just over 5 feet tall when extended with extra overlap (although this overlap makes it reasonable to add a seventh tier) the bellow picture is with the old overlap so is over SIX feet high; its not touching the wall at any point but the celling (a bit too flex for me but can still support its full length horizontal so vertical is no problem)

IMG_0411 by michael waterfield, on Flickr

 

Edited September 28, 2019 by Aerolight
update pics

[Saberwing40k]

Pics or it didn't happen. It sounds cool, but I have trouble picturing it, and pics of progress would be helpful, for anyone who wants to build a crane.

[lcvisser]

We had a Liebherr LTM 1450 at work last month*. It extends one section at the time with a giant hydraulic ram inside the boom: the ram extends the section, it's locked in place, the ram retracts and locks into the next section. Just some food for thought if the rigging becomes impossible.

But indeed: pictures please!

*) we had to lift a 20kg box up to 100m. The crane driver was amused and had to actually add some dead weight to keep the crane stable...

[Jeroen Ottens]

It sounds really interesting, but I'd also like to see some pics. With a cross-section of 7x11 I wonder how you managed to get 6 sections inside. With normal 1 stud thick walls, you can only get 4 sections at best (with the last section being 1 stud wide). So I assume you have a different kind of wall structure?

[Aerolight]

With the mark ii style rigging it telescoped smooth but it still cant be driven from below due to friction (it can only extend/retract if held by the later sections) so not sure what to do. I could make it a manual function but would love to find a way to motorise it, I started to build a method like the real cranes (as was mentioned before) But I count not find a way of locking the sections when extended but I will keep trying. The actual cross section of the largest segment is 5x11 the panels are just for looks.

IMG_0408 by michael waterfield, on Flickr

IMG_0409 by michael waterfield, on Flickr

[Jeroen Ottens]

Very interesting solution.

You can reduce friction by adding small wheels to the front (bottom) and back (top and bottom) of each section. You'll have to puzzle a bit with the various wheels & tires that LEGO offers, but it is possible to find a combination that will put the edge of the wheel just a bit higher than the beam. Since the beams are not exactly one stud high, but a bit less, you can make the whole section run on wheels without the beams touching the beams above or below them. The wheel in the front has to guide the next smaller section, the ones in the back are for guiding the section itself.

You mention that you want to double the sections in length. Without any sides on the sections you basically have the bending strength of only the beams in the top and bottom layer. With sides you get a much, much stiffer section. But who knows, maybe that is overkill anyways. I would recommend to test it though, bending stiffness goes with the third power of the length, so a double as long section will be 8 times less stiff...

And allthough I love the use of panels for their stiffness, those pesky holes in them are 1 stud deep and therefor stick out just a few tenth of a millimeter. You have to take care how you slide your sections along those holes to prevent them getting stuck.

Finally I can imagine that those new 7x11 frames could be put to good use here as the endpoints of some of the sections. They will provide a nice and stiff base for the rest of the section (and maybe you can use a 5x7 frame in the back as well?

Keep up the good work.

[BrickbyBrickTechnic]

Your boom seems really flimsy, those beams will bend at any opportunity they get. Try reinforcing the sections maybe? More connection points could give you more options to reduce friction.

[Aerolight]

just finished the y frame (ish), add some tension from the y frame and it can happily lift well over a kilo (without bending now) I was actually struggling to hold the boom up at that point (used it like a barge pole no base superstructure yet. No lego has broken and the boom is surprisingly stiff when the y frame cables are taught. But I still am struggling to motorise the extension so for this test (and pic) the boom is locked with easily removable pins and this, for the moment, is the plan for the full length version so manual extension but rc everything else. Will still try to motorise it but I just cant wait to make the full size jib! remember the full size one will be far stronger at the same length due to overlap and is meant for length not weight so only a few hundred grams at the tip would be a scale weight I think.

IMG_0410 by michael waterfield, on Flickr

[Aerolight]

Right at the beginning I said I was not making a 1200 tonne style crane well..... now its a 12000 style. I have added 2 more sections for a total of 8 (as after checking the largest crane has 8 not 7) and now the boom is 6 foot 4 when extended which it can do while being held horizontal from the bottom section alone. There are two reasons this is so strong when you would think it should be a limp noddle;

1 a track in every section that the next section engages witch reduces side to side movement to a minimum (you can even hold it a full extension sideways) and,

2 the design of the sections and the way they are supported makes them want to close up with force (from extension/load) so with the end of the next section being where that section want to close (about halfway down the section) the whole boom locks its self together; this is the primary reason for the increased overlap compared to earlier versions.

It way sound ridicules but I want to make the sections longer, not just for the sake of length and strength (for a given extension) but because the biggest section just looks so out of anything even resembling scale, it needs to double in length to look reasonable I would say. But I'm afraid I don't have enough lego to make the sections any longer so will consult bricklink for aid and will focus on a super structure that can not only hold this beast (if I get the parts it will be north of TEN feet) but counterbalance it. 

will post a picture of the newest boom tomorrow (hopefully with a better camera)

[Aerolight]

(Sorry for old iPhone picture quality) only the tip is touching the wall. SIX FOOT FOUR and still fully telescopic with 8 tiers.

IMG_0413 by michael waterfield, on Flickr

[M_longer]

I can't wait to see how you will manage bending frame, loose wheels and weight distribution between counterweights and boom.

[Kladovec]

Hi, there. This is only for inspiration. I´ve found this massive crane several weeks ago. It´s almost one year old and creator is no longer working on it. This guy is from Italy. His crane is massive and he solved the boom extensions with some locking mechanismus. But no video. So you can inspire how it could be done.

https://itlug.org/forum/topic/7536-gru-telescopica/page/1/

 

Edited September 29, 2019 by Kladovec

[Aerolight]

wow that controller is S rank, the locking system is exactly the one I am trying to make thanks; not sure if I am going for an external ram or a more accurate internal ram (like the moc)  as I would have to make the smallest sections larger to accommodate it. (shout out to google translate)

[Kio Liex]

WOW. That is crazy, but really impressive. I am following this MOC.