Nequmodiva

Now I made a mini Harbour Crane MOC. It's an alternate from parts of 8067 Mini Mobile Crane. Photographic building instructions are available in my brickshelf folder or for download as PDF (3,48 MB).

Thanks, that's a good idea. Wondering about how to adopt this for a horizontal movement I came up with the following concept. The mechanism is known as scissor arm or pantograph. It's an odd design for a crane but it's level-luffing (hook remains at the same height).

I always liked harbour cranes. Especially the level-luffing cranes with their unique shape. But until recently I knew neither the purpose of their structure nor that they're called level-luffing. Only the official B model of 8053 Mobile Crane made me look into harbour cranes. For all of you who don't instantly remember this model, here is the official product image of 8053 Harbour Crane: While building and playing with this model, I became aware of how accurate this model is. By way of comparison, here is a photo of a real level-luffing crane: Dillingen Kran [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (www.creativecommons.org/licenses/by-sa/3.0/) or CC-BY-SA-2.5-2.0-1.0 (www.creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], by Lokilech (Own work), from Wikimedia Commons Cranes like these are called "horse-head" cranes, because of the additional horse-head jib on top of the main jib. To make sure you understand what I'm talking about, I labelled the elements in a picture: The structure has a purpose: level-luffing. Level-luffing means, that the hook remains at the same height when moving the main jib back and forth. There are two benefits from that: it's easier to control the movement of the hook, especially useful where precise positioning of the hook is required. when a load is moved horizontally there's no energy wasted on lifting the load. Here is an animation of level-luffing from Wikipedia: Crane double-lever-jib-type sideview animated [CC-BY-SA-2.5 (www.creativecommons.org/licenses/by-sa/2.5)], by Silberwolf (created by Silberwolf), from Wikimedia Commons And here is an animation I made of the 8053 Harbour Crane luffing: From the following montage I made it's clearly visible, that the hook of the Harbour Crane does not remain exactly at the same height. I think it's pretty accurate, though. A bigger version of this and a few other montages can be found in my brickshelf folder. Another two details I want to highlight for their accuracy: when moving the main jib the counterweight also changes position. In reality this is needed to keep the crane in balance. the rope is guided along the tieback and the horse-head jib and through pulleys in the joints, because if hung straight through the quadrangle the rope would change length while luffing and therefore raise or lower the hook. As I told you, the purpose of the harbour crane geometry is to achieve a linear movement which is in the best case horizontal. Furthermore we've seen, that in the 8053 Harbour Crane the movement isn't exactly horizontal, but it's linear, though. It could be easily modified into a horizontal movement by tilting the structure. The remaining question is, how did they achieve to make it a linear movement? Actually the movement is only approximately a linear one. When skewing the geometry of a harbour crane the lower end of the horse-head jib describes a coupler curve. Only when cleverly constructed the coupler curve is partially an approximated straight line. To show this I've constructed this test apparatus: Then I made an animation and recorded the position of the yellow Technic Bush. The measurements of this apparatus are orientated by the values form this site. So now to my last question, and this question is for you: What other LEGO models are there that have a somehow clever mechanism to achieve level-luffing? I took a look around already, but I found no prove for a working level-luffing mechanism. Among the official Technic models there have only been very few stationary cranes. The second model of 8074 Universal Building Set is one of them. But as these animations made by Blakbird from Technicopedia show, this crane does not care about level-luffing: In LEGO's City line there have been some harbour cranes. But I guess no one precisely recorded their movement. As I own none of them I wasn't able to check either. The only thing I was able to do is this montage made of two photos of 7994 LEGO City Harbour photographed by Dandily: While this crane is obviously a horse-head design, it clearly fails to achieve level-luffing. It seems harbour cranes aren't a very popular subject for MOC building too. Nevertheless there are some models. The most accurate ones I found were these two build by Marinus: Figee level luffing shipyard crane http://www.youtube.com/watch?v=QF1zPjQStTA However level-luffing is not limited to harbour cranes. There are other solutions than horse-head designs too. For example think about a system where the movement of a boom is coupled with the winch to compensate rope length. If you've seen or built something like this let me know.

I've used them. Interlocking two of them to transfer two rotations around on axle. Using an old differential instead would have been a nicer solution, but this was a moc build form the parts of one set. (brickshelf, building instructions)

Four-Winged Plane (I know, technically it's still a bi-plane. But for all of you who aren't that fussy, it should be obvious that there's something this plane has got four of.)

Thanks for the link to this picture, JunkstyleGio. My hope for 8071 was, that it would have a mini LA. But from this picture I rather conclude that it uses a Worm Screw and a 24 Tooth Gear for raising the platform.

No, you did not post in this topic. You got into the wrong topic and your post is there: http://www.eurobricks.com/forum/index.php?showtopic=49918&st=165&p=916917entry916917

I bought this set, too. Compared to similar prized sets it's one of the best. That the function involves a worm gear and a 8 tooth gear is kind of standard for these sets, just like 8045 Mini Telehandler, 8259 Mini Bulldozer or 8260 Tractor. But to have another two gears to convert the rotation from the top to the worm gear adds complexity. Not much, but for a set of this size, it's like a plus of 50%. I would have never imagined the mechanism to work this smoothly as it does. But like you said when sliding the container everything falls out. That's very frustrating. I've got this set on my desk for some days now with the spare parts in the container. Again and again I want to offload the container and every time some of them fall out. Really annoying. Maybe I should load it with rubber or something like that. Nevertheless this set looks great. At first for me this container-piece appeared to be odd inside a technic set, but I got used to it. The whole thing certainly looks much better than last years Mini Telehandler. The not-tilting cabin is a mystery. It's kind of obvious the set was designed to allow this. Since it's easy to change, this is not really a problem. Why there are two booklets for the main model (and in a different size than the one for the b-model) I will never understand. But Lego did the same with 8259 Mini Bulldozer and 8260 Tractor. I see you too got two 6 wide axles with this set, while both the main and b-model only need one. Just one thing more to keep me wondering. It would not make much sense to consider this being a spare part for replacement. There's no reason the other axle 6 would break or get lost. Anyway this set tops with its look and the complexity of both construction and functionality. And this is what counts.

I never saw an image of the robot coming next year. I thought I might post a link to the picture I found today: http://www.spielwarenoase.com/images/product_images/original_images/5702014732766.jpg And here's a picture of the log cabin: http://www.spielwarenoase.com/images/product_images/original_images/5702014732735.jpg I'm sorry to say, but on this preliminary image the roof looks pink.