Robert Cailliau

Eurobricks Vassals
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About Robert Cailliau

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  1. Robert Cailliau

    Duplo Trains discussion

    It is a funny piece in more ways than one. It follows the old style, where they could not be put on top of bricks or plates because the coupling bits went down too far, getting in the way of the studs of the plates or bricks. Therefore they cannot be used to build on supported slopes or bridges, only laid out flat. You may wish to explore /L/Lego/Duplo/Train/Rails/Dimensions/ (on first visit you may have to click the "Englsih" button and then reload the link; I'll change that asap) So who wrote the track planning app? Can I get it? BTW, also note this: /M/Mathematics/APR/Description/
  2. Robert Cailliau

    Duplo Trains discussion

    Goede middag Edge_nl, For some reason I did not see your thank-you (thanks!) nor your very interesting 3D printing suggestions for more rail formats. Sorry for that, I just saw them this morning. And yes, a topic for 3D printing of compatible parts is a very good idea. I have a printer (Ultimaker-2), but the grandchildren have outgrown Duplo… Does a 3D group of topics not already exist? I have not looked. In any case, Duplo rails do not require the same precision in 3D printing as standard Lego pieces do. Unless parhaps for sticking to Duplo bricks. Thanks! (I've got OpenSCAD too)
  3. Robert Cailliau

    Duplo Trains discussion

    There you go: So it's three studs by four. These bits are useful to close some layouts with tracks at angles other than 90º. However, they do not stick to plates or blocks and there is quite a lot of play. The answer then is: 3x8=24, so 8 small ones will have the same length as 3 standard ones. Nothing in between.
  4. Yes, "someday" is also on many of my lists… ;-) Anyway, perhaps I should research techniques for getting 0.5 unit distances with the studless beams. Another "someday": publish a list of parts that would be useful but do not exist. Many of them are connectors.
  5. I did not find this set so very good. The pneumatics don't really work as well as I would expect, probably due to the not so very good compressor, but also due to the hoses to the pistons. The gearbox that drives it all is complex and has a lot of friction. The geometry of the steering is good though. But I would certainly not rate it as the best Technics set ever. There are some excellent sets, and some that are rather disappointing. Admittedly, it's very difficult to make Technics sets that work well and in the end are also good-looking. The Arocs gets 5 out of 10 from me. The bucket wheel excavator (42055) is the best one I have built: everything works well and all dimensioning is correct (*) Then there is the whole issue of creativity: building a mechanism with the new-fashion beams that have no studs is sometimes frustrating, as there is no easy way of getting a half-unit offset. (**) But that has nothing to do with this particular set, it's a general remark. Robert. (*) the ferris wheel, 10247, has Pythagorean triangles that are wrong, one of them has a side that is off by 2.77mm (implemented: 132mm, Pythagoras: 129.2308mm); there are several Pythagorean triangles in the bucket wheel excavator but every one of them is correct! (If you need elucidation: a Pythagorean triangle is a right-angled triangle in which all sides have integer lengths, such as 3-4-5 (because 3x3+4x4=5x5), which is needed in the case of Lego where everything has to fit a discrete grid). (**) For example: making a 40 tooth wheel mesh with a 16 tooth is difficult: the axles need to be (40+16)/16 = 3.5 units apart. 3.5 is easy with the bricks with studs but not with the studless beams. I'm trying to design an astronomical clock that's as good as John Stouffer's (https://www.buildsteam.com/home/introduction-to-the-lego-astronomical-clock) but will sit on a table top instead of needing a large drop. Using only the "new" Technics "religion" of studless beams is very difficult, and I have actually given up and reverted to the beams with studs.
  6. Robert Cailliau

    Duplo Trains discussion

    I never see a reason why an old thread would necessarily mean it's inferior. As to your observations, I may have posted the url https://www.cailliau.org/Alphabetical/L/Lego/Duplo/Train/Rails/Dimensions/ before, or not. And yes, my (my granddaughter's) locomotives can also pull many carriages. The locomotives have changed. It also depends on the wear on the rubber tyres, the state of the batteries etc. Many parameters. Have fun, Robert.
  7. Jim, you wrote: In the thoughts below I used the part numbers as they appear on pages 481 and following of the construction manual. (1) In the construction manual on page 163, on the frame, the rubber liftarms (4198367 rubber liftarm length 2) lie horizontally. They connect to vertical black beams (4142822 beam length 3) that can rotate around fixed blue pins that go through their centre hole. (2) On page 200 the bottom holes of these black vertical beams each get a suspension arm (6055628 steering arm with ball socket) connected to them (the picture on page 200 shows the assembly downside-up, so the bottom holes are at the top in that image). Note that these arms are shown at an angle in all illustrations. Geometrically the sockets for the ball heads are therefore closer together than they would be if the arms were horizontal. They need to be pulled apart slightly if they are to adjust to the Lego grid. (3) On page 218 these arms get the ball heads of the four pegs (4184169 pin with ball head) of the double differential. (4) On page 219 the "shock absorbers" (they are only suspension springs really) are attached and they push the differential away from the frame. That distance puts the steering arms at the angle they were already depicted at, which pulls outwards on the vertical beams. The necessary flexibility can only be achieved by the stretching of the rubber liftarms. If you replace the rubber ones with normal, stiff ones (4211741 for example) then it all feels very different. There is an image at http://www.cailliau.org/Alphabetical/L/Lego/Models/42043-Arocs/RubberLiftarms.jpeg The distance between the black ball heads indicated by the red line with arrows is a fixed distance (on the differential assembly)
  8. OK. Sorry, I did not know there was more about this specific thing elsewhere. The only reason I wrote anything at all was to point out that the different angles Jim mentioned in his review are indeed desired and not a design mishap in the Arocs. Off for now, R.
  9. Well, I did have a go at Ackerman steering in Lego. Competion: anyone can do it nicer, more robust, more compact? See this page: http://www.cailliau.org/Alphabetical/L/Lego/Models/42043-Arocs/AckermanSteering/'>http://www.cailliau.org/Alphabetical/L/Lego/Models/42043-Arocs/AckermanSteering/ There is a link to an .lfx file so those who want to try it may use buiding guide mode in LDD to see how I did it. I'll put some real photos up too, and will make it into a remote-controlled car. (you can also watch http://www.cailliau.org/Alphabetical/L/Lego/Models/42043-Arocs/ and http://www.cailliau.org/Alphabetical/L/Lego/Models/42043-Arocs/Steering/ ) to Starmort: it's all a matter of local taxes, people getting money off you just for postage, and other weird things, nothing to do with an open market. That needs a lot more hammering from the European Commission.
  10. To wildboar: coop :-) To 750ACE: thanks, actually I did not know the name! I only remembered the text and diagrams from the Meccano instructions (back in 1955…) Yes, I should have looked for it on Wikipedia & sent the link. I found this: https://en.wikipedia.org/wiki/Ackermann_steering_geometry (quite incomprehensible article in fact) There is a lot more, not to mention suspension methods. To LXF: Hope you found my page & were able to read it. In the intervening hours, I have attempted that steering with Lego, with moderate success. I may publish it. Or not.
  11. Hi LXF: How about this: http://www.cailliau.org/Alphabetical/L/Lego/Models/42043-Arocs/Steering/ (there is nothing else yet about this model though) (And to make some of you jealous: I got my box for 85CHF = 77€ in an after-Christmas sale where I spotted it at 170CHF but was told at the checkout it was 50% off…)
  12. Congratulations on highly professional photos! I was even fooled by some of the outdoor pictures! Just a small thing: you write "Using different links results in different steering angles for both axles." Yes, and you might add that that is desired. In fact when I decided to buy it I was wondering how they would deal with the problem of making all wheels point to the same centre of rotation. Unfortunately the rear wheels do not turn, and at the front wheels in each pair are always kept parallel whereas they should not be. The latter problem is easy to solve in Meccano and almost impossible in Lego. I'd upload a picture, but I'm out of attachment space. For those who are interested: draw a top view of the truck, with rectangles for the wheels. Then draw a line extending one of the two rear axles, say to the left. Choose a point on that line, the point of rotation. From that point, draw lines to the centres of all other wheels. Then rotate the rectangles that represent the wheels so that each is perpendicular to the line that goes through it. Those are the only positions of the wheels that will make the truck steer a circle around the point of rotation without making the tyres slip and therefore wear out. You will notice that the first pair of wheels must turn a little more than the second pair and that at least some of the rear wheels should also turn. I have seen real platforms with four rear axles, all of which turn correctly as well as the double front axle. You will also notice that in each pair the wheel closer to the point of rotation needs to swivel a little more than the wheel on the other side. I know of no Lego set in which steering wheels do that (but there may be some).
  13. Robert Cailliau

    Duplo Trains discussion

    GallardoLU, it is hard for fathers to wait, but you will have to… It's even harder for grandfathers :-)
  14. Robert Cailliau

    Duplo Trains discussion

    Hi GallardoLU, 9 months seems very young indeed! I just looked back into our photo/movie archives: our granddaughter Nora had Duplo when she was 1 year old. At that point she could not put blocks on each other, but thouroughly enjoyed the "dolls", especially the very old type (that were only "heads", see http://alpha.bricklink.com/pages/clone/catalogitem.page?M=dupfig030#T=S&O={"ii":1} ). She played a lot with figures and with separate objects such as cars and the plane until she was 3 or 4. She got her first Duplo train set at her second birthday, and the school (kindergarten) where she went in Paris also had a duplo train set. At 2.5 she discovered her grandmother's normal Lego, which is very neatly kept in a storage box with little trays, all types and colours sorted. She loved that, but only because it was a lot of orderly stuff with lots of the same pieces, not because she constructed much with it. (unfortunately my status here does not allow me to post more pictures). She walked at just under 1 year, and talked (a lot) from somewhat later. She is now 6 and still gets the train out to play with, as well as the farm animals, cars, and things, but for construction she is now into the Lego Friends series and of course did the Ice castle from "Frozen" (41062). The locomotives have a big button on top to make them go, and that was fun when she had enough hand coordination to push that button accurately even when the train was moving. So maybe that is a "turning point": sufficient eye-hand coordination. It's also not easy to put trains onto the rails (see http://www.cailliau.org/Alphabetical/L/Lego/Duplo/Train/Rails/Dimensions/ ) We have 5 locomotives, but two are certainly sufficient, as it all takes a lot of room on the floor. There are some older style railway cars with roofs that open so little figures can be put in, and she also loved to do that, as well as making long trains with lots of figures on them.
  15. Robert Cailliau

    Duplo Trains discussion

    It will fit: there is enough play. Most of Lego's own examples of layouts do not fit exactly and need the play. As soon as there is a piec of track at an angle the trancendental lengths of cos(L) and/or sin(L) give those problems (L being the length of a straight track). See pages linked to from http://www.cailliau.org/Alphabetical/L/Lego/Duplo/ As to the custom-built locomotives with different wheels not going up bridges, that is because the Duplo locomotives have wheels that act as pinions on the racks at the sied of the bridge slopes (see same pages). A good custom-built locomotive would probably have to use those wheels. Can be done with "destructive" techniques, meaning taking a real Duplo loco to pieces to use its parts in another construction.