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DrJB

Eurobricks Dukes
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Everything posted by DrJB

  1. DrJB
    I read Blakbird's review and now ... not wanting to disassemble the helicopter, I' working on the dino. I in fact managed to get two sets for the original MSRP (not complete), but I have enough spare parts to make that work. Will post pics once finalized.
  2. DrJB
    I read through the thread but could not find the answer to this question. I must say though that those are beautiful trucks, and someday I'd build one. The question is this: For some of the colors (blue/red/dark red), has the author checked that all the parts do in fact exist? I know all the rounded parts for trim may not be available in dark red and blue ...
  3. DrJB
    Very nice. Seeing how the whole vehicle wobbles when moving/stopping ... I can't help but think of how it's done in real life. Maybe a control algorithm that optimizes trajectory/acceleration so as to minimize oscillation back/forth?
  4. DrJB
    Nicely done! Love the sound effects of engine starting (at the beginning of video). Small detail: a balloon tire might be better at front, for turning.
  5. DrJB
    Agreed ... I think for its time it may have been a super set ... but once you've tried Mindstorms, it's 'difficult' to see the value. I had to open the controller box and redo some of the wires (rubber gets brittle after a while) .. and I'm simply 'fascinated' as to the level of electronics in the earlier lego sets ... it is not just about plastic bricks.
  6. DrJB
    I finally managed to get such set, and after putting the helicopter together, I was not impressed by the 'Play Value'. The build itself is nice, but the large programmable block ... I'm not sure what TLG was thinking when designing/releasing such set. Unless it may have been 'high tech' for its time, until fancier computers rolled in. 1. What's your opinion? 2. You know of any interesting builds out there? (besides Sariel's harbor crane). I've been 'thinking' of what else I could use it for but ... nothing 'that' interesting after all. Lastly, and per Peeron, it was released 19 years ago with an MSRP of $219. I was a graduate student back then, and that was a LOT of money.
  7. DrJB
    Check Sariel's applet (above). I was merely you expand your horizons a bit and need to think BEYOND the horizontal/vertical spacing ... which can only be incremented by 0.5 stud (or module). If you think of a matrix of pinholes (kinda like beams/liftarms stacked above each other) then you need not restrict yourself to X or Y motion only i.e., the gears need NOT be on the SAME row or column of the matrix I mentioned above. Makes sense?
  8. DrJB
    Well ... The real question is whether one accomplish the needed gear ratios and kinematics with the gears available from lego ... I was thinking of the Antikythera when I posted that. The Lego version has way more gears than the original, most likely to mimic the necessary gear ratios.
  9. DrJB
    Agreed that the steel (heavy) balls make a difference. Yes, the Theo Jansen and Cardan are neat ... I wonder if the latter can be replicated with standard lego gears.
  10. DrJB
    I stumbled upon these videos on youtube ... would be interesting to see these replicated in Lego. Any volunteer? The last one appears to be Akiyuki's inspiration for his zig-zag lift
  11. DrJB
    The OP is referring to this post, in another thread he started. http://www.eurobrick...showtopic=95164 It is essentially a neat way to use non-lego tires with lego cars ... a lego wheel/tire is forced/pushed into the rim of a much larger tire.
  12. DrJB
    How was I (or anyone) supposed guess what you were after? Your original post was very vague at the very best, and when people (e.g. I) ask questions ... you start lecturing! You should be VERY clear in your post, so you do not get equally non-sensical answers. I stand by my comments, as nowhere in your post you hinted that you were after replicating a 'certain' gear mechanism (the one in the video). Lastly, you CAN reproduce a similar mechanism with diagonal bracing ... I have a 7-volume book-set (MIR Editions) on mechanisms, and the one in the video is one of the simplest.
  13. DrJB
    What do you see? ... cuz I can't see anything ....
  14. DrJB
    You can even print your own stickers if needed ... Though, that specific part (1×2) is only 15-20 cents on bricklink. How many do you need?
  15. DrJB
    Thank you, that's exactly it.
  16. DrJB
    Not sure what you mean exactly by 'kinematic pair' ... your lists is more about 'misfits'. Not every gear will mesh with any other, and yet have a spacing that is multiple of a stud length (M). Only some given combinations are allowed. If however, you still want some 'non-standard' gear ratios (such as those you're showing above), then you'd need more work, to come up with something a bit smarter than a full stud length. The gearboxes on the 8448 and 8466 have spacing of 2.5 stud length, and that is because they use technic 1x2 bricks that have 2 holes, not just one ... I can't find it now, but I know of a graphical tool that shows you the spacing you need and few optional constructions if you pick any combination of the standard lego gears. Some of them require that you go diagonally with the construction, not just up-down or side-to-side ...
  17. DrJB
    Back to the OP's original question ... I started a similar thread a while back. Check it out. http://www.eurobrick...showtopic=87935
  18. DrJB
    Can't you just take current gears and drill them? For sure will be much cheaper than a 3D printed version ...
  19. DrJB
    Correct, my attempt here was meant to build it and see how it behaves. Ultimately, what is important is the difference in number of teeth between stator and rotor. When the flex rotor is stretched by the wave-generator, the two anti-lobes on the rotor must retract enough to yield clearance between the teeth there and those on the stator (inner gear). I guess one can run a simple calculation, start with the circumferences of the two gears (primitive diameters) .. then push the lobes out, and calculate how much retraction in the anti-lobes. To simplify the calculation, one can assume that the deformed rotor has the shape of an ellipse with major axis aligned with the lobes, and minor axis perpendicular (aligned with the antilobes) ... the circumference of the ellipse is the easily calculated. The sketch below explains the approach.
  20. DrJB
    Effe, Based on the image below, I think a harmonic drive is feasible with the number of teeth below: - Stator: Internal gear, with 36 teeth - Rotor: External gear, with 34 teeth (mounted on flexible cylindrical shell. For the rotor, the thickness under the shell should be as small as possible (1 mm?) The wave-generator is made as shown in the attachment, with two rubber wheels. Also, the teeth shall be the same size as Lego Teeth, for compatibility of course. One can make a larger drive, but the one below is the minimum 'possible' based on the size of the wave generator.
  21. DrJB
    Looks nice ... I'm wondering if this applies to the often mentioned tatra suspension ... Can't shift side-side then fore-aft at the same time ... though there is no need for that.
  22. DrJB
    Yes, pictures please.
  23. DrJB
    True story .... about 10 years ago, at a Toys-R-Us store ... I was asking if they had any Technic Sets (was looking for the 8455 BackHoe) ... The young employee there, eager to please: No we do not, but we have the next thing UP... it's called Bionicle, it's very new, and combines parts from classic lego, technic, and some 'bionic' parts. It's way more intricate than technic, you'll love it!!! My Son: Dad, this train has new parts that we do not have ... we should buy it ...
  24. DrJB
    I've seen few instances where lego technic parts were being used in Non-Toy applications. I can name a rack for glass tubes (for chemistry buffs) and the antikythera in a current thread. Can you think of (and post links to) info on the use of Lego (technic) in 'serious' applications?
  25. DrJB
    Effe, it's really not that complicated. Let us say that the stator (rigid internal gear) has 30 gears. The rotor (flexible cylinder with external teeth) needs to have few teeth (2-4) less (in this example 28). The mechanism that flexes the rotor, and make it mesh, can be made with 2 small rollers that push the cylindrical shell (and meshes it against the internal gear (stator). I'll try to make a sketch and post it.
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