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About Davidz90

  • Birthday 01/09/1990

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    <p> Technic </p>

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  1. Davidz90

    Half beam problems.

    Yes, they tend to break all the time, even when not stressed at all. It seems that better structural solution is there arleady - I've never had issues with the shortest half beams (with two x holes).
  2. Davidz90

    [MOC] Trebuchet

    Maybe a battery box? The black bricks are around 50g each, AFAIK a full box is 250-300.
  3. Davidz90

    [MOC] Trebuchet

    I believe it would definitely help with jumping - ideally, with sufficiently long rope (and maybe heavier projectile), the trowing arm brakes almost completely, with no energy left for any jumping. Lightening the arm is an option too - that would also help with throwing power. Motorized rewinding would be cool, waiting for results [EDIT] You inspired me to make some experiments. Here's a quick and dirty prototype: I have used longer rope and there is dramatic difference when firing with and without projectile. The counterweight is somewhat overdone - it is over 2x heavier than the rest of the machine :D As You said, there is a lot of physics involved - light arm allowed me to move pivot point closer to the weight and get more velocity despite shorter drop.
  4. Davidz90

    [MOC] Trebuchet

    Awesome! How about making the sling ropes longer? This might also increase the efficiency of energy transfer, besides the base wheels. The "stone" is many times lighter than the trebuchet arm and with such short sling, not much faster than it - this results in rather low efficiency and lots of energy wasted in jumping.
  5. Happy new year! Maybe go a step further and make an actual Lego cannon - that is a sure way to beat absolute speed record
  6. I'd try to find a way to connect both sails to single axle, effectively halving the weight here. It would be less rigid, but less mass = way slower speed = smaller forces. The classical, triangular paper airplanes work well ONLY because the wing loading (e. g. mass divided by wing area) is small. One can test this by adding mass to the paper airplane while keeping the COG - the speed (and the so-called Reynolds number) will increase and at some point, this type of wing will just refuse to work, basically producing more drag than lift. You are right that reducing mass at the rear is critical - every gram at the rear means few additional grams at the front to keep COG. Unless the front sticks out far away, but that tends to destabilize the aircraft. Flex hoses are worth trying. Alternatively, maybe hold the rear sail tips with rope only?
  7. This is super cool! Now I want to get those sails :D I'm also curious how this works out. How about replacing some axles with hoses (the thin, rigid ones)? Might save some weight.
  8. Davidz90

    Lego Dishwasher

    Now that is something unusual. Cool!
  9. Davidz90

    [MOC] Blade Runner Spinner

    For more German insanity, I can recommend this page: http://www.luft46.com/
  10. Davidz90

    Technic Walker

    Very interesting linkage, a bit like Theo Jansen's, but not quite. Very smooth and fast! (and yes, a bit creepy :D) Nice job!
  11. Davidz90

    [MOC] Blade Runner Spinner

    The engine looks great! If You want a twin engine with radial and twin boom configuration like P38, there is P-61 Black widow. For single engined fighters, I'm a big fan of Polikarpov I-16. That thing is cute
  12. Fantastic build and brilliant engineering! I'm also curious if the mechanism is inspired by some other mechanical solvers or original. Either way, fantastic
  13. Davidz90

    Compact heavy ratchet joint techniques?

    The legs are very narrow (seems like 2 studs to me), but somewhat wide in the other direction. There might be enough leverage for linear actuator to do the job.
  14. Davidz90

    Quadruped kinematic workbench

    I mean something like this: https://www.youtube.com/watch?v=GUsOouwjsL4 One leg is moving at a time. The tree legs form a stable base, and the centre of gravity (Cg) is moving to keep within this base. I've made schematics: walk by David_Z1, on Flickr Blue circle is the moving leg. Triangle is the current base. Note that Cg could simply move in a circle, either by rotating counterweight or by leaning whole quadruped on the standing legs.
  15. Davidz90

    Quadruped kinematic workbench

    That's a great idea! I'm a big fan of walking Lego contraptions and actually used Algodoo in the past, but this is much more convenient. I always wondered if one could make a quadruped with walking pattern similar to star wars AT-AT e.g. moving only a single leg at a time, while standing on the remaining three. Potentially, that would be more stable than usual solutions.