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Captainowie

Eurobricks Knights
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Everything posted by Captainowie

  1. Captainowie
    Small wonder that timber and brass were the materials of choice for precision instruments a hundred years ago! This one from the same chap blew my mind!
  2. Captainowie
    Some years ago I used some of my technic to build tie/belt holders.
  3. Captainowie
    I have never taken apart PF connectors (or the 9V ones, for that matter) by pulling on the wires.
  4. Captainowie
    An alternative might be a 16-tooth gear with the teeth slightly mis-aligned with the cross-axle. This has the advantage of being able to be used in almost any situation you would need an ordinary 16-tooth gear. Owen.
  5. Captainowie
    You could use 3x 8 tooth gears rather than 2x 16. However, if you're concerned about the axles being 1/32 of a rotation out, then the backlash in 3 gears might be too much for your application. Owen.
  6. Captainowie
    Yes!! Also "It works flawlessly for 30 minutes straight at home, so it should be fine all weekend on display".
  7. Captainowie
    "At some stage I'll have to route this motion to that mechanism, but I can do that later, it'll be easy"
  8. Captainowie
    Surely that's more to do with the properties of the material concerned? i.e you put steel in tension, because it buckles under compression. On the other hand, if you were building in concrete, you'd put the braces under compression, because concrete crumbles under tension. That's why steel-reinfocred concrete is so strong - the concrete resists compression and the steel resists tension.
  9. Captainowie
    I'm glad you agree that this is a 'healthy' debate - there aren't many places on the Internet where such things don't disintegrate into name-calling and worse. I have not seen (3,4,5) called "Pythagoras' Triangle" - to my mind that triangle would be no more Pythagorean than any other right-angled triangle. However, triplets of numbers such as (3,4,5), (5,12,13), (7, 24, 25), and (infinitely) many more besides, as well as all their integer multiples, are known as Pythagorean Triads, or Pythagorean Triples. To insist that the (3,4,5) triangle is properly called an Egyptian Triangle and not Pythagoras' Triangle on the basis that the Egyptians came before Pythagoras is to assert that it was discovered by the Egyptians. Certainly we know they used it, but what evidence is there that they didn't copy it from the Babylonians? Or the Arabs? Or the Chinese? (okay, maybe China is not very likely). Incidentally, the sole reason I mentioned him in the first place is so that readers who maybe didn't like having to sit through that stuff in school can see that it's not so useless and irrelevant after all. I'm not sure what you mean by 3D bracing - if you mean something like connecting the diagonally opposite vertices of a box, then the appropriate equation is a^2 + b^2 + c^2 = d^2 (where a, b, and c are side lengths of the box) which again has nothing to do with Fermat. But I'll bet you can do it with LEGO! Though it might not be particularly structurally sound, I'll grant you that. Owen.
  10. Captainowie
    Hi. Why would the pattern not repeat? If it repeats with a turntable after a certain amount of time, surely if there are no changes in gearing it should repeat with an egg after the same amount of time? It seems to me that the problem you're having is that in changing the axis of rotation from vertical to horizontal, you've made left-to-right movement of the pen across the egg the same as rotation of the egg itself. I don't know how easy it is to make modifications, but if you could decouple the left-to-right motion of the pen from the front-to-back motion, and had the left-to-right motion much smaller than the front-to-back motion, you might end up with a prettier pattern. Does that make sense? Owen.
  11. Captainowie
    Ok, I'm sorry for pursuing this, but I can't let it slide. What you've said is simply not true. The only relationship that I can think of between the lengths of an arbitrary triangle is that each side must be shorter than the sum of the other two (otherwise the shape wouldn't be able to close). Pythagoras' theorem applies ONLY to right-angled triangles. You're right that nothing in the theorem restricts the solution to whole numbers, but as you said earlier, the existance of the 3-4-5 triangle has been known for thousands of years, and has nothing to do with Fermat. You're perhaps getting confused with Fermat's Last Theorem, which states that there are no whole-number solutions to equations of the form x^n + y^n = z^n for any n greater than two. We know there exist solutions for n = 2, because that's just Pythagoras' theorem. We also know there exist solutions for n = 1, because that's just adding numbers. But there is no perfect cube that is the sum of two other perfect cubes, and so on for higher powers. Owen.
  12. Captainowie
    Thanks, that's exactly the answer I was looking for.
  13. Captainowie
    The angles are the same in both cases. The difference between them is the orientation - whether the small angle is on the horizontal or vertical brick. Surely you mean "as well as" rather than "instead of" for the liftarm. I would wager that what I've got there would withstand a lot more pressure than if I replaced the diagonal brick with the liftarm. Most things aren't named after the person who invented them. That doesn't make it incorrect to refer to things by their names.
  14. Captainowie
    One for the structural engineers out there... I am building a structure to support my latest GBC module. I have vertical supports, and a horizontal cross-member. I am using a 12-long brick to form a 6-8-10 triangle to maintain the right angle between the support and the cross-member (thank you Pythagoras!). But which is the best way to do it? In the red version (on the left), the 6 side is horizontal, and the 8 side is vertical. In the blue version, it's the other way around. Which one should I use? Or are they equivalent? Under which circumstances should I use one over the other? In this case, the brace will be under compression (holdling something up). Would the answer be any different if it was under tension (holding something down)? Thanks Owen. P.S. The forces involved are not great, so I'm certain that either one would suffice. I'm just curious about whether one is better than the other. I'd settle for which one is more asthetically pleasing.
  15. Captainowie
    If acceleration is an issue, then it may be that it proves tough to find an indoor smooth floor large enough.
  16. Captainowie
    Are you sure it isn't already made of LEGO? That cover over the front mechanism looks to have been built out of plate :-)
  17. Captainowie
    My goodness. Those GBCs are incredible! I particularly like the swing arm from GBC 6 - it must have been tough finding the right gearing and geometry to get the arc oscilating in phase with the natural frequency of the balls. I also like your use of planteary gearing with a fixed sun gear. I may have to steal some of those concepts for my own modules :-) Nice work.
  18. Captainowie
    Great job. Is there a reason why you inverted one of the shock absorbers? Also, from your blog post you say If you're aiming for top speed, surely it doesn't matter how long it accelerates for? If you're aiming for shortest time along a given path, though, that's a different matter. Owen.
  19. Captainowie
    If I was the type of person who regularly didn't believe what people claim, I'd suggest that you set both your camera and the picture on your wall at an angle, and drove it along your bed!
  20. Captainowie
    Even if you could get 1.5 amps through the reciever, the standard battery box current protection kicks in at less than that, so you're still going to have issues.
  21. Captainowie
    The S in MISB stands for Sealed. If you open the box to check that all the bags are there, you can no longer advertise it as MISB. The question then becomes whether "MISB" is worth more or less than "MIB (checked - all bags are there)". LEGO is famous for its quality control. I'd say the chances of there being a missing bag is far less than the chances of someone losing or stealing a bag from a pre-opened box and saying "they're all there, I promise" (Not saying that anyone here would do such a thing, of course, but there are some unscrupulous types out there).
  22. Captainowie
    There are in fact 40 plates containing 666. Consider: 666 in the last three positions. The first digit can be 0 or 1, and the second digit can be 0-9 = 20 plates of the form xx666 666 in the middle three positions. The first digit has the same restrictions, and the last digit can be 0-9, for another 20 plates of the form x666x Anyway, my plate number is 09059.
  23. Captainowie
    (I may have paraphrased a bit there!) Ok, so here's the general idea. (sorry about the crappy picture) In the above pics, the connector block hitting the pin represents a large load on a drivetrain. In the image on the left, if you turn the liftarm, the load is engaged, and because there's no bracing, the bricks separate. In the image on the right, however, if you turn the liftarm, the load is engaged, and the clutch begins to slip. The gripping power of the studs is sufficient, and no further bracing is needed - any bracing you put there is just going to add weight and complexity to your model without serving any function. I guess the lesson I've learned is to design your supporting structure for the load it has to take. If it's going to have to handle a lot of torque, then you need to make sure it's properly braced. If it's only going to have a light load, then just the gripping power of the bricks might be sufficient (there's bound to be some equivalent for studless building, but it escapes me at the moment). Actually, when I put it like that, it seems kind of obvious really :-) Owen.
  24. Captainowie
    I just had a "Eureka" moment. I have recently been spending a fair bit of time re-designing the power transmissions for some of my GBC modules. I made sure that everything was properly braced, all the axles were supported in at least two places, etc. I also took the opportunity to include one of the torque-limiting clutch gears, in case something goes wrong and the mechanism binds. My realisation was that if I'm going to put in the clutch gear, I don't need to go overboard re-inforcing the structure - I only need it to be strong enough to withstand the amount of torque that the clutch gear can provide, rather than being able to withstand the torque of the driving motor. The clutch gear will slip before the bricks come apart. I guess my point is that bracing and structural soundness is all well and good, but it is certainly possible to make it far sturdier than you need. Owen.
  25. Captainowie
    True, but how much will the performance suffer? That extra weight is probably no more than maybe 20% of the vehicle weight (happy to be corrected here). At least the OP can get an accurate lower bound for the maximum speed - what he's got now is essentially wothless, as others have said.
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