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Captainowie

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Everything posted by Captainowie

  1. Captainowie
    That was with a load (the track links). Unloaded, the diagonals within the horizontal section made about the same difference to the sag as the diagonal braces at either end, but there was no measurable difference using both as compared to using one or the other. But with the load I was able to measure a small difference - and then it was easier to decide to keep it as it was than to take the members out of the structure! Ok then, here's a thought experiment for you. Suppose you did construct a structure that used very strong pins connecting a stack of many members. Suppose you then welded those pins in place such that they could no longer pivot. Is the result still a truss? If it is (because simply welding the pins in place doesn't change the forces acting on the members), does it then suddenly become not a truss once a load is placed on the structure? Can you design a bridge whose truss-ness depends on whether there's any traffic on it? Conversely, if it isn't (because you're requiring freely-rotating joints - even though their configuration is stable and don't actually rotate, but whatever), then what happens as the original truss rusts? The joints move over time from freely-rotating to rusted-stiff - does the structure similarly change continuously from truss to non-truss? For flexibility of configuration. If I want to make it higher (shorter) or wider (narrower) I can just add (remove) length to (from) each section.
  2. Captainowie
    Ok, so I may have been a bit guilty of sloppy language. Point taken. I still contend, however, that a 5x7 frame is lighter and stiffer than anything of comparable size that you could make with LEGO triangles, if only for the little bit of give that's present in the pin joints. Nonetheless, I added some diagonal members to the horizontal ... section, which has reduced the sag by about 2mm. I think I'll keep it like this: It is hard, though, to accurately measure the sag. I'm trying to measure a difference of a couple of mm, using a tape measure that's tricky to keep vertical from a long way off the table.
  3. Captainowie
    Well I thought about that, but decided in the end that 8mm over 1.3m was an acceptable level of sag, compared to the engineering effort required to eliminate it. I've not tested it yet, but I'm confident one motor will suffice. I can turn the driving axle with my fingers without too much effort. In any case, the clutch gear doesn't slip, and the gear would slip long before the motor runs out of torque. I'm not convinced. I found this reference to a truss not made of triangles (https://en.wikipedia.org/wiki/Truss#Vierendeel_truss), although I'll concede the technicality - even though it's called a truss, that article says "it does not fit the strict definition of a truss (since it contains non-two-force members)". Regardless, I don't think that adding diagonals would help. The reason you see triangles all the time (in trusses and elsewhere) is that they're a stable shape when all you have are joints and rods. But I'm using 5x7 beams, which are a stable square all by themselves. Having said that, I'm willing to give it a try. I'll report back. Owen.
  4. Captainowie
    And, after a long wait for parts and numerous prototypes of varying size, it's pretty much done. That's a 32x32 baseplate, for scale. The structure measures 170cm across the bottom and 136cm in height, with a gap of 109cm between the base supports. At the top, the horizontal truss spans 130cm, and has 124cm clearance from the ground. It sags approximately 8mm in the middle, which increases to about 10mm in the absence of the diagonal braces. It contains over 500 15- and 11-long beams (plus about 50 other beams of various lengths and shapes), and more than 2100 pins. It weighs a bit less than 4.4kg. The belt, all 737cm of it, takes a little more force to move than I would like, but the clutch gear in the drivetrain provides sufficient torque. I am hopeful that the smaller-scale (full width, half height) run that I have for it in a couple of weeks will allow me to find improvements. LDraw file can be found here http://bricksafe.com/files/Captainowie/spanner/Spanner.ldr
  5. Captainowie
    Nice. I do like to see independent modules with a common driveshaft! I also particularly liked the Friends slide Archimedes screw, that was pretty neat. Pity about the spill rate on that one though. Owen.
  6. Captainowie
    In general, if you have to ask "Is this sketchy?", the answer is probably Yes.
  7. Captainowie
    Yep, that's what happens with GBC!
  8. Captainowie
    That's brilliant! Though it does mean that you can't, say, run something backwards for a second to deal with a bind. Maybe something with a shock absorber could be used to have a spring-loaded return-to-zero.
  9. Captainowie
    No, it's not. That suffers the same problem - you'd need to do exactly the same hack in order to get the IR receiver to work. Ah yep, that'd work too.
  10. Captainowie
    You've hit the right cause to your problem. The basic solution is to have a battery box in the middle, as you've suggested. If you don't want that, I think your only option is to break out the soldering iron and physically join the C1 and C2 lines to the 0 and 9V lines. You may want to investigate using the smaller battery box that holds AAA batteries - that might look a little less ugly. Owen.
  11. Captainowie
    http://www.eurobricks.com/forum/index.php?/tags/gbc/ Shows all topics tagged gbc. It does rely on people using the tagging system, but it works quite well as a filtering mechanism.
  12. Captainowie
    That's a shame - Technica had a wealth of information on 00s and earlier parts.
  13. Captainowie
    I feel that the threshold for removal of a module is somewhat higher than 1/3. I'd be inclined to drop any module that couldn't do at least 2/3 bps (especially if it doesn't deal well with a buildup of balls). I think the discrepancy between slowest module and observed ball rate is down to ball spillage.
  14. Captainowie
    Oh, and in case anyone's interested... I had a RCX-powered ball counter running - 22k balls went past the counter, at a rate of between 1/4 and 1/2 ball per second. Once I saw it up around 3/4 bps, but most of the time it sat about 1/3.
  15. Captainowie
    Not sure I can support a "standard speed" of less than full power - it means that anyone who doesn't invest in a train controller can't test their module under standard conditions. This does two things: 1) it raises the barrier to entry (which, let's face it, is already high enough) and 2) it means fewer train controllers will be available for us to purchase!
  16. Captainowie
    Do you also use the lingerie bag? Or do you just throw them in loose? I can imagine that just soap and water won't do, you'd need something to physically rub against the ball. Presumably that's provided by the bag itself. It's a trade-off: Either you have lots of extension cables, or you have lots of train controllers. If you have lots of motors from one controller and you hit the current limit, it's easy to see because it's right there on the table. If you have lots of controllers on one power point, you get more choice in the current limit (whatever you spec your adaptor for), but it becomes a lot harder to see whether you've hit it. Also, in my setup I run the train controllers off 12V, so that they give the full 9V output at full power (I found that if you only give them 9V input, full power tops out at about 8.5V). I haven't experimented with putting 12V into a PF battery box - would it limit to 9V output? Or would it pass the full voltage on to the motor? If the latter, I'd be reluctant to have it too easy to plug something into the wrong port.
  17. Captainowie
    You can get a LEGO plane to look right, or you can get it to balance on its wheels. Both at the same time is very tricky. This is because in a real plane (particularly the single-engined ones like this one) the engine is vastly denser than the rest of the plane, so pulls the centre of gravity forward. Great job! Owen.
  18. Captainowie
    I'm in the process of unpacking after Brickvention, and I'm wondering what to do about the balls we used: they're filthy. Assuming this problem is suffered equally by other GBCs around the world, what do people do? Do you clean your balls? If so, how do you do it efficiently? I'm not particularly keen to hand-wipe three hundred balls. Owen.
  19. Captainowie
    Another way to reduce the speed would be to swap out the gears at the motor for an 8t and a 24t crown gear. That's how we did it back in the old days, before this newfangled studless nonsense. :-) Or you could use a PF train controller to make the motor turn slower. Or you could use a battery box with two 'dummy' batteries in it. As far as the motor burning out, if you can lock the wheel and remove the motor and turn the axle with your fingers (i.e. so that the rubber bands are slipping) without having to really grip the axle, then your motor should run all weekend without trouble. Owen.
  20. Captainowie
    Shadow, you're the only one that can possibly make that decision. You've done all the hard work to list the pros and cons of each approach - the right decision for you will come down to how highly you value each of the pros vs each of the cons, and none of us can know that. All you need to do now is decide how much importance you attach to each of those things, and the decision will virtually make itself! As to what it is, I would guess that it's a device that circulates that red cube around inside itself. Owen.
  21. Captainowie
    I'm sad to report that after a year and a half of use, my Brickworld '15 retracting pass-holder-zigger thing finally bit the dust. The clip on the back has come partially off, so the clip can no longer grip anything. I guess I'm going to have to go back to using the boring old office-issued retracting pass-holder-zigger thing.
  22. Captainowie
    I don't know much about suspension specifically, but I can't see why it couldn't work. You might need to play around a bit to get the leverage right though.
  23. Captainowie
    Yep, lots of progress. But everyone was just waiting for people to ask before posting.
  24. Captainowie
    Well you certainly could do that, but it seems like a bit of overkill. Why do you need voltage meters? If your regulators are putting out 9V, then 9V is what your voltmeter will say! You could probably do away with the ammeter too (depending on the behaviour of your amp limiter) - when it cuts out, you've got too much current draw! You might find it easier to go directly into a battery box - that gives you a current limiter, as well as an on-off-reverse switch and power indicator for about the same price as a PF extension cable. Either way, let us all know how you get on. Owen.
  25. Captainowie
    You have a couple of options, depending on how pure you want to be. If you're up for a little modification and have some skills with a soldering iron, it isn't too hard to hotwire the battery box so that you can power it from a wall transformer. It is even possible to do this while retaining the ability to use batteries (but don't plug it in to the wall if there are batteries in it!). As others have mentioned, the train controller is also a good solution, with the advantage of not having to make any modifications. They're pretty generous with what they'll accept as an input - they have an onboard bridge rectifier, so AC or DC both work, at 9-12 volts (in fact, I think that the circuitry can handle higher voltages than even that, but I don't recall the details, so I'm not going to put a number on the upper limit). I'd suggest 12 volts though, because there's some voltage drop in the circuitry, so if you put 12V in you get 9V out, but if you put 9V in you only get up to ~8V out. I say "up to" because the controller can also output lower voltages by setting the big yellow dial to anything other than full-lock either way. Hope this helps. Owen.
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