Captainowie

The PF switch has little plastic ridges in the throw arm to make it snap in to the extreme positions. That might be what's getting in your way.

That's a neat gear shifting system you've got there Paul! Thanks also for explaining the difference between the old and new driving rings - I should have guessed it was to make it an odd length. I would suggest that these parts have been in the works for a long time - ever since the axle joiners lost their ridges. Owen.

There shouldn't be an issue using a M motor in place of a servo motor, but you shouldn't expect to be able to just swap motors and get the same performance. You'll need to gear down the M motor somewhat to get enough torque. As far as the whining noise goes, I'm afraid I can't help you. It's possible that your receiver might be faulty if the model drives OK without the receiver and not OK with it.

See also http://www.teamhassenplug.org/GBC/ for the original specification. A GBC module would be ideal for someone interested in Mindstorms or Wedo and wants to do more than just vehicles. Owen.

The pulleys most certainly DO rotate by the same amount, at least in this example. They must because they're all pinned together! DrJB is right that if this were done in real life the pulleys would free-wheel on the axle. In this case my guess is that the pulley block will rotate at something like the average speed of the strings. The faster strings will suffer friction, but the slower strings will be pulled along by the faster-rotating pulley block and shouldn't (I don't think) contribute to the overall friction losses too much. If the axle that the pulleys are on was locked, then that's when you'd get your 4x360 degree exponential friction growth. Owen.

I don't know if this is really considered a MOD, but I turned my Unimog into a GBC module... http://www.eurobrick...3 The only things that are not Unimog parts are the baseplates and the bricks that secure the model to them, a 1x4 brick to give the motor a studded mount point, and two of these to secure the frame around the slightly-wider-than-one-stud spring.

I've been able to improve the misfire rate down to a couple of percent, by strategically placing a piece of wire (actually, a twist-tie) such that the balls aren't able to rest in the lip around the edge of the portal hub. I'm now happy enough to say that this module is essentially finished. There are a couple of minor aesthetic changes to make, and I'll do those when I break it down into pieces for transport. One question I was kind of expecting to be asked was "this is built from Unimog parts - where's the orange?" Well, I thought it would be a little bit cool if as well as being a GBC module, it still looked like a Unimog. So I kept all the bits for the cabin separate when building the catapaults, and made a frame to support it and the engine. I also added space for the wheels, so this is what the completed module looks like. It's a bit hollow in the middle, and the wheelbase is just a bit too long for my liking, but I'm really happy with how it's turned out. Of course, the wheels and engine are powered! I realise that the input chute is way too high for a standard GBC module. I have designed a feeder module that delivers the balls to the right place. Now I just need to make the catcher module - using the parts from the tray. (yes, I'm posting to a web forum on Christmas day. No, I'm not spending time with my family - they're four thousand km away)

Of course! That's because they're awesome! I'd not seen the tow truck before - that looks like an amazing model, absolute state of the art in the pre-PF days. I'm loving the extensible axle with the worm gear in the steering and drive train.

Yes, TLG. They sell them from their website, and there's a large second hand market. :-) Anything homebrew is going to necessarily have some slightly different specs, even if only in form factor. I would hazard a guess that it's going to be worth your time to just buy the LEGO ones. Sure it might be cheaper to hack something together yourself, but unless you're a pro at it, you'll probably be working for far less than minimum wage with the time you spend vs the money you save. Owen.

Hi Myxo. Yes I have given it some thought. But the outer part is a bit big - the ball rattles around for a second before settling down - so that is likely to impact accuracy. The inner part has a nice cup, but will require a complete redesign of the top part to fit it on the throwing arm. If I can't get something working with the portal axle then I'll look into it further. Thanks for the suggestion. Owen.

This afternoon I ran a test with this module fed by its feeder module rather than my fingers. The spill rate was about 1 ball in 4 :-( But after some minor adjustments I got that down to about 1 ball in 10. The vast majority of this spill is due to misfire (rather than a ball popping out of its track), which happens when the ball doesn't sit in the holder properly before being launched - it stays in the lip around the edge. I will try to jam some putty or something in the gap to prevent this. Owen.

Lovely mechanism, nice implementation, and great video. You may have some difficulty getting a previous module to split the balls into two streams that the input to this one needs. For one idea you can see what I've done to solve that exact problem here.

So I've made some progress lately. I've got a rough video up here. Let me know what you think! Owen.

But of course you can! If you can imagine it, you can build it! Regarding hypoid gears in particular, if what Boxerlego says is correct and the "hypoid" bit just means that the axles are not in the same plane, then that's easy to do with a crown gear or the oldest style differential. If you insist on having the helical teeth that's fine - it just means that the resulting gears will be more ... complex (and too large and too weak to be of any practical use whatsoever). I'm imagining something using a bunch of ribbed hoses held in the right shape. Owen.

Ok, let me try again. I think this came out in Lipko's post, but I want to make it more explicit. You said: LEGO mechanisms are generally simpler than those in real life because they generally do simpler things. Staying with transmissions for the moment, consider what was perhaps the first LEGO transmission (http://technicopedia.com/853.html) - just two speeds, certainly simpler than a 'modern' (even in the 70's) 4+R transmission with synchromesh and a whole bunch of other stuff, but there's a lot that the modern transmission can do that the LEGO version can't, because of that simplicity. If you want to replicate all the functions of the modern transmission, then you need to use more gears, making the LEGO version more complex than the real-world version. On the other hand, let's look at something you've identified as simpler in LEGO than in real life - steering. Even without the rack-and-pinion vs bearing-screw difference, a real-life steering system has the pivot point of the tyre inside the footprint of the tyre itself, and turns the inside wheel more than the outside wheel, and presumably a whole bunch of other stuff as well. It's certainly possible to replicate this behaviour with LEGO but, like with the transmission, it bumps up the complexity of the build until it becomes greater than that of the real-life version. Even something as straightforward as a simple gear reduction is often a lot more complex in LEGO. Want a 6:1 gear reduction? In real life you just need two gears. In LEGO your best bet would probably be a two stage system consisting of 2:1 and 3:1 reductions. What about a 12:7 reduction? There exist 14t gears and 24t gears, but the axles need to be spaced 2.375 studs apart, so again the complexity grows. This is why I stand by my answer of "All of them". Anything that is simpler in LEGO than in real life is only simpler because it is representing a subset of the capabilities (albeit including the defining feature) of whatever is being built. Is that clearer? Owen.

All of them? Reason I say this is that if there is any LEGO mechanism that is less complex than its real-life counterpart, then almost by definition the LEGO version is not as capable, or not as strong, or not as something else.

I thought so too, but recently I've found some use for them. Need to join two parts of your model together but there's a cross-beam in the way? This puppy's got you sorted (so long as there's space for that long pin-hole). Also, the rim and tyre of these wheels fit nicely in the gap in the beam when you attach the wheel to the long pin-hole.

Sorry everyone for the lack of updates - I've been distracted by other (both LEGO and non-LEGO) things. I now have a pair of nice ball launchers in a red, grey and black (with a hint of yellow and blue) colour scheme, and I've got a drivetrain that delivers 30 rpm to the flicker arm cams (giving the requisite 1 ball per second between the two launchers). What I'm trying to do now is design the middle bits of the module (the drivetrain, and a couple of visual-effects mechanisms) so that I can join the two halves together in such a way that: It's actually possible to assemble it in a nice order It's sturdy in all three dimensions It can be broken down into relatively dense chunks for transport It can actually be disassembled at all Photos and hopefully video to come when these simple requirements are met. Owen.

One WIP thread here http://www.eurobricks.com/forum/index.php?showtopic=101053 I've put that one on hold for a bit while I convert some of my others to work with standard balls vs zamor spheres, and to pass straight rather than turn 90 degrees.

Sorry. The end of the year is fast approaching, and I've got a bunch of GBC modules to make before Brickvention in January. Owen.

Perhaps a compromise could be to allow the "leftover parts" image to be produced digitally (i.e. LDraw or LDD or a montage of pictures from Brickset).

Ha! I didn't even notice that. A nice touch. I also echo the sentiments of the others here - this is a glorious piece of kit. Owen.

I don't think it's a good idea to mix batteries of different voltages - for the same reason that you shouldn't mix batteries at different charge levels (i.e., you should change all the batteries at the same time). As I understand it, this is because the higher voltage battery will end up trying to charge the lower voltage battery, rather than power the rest of the circuit. If the normal battery is non-rechargable, it won't like this at all, and could overheat. And catch fire. And explode. This would not be a good thing. Technic motors are just DC motors with some fancy coverings. They'll run just fine (though faster) at the higher voltage. However, they are designed for 9 volts, so they'll wear out considerably faster if you 'overclock' them too much. PROlego - finding a Bricklink store with all you need at a reasonable price is something of a black art. Nobody is going to be able to recommend a particular store, unless they're advertising their own store. You might find you need to split your order across multiple stores to get the bargains. Owen.

This is true, but often the missing 5% is critical - they're the pieces that make that set unique. For example, I'd probably have 95% of any pull-back set you'd care to name, but without a pull-back motor, any C-model I make will be somewhat mediocre.

You may even be able to drive your parallel axles with 8t gears engaging with the inner ring of the turntable. Also, don't rue the chain links you bought - they have a tendency to come in handy. Owen.