DrJB

I've tried this repeatedly but to no avail. Is there a way to group parts such that, if I click one and move it, they all move together? There are obvious benefits to this of course ...

'scaffolding' is the best approach. If you want only the goggles and not the helmet, put the goggles on the helmet, select (Ctrl+click) helmet+goggles together, put them on the minifig, then delete the helmet only.

I was going to point this out but decided to read all the posts first. Redoing the molds because of different plastic shrinkage is most likely the biggest hurdle .. and I agree, it won't come cheap.

Great video, I think we're getting close ... If you look carefully, you'll see that the flat wire twists one way from the bottom to the top (long segment), and then twists the other way from the top to the rotating turntable. The 'weakness' in your implementation is that a flat cable does not lend itself very well to circular bending. Try it again, but with a circular wire and you can put some white marking ALONG the length of the cable ... Make sure the wire though is soft in bending.

I can do the math, no issue there :) ... Thinking that the controller might be a challenge, something like a joystick with xy and YAW controls ...

I've been contemplating building a holonomic drive based on http://www.eurobricks.com/forum/index.php?showtopic=92575#entry1830122 Then the question is how do you control this? Thinking of using the EV3 to drive the robots, and the NXT to control via BT/else. I'm thinking a joystick with both pitch/roll controls to command XY motion, and joystick yaw to control the robot's rotation. Anyone has done/seen something of sorts?

LOL ... my comment was about people 'bashing' my rotating hose connection ... not your motor-generator combination ... lol

Again, we have a lot of opinions, based purely on 'gut' feeling ... but no absolute proof ... That's ok.

If you're 3D printing the turntable, why make it in 3 separate parts? You can get away with only 2 (and that might bring the cost down). Of course, if the parts were injection molded, you would not be able to assemble them.

Well ... I tried it, and it does work ... though not with Lego yet. I described that such problem has a solution (mathematically). Whether the solution can be implemented with regular lego parts ... that requires some skills. Will absolutely/definitely/positively NOT twist the cable ... You should try it, it's one of those not-so-trivial solutions. The trick is that the cable has to be soft in bending, so that it can bend in a circular fashion repeatedly back and forth, without breaking. Try it first, you'll be surprised!

It's a classical problem (with solution) in mathematical topology ... http://www.eurobrick...=0#entry1832795

This appears to be a puzzle and I have seen few contraptions (or proposals for new parts) that various people have attempted. Picture this: You want to transfer an air-line (or electric wire) between the bottom of a crawler (track-drive) to the top superstructure ... and you want to do this without twisting the air-hose ... Most will say 'impossible'. Well, not quite (and hence the reason behind this thread). This is a classical problem in mathematical topology, and was resolved a while back. In the picture to the left, the wire will twist if the blue part rotates. In contrast, in the right figure, the air-hose will not twist. It will however bend back and forth once per revolution and is thus a good idea to make the radius of curvature a bit large so as not to damage the wiring after multiple cycles.

Very interesting question/thought. Though, difficult to tell as such spec is not clearly stated on the sensor's description. Might be worthwhile to measure the 'time constant' of such sensor i.e., how fast it responds to inputs. My guess is that the sensor is not sensitive (cannot detect) slow varying changes in tilt. This is not fact, just my gut feeling. Again, best answer is to actually measure such performance/property of the sensor. To keep a vehicle level, might be more effective to use a 'level' sensor (instead of the gyro). The vehicle in the movie you reference uses actuators (an active suspension) to move the tires up/down as the road profile changes ... Assuming you can measure the vehicle's level ... you need a very fast actuator to keep up with the road's inputs. Not sure the LA's/mLA's are up to the job.

I saw that as well at a rest stop in between Hanover and Hamburg, though primarily small sets. Now, I have also been to some toy stores in Italy, and prices were rather high ...

My calculations were not based on theoretical figures. Those are actual prices I paid today at TRU ... I never suggested it was a good deal across the board, but you have to do the math for the specific set you're interested in. I for one, am interested primarily in the large stes, where the markup typically does not exceed 10% ... Sorry if it's not that good of a deal for other smaller sets. Now, on a different note, and not related to the sale, I got the large technic helicopter for $60 only ... Why? Because the gentleman at TRU was kind enough to price match the price on TLG, which is having those as well for half-price ... Not to bash anyone but, asides from the VIP points, I have never seen any sales at the Lego store. My experience with most Lego stores, is that many salespeople there are too 'stiff' with some rules ... No need to go into details here. I am not promoting any given store, just found a bargin and thought I'd share with the community. Happy 'Bricking' I was tempted to ignore this comment but could not ... No one ever implied the US is the Center of the World ... I also see many eBay sellers in Germany who refuse to sell to people located in the US. Does it upset me? Absolutely not. This is a hobby to be enjoyed and everyone takes away from it what works for them. My intention was not to make the rest of the world envious of TRU prices or deals ... Again, just sharing that some can get a bargain ... Especially the large technic sets.

We do not see such price difference in the US, across different vendors. Here, there are primarily 3/4 stores that carry the large Technic Sets (Lego, Amazon, Toys-R-Us, and sometimes Target) ... and all but TRU sell at the same price as TLG ...

Looks like I need to schedule a 'business' trip to Berlin ... I know of a Toys-R-Us store there (got my 8421 from there), but have not seen a Lego Store ... I know in Hanover Lego was rather expensive ... but that was in the premium stores by the downtown Banhoff (train station).

There is a much easier alternative, but works for a single wire/tube ... or maybe few, but they must be bundled together. Here is a little puzzle in topology ... how do you transmit electrical/pneumatic power from a part that is fixed, to one that is rotating, WITHOUT any twisting? This can be done rather 'easily', without any complex seals/rings/ ...

Thank you, that's exactly the kind of observations I'm looking for. On a different note, I built your 3-omni-wheel robot, used the new EV3 motors (2×) and one NXT motor .... only about 90% into the build, I realized the pins locations are not compatible on the NXT/EV3 motors ... They both looked the same for as long as I've had them. Now I realize they are not. Two options for me: buy an EV3 motor ... or build the NXT version.

For those of us who bought recent sets, how about some ratings to help prospective buyers/collectors? The scale is from 0 to 10, and we'll have two lists: Display Sets, and those as parts Packs. I'll start, based on sets I have. I must mention I primarily buy large sets only. Display Sets: 42000 Grand Prix - 8/10 42009 Mobile Crane - 10/10 41999 Egor 4×4 - 10/10 9398 4×4 Crawler - 8/10 8110 Unimog - 10/10 9394 Jet Plane - 9/10 9395 PickUp Truck - 6/10 9396 Helicopter - 10/10 9397 Logging Truck - 6/10 Spare-Parts Sets: 42000 Grand Prix - 8/10 42009 Mobile Crane - 10/10 41999 Egor 4×4 - 10/10 9398 4×4 Crawler - 10/10 8110 Unimog - 8/10 9394 Jet Plane - 10/10 9395 PickUp Truck - 7/10 9396 Helicopter - 10/10 9397 Logging Truck - 10/10 What's YOUR take?

Every time I search for specific parts (or sets) on Bricklink, the cheapest are always from the Netherlands. A seller has the 42009 listed for $170.00 ... Is this a simple coincidence, supply vs. demand, ... or they simply get it cheaper than the rest of us ... Seems to me, if you're a Lego addict (and not want to break the bank), the Netherlands is the place to be ...

Let me do the math again ... If I buy 2x 42009 at TRU, I'll pay: 1.5×($239.99)×1.10%(Tax)=$395.98 If I buy 2× 42009 at Lego, I'll pay: 2.0×($219.99)×1.10%(Tax) - 5% (VIP rewards) = $461.98 Thus, it's a $66 savings total for 2 ... what am I missing? It certainly is NOT the deal of the century, but makes 42009 a bit less than $200 a piece (all inclusive) ... much better than the 440 I get from TLG (including taxes and VIP rewards), right?

The sale ends tomorrow, so if you've been waiting to get those expensive sets, now's the time ... Sale unfortunately is NOT valid for Mindstorms, but the 42009 Crane Mk2 sure qualifies.

...removed

At a loss of words here and having tears as well ... My condolences, and may you, your wife and daughter find the strength/courage/faith to 'deal' with this. They sure were beautiful kids, and now they are beautiful angels, watching over you from up above ... Sometimes the Lord has 'strange' ways to get those of us he loves most closer to him. Have Faith and Courage.