Thursday, January 31, 2008

The Mechanical Muscle Mash


Picking up on the subject of pneumatics and the new 2008 TECHNIC sets, the question arose: will the new linear actuators, debuting in the upcoming 8294 and 8295 sets, completely replace the traditional Pneumatic system, whose current incarnation has been with us since 1989?
I’ve seen opinions claiming the new system is light-years ahead of the older, and others alleging the opposite; let’s compare them, shall we?

First, the "old champ", pneumatic cylinders (PC's).
Strengths:

  • Realistic;
  • Easy to transmit power from long distances and awkward/variable angles;
  • Motion is automatically distributed.

Weaknesses:

  • Imprecise;
  • Hard to power/control automatically;
  • Motion is automatically distributed.
Next, the "newcomer", linear actuators (LA's).
Strengths:
  • Precise;
  • Easy to power/control automatically;
  • Motion is always evenly distributed.

Weaknesses:

  • Unrealistic;
  • Difficult to transmit power from long distances and awkward/variable angles;
  • Motion is always evenly distributed.

I feel I need to explain what I mean with "motion distribution", because it can be both a bless and a curse. In spite of having more to do with MINDSTORMS than with TECHNIC (fans of one theme are almost always fans of the other, anyway), I'll use as example a walking robot.
Linked LA's have an even distribution of motion (unless you complicate the mechanism and insert a differential between them), whereas linked PC's have an even distribution of force.
If your robot has a head that rotates while it's walking, you may want to ensure it faces left when the right foot is advancing (to watch its step, obviously). The torques for moving a head and moving a leg are vastly different, yet you want to have the movements synchronised. This is an ideal application for LA's and terrible for PC's.
If the robot has multiple legs (six, for example) and it is standing on rough terrain, they can't touch the ground all in the same angle, or else the robot will tumble (think of a table with a leg longer than the others). The desired action is to have all legs contact the floor in a manner that the weight of your robot is equally distributed among them (no legs are "floating"). This is an ideal application for PC's and terrible for LA's.

So, after presenting each "fighter's" profile, which one would you bet on? If you want my opinion, I hope LEGO maintains both systems, because, like you saw above, their fields of application almost don't overlap, and therefore they complement each other nicely. Now it's your turn to give your opinion: that's what the poll (when Fernando closes the current one) and the comments section are for. ;-)

(note: naturally, the picture is just a lousy mock-up, for illustration purposes only)

Tuesday, January 29, 2008

Yet another compressor design from iLegos

My friend Mauricio, who runs iLegos just came with another cool design proposal for a LEGO TECHNIC compressor.


This one, includes a new PF Motor ('M' size)*, a Mini-Pump, a Switch, an Air Tank of-course and some colored Pneumatic Hoses to easy air flow identification. You can find it here and just though interesting to highlight it today at TBs, as I loved its simple and cute design.

Integrated Pneumatic Switch allows Cylinders to move both ways.
Just miss the inclusion of an automatic pressure control mechanism. May be for the next time Mauricio... ;)


*) This allows to easily remote control the compressor, by using a Power Functions Remote and an IR Receiver.

Monday, January 28, 2008

LEGO brick turns 50!

When the TECHNIC brick is also over 30 years (and here finishes this post relation with TBs theme...), its older brother 'LEGO® Brick' celebrates its 50 years this January 2008.
It happens today (January 28, 2008) at exactly 1:58pm, according to this timeline (rests to know in which timezone...).

The LEGO history began in 1932 in Denmark, when Ole Kirk Christiansen (OKC) founded a small factory for wooden toys in the unknown town of Billund in the south of the country.
Barely 15 years later Christiansen discovered plastic as the ideal material for toy production, and bought the first injection molding machine in Denmark. His courage, input and investment paid off: in 1949 he developed the LEGO brick prototype, which continues to excite countless children and adults to this very day. Over the years he perfected the brick, which is still the basis of the entire LEGO game and building system today. Of course there have been small adjustments in shape, colour and design from time to time, but today’s LEGO bricks still fit bricks from 1958 (Read more and see the official LEGO commemorative video of 50 years of the brick, plenty of history and some interesting old scenes).

To celebrate the 50th anniversary of the modern brick, LEGO released this year a special-edition update of the classic Town Plan set (10184), completely redesigned with the best of modern bricks, details and design. The all-new Town Plan features a 1950s-style gas station with pumps, carwash and garage, a town hall, a movie theater, 2 automobiles, 8 minifigures, rare LEGO colors and elements, and more.

  • It includes a letter from company owner Kjeld Kirk Kristiansen (KKK), who appeared as a kid on the original Town Plan box and returns on this one.
  • Also includes 3 2x2 bricks with 'gold' finish, to celebrate the 50th anniversary of the LEGO brick.

Meanwhile Google
, whose founders Larry Page and Sergey Brin are known to be avid lovers* of the LEGO brick, also joined the celebration by displaying a commemorative image at Google's homepage (below left), after have added a Google logo made of LEGO bricks into the company office in NY** last year (below right).




Did you notice that, LEGO is a kind of GOogLE anagram. And that, "Go LEGO" would be a perfect anagram for "Google"... what a coincidence. ;)


*) The first storage system ever used by Google was built by co-founders Larry Page and Sergey Brin themselves. Hard drives at the time maxed out at 4GB, and they piled 10 into a case made of LEGO. Google took it offline in 1999 and gave it to Stanford University.


**) Sean Kenny (A LEGO Certified Professional) was approached by the head of Google New York about bringing LEGO to their offices. The astonishing resulting sculpture was installed at Google's New York office in April 2007.


Sunday, January 27, 2008

TBs TechReview 01 - PF/9V conversion cable, Review & Usecases

This week my order with some units of 'PF/9V conversion cable' or 'PF extension wire', as it is their official name, arrived.

They are ~25 studs length (20cm / 8") or ~29 studs including the connectors at both ends. These cables also look very nice and well done.
Each cable has a standard PF plug at one side and an hybrid plug on the other side, which is PF on top and have a 9V form factor on bottom. This combination would allow to:

  • Make easy conversion between systems and bring PF electrical compatibility to legacy 9V parts.
  • Extend wires that came attached and with fixed size, on the new PF elements.

The first good surprise, I was not expecting, is the plug color differentiation. 'Dark Bluish Gray' (DBG) for the PF connector and 'Light Bluish Gray' (LBG) for the PF/9V connector. A good idea and not exactly as in the LEGO marketing material, as you can compare from the images below.




Another surprise concerns with the way plugs are connected. If you flatten the cable you see one plug is upside-down in relation to the other. Still didn't decided if this an advantage or disadvantage...



However personally had preferred if LEGO put them straight, but with the wire leaving the PF/PF plug (DBG) from the studs side. This would allow to connect extension wires without having to bend them backwards like in the image below (despite this may be the desired configuration in some cases, like at star or 'Y' configurations, on the right side).




This limitation derivate not specifically from a characteristic of this cable, but from the new PF connector in general and its inability to be turned by 90º or 180º, like the 9V predecessor.

Cables could of course be arranged in different ways from the one above left, but the linear extension is not optimally achieved also.



Below a few more images that suggest how this cable, can be used as a PF extension wire, or to interconnect PF and old 9V elements (motors, battery boxes, etc...). Click on images to enlarge and see the details.


Direct conversion (some 9V elements, those with bottom or non-stud contacts only, require the use of an electric plate)


Simple PF extension (left), and conversion plus extension with PF cable (center) or 9V (right)


Multi span for longer extension lengths.
PF only (left); Combined with 9V cable for bigger flexibility due to large range of lengths available (center); Multispan with conversion and extension (right)


Chain of 3 different devices (PF and 9V)


Simple Star configurations (also with extension on the rigth)


Some larger combined configurations (some also with the IR Receiver included)
Note that with the extension/conversion wire and IR Receiver, it is possible to control old 9V motors direction with PF remote


Finally, this cable should also bring wired compatibility from PF motors with the NXT, when combined with 8528 (Converter Cables for MINDSTORMS® NXT) and the NXT-G programming Block for standard motors.
This kind of compatibility was already possible wireless, but via IR with OEM parts like HiTechnic 'NXT IRLink Sensor' and others (see video with application example, here).


One possible setup for a PF motor connection to NXT (left) and respective connections detail (right)


A few more variations, can be also seen from this Brickshelf folder.


Edit:
According to the information on this post at Eurobricks, it was recently found that the configuration on the red crossed photo above, is not allowed. Appart from the PF battery box and remote, the 9V black battery box was the only one without batteries when I took the photos (Murphy...).
Sadly it was found that the IR Receiver does not work when powered by the an old 9V battery box! It was a design flaw, that LEGO only recently discovered when playing around with the new system...
On the same topic there are a few workarounds possible to make it work. One can be seen from this image (bottom left), another is to connect the old battery box into one of IR Receiver outputs instead of using the cable attached to it. This only leaves you with one output left to control remotely, instead of two. Not really that handy, but if you only want to control one function it might be sufficient.
Well... a minor issue IMHO.


Last Update:
2008.Feb.06 19:35 GMT

Friday, January 25, 2008

LEGO® released Power Functions RC protocol, as open source

Today LEGO® released the Power Functions RC protocol, as open source. See below, the announcement in the transcription from the official communication.


Last year we introduced a range of products using our new electric building system: LEGO Power Functions. This new electric building system will open up a lot of possibilities now and in the future.

One of the new things we offer now is modular remote control. In the process of designing the Power Functions RC system we did a mapping of different RC functionalities. This mapping formed the basis of the Power Functions RC protocol and most of this is build into the Power Functions RC Receiver. The RC Handset launched now provides direct ‘bang-bang’ control, but the RC Receiver supports much more functionality like PWM speed control and single pin operation.

Now that the Power Functions elements are available at the LEGO Shop online we have decided to release the Power Functions RC protocol as open source.Please feel free to use any information from the protocol document for personal, non-commercial use only, provided you keep intact copyright, trademarks and other proprietary rights of the LEGO Company

Have fun.

Gaute Munch
Technology Product Manager
LEGO Company


So the specification should allow custom remotes to produce more sophisticated behaviors. This opens the door for technically skilled enough individuals to customize their remotes, build new ones or third party manufacturers to develop their own products based on the published protocol (like it happened for the MINDSTORMS NXT specification).
And those fancy commands that many of us would like to have and most likely LEGO would never produce, have now a good chance to see the daylight from OEMs.

This RC protocol was designed with further developments in mind, that are now possible. Despite the limited existing capabilities of actual Bulldozer remote, which uses the 'Combo direct Mode' (see technical documentation below) and timeout feature for lost IR (commands sent keep the motors running for a bit more than a second), protocol would allow other features like:

  • Remote control of several motors speed, in multiple modes.
    7 speeds forward plus backward, are possible via PWM motor control, which will be also great for the new PF trains coming in 2009.
  • Individual control (clear/set/toggle) of PF C1/C2 pins.
  • Handling of extra 4 channels possible for future use, with new RC receivers.
  • etc...

See the full technical specification document, here.

With some luck we could even get someone who develops an RF expansion, that reproduces the same protocol, and brings more flexibility/freedom to the PF devices.
The ability control step motors would be also a very interesting possibility to add into PF. However even if possible, that would require a much more 'intelligent' remote brick to control it, like an RCX or similar!?

Thursday, January 24, 2008

TBs TechTips 007 - Clutch designs

Following the info from the Geneva Mechanism previous post, found its true origin. Another blog also with some more interesting topics about LEGO TECHNIC.
It calls BrickEngineer (from Kevin Knuth) and I want to highlight today a design for an interesting smooth clutch.
A clutch is a mechanism which allows to engage or disengage an axle from a motor, when we want to control the transmission of a rotational motion.

LEGO has special parts that can be used to make a transmission clutch, like: 6542 and 6539. However, these are relatively hard to find, and take some force to engage or disengage.

Many clutch designs simply move gears back and forth across one another, but this causes the gears to grind and eventually wears down the parts. In these systems, the clutch does not engage smoothly.

Below a few animations that show a possible solution made of common parts and requiring little force for engage/disengage (see the author page linked above, for instructions and LDraw files).
On the right, the details from coupling mechanism (bottom view).




Below also a few images from other clutch mechanism implementation ideas, found at Brickshelf (click to enlarge and see more details).


Credits from left to right: [1], [2], [2], [3], [4]


Learn more about, how clutches work, here.


Tuesday, January 22, 2008

Power Functions elements, price hike at LEGO S@H (Europe)

After a few weeks online, the prices for PF elements suddenly arose significantly, at LEGO S@H across all Europe.
Those prices were in fact surprisingly reasonable when these products became available as individual parts, but now that's all gone...

Unfortunately, I didn't took note of the original prices to compare now (who would imagine this?), but there is always someone who does...

By reading also a post about this issue at Brickset, I found someone who did it and posted them in a comment:

  • 8881 - Battery Box from 4,99€ to 7,49€ (50% inc.)
  • 8882 - XL Motor from 6,99€ to 11,49€ (64% inc.)
  • 8883 - M Motor from 5,99€ to 8,49€ (42% inc.)
  • 8884 - IR Receiver from 10,99€ to 16,49€ (50% inc.)
  • 8885 - IR Remote from 6,99€ to 10,49€ (67% inc.)
  • 8886 - Extension Wire from 2,99€ to 3,49€ (17% inc.)*
However it seems there is still a trick to order them at original prices till the release of a new S@H catalog next end of March, but valid only for those countries where such catalog exists. See the details here at Brickset.


* For this one, I remember the price was 2,95€ for my country, because I've ordered some ;)

Week TechVideo, 2008 #04 - Bumper Cars

This week I bring a video, which is not exactly a TECHNIC model, but have a least a TECHNIC soul...
Play the video and take a look into the MOC internals, so you see what I mean.

It is from João Figueiredo, a builder from my LUG (PLUG), so I'm proud for this week TechVideo. ;)


Look how real, the movements seem to be.


See the photos here.

All this began, with a great discussion, months ago at PLUG Forum, about how did the cars from the videos below, could be moving alone.
These appeared at '2007 Great Train Expo in Novi, Michigan' (MichLUG events).

Monday, January 21, 2008

TBs TechTips 006 - The Geneva Mechanism

By reading the HispaLUG forum, I found a description and animation for a 'Geneva Mechanism' implementation with LEGO TECHNIC.
The Geneva drive or Maltese cross is a mechanism that translates a continuous rotation into an intermittent rotary motion. It is an intermittent gear where the drive wheel has a pin that reaches into a slot of the driven wheel and thereby advances it by one step. The drive wheel also has a raised circular blocking disc that locks the driven wheel in position between steps.


I guess the 'TECHNIC Cam' part on the center should turn all around, but author
must have simplified the CAD animation process by reducing number of frames to 1/4.



Below also a draft for a similar and compact design from a different author. At its right another Geneva Mechanism implementation from Philo.




Mechanisms like this, have their application inside machines like mechanic watches and celluloid movie projectors just to give a few examples. See below a schematic for the application inside a movie projector.
Among LEGO and AFOLs, a mechanism like this, maybe of great use for GBC for instance (something to talk about, into a later TBs post...).




Below some animations, that also help to better understand how the mechanism works (standard version on the left and 'Internal Geneva Drive' on the right).



Another example where the concept gets furthers extended, with higher number of steps per mechanism output revolution.




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