Saturday, January 29, 2011

Studded vs Studless Design. The Question Is, Does It Matter?

It seems that it's expected of just about anyone even slightly related to Lego Technic to have a strong opinion on Studded vs Studless debate. So I'll add my spoonful of thoughts as well.

First of all, having used both Technic types, I can confirm the arguments and counterarguments of the opposing sides. Studded Technic is a "Classic" Lego, somewhat easier to build from the bottom up, and the beams are stronger. Studless parts offer more elegant and compact mechanical solutions (what Technic is all about), but are more difficult to build and somewhat more brittle than the studded beams.

But, the more I build, the more I tend not to think of the problem as the question "Studded or Studless?", but rather ― does it matter at all? A good design should always use the optimal parts and systems for the given problem, and sometimes it will be studded, sometimes not. Why should we strictly adhere to the one or the other side if the optimal design will probably often incorporate both (hybrid)?


I can understand the viewpoint of the builders that see the two sides as incompatible due to different engineering philosophy, but after all ― studded and studless, it's all perfectly legitimate Lego Technic, and should be used according to the purpose and function, not its ancestry.

Limiting the spectrum of available bricks can make sense in some special categories, such as the modelers contests where a certain style is required, but the essence of Technic is finding a best mechanical solution for the given task. It doesn't matter whether does it have studs as long as it's mechanically clever altogether, does it?

After all, that is the approach Lego Group employs as well (though not often, I admit). The 8053 Crane, reviewed here on Legoism, uses both types. Studless design in majority, but where it was practical to employ the good old studded beams, they did so.

Wednesday, January 26, 2011

We All Live in a Yellow Crane: Lego Technic 8053 Review

Though I'm rarely building the original Lego models according to the schematics, I'll be the first to admit that they are often a fantastic source of tricks and ideas. And the larger the set, usually the more tricks one can expect. Therefore, I've had lots of expectations from the 8053 Mobile Crane ― while not a flagship model, its size and almost 1300 parts nevertheless place it firmly in the upper Technic echelon.



Let's begin with a brief description and features. The massive chassis houses eight wheels, each with its rack & pinion steering. All of them are operated by one large longitudinal steering axle, rotatable manually from the rear. The inner four wheels steer less than the outer (as they should), what makes the crane both very easy to steer and really stable in a curve. In case you've considered using it for racing...

The chassis also offers four extendable "butterfly" stabilizer arms. They can be easily extended and retracted through a clever system of gears and ball-joints, and each has an adjustable "foot", just like the real cranes. Nice usage of friction connectors and worm gears! The chassis also carries a basic cabin. It's cute, but offers no special functionality. But hey, it's Technic ― it doesn't have to, does it?

To simplify the construction process, the superstructure is built independently from the chassis, only for the whole lot to be easily connected together in the last steps.

It rests on a Technic turntable and, thanks to a well-judged balance above, rotates quite easily. Here we will find three separate systems, all handled by their proprietary gearboxes ― rope winder with a set of rings and pulleys, linear actuator that raises and lowers the crane, and a crane extender (it can almost double in total length). Interestingly, all three functions are operated through the same axle; it's up to the user to activate the functions he wants to control, with levers that move the underlying dog-clutches (stuff usually seen in the gearboxes). Plenty of gears and various moving parts, but nevertheless everything runs smoothly. It's not the easiest model to build, but isn't overwhelmingly complex either, and provides lots of fun.



So that's it with the general information, let's focus now on some specific areas of interest, which I suppose the avid "Technicians" will find more relevant.

▪ IDEAS AND CONCEPTS
Although there are no groundbreaking new ideas or concepts in this model, it is still a fantastic demonstration of highly efficient Technic design: sturdy, compact, well-packed with features, cleverly using a wide array of parts and yet not overencumbered by extreme reinforcements where unnecessary. And as such, it is a great source to learn construction techniques from.
Worth noting are the long steering hub arms for the four inner wheels that reduce the amount of steering; using the rare worm-rack gear combination to extend the crane; two dog-clutch gearboxes that allow the crane to run two operations (lifting and pulling the rope) simultaneously using the same driver axle; a quadruple butterfly arm mechanism combining the rack gears, "plus" gears and ball joints; using the friction pin to fix the rope somewhat, to hold the lifted weight without unwinding; and a truly modular design that allows the superstructure and the chassis to be built completely independently and connected only in the very final stage of construction.

▪ PARTS SUPPLY
Great for anyone looking for standard universal Technic "raw materials" ― plenty of beams, pins, axles, gears and a nice assortment of some little extras. The design is almost completely studless, with the exception of several long 16-stud old technic beams that are required to form a flat rail for the crane extension to slide over. It also features a modern technic turntable (though not driven with gears in this model), and a linear actuator, which lifts the crane. Eight nice off-road-friendly wheels are welcome, too.



▪ EXPANSIONS
The crane can be combined with the Power functions set to electrify the main driver axle ― it's nicely shown in the instructions, and the model itself has the cradle ready for the purpose, where the power components can fit quickly and painlessly. It could be build also with different wheels, or featuring sa longer crane (and its extension).

▪ OPERATION
Thanks to the steering and stabilizer controls being mounted at the rear of the chassis and all the superstructure controls coupled near its middle, the crane is quite easy to handle. However, due to the high ratios in the gearing, it takes plenty of tedious spinning of the driver axle to get anything done. It may be a subtle motivator to buy the Power functions set, which does everything much faster.

▪ WEAK SPOTS
Besides the mentioned occasional muscle workout required to extend or retract the crane in full length, and butterfly stabilizers that are somewhat fragile, no complaints. Some components are tricky to disassemble, but I'd classify that rather as a consequence of a strong, sturdy design, than a disadvantage in itself.


▪▪ VERDICT ▪▪
8053 is a fantastic set, whether you like playing with the original model, learning tricks from it or collecting the raw material and occasional special parts for your other designs. Although we've seen a number of various Lego cranes throughout the years, this one easily manages to feel fresh. Two thumbs up!

Tuesday, January 25, 2011

Fun With Numbers: A Demon Gearbox

Not everything has to be strictly useful, right? I admit (and this is a sort of a Disclaimer) that this is something without even remotely imaginable practical purpose, but it may provide some fun with numbers. Namely, it's a "Super-Gearbox" that gears the initial axle's rotation down through sixteen stages.

The input axle (a small black rubber tyre at the far left hand side) passes through nine worm gears that drive 24-tooth gears in sequence, and proceeds through another seven stages of various gears, to end on the right hand side, on the linear rack (near the beige gear).


 So, what is the input-output ratio? To have the output axle (8-tooth gear on the rack) make one full turn, the input axle needs to be rotated 5349660268953600 times, or about five point something million billion revolutions. Of course, the gearing could be reduced even further.

Let's imagine this gearbox to be constructed with hypothetical infinitely strong and hard parts, and that the axle friction is negligible (yes, I told you there would be no practical usage). What would that mean?

Suppose we put an NXT motor on the input axle. It can provide about 16 Ncm of torque (thanks to Philo for this information) on its output. Through the gearbox, the torque would increase to 856 TNm (terranewton-meters), and the rack would exert a force of 171 EN (exanewton). In other words, it could lift (and still have some force to spare) all the water in Lake Superior. However, with the NXT motor's output speed of 117 rounds per minute, it would take about 2.8 million years to lift it one millimeter. Though, I suspect the batteries would get flat somewhat earlier.

On the other hand, if we rotate the output shaft with a speed of one revolution per second, a little rubber wheel on the input would have a tangential speed of almost a million times the speed of light (if there was no relativity to prevent that).

So what have we learned from that? Nothing. Nothing, except that in reality we don't have the theoretical infinitely hard Lego parts, but ABS plastic. Gear the motor up more than ten, fifteen times, and the combination of friction and low torque will make it difficult even to rev up, and forget the work done; gear it down more than ten, fifteen times, and if something gets stuck on the output terminal, prepare to hear a thin crack and say goodbye to some of your parts.

Monday, January 24, 2011

Inclination-Azimuth-Shoot: Automatic Panorama Photography Rig

One of the first projects I've done with the NXT set was a panorama photography robot ― as I needed it for some landscapes I wanted to photograph (clich├ęs, yes). The basic idea is quite simple: have a camera take a sequence of overlapping photographs (both in X and Y axes, that is, to form a grid), and then download everything to the computer and assemble it into a large panorama photo using a Microsoft ICE (What does ice have to do with it?). Here's a video, with narration:


Construction itself isn't too complex either ― a camera cradle with a motorized shutter pusher, a tilting mechanism underneath, resting on a powered turntable. Everything sits on a suspension. Since the functioning is rather self-explanatory, I won't bore you with that. Let's focus rather on a several points of interest that might be useful if you consider doing something similar. (Some are already mentioned in the video.)



▪ BALANCE
To minimize the strain on motors and parts while tilting and turning, it's a good idea to position the axes directly below the camera's (or, camera's and cradle's together) center of gravity. Try to keep it more or less in the center of the structure, to make it as stable as possible. Also, it's a good idea to use the NXT smart brick for additional stability by attaching it somewhere near the bottom.

▪ FORCES
Even with well-balanced setup, it will require considerable force to tilt and turn the superstructure, so try not to do that with the axle that carries the axis (like a tyre on a car, for example), but offset, with the arms, pushrods, rack gears, or something similar. Gearboxes won't help much because the axles themselves will twist horribly under the strain of the camera weight, and plenty of gears will increase the slack between the gears, that in turn reduces precision.

▪ CRADLE
After constructing the fifth consecutive unsuccessful "universal" SLR-type cradle, I gave up and set to build one adapted to my camera (Fujifilm S100fs). There are simply too many variations to cover enough camera models, especially with the motorized shutter, so build it for your camera and spare yourself some trouble. Don't forget building it so that the camera controls remain accessible as much as possible!



▪ SHUTTER
Building the motorized shutter is tricky. Many cameras will take a shot only if the button is pushed at certain angle. Force needs to be considered too, as too strong will deform or bend the cradle and throw the camera off target, and too weak will not be registered consistently. To avoid any breakages or similar troubles, I've resorted to springs: two of them, pushed about halfway, will produce just the required force. Of course, depending on your model, you will need to adjust the leverage, number of springs, angles, etc.

▪ TURNTABLE
Although vice versa should work too, I decided to build the tilting mechanism on the turntable. Turntables can comfortably carry more weight, and they at least don't have to lift anything.

▪ SUSPENSION
I'll be the first to admit that this component is probably unnecessary in 95% of cases and can easily be ignored. However, I've experienced that the rapid starts and stops of NXT motors, due to the amount of mass and torque on the structures, tend to displace the whole rig slightly if resting on a very slippery surface (such as the glass table). The offsets are initially negligible, but over a span of dozens of photos, they accumulate enough to throw the photos noticeably off target. Therefore, everything floats on a structure of eight springs. Not too elegant, but efficient. I guess it could be built as a detachable component as well.

▪ PROGRAMMING
In its essence, the software is primitive: turn horizontally, shoot, and repeat until finished with the row. Then tilt a bit and repeat everything until finished with all the rows. However, depending on the camera zoom, the angular width and height will vary considerably. You can simplify things by making a program specifically for a certain zoom and target size, or in a more advanced setting, enter the viewport and target size into the NXT and calculate the necessary X/Y increments accordingly. An even more advanced version could measure the zoom by some kind of a sensor (perhaps measuring the lens' length) and calculate the rest itself, but I didn't get that far, because I was kidnapped by the 8053 Mobile Crane.

All in all ― does the rig do the job? Yes, partially. It doesn't make the process any faster (anyone could manually do the same in half the time), but it spares you from the effort moving and memorizing what areas of the grid you've photographed and what are your horizon reference points. (Blah, blah...)

T Zero: Let the Experiments Begin!

Greetings and welcome to a playground bulletin board of one Lego fan(atic). I will occasionally post some works, ideas and any other kinds of Lego-related stuff here. If you find it interesting, great, and if you find it useful for your own projects, even better. I’m continuously amazed by the sheer amount of work done by the Lego community on the Internet, and I have to join the crowd. :)

Nowadays I’m mostly into Technic and Mindstorms, and that will probably reflect on the posts, but I love System just as much; in fact, I’ve been addicted to Classic Town/City Legos a long time before getting into Technic.

That’s it for the introduction, let’s get some bricks in the spotlight...