Housekeeping: A new Links section

A website without external links is just like a sportscar with an automatic gearbox: it can work, but one just feels something is missing. So as of today, on Legoism you can find the new section with links to the Lego sites I like and recommend. Don't get too excited, though; the fact that you are here, reading this, means you probably know the most of them well.

Lego Technic 8070 Super Car Review: A serious road beast

Supercars have always had a distinguished position in the Technic world, often pushing the boundaries of what was achievable, introducing new parts and techniques, and being among the largest available models. It all began in 1977 with the set 853 which was built without friction pins and dedicated steering parts, continued through a couple of studded models culminating in 8880 and continuing in the studless era with ever more advanced models. The newest, recently launched member of the family is the 8070 Supercar, reviewed here.

Expectations from this type of a set are undoubtedly high, as the supercars are one of the toughest models to design. They need to cramp as many functions as possible within a limited volume, be sturdy, and yet be modelled to look nice, though not as much to hide the underlying mechanics. And above all that, they need to introduce new ideas and concepts, rather than just recycle some previously seen chassis.

This machine did not fail to do so. Already first half an hour into building, it is obvious that 8070 means business. The gearbox in the middle of the chassis and its surrounding area must be one of the most tightly packed systems one can hope to see. The gearbox isn't actually here to provide various ratios for the drive, but to choose between four motorized functions around the car: operating the left and right gullwing doors independently, opening the bonnet, and extending the rear wing. The PF motor serves only these purposes, not the drive or steering which are still manual.

There is a V8 engine under the bonnet powered by the rear wheels, and the car is steered by the knob behind the cabin (a well-known Hand-of-God method). All wheels have fully independent double wishbone suspension. The rear wheels' parts actually theoretically allows them to steer too, but they are fixed in place ― however it may be useful for your MOC's. The rear hood opens manually, and is cleverly designed to allow the wing underneath it to slide freely.

Looks are a matter of personal taste, but I find them fantastic. It is so nicely modelled and features many subtle angles and triangular structures in the bodywork, that I could easily believe it is an accurate model of a real-life sportscar. As usual, the chassis is built very strongly, while the bodywork panels usually connect to an axle or a friction pin, for the possible collisions not to incur too much damage.

With all these functions, there is hardly any remaining free space in the car. As a result, it is not the easiest to build either, with lots of delicate parts and components, mechanisms that need fine adjustments and many moving parts. By no means should it worry an experienced Technic builder (it took me about 4:30 from the unboxing to the finish), but you ― moms who are idolizing your 6-year-olds, please don't just rush buying the 8070 to your children as it doesn't ask just for dexterity, but plenty of patience too. Even more, dare I say.

But it is a great experience and a mechanical lesson, though at first you may be a bit confused about the seemingly unlogical steps you have to make, but after a while, it just comes all together into a great machine. The unusual steps in the beginning are just a normal consequence of the inside-out studless construction.

Therefore, a great set, whether you just like cars, want to play with an interesting one, need useful parts, or want to learn from it.

▪ BUILDING, IDEAS AND CONCEPTS

Fantastic construction ― nice, efficient and strong, though not the easiest to build. So tightly packed with functions, it is almost impossible to put a sugarcube anywhere in the model. Interesting concepts too with the motorized panels around the car controlled by the centralized gearbox. Although there is not anything we haven't seen yet, the feat of putting all that within the given volume (quite small in sportscars) is in itself a very good learning material.

It is not overly difficult for disassembly either, avoiding difficult parts (half-width 2L Technic beams) as much as possible.

▪ PARTS SUPPLY

You will find some very useful parts for any car, such as the suspension wishbones, hubs, engine, racing tyres, etc., and the set contains also a PF battery pack and a medium-size motor. The rest is a standard Technic building material with plenty of beams, pins, axles and a couple of panels. And with a bit over 1200 parts, it is a good amount, too.

▪ EXPANSIONS

Since the machinery is so deeply integrated, there's not much freedom to modify the car without having to rebuild some components entirely. A most basic addition would be to introduce PF lights in the headlights (this is so obvious that I'm somewhat confused TLG did not do it already). But there's little else to add.

▪ GENERAL PROS & CONS

+ Clever construction, great to learn strong and efficient Technic design
+ Lots of functions
+ Considerable supply of parts
+ Really nice to play with
+ Superb looks, very realistic

- Not trivial to build, needs some patience
- Steering wheel in the cabin does not work

▪▪ VERDICT ▪▪

With its complexity, advanced ideas and intelligent construction, the new addition to the Technic Supercars line up is certainly up to standard. It is not among the cheaper models, but one really does get a lot in return. Highly recommended, especially if you're into building MOC cars ― in that case you will find some very useful specialized parts here.

Small NXT CNC machine: A bit too ambitious, really

Since the NXT 2.0 set contains three motors, it should be possible to build a Lego CNC machine with a little help from some external parts. Its construction would be quite straightforward and use most concepts we are already well familiar with. Based on those assumptions, I've tried to build one ― or more precisely, its early prototype.

I'm sure it could be built very nicely on a large scale, but the intention was to make it smaller ― that is, small and brick-economical enough to fit entirely on a 48x48 baseplate, yet provide at least 10x10 studs (8x8 cm) of grinding area.

So here it is! Its components are quite self-explanatory. On one end of the platform we've got two motors; each moves a pair of beams along a rail via rack&pinion system, that move the cradle. The X-rail is stationary, while the Y-rail is mounted on the X-beams. Thus, the cradle easily moves in both axes. It is nothing more than a simple little "pool" where I have fitted a thick piece of bakelite, and which slides freely over the surface thanks to the tiles on its bottom.

A bridge is built above the cradle area, heavily reinforced with four rows of interconnected studded beams. It carries a large moveable cradle built specifically for this standard-issue electric drill. The cradle is attached to four strong arms, and there is significant counterweight on the other side, with four large old Technic wheels attached to long arms. The counterweight compensates for the drill weight (approx. 2.2 kg), so the bridge needs to withstand only vertical force, and not the sideways too, which would complicate construction.

The drill is raised and lowered by just a few millimeters at full extents, but it is more than enough for a sheet of bakelite. Its height is actually controlled by raising and lowering the counterweight arms with one linear actuator, connected to an NXT motor. Since the drill and the counterweight are in a fine balance, the actuator doesn't need to produce much force, but I've opted to use it for its precision. (To increase precision of X-Y movements, the motors are also directly connected to the driving pinions ― no gears that would introduce backlash.)

A simple clutch holds the electric drill at a desired power, and a very fine yet hard grinding drill bit with a 0.8 mm head diameter is mounted in it. The NXT module that controls all three motors is resting on the side, connected to a laptop that sends the machining data.

Obviously, this is a quite limited CNC contraption, as the drill can access the surface only from above, so it acts more like a carving machine. The input is really straightforward: a simple script analyses a greyscale bitmap (which is a depth map), calculates the area that needs to be grinded out for each layer, and then "carves" them out, layer by layer. The X-Y resolution is 80x80 pixels, so the pixel amounts to 1 mm ― less would anyway make little sense with the grinding bit of this size, and while the depth could theoretically reach 256 layers, that would be insane ― 10 is more than enough. Or to be very precise, we're not dealing with pixels here, but voxels. Anyway, such configuration amounted to approximately 5500 instructions (motor movements) for an averagely complicated desired result: a tiny physical model of Iceland with scaled altitudes I chose as a first test.

So I've built the prototype (yes, please excuse the horrible colours, but facing running out of beams I've had little choice), programmed the script and happily pushed 'Start'. And quickly learned that the above idealism works only in theory, while in practice, this CNC design has serious flaws, serious enough to classify it as a failure.

Namely, I have terribly, horribly, enormously underestimated the forces that act on the cradle during grinding. Not only does the whole X-Y beam structure bend significantly under lateral forces during the drilling, but the drill itself has the tendency to "dance" around as well, and miss its targets by 2-3 millimeters at least. Of course, the bakelite looks massacred rather than accurately carved.

Theoretically, this problem could be overcome by forcing the drill to always act vertically, and drilling each target pixel separately. Again, this is just a theory: not only would drilling a millimeter from the already drilled area push the drill there to the path of least resistance, but the operation would have to be done for each pixel that needs to be grinded. And that would also last forever, and breach one of the primary rules of engineering ― that the machine should not be as inefficient to actually get the job done slower than an averagely inexperienced person would manually. Finally, even if I was like the Master from the Exile of the Eons (Arthur C. Clarke, 1950) and waited several dozen billion years in suspended animation until it is done, this approach would make very rough, spiky surface on the material.

I guess these problems could be solved by using much more stable X-Y beams, both probably having large pinions on both ends and tighter rails, and attaching a different drill. Perhaps a faster, specialized one would do the job better, but I've intentionally tried to use one of type almost everybody has somewhere at home. These improvements will be the objectives for the second prototype, significantly larger and architecturally different.

P.S. I've tried carving other materials since, such as the brittle spongy plasticky material I've found and can be seen on the photos (a white block), but that didn't seem to solve the mentioned problems.

Mechanical strength of Technic parts - A few measurements

One of the common points in the never-ending "Studded vs studless Technic" debates is the difference in mechanical strain that the two sorts of beams can withstand. There is no doubt that the studless beams offer less structural strength than studded ― but they are also lighter, somewhat countering that disadvantage. But how much exactly, is the question that we'll try to answer here, with a few simple measurements. And while at it, this is a good opportunity to expand the measurements to connectors as well and analyse their effect on beam strength.

(A description of the measurements and results follows now; however, if you are just interested in results and implications, skip down to the "Conclusion" section.)

Let us first consider the forces that are relevant in the Lego Technic world. For most practical matters, we can assume that the beams are always strong enough when under compression or tension ("pushed and pulled"). It is usually bending that causes troubles, and that is what we will measure. Arguably, torsion (twisting) can play a role too, but let's keep that for the future posts. ☻

There are many methods to measure resistence to bending, and one of the simplest is to construct a simple bridge with a desired beam, push it down in the center with a known force, and measure the resulting descent.

15L studless, and 16L studded beams - the mainstays of Technic constructions.

In this case, two beams that are roughly equivalent were used for comparison - 16L studded, and 15L studless. The force applied on their center was 25 N (approx. the gravitational force of an object weighing 2.5 kg or 5.5 lbs), but as the aim of the experiment is to measure relative strength rather than absolute units, its amount is not that important as long as it is equal in all measurements.

Since the beams aren't symmetric in this case due to their axle holes, there is an important difference between resistances to bending from the side (along the same axis as the axle holes), and in the vertical axis. As many Technic builders already know, beams are significantly stronger vertically.

Horizontal (top) and vertical (bottom) force application. Due to the construction of Technic beams, they will not yield same results.

So, let's get down to measurements ― firstly with bending in the vertical plane (i.e. the force applied to the top of the brick). The studded 16L beam's center descended 0.8 mm, while the 15L studless did 1.5 mm. Studded is almost twice as strong! Applied to the side of the beams, the beams are, as expected, slightly weaker: the studded 16L's center descended 1.5 mm, while the amount for studless 15L was 2.5 mm. This time, the studless did not lose that heavily, which can be explained by the studded beams being taller but not wider than studless, however studless is still 67% weaker.

Let's add their weights into the account. A studded beam weighs 4.1 g, and a studless 3.1 g. Therefore, the latter is only 24% lighter than the former, much less than the difference in strength. Therefore, we can conclude that the studless beams, besides less strength, have a lower strength-to-weight ratio, too. Of course, our constructions do not consist of beams only, but they have an importantly high weight portion.

That's about the beams alone; however, beam connectors need to be taken in account as well, as the larger constructions depend on them too. So another batch of measurements was done, using two beams of various lengths, connected to form a total 16L size with different connectors, for easier comparison to the earlier results. Only the vertical measurements make sense here, as the horizontal disconnect the beams easily ― this problem has to be overcome with the construction itself in the model.

The first one consists of two 10L studded beams (having a 4L joint section), connected with two friction pins. Its descent amounts to 4 mm, suggesting that strength drops rapidly with small joints ― in this case, five times!

Increasing the connection width dramatically increases overall strength.

However, increasing the joint section helps significantly; two 12L studded beams with a section of 8L and four friction pins descended only 0.7 mm, providing even more strength than the full 16L beam! Reducing the number of pins of the latter configuration did a noticeable difference ― removing the inner two pins increased descent to 1.5 mm: half the strength, and in total, just like the 15L studless beam.

It helps strength to keep the inner pins within the connected sections.

Replacing the two remaining friction pins with the frictionless pins or a pair of 4L axles with bushings at the ends added further 0.2 mm to the descent: not a drama, but if you can choose, prefer friction pins to other methods whenever possible.

Frictionless pins and axles are slightly weaker connectors than friction pins.

Taking all into account, a few general facts can now be drawn.

▪▪ CONCLUSIONS ▪▪

▪ Studded beams are almost double as strong vertically and about two thirds stronger horizontally than the studless beams, despite being only a third heavier.

▪ Beam connections affect the total strength more widely than the differences between studded and studless.

▪ Widely and strongly joined beams (e.g. 8L, with 4 friction pins) do not reduce strength, but could even increase it.

▪ When connecting the beams widely, increasing the density of pins (as opposed to just the pins in the outermost holes) increases the strength, too.

▪ Narrow beam connections (e.g. 4L, with two friction pins) reduce overall strength several times, making the question whether it's the matter of studded or studless beams less important.

▪ Friction pins are better connectors than frictionless and axles, but the choice of pins is less important for general strength than the width of the beam connections and the type of beams themselves.

Hope you will find this useful!

Beginners' guide: Even and odd-width vehicles

One of the common problems planning and designing a Technic vehicle, or any Lego vehicle for that matter, is determining its exact width. While the rough width is determined by the scale of the vehicle (as described in an earlier article), choosing between even and odd width is a more subtle question.

A difference of one stud on such a scale may seem irrelevant at first, and from the observers viewpoint, it probably is. However, the construction varies significantly depending on the approach used.

One part of the answer lies in the available Lego parts. Namely, if you have experience with both types, you have probably already noticed that the studded Technic "prefers" being built in even widths, whereas the new studless designs tend to have odd widths. This is caused by the differences in these parts' dimensions: studded beams are generally of even, and studless of odd widths. Positioning any beam in the center perpendicularly to the axis of motion (and a vehicle will usually have dozens of those), will thus set the practical width, except if you are prepared for some impractical half-stud manuevers.

8070: New paradigm, new approach: studless designs prefer odd widths

Therefore, the preferred with will usually depend on the type of parts you are using. You can notice the general rule and the transition to odd-width vehicles on original TLC models too at the time they moved to studless. And it is actually noticeable today, as the studded vehicles (present, etc. in Creator series) are still even amount of studs wide, even if they have a Technic chassis. Many decorative parts are offered in even widths too, so it is a direction to take if you intend to build for looks as much as for functionality.

The remaining question addresses the hybrid constructions, i.e. combinations of studded and studless designs. Both odd and even approaches work here, and the case usually depends on the types of bricks you intend to use for the skeleton of the chassis. Try to build the skeleton using one brick type only, as the half-stud connections between even and odd-width components aren't as strong.

8880 Supercar: A good representative of a classic, studded even-width design

General experience of many builders is that, in very large hybrid designs with plenty of motors and components, studded chassis tends to have a slight advantage over studless due to its strength. However, for anything shorter than half a meter or so, studless should be just as fine.

If it is applicable to your design, it is worth to try buidling the studded chassis and a studless bodywork above, both sturdy and reinforced alone, and have them attached to each other on just a few strong points in one of the final phases of building. That way you will not have too many half-width connections, the vehicle will be easy to open and modify if needed, and will have all the advantages of studless look from the outside. (It is, agreeably, a matter of taste but it seems that the majority actually find the studless designs prettier.)

Shock absorber with adjustable damping

Though the full suspension could be considered standard on large Lego Technic cars, they rarely feature shock absorbers. Let's just remind those not familiar with car mechanics that the role of shock absorbers on real cars is to dampen the rapid movements of each wheel, caused by bumpy road surface. They also prevent the chassis from bouncing excessively after a bump, which reduces stability and handling.

Most Lego cars need no shock absorption, but they may actually prove useful in heavy vehicles on very difficult terrains, or could be added for realism. Here is one concept of a shock absorber mounted on springs, and based on a standard pneumatic piston.

Its principle is quite simple: when the springs move, they force the piston to move along. Since the air being compressed out or sucked in the cylinder offers some resistance and friction which is independent of the piston position, it serves nicely as a shock absorber.

Just attaching a disconnected pneumatic cylinder to the springs will absorb shocks, but the concept can actually be extended. By reducing the cross section of the passage air travels through, resistance the air offers changes as well, making the cylinder more difficult to move ― effectively stiffening the suspension. This is mechanically easily accomplished by attaching a hose to a cylinder (of course, not connected to anything else on the other side), and using some kind of a clutch to squeeze it. Here's an example utilising the linear actuator which requires very little input torque and allows very smooth adjustment, and there are tons of other options. This one can be easily expanded to compress four or more hoses at once, for all wheels at once.

This is more of a gimmick than a really useful option, as it is rarely seen even on real cars. However, some high-end cars actually do feature adjustable shock absorption, to balance between ride comfort and sport performance.

If the linear actuators or other continuous regulators are too much for your taste but you'd prefer to at least have a choice between hard and soft suspension, connect the other side of the hose to a valve switch, and choose simply between the air running freely through, or not at all. In the latter case, it will still offer a little bit of absorption due to flexibility of the hose and air compressibility.

Since the pneumatic cylinders have high structural strength, this system can be comfortably mounted into very demanding and heavy vehicles. Or in other words, it will be other bricks invoved in the wheel suspension that will break sooner than the cylinder!

Pratical power transfer: Linear actuator-driven pneumatics

Here is one solution I came up with while looking for a practical way to transfer significant forces over large distances or into moving components, without the headaches related to gearing mechanisms, axle extenders, etc. It is a linear actuator that drives the piston of a standard pneumatic cylinder directly, and the piston is cross-connected to another one, which reflects its motion and does the required job. (It can also inverse the motion by connecting them directly, rather than "crosswise".)

Of course, this is just a concept and design could be vastly improved on, especially regarding reinforcements that may be needed when the forces become really large. Theoretically, it could work with only one of these two hoses as well if the power is needed only in one direction, but is much more reliable and easier to control when their both ports are in use.

Unfortunately, due to the friction within the cylinders, the target piston is not nearly as precise as the input set by the linear actuator. However, its primary task is to transfer serious force, rather than do it extremely precisely. Due to an enormous gearing ratio of the linear actuator, its input torque is easily handled by almost any Lego motor. Just keep in mind that the total stroke length of the linear actuator exceeds that of a pneumatic cylinder, therefore (at least in this configuration) it can't be retracted completely.

Of course, the concept of cross-connected pneumatic cylinders that follow each other's motion can be practically applied in various other ways, however they must be driven "externally" ― that is, introducing a pump with a T-connector would not work as there is no output for the compressed air to escape from the system!