Tuesday, March 8, 2011

TBs TechPoll 24 - Should the Flex System return?

In 1991, LEGO Technic introduced the Flex System [1]. With two generations it was used in several Technic sets, between 1991 and 2003.

The Flex System was a brilliant LEGO Technic realization, based on real concepts, but which was rarely used to its fullest potential. It was only ever included in 17 LEGO Technic sets, probably due to the fragility of its cables if not handled with care.

Probably the most important sets using this system were the:

  • 8856, Whirlwind Rescue which was on the sets introducing the Flex System in 1991.
  • 8479, Barcode Multi-set from 1997 - IMHO the pinnacle of the LEGO Technic studded sets.

This system was used in a few main applications:
  • A flexible push-pull cable system (Bowden cable) in a standard link configuration, to transmit force around curves, corners or even straight links.
    One pair of these combined with some other specific parts, allowed to build a cyclic motion for the main rotor in the large helicopter (8856).
  • A diagonal brace system for trusses and booms, like in 8074 and 8856.

The Flex System main components:
  • The central cables - A flexible plastic cable with a small neck on either end used for clamping. The cable was produced in a variety of lengths over the years, from 4L all the way to 33L.
  • The sleeves - A flexible and hollow cylindrical tube which is not brittle like the inner cable. It serves as a sheath for the cable, guiding it through the structure and preventing buckling under compression loading. The same type of tubbing became later also used as an extension and connector for pneumatic tubing.
  • The connectors which were available in a few configurations and had one slot with a tab to grab the necked portion of the cable in each end. The cable snaps into place when inserted from the side.
    The configurations available included a pin connection (part 2900) and one ball joint connection (part 2901). Both were later replaced with different versions which were easier to install and less prone to damage the cables (respectively parts 6643 and 6644).
    The 2nd generation connectors included also a double-end with central pin connection (part 6642).

Below, two great examples on how the Flex System was used in the sets above mentioned and what it allowed to achieve, without complex and space consuming designs with shafts and gears.

The image on the right was taken from Blakbird's Technicopedia. Parts of the text on this post were also partially inspired on the same source.

On the left one illustration from 8479 building instructions, showing how the two Bowden cables control the front claw movement and another two Flex cables to enforce arm stiffness on each side.
The CAD representation on the right, shows the control of the Cyclic mechanism from a stick in front of the pilot's seat.  There is one flex cable and sleeve for each axis. Fore and aft motion of the stick pushes and pulls the cable using a ball joint. The flex cable runs up to a link which lifts the swashplate using a suspension control arm. Lateral motion of the stick rotates an axle which runs aft.  At the end of the axle is a ball joint which connects to another flex cable.  This flex cable attaches to a ball joint on the side of the swashplate.

The cables are made of a different type of plastic than regular LEGO parts. While flexible up to a point, can easily end up with brittle fracture if bent too far. This is especially a problem when removing the ends. Later, different connectors were introduced which made it easier to attach and remove them.

The old connector style with cable "snap-and-slide" system on the left, and the newer "crimp" system in a double-end connector on the right.

Given a bit of an explanation about the old Flex System, let us ask your opinion.

Would you like to see the Flex System returning into future and even more realistic Technic sets?

Choose one option from the poll on the right colunm, running for the next two weeks.
If you have specific concerns regarding the Flex System parts fragility, you may express them leaving your comments to this post.


Anonymous said...

Flex cables would be extremely useful for driving linear actuators in situations where a straight axle is not practical.

Given the advances in the plastics and/or carbon fiber manufacturing technology, Lego should be able to manufacture flex cables from a more resilient material.

Jetro said...

I'm afraid that wouldn't work. Flex axles are great for structural reinforcements and for push/pull configurations, but no use for rotational movements.

There are flex axles though. Both if the soft decorative type and the tough 'heavy-duty' type that was used in the Znap sets 3571 and 3552,

Michael R said...

I've never used the flex system, but I think it would be really cool if they could find a better plastic (or metal wire) to make the cables from.

Anonymous said...

I've used them in several MOCs years ago, they were very useful in putting a small motion in a tight place. They are however fragile and therefore not meant for an eight year old. One of the difficulties was they were never quite the right length, so if LEGO were to bring them back they'd have to be in lots more lengths :)

Anonymous said...

think how much better 8043 wold have been with flex cables instead of axles driving a heavy linear actualtor. With 10 years of plastics devlopment they should beable to make them stronger or longer lasting Hot Wheel tracks use to use a flex cable system to switch lanes on race tracks and I remember those were pretty abuse proof.

Anonymous said...

There's been a few concepts running through my mind that are yet to manifest, but involve a variety of mechanisms including the Flex system. Considering all the tools we have so far - linear actuators, pneumatics, power functions, etc. - and with each excelling in its own unique way, the Flex system would be another welcome system to add to the arsenal. Like a few have already commented, it would be crucial for the cables to be improved to make it more viable. Would love to see it again nonetheless!

Paul Boratko said...

The Flex system is/was great... But only used within reason...

Just like most Parts/functions, people will use them past their limitations and then complain that they are no good.

I personally think that the flex system could really be used better with the current studless style than it was when it was first introduced...

HOWEVER... The actual foldover piece would need to be redone into 2 pieces in order to avoid breakage over a short time...

Junkstyle Gio said...

I wasn't a fan way back when, and I don't think I am going to be a fan when/if they are going to be reintroduced
The flex-cables and tubes where "one use only": once bent in a certain way the stayed that way an were almost unusable for an next job.

So a big no-no for me!

Anonymous said...

Actually, in 2004, LEGO used something similar to the Flex system in a couple of BIONICLE sets. Nidhiki used the system on his legs and claws. Turaga Dume & Nivawk featured pop-out wings and an opening passenger hatch made with the system.

In 2005, Sidorak had a pop-out blade, which used the same system.

The system returned in 2007 on Lesovikk (in his Sea Sled's landing gear) and Karzahni (in the "trap").

The system used stiff rubber (?) TECHNIC flexible axles (as seen in Super Street Sensation, for instance). So in a way, the Flex system *has* returned. I'd like to see it in some TECHNIC sets though.

-Toa Of Justice

Al said...

The flex system was/is great for a variety of applications. Whilst I still believe the priority should be to build on the pneumatic range of elements, flex system would still be great especially if they used them in a big helicopter with cyclic and collective control.

They obviously have many other uses like bracing and getting limited but fairly accurate movement to hard to reach places. However they do seem to be mistreated alot of the time and then people complain about them, even when used poorly in a proper set by a TLG designer cough power cough puller!

blakbird said...

I loved the flex system when properly used including the examples mentioned and the 8485 dinosaur. There were some examples of it being used poorly such as the Power Puller or being used in places it was totally unnecessary (functions which could have used a rigid link).

It was never used in a realistic application though. Although the Code Pilot and the Whirlwind heli were cool, real garabage trucks and helicopters do not use push-pull cables. Some real applications would be bicycles, automotive throttle cables, or aircraft control cables. I always wished they had been used for one of those things.

Anonymous said...

I've never been a big fan of these flex.
Yes, the flexs on the arm are VERY interesting since they enables to make 1 stone 2 shots (closing the clamp and rising the arm).
But generally, they make things too easy and thus not very interesting (the arm 8479 is the exception, but not the one used in the chassis). For example, helicopters would be much more interesting if built like some MOCers do with "regular" parts.
On 8457, steering mechanism with flex system is also VERY bad.

So, to the question "Should the Flex System return?", I would answer "No".

"8479 - the pinnacle of the LEGO Technic studded sets"
Did you forget 8480 ? :D


Wiseman_2 said...

@ toa-of-justice:
Those parts are not Flex-System, they are just normal Technic parts.

I never had any sets with Flex System, and personally am not bothered about it whatsoever. It might have some uses but to me those are pretty limited or can be achieved with other parts.

TechnicBRICKs said...


Well, they are different... but lets say these were two extremely good sets.
Among other very good studded sets as well. Like 8485, 8880, 8868, just to list in reverse chronological order.

However my personal preference still goes for the Code Pilot. :)
The 8480 is more prone to failures.

Anonymous said...


When I built it for the first time, I was 10, and it didn't work very well. :-S

When I rebuilt it few days later, it was ok (I may have pay more attention to the building process :) ). But it was still very fragile.


TechnicBRICKs said...

And after a few years built, it tends again to not work very well. :)

Al said...

@ Blakbird

Actually I think many helicopters do use cables, although not push-pull, but paired so one would pull one side of a pivot, the other pull the other side of a pivot. Standard lego string could be used to achive the same thing, but I guess the flex systen is a pretty close recreation. Is that what you meant by aircraft control cables?

A big flagship cable/string controlled helicopter would be ace!

Mashua7 said...

I have used this system heavily in steering applications, or anywhere else that I needed a ball joint socket in a different orientation or length than 6L or 9L.

Menno Gorter said...

@Mashua7: Exactly!
Same here, about the different orientation and length ;-)

Also it's lightweight; that's an advantage in walkers.
It's even possible to get other lengths when combining the old and new connectors.
Hence the name "Flex System" is very well chosen, since the connectors can turn 360 degrees and the cables can go through almost any part and construction.

Anonymous said...

Don't forget the 8485 Dinosaur! That was a masterpiece.

Sylca said...

There is also the 7471, mars rover explorer, which uses this flex cable for direction.

Dryw Filtiarn said...

If it wasn't for the flex-system, my Factory would never have been able to build bricks ;-)

Related Posts Plugin for WordPress, Blogger...

© 2007-2014 TechnicBRICKs
TechnicBRICKs contents may be sporadically updated, if the authors finds further relevant info about a certain post, or content/spell mistakes. Hence please don't be surprised if you find few changes at later visits, relative to a previous read.

TechnicBRICKs often shows other peoples' creations and/or images. We always try to credit the author(s) and link to their main publishing website, and if possible with their name in real life.
Since this is not always possible, we request that if you find something here that is yours or from someone you know, you leave a comment on the respective post and claim the authorship.

TechnicBRICKs is optimized for Firefox 16.0 and 1600x1200 resolution displays or wider.

LEGO® is a trademark of The LEGO Group of companies which does not sponsor, authorize or endorse this blog.
LEGO, the LEGO logo, the Brick and Knob configurations, the Minifigure and MINDSTORMS, are registered trademarks of The LEGO Group.
Original LEGO images are copyrighted by The LEGO Group and are used here in accordance with their fair play policy.
You can visit the official LEGO® website at www.LEGO.com.