Thursday, December 9, 2010

TBs TechReview 11 - The mLA under magnifying glass

Today, TBs will examine and present the details about the new LEGO Technic mini Linear Actuator (mLA), which will debut into the new 8069 Backhoe, already in the 1H2011.

With this post we aim to show you, how it works and its internals.

1. One first look

The new mLA (element ID: 92693) is delivered as one single element, thus not needing or having different interchangeable coupling brackets available, unlike its larger predecessor. Despite the small size, it looks quite robust, well designed and produced with the highest quality standards.
From the images below you can see how the mLA compares with its big brother, the classic Linear Actuator (LA), and also a couple of possible gear combinations (5:3 and 1:1 ratios) allowed by the mLA bracket geometry. Notice this geometry is exactly the same as in the 61904 bracket for the larger LA, thus making their connectivity requirements quite identical.

Because the classic LA cylinder is larger and thicker, it fits nicely on a 3L wide bracket. However we can't say the same from the new mLA, which cylinder with 1L diameter is much thiner than its 3L wide bracket, making it look a bit "clumsy". But this is probably the only possible design, that allows for the use of existing Technic bevel gears.
Somehow it seems the mLAs will always exhibit a disproportional fit, in the models where they will be used. Time will tell if I'm making an incorrect judgment.

The mLA is 3L wide and 7L long when fully retracted. It has a 3L course, thus extending to a maximum length of 10L.
In order to full extend or retract, the mLA axle needs to complete 19 revolutions.

2. The inside view

In the video below you can see one of the simplest mLA setups being exercised, its inner parts as well as how to put them apart.
Please notice the disassemble steps look that easy, just because the mLA was already disassembled once before, otherwise it should have taken a lot more effort to break it apart. Also the "collar" that may be seen near the sleeve extreme in the photos and video below, is not an original characteristic from this part, but instead caused by the stress it was subject at the first time disassemble...

Unlike some of you may have expected initially, there are no metallic elements used in this element, as all the mLA subparts are made of plastics.
This should allow the cheapest production costs, thus making it possible that one single set from the mid cost range (8069, Backhoe), can include a good bunch of them.
All the subparts can be seen with more detail, from the few following images.

As seen from the above, like its bigger brother the mLA also features an internal clutch mechanism for both ends, thus making it usable with motorized functions. However this mLA part, is not suitable for other functions than those dealing with relative small loads.
But this is an issue to analyze with more detail ahead in this post.

The clutch function is achieved through the smart design of the tip from the inner rod, which runs into the sleeve inner screw, as seen also from the images above. The tip has two threaded turns on the surface, and a flexible design that allows for its contraction whenever one of the mLA course limits is reached, thereby making a thread pitch jump every turn, while it continues to run.
Lets say the clutch mechanism should be the most clever element developed for this mLA. I would not get surprised at all, if this genius clutch solution itself, was registered in the Patent Office by TLG.

Now, it's time to see it in action...

I took the opportunity to develop a bit my 3D modeling skills and here are the results. Hope you to like them.

3D Renders


3. The load tests

But... as stated before and as the video above also suggests, these mLAs were not designed to deal with the heaviest loads on earth. Not at all...

Using a very similar setup to the one once used to measure the classic LAs strength [1], we have now made some new measurements to compare all the LEGO LAs (including the newly redesigned classic LA, after its bad fate under the heaviest demands from the new 8043, Motorized Excavator). The load performance tests were made with both PF M and XL motors, for each LA tested.

mLA load performance with M and XL motors.

Linear Actuator load performance (version 1, production code ≤35X0) with M and XL motors.

Linear Actuator load performance (version 2, production code ≥36X0) with M and XL motors.

As you may see from these results, and as already expected, the load capacity from each LA does not change significantly whether it is driven with one M-motor or one XL-motor. Although the values observed tend to decrease on successive tests, but recover after some rest.
The tests also confirmed the mLA has a much lower performance than the larger and more robust classic LA. The mLA sustains up to about 900g, before yielding to the load, while the LA sustains up to 4.100g - 5.200g depending if it is used the first LA release or the recently updated release.
From the results observed the first release LA now tested, seems to be a bit stronger than those tested in the post above mentioned. Probably it may be explained by small variations among the characteristics from different LAs, their use condition (to which these first LAs were quite sensitive [2]) or even by the small modifications made to the new test setup.

Is the mLA what you were expecting?
The 8069 (Backhoe) should soon hit the market shelves, so that you could try the mLAs yourself.


Gerhard said...

Very interesting. But unfortunately you used some music in your last video, that is not mentioned to be used in Germany. So youtube blocks the video. :o(

Anonymous said...

Almost a kilogram! Thats a lot for the mini LA! Any idea how much does big pneumatic cylinder achieve? Are they comparable? Also the lubricated LA lifts a kilogram more than the old one? Thats really cool info, thank you!

TechnicBRICKs said...


Never understood how YT manages the copyrights and blocks some videos with music content.
I though to know this was an issue already addressed, adding adds to these videos and Google sharing the revenue with the Music Publisher.
Even when there is some copyright used material, the YT uploader receives an e-mail notification, stating the fact but that there is also action required from him.
However it seems there are still some videos being blocked at different countries...
Guess this might be happening with videos using older tracks (as it is the case), when the actual rules were not yet in place. :/


In fact I never tested the pneumatic cylinders this way.
It might be a possibility for the future, as I still have the setup mounted.
However I'd expect them to be quite strong, but a larger variation because they will be yielding on air leaks trough the cylinder seal and connections to to the pneumatic pipes.

Yes, the classic LA 2nd release seems a bit stronger than the 1st release.
However please notice that I've not performed statistical measurements with a significant sample. So this might be just an indication of performance.

Junkstyle Gio said...

Great review!
It looks like this new LA is going to be a great addition to the powerfunctions so far.

By the way: how did you get your hand on this new LA? Is this one of the benefits of being a Lego Ambassador?

TechnicBRICKs said...


no, it is not a LA benefit! Which BTW I'm not anymore. :)
Maybe sometime later again... ;)

I asked it, with the purpose of this review.
Since TBs has now a good reach among Technic fans, I was lucky enough to see my request granted. :)

Barman said...

indeed a great review.
Excellent that TLC gave you the mLA for testing and doing this review.
Thanks for sharing Conchas

Anonymous said...

When you took LA apart, you think there is a chance to use parts like screw and rod outside LA like putting orange axle through a beam and tread part on top, to improvise?

TechnicBRICKs said...


I'm not seeing exactly what you're trying. But if with tread you mean some gear racks... no way! Tolerances do not match.

But I guess you mean something different. ;)

Anonymous said...

I mean putting the orange screw and the LA rod and putting them somewhere else, NOT in the LA casing. Does the orange axle fit like inside a beam?

thirdwig said...

Great review. I don't think the mLA will be quite as useful as the LA or Pneumatics, but the aim is different. I think this will be a great addition, and the application I think we will soon begin to see. I see this working well for gear changers, steering, or various rack and pinion applications require rotational movement with low resistance. I think I might use them on some Truck Trial applications.

TechnicBRICKs said...


The orange rod has an axle in one end that fits into any Axle Hole (the circular disc doesn't go through a Pin Hole). On the other end (treaded tip) the rod has about 3mm diameter, so it fits into any Pin Hole but also any Axle Hole.

Anonymous said...

Does the dark grey rod fit through a Technic pin hole?

TechnicBRICKs said...


Very tight but if fits.
However it doesn't pass trough because of the small latches that prevents this part from getting of the mLA body at the front.

TechnicBRICKs said...

Please notice, that it is almost impossible to extract the DBG rod, without damaging the LBG mLA body.

I had to make a small cut, but have hidden it for the photos and videos.

Anonymous said...

One other way to 'connect' the 3L wide 'base' of the mLA is to use
a 3L universal joint and two thin
liftarms. This way there is no surrounding 'mount' required.
This would mean the full mLA +
support lego only is 3L wide...

TechnicBRICKs said...

Something like done in the 8069 B-model, with an axle with stop, would be also a very nice and compact solution. :)

Mortymore said...

Great review and great mLA renders.
I just want to point though, that I was not convinced that the max force sustained by the new LA's (v2) was 5.2Kg, since the meter blanked for a moment and recovered above the 5.2Kg, and that's because of the 5Kg max supported (advertised) by the digital weighing scale used, I believe.
So.. it could be more, which is good.

Congratulations for the review, for having convinced TLG to provide those mLA, and for sharing.

TechnicBRICKs said...


Yes you're right in your observation!
We are above the equipment specifications, so we can't be sure. But it is certainly above the 5Kg. At least for not continued measurements.

Also notice this is not a precision device, but a kitchen weighing scale.
However it looks adequate for the purpose, as the device under test itself, is prone to variations due to its mechanical nature.

Anonymous said...

Great work and article Conchas!
However, please do yourself and all a favor by respecting copyright if at all possible. Consider for example syncing with music with the proper Creative Commons license. You may want to check out or
Thanks and keep up the good work :)

TechnicBRICKs said...


Thanks for the compliment and for the advice.

AFAIK YouTube actually applies ads to the videos which contain copyrighted audio, in order to get fees which they can use to pay the copyright owners (music publishers), who want to be paid for the usage of their content in videos uploaded at YouTube.

Anonymous said...

Thanks for the DETAILED review, Conchas. Now TLG needs to produce a new, PF "Small" motor to mate onto the mLA!

Mark Bellis said...

At 900g the mLA should be strong enough to change rail points. The movement will not use the full travel, so it might wear the clutch mechanism with repeated use. The motor would be at right angles to the mLA, keeping it alongside the track but far enough away from it for vehicle clearances to be OK. My current mechanism uses a 2.5Ncm clutch gear with 3:1 gear-down and a rack, a force of about 3N (300g).

Anonymous said...

New parts are always welcome, but I always felt uneasy about LAs. They are too far from the real thing. I would prefer TLG to focus on the pneumatic system.

JAMS said...

a simply way of increasing the max force with these new mLA's is to fill the void in the tip of the orange clutch part with some type of flexible rubber cement, it would all the clutch to still engage, however at a much higher load

TechnicBRICKs said...


that seems to be a good idea.
At least to make such modification you won't need to extract the DBG sleeve, from the mLA main body, which is a destructive process.

However, while it may increase the max force supported by the mLA, it may also stall the motor when the mLA reaches on of its travel limits... :/

Obag said...

if I gear it down e.g. 3:1 the LAv2 could handle ~15 kg with an M-motor?

Jetro said...

@obag no. The article states "the LA sustains up to 4.100g - 5.200g depending if it is used the first LA release or the recently updated release."

Obag said...

so it will just effect the speed?

TechnicBRICKs said...


While in general there is an inverse relation between torque in speed, in this case it should not behave like that, because the limit is not in the external motor strength, but instead it is on the internal LA clutch mechanism.
So if you make a reduction I'd expect the the LA to move slower, but the internal clutch should trigger at approximately the same load.
Please tell us if you manage to get a different observation.

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