Yesterday a few PF new elements hit my workbench… ;)
Among them, two Linear Actuators (LAs) with respective brackets and one of the new PF lights.
So, I decided for a review to the Linear Actuators.
The first impressions were:
- LAs are proportionally thinner than I’ve imagined from the several images seen before, which is positive and more realistic for most of the existing machines you may want to build.
- As an introductory note, each LA has a simple and standard interface in its base, where you can find the access to a driving axle-hole (orange part) and a simple connecting interface. This connecting interface is built so and adapter part (bracket) could fit to adapt LA connection type or geometry and apply for different use cases. We may also speculate if there will be in the future, a small PF motor which adapts directly into the LA base/driving interface... :)
I got two different of these brackets for each LA, which was a surprise for me. Until then I imagined to actually exist just one (the one we have seen for months on all previous Excavator images).
But in fact there is a second and different one, which I imagine to be used at Telescopic Handler (8295) B-model, whose instructions are not yet available.
Because these new information became all available at almost the same time, I was able to check it appears at inventory listing from 8295 building instructions, but it is not used with the main model.
Hopefully (at least I wish it...) we will see some sort of Service Pack at S@H, with at least one LA and one bracket of each, in the future.
The rightmost adapter looks to have been designed, to adapt directly in front of the XL and M PF motors. Just great! :)
The Linear Actuator characteristics:
Despite being something easy to imagine for those with some technical knowledge, first thing I was willing to do, was opening one to look at the internals and show here at TBs how does it looks inside and how does it really works (kill your curiosity, and of course mine also)… :P
Don’t worry… I’ve four of them, at the moment and more on the way. :)
Below you have the resulting images.
Attention: Don’t try this yourself unless you are prepared to loose one LA!...
The disassembling process is destructive, mainly because some parts are strongly glued (if clicking at some of the images below to see them larger, you will see still some glue residues on the 'Dark Bluish Gray' base, which I wasn't able to remove completely).
Despite the appearance that disassembling the unit is a manageable issue, it happens no to be the case. At least not without significant damage!
LAs look solid and robust, with both plastic and metallic parts being strong, very nice looking and well finished, as usual for the LEGO parts.
Despite this, the assembly internal parts are able to shake to some extent, which denotes some internal space gaps existing. This naturally allows keeping the operating friction at minimum levels, but I believe it would have been possible to minimize this internal spacing even further and give the LA a more solid touch.
The LA consists of a metallic piston rod with a terminal screw, which runs inside a plastic cylindrical case. Together they act like a worm gear setup.
Like any worm gear arrangement, LAs behave:
- Reducing the rotational speed at the input, to increase the torque (linear force in this case) at the output.
- The direction of transmission (input shaft vs output shaft) is not reversible, due to the greater friction involved between the rod terminal screw (worm) and the plastic case where it turns (worm-wheel). This has the advantage to eliminate any possibility of the output driving the input at any load circumstances.
Both LA piston head and base fixing points are similar to one of the recent 1x2 thick liftarms, with pinhole and axle-hole. This design option for a mixed connection type, makes it more versatile and suitable for several applications/uses.
Also the brackets that fit into LA base use the same solution, which makes them very useful as well.
The plastic piston head (1x2 liftarm like) is strongly attached to the metallic rod, which I didn’t want to disassemble and break into more parts (despite the unit being already lost…). :(
The LA driving interface is an axle hole on its basis (the orange part) which also maximizes its applicability, in opposition to an eventual protruding axle, which was for me the most probable expected solution till certain point in time.
If not fixed, the piston rod tends to freely rotate as the driving axle gets turning. Mainly because the low internal friction, mentioned above.
From end-to-end the LA measures 11L when retracted and 16L when extended. This means the rod to extend about 5L or 40mm (LA linear extent).
On the diameter side, LA cylinder measures 15mm i.e. nearly 2L.
As commented in the beginning of this post, this makes the LA realistic and relative well proportioned. This was one of my fears when I saw the first images available, because it looked not realistically proportioned. Although IMHO, from the technical construction point of view, it could have been even thinner making it to look further with the real thing.
However we must realize that LEGO natural dimensions and intrinsic spacing required for pin or axle-holes impose some limitations here, which lead into the actual design.
The metallic rod diameter, measures ~5mm which just a bit above any TECHNIC whole diameter, if it is of any importance...
In order to achieve the full LA extent, the driving axle-hole needs to turn 26 full revolutions.
To be more precise it is in fact around 26,5 full revolutions. However it would be not significant trying to bet on precise number, as you can always force a bit at both ends which also makes some variation among readings.
Anyway this means, if using a direct motor drive and without considerable load, that a motor should be running approximately for:
To be continued…
Corrected above the statement where I wrote that LAs don't have internal clutching.
In fact they have! More to come on the review 2nd part.
The link for 2nd part of this review was added.
Last Update: 2008.Aug.03 11:39 GMT