...virtually any LEGO set with moving parts, is wearing into dust over time (a very long time hopefully). But this one maybe into an accelerated path.
When the first LEGO Linear Actuators (LAs) were released back in 2008, I opened one for a couple of review here at TBs  . Fortunately I still have it with me and decided to make a test.
Like a blade, it looks the rod screw is sharp enough to cut the sleeve into pairings, if submitted above a certain pressure. Some manual tests confirmed it right away.
Whether this can be the root cause of the problems that many experienced with the 8043 Motorized Excavator, is still requiring confirmation, but nevertheless I thought worthwhile to show it in the video below.
Sorry for the video darkness, but it was filmed at late night with a compact camera and poor lightning conditions.
Yes, the video is almost one month old and it has been kept unlisted at YouTube, but I just didn't want to release it before.
However after the first idea and tests, something was still not making sense for me...
Because the steel rod has a right-handed screw, damage could happen while retracting the LA under compression (pushing strong the rod), or extending the LA under negative compression (pulling strong the rod).
The Excavator shows major problems in a different situation - While extending the LAs under compression (pushing the rods heavily, under the boom weight).
But why should this become an issue? Why the damage could not be happening whenever the Boom descends under the stress of its weight, instead of when it raises?
I think this could be exactly what it is happening.
It was to demonstrate this effect that I've prepared the video above, where you can see the sleeve (guess it might be Teflon) to discard into parings.
The remains are so thin that you can't see them directly on the video, but just on the final snapshots taken with macro mode.
Again, I don't know if this is the cause of the problems, but it could perfectly be at least part of it.
It may not explain all the observations, but when it comes to failures, many events could be happening and triggering other side effects or secondary failures. Furthermore, multiple failures are the hardest ones to understand.
Notice this video was produced with an LA from 2008, so it can't have any relation with an eventual problem with a recent production batch. Thus if it has any relation with the boom problems of 8043, it may affect every LA produced since ever. Furthermore at the Designers blog it is written "The solution was to modify them and place the new linear actuators in all new sets that we will produce").
I don't know which process does the TLG subcontractor uses to produce the steel rods with terminal screw (machining doesn't look to be, injection or press molding maybe), but even if this doesn't explains it all, it looks the screw finishing may need some improvements in order to avoid wearing the sleeve under heavy loads.
Of course, with the limited technical resources that I have access, there is no way to compare the force I'm doing in the video, with that caused by the excavator digging arm over the LAs. So the video can't be taken as an evidence of what's going on inside 8043 LAs.
Despite my curiosity, I have not yet decided to break and open another LA from those running in my excavator arm, to see what's going on inside. Also because the casing parts are glued together and it wouldn't be easy to open one with a saw, without contaminating the interior with some sawdust, regardless if there is already some dust inside or not. Thus making it difficult to become conclusive.
But one thing is for sure, once I get some of the LAs in my hand, I must open one trying see how they differ from the initial ones.
Meanwhile more information coming from TLG, provides answers to some questions previously raised at several forums:
- There will be no immediate difference between the old and the new Linear Actuator, thus a different color coding is not going to be used.
However it will be possible to see the difference by checking the production code on the actuator. It's located just below the orange cross hole (code yet to be known).
This way it will be possible to avoid mixing old and new LAs, preventing you to use the wrong ones at your 8043 again.
- The Service Bag will contain 4 new Linear Actuators and a few extra parts to fix the track problem..