Linear Actuators

[JunkstyleGio]

With all the fuss about the LA's on the new 8043 set, i tested the one's i already have.

Some of them do not seem to work that well anymore.

Is there a way to keep them working smoothly (even on display for many years)?

[Blakbird]

With all the fuss about the LA's on the new 8043 set, i tested the one's i already have.

Some of them do not seem to work that well anymore.

Is there a way to keep them working smoothly (even on display for many years)?

Unlike pneumatic actuators, linear actuators do not have any seals so there should really not be much to wear out. I suppose it is possible for the rod to corrode over time, but the internal threads are plastic and protected from UV, so I would not expect them to degrade. What is the problem with your older LA's? I just checked mine and they seem to be OK.

[DLuders]

Use Olive Oil: http://www.eurobricks.com/forum/index.php?showtopic=26091 . Seriously, it works well in lubricating Lego Technic parts without degrading the plastic.

[JunkstyleGio]

@ Blakbird:

The two La's on the 8265 seem to get stuck....

But that is just another problem that we will get in to....

@DLuders:

Don't think feeding them spinache will do what it did to Popeye...

[shimon]

it happened to me once when the actuator was already extended but the motor kept running and then the actuator got stuck with no linear movement only rotation

that is only if it is extended, just push with your fingers very hard and try to rotate, it will work again (it might lose the rack)

but if its stuck in the middle .. that's a wierd problem

[Jetro]

@ Blakbird:

The two La's on the 8265 seem to get stuck....

But that is just another problem that we will get in to....

I had to carefully align mine when I first built the model. The trick seemed to be taking them to their top position and then going back just enough to undo the binding that occurs when you hit the limit.

If the LA's are not properly aligned (more than about half a turn off) the stress that puts on the arm makes it really hard to operate. If yours was working fine before, maybe you extended to max length and the clutch kicked in. Unbinding from that position takes a different amount of force for each LA, so maybe that's where your model started to malfunction.

[eMHa]

To get a impression of the LA looks like inside:

http://technicbricks.blogspot.com/2008/07/tbs-techreview-02-technic-pf-linear.html

I don't see much what can get worse over time.

[DLuders]

The trick seemed to be taking them to their top position and then going back just enough to undo the binding that occurs when you hit the limit.

To get a impression of the LA looks like inside: http://technicbricks.blogspot.com/2008/07/tbs-techreview-02-technic-pf-linear.html

On that TechnicBRICKS post, Conchas wrote "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." So, maybe if one counts 26.0 revolutions (from zero to full extension) on both Linear Actuators, they would be set up equally in an ideal, non-binding way.

Conchas continues his Linear Actuator review in Part II: http://technicbricks.blogspot.com/2008/08/tbs-techreview-05-technic-pf-linear.html . Of note is his "Parallel Synchronous Setup" picture 3/4 of the way down that webpage. Note that the Gray Idler Gears are on the SAME side (which may help in the 8043 Motorized Excavator set):

[Jetro]

In this particular case they can only be on the same side as they are not idler gears but connected to the drive shaft ;)

[eMHa]

In this particular case they can only be on the same side as they are not idler gears but connected to the drive shaft ;)

Yes, at this time there was no idler gear in this form!

The second post is over two years old, but still useful. You can see that the safety clutch is between the orange axle connector and the white tube. If this safety clutch is used only by one LA but not on the other, they will for sure get out of sync. And if that happens, the only thing which could help is to seperate the gearing between the two LAs and recalibrate.

This is getting very interesting...

[freakwave]

Unlike pneumatic actuators, linear actuators do not have any seals so there should really not be much to wear out. I suppose it is possible for the rod to corrode over time, but the internal threads are plastic and protected from UV, so I would not expect them to degrade. What is the problem with your older LA's? I just checked mine and they seem to be OK.

If you look at the construction that Conchas posted at Technicbricks you can see that the rod has a thread of metal whereas the thread on the fix past, respectively the base is made of plastic.

What I can imagine is when the model is on display and the LA is in a position that it needs to take some load, the (plastic) thread is under stress and might transform a bit over (a longer) time . This would lead to a position where the LA will not move that smooth anymore.

On the other hand as you write there are no seals, so dust particles, sand etc, might end up inside and clog the thread. This in turn would also work against a smooth operation.

I need to agree that a little bit of lube will help. However I did not test this by myself.

I do have close to 10 of them with me and two of them in a MOC that might push them to the limit (once it is finished) as they will need to push around 2-3 kg vertically

fW