Hi all!

Some of my models have been assembled for several years (3.5..4 years). They were okay until I tried two of them today, both of them had jamming transmissions (total jamming) in some speeds (cars). Last time I tried some months ago and I didn't notice anything.

Did anyone experience similar issues of models that are built long ago? What is the reason? I don't see any hair wrapped around axles and all axles I could reach had sufficient axial play. Dust? Permanent deformation of some parts? Can it be solved without disassembling the whole model, for example with some lubricants? I don't plan to disassemble them ever, so I would be okay with "permanent" solutions too.

Thanks for any hints!

No idea about the cause (only the same guesses as you) nor solutions, but apparently the Land Rover is like this. When freshly assembled, it would work well, but after few months on shelf it would have parts jamming and gears cracking, so I believe this isn't just your problem.

58 minutes ago, howitzer said:

after few months on shelf it would have parts jamming and gears cracking

Hmmm ... these are two worlds, aren't they? Parts jamming is an observation of a maybe complex matter, gears cracking is a clear cause.

I'd say dust - never. Hair - sure, but when there is no hair, then this is out. Permanent deformation? Absolutely - but this means there is mechanical stress on the relevant parts - otherwise they won't deform.

May lubrication help? Yes, but "jamming" means friction has become so large. In that case: May repeated and careful actuation (using things like screwdrivers etc. in remote areas) of the mechanism remove the locking? Then lubrication is the way to go.

Best,
Thorsten

Maybe beams, frames atc. are slowly sliding out of pins under gravity. In every connection just littlebit, in total, maybe it is even not noticable, but for some parts of drivetrain it is critical. Maybe geaorbox top is still together, bottom already wider/longer. It is bent, not square anymore.

Juts my guess. 

Maybe try to push together some sections of build?

7 hours ago, Toastie said:

Hmmm ... these are two worlds, aren't they? Parts jamming is an observation of a maybe complex matter, gears cracking is a clear cause.

I'd say dust - never. Hair - sure, but when there is no hair, then this is out. Permanent deformation? Absolutely - but this means there is mechanical stress on the relevant parts - otherwise they won't deform.

May lubrication help? Yes, but "jamming" means friction has become so large. In that case: May repeated and careful actuation (using things like screwdrivers etc. in remote areas) of the mechanism remove the locking? Then lubrication is the way to go.

Best,
Thorsten

Cracking is caused by parts jamming (=too much resistance in the drivetrain), is it not? What I was trying to say was that the Land Rover seemed to be particularly susceptible for this kind of problem even when correctly and carefully assembled, as I've seen multiple comments about it while none for other sets like the UCS cars.

Edited October 30, 20222 yr by howitzer

My models have very simple gearboxes, and was working for years without problems.

Relatíve humidity is around 80%, that's very high... Could that be a problem?

Edited October 30, 20222 yr by Lipko

14 hours ago, Jurss said:

sliding out of pins under gravity

I believe not due to gravity, but maybe unforeseen or even "natural" shear forces and the like? Every build has these because of the tolerances you mentioned.

12 hours ago, Lipko said:

Relatíve humidity is around 80%, that's very high...

At what temperature? But even when low or high - ABS is not prone to water uptake. I believe it must be some mechanical stress. Not at all illegal connections, no, just some stress due to the overall weight/final alignment, when put aside.

But who knows ...

Best,
Thorsten   

I hypothesize that the models getting rougher has to do with expansion and contraction under different temperatures and seasons. My older models do not run very nice until I rebuild them.

1 hour ago, TechnicRCRacer said:

I hypothesize that the models getting rougher has to do with expansion and contraction under different temperatures and seasons. My older models do not run very nice until I rebuild them.

I do go along with that hypothesis. Plus hidden stress.

Best,
Thorsten

I would caution against lubrication. The problem is, if you add some lubricant today, that will collect some dust and become serious 'paste' in a while. If the set contains no electrical parts, I wash the whole thing in soapy water. I even let the set sit overnight in hot water. Machine detergent is best as it 'eats' the grime like no other.

I'm sure you care, so I thought I report on the issue.

After eliminating the high humidity issue (from 80% to 60...70%) the problem is gone, the models work (not as smoothly as new, but that's dust I guess).

Now only the smaller issue remains, the mould destroying the house...

Hey, there is a similar effect on some of my models which spend their time in a display case and are thus dust protected. Most of them are RC and used to play every now and then. Recently I took 42030 for a ride and it was really driving slow/bad. I always remove all batteries when putting the models away as I had problems with leaking batteries before thus the used batteries were new. After some research I believe that creeping of the plastic is one of the problems. Creeping (could be wrongly translated by me) means the plastic deforms under load over time. I think the whole models "creeps" and thus beams, axles and gears change their shape a tiny bit over time. All those tiny changes add up and cause friction in the drivetrain. If a model is disasamble and put back together the problem disappears because only the pieces which the highest load 'creeped' and are most probably put into different places which don't add up causing problems anymore. Hope this makes sense as it is only a theory  :)

There are compressed air sprays which are often used to clean keyboards or similar. Has anyone ever tried such a spray to remove dust from Lego?

i'm pretty sure dust + humidity + maybe air pollution glues every gear in a model...
I remember noticing that on models i had in my house in rome where the pollution is high and the dust is sticky.

I have the same problem with the Chiron

I strongly suspect dust is to blame, although like everyone else I have no definitive proof!

I find compressed gas dusters somewhat useful for Lego, but really I think the only solution is keeping models in sealed cabinets.

On 12/25/2022 at 11:54 PM, aeh5040 said:

but really I think the only solution is keeping models in sealed cabinets.

I am not sure about this (the dust only bit). Yes, dust is a devil, as there are Dirt Devils to take care of dust.

However, When you look at the behavior of ABS exposed to different levels of humidity at different temperatures (there are ample references out there), you'll find that ABS is changing shape. Not much, so little. Well, with all these super refined drive trains and all that - it just may jam up. Built at 40% rel humidity, 25°C, may have issues at 80% rel humidity and 15°C.

Go all metal if you want to avoid that - as they do in real life - or rebuild your model with parts equilibrated to new conditions (takes time though, days or even several months).

And yes, keep the dust out.

Conclusion: Build your complex LEGO models in a Class 7 (or better) clean room operated at specs (pressure, temp, humidity) and leave it there. And run it there.

Best,
Thorsten 

Well ... there is a way to answer whether it's dust or stresses. Plus, which stresses are we talking about? The stresses due to assembly or those due to the weight of the vehicle and some parts being exercised along many directions (torsion/bending/etc). One way to answer the latter is to send the assembled model to the space-station (zero gravity), let it sit/relax there for few months (astronauts are allowed to enjoy Lego as well), bring it back to earth, and see what happens. Incidentally, one can build a 'twin' and keep it on earth for reference/control. They did send a Raspberry PI to the ISS, why not a Sian?  

Seriously ... we're dealing here with plastic (ABS or else), and plastic does 'creep' with time. I 'believe' it is a combination of dust/humidity and of course creep/relaxation.... My 0.02, though same answer as everyone else, nothing new.

Hey! I had the same proem in $2056 Orange Porsche. It was assembled in 2016. I played with it, everything was fine. Than in a year a two I washed it in a shower and put backk to the shelf. In a year after that I trried to play with it - but everything has jamming efffect. I don't know why. I reassemble the drivetrainn and everything works fine. Note that disassempling pins was too hard. Maybe because of the dust and water together.